Digitized by tlie Internet Arcliive in 2015 https://archive.org/cletails/buildingconstruc01kicld_0 EXTRACT FROM TABLE OF CONTENTS. PART II. Chapter I. The Building and Finishing Woods of the United States. — Their char- acteristics, properties and uses. Chapter II. Wood Framing — Ordinary Construction. — Framing timber — Framing of wooden buildings — Framing of floors, supports for partitions, roof construc- tion — Superintendence. Chapter III. Sheathing, Windows and Outside Door Frames. — Sheathing of walls and roof — Cellar frames — Types of windows, construction of window frames in frame and brick walls, patent windows, casement windows, pivoted windows, bay windows — Sash, store fronts — Glass and glazing — Outside door frames. Chapter IV. * Outside Finish, Gutters, Shingle Roofs. — Eaves and gable finish, gutters and conductors — Siding — Porches — Dormers — Shingling, flashing — Wood sky- lights. Chapter V. Furring, Inside Finish, Doors, Stairs. — Furring for finish and plastermg — Grounds and corner beads — Flooring — Doors and door frames — Casing of doors and windows — Paneling, beams, columns, stairs. Chapter VI. Builders' Hardware, — Heavy hardware, bolts, nails, screws — Finishing hard- ware, butts, locks, knobs, bolts, window trimmings, trimmings for blinds and shutters Chapter VII. Heavy Framing. — Framing of posts and girders, bracing, mill floors — Compound and trussed girders — Suspended floors, galleries. Chapter VIIL Specifications. — Carpenters' work — Joiners* Work — Hardware. Appendix. * Tables of Strength of wood and cast iron columns, wooden beams, maximum spaa for floor joists. PART III. TRUSSED ROOFS AND ROOF TRUSSES. (IN PREPARATION) TABLE OF CONTENTS. INTRODUCTION. Chapter I. Types of Wooden Trusses and the Mechanical Principles involved. Chapter II. Types of Steel Trusses. Chapter III. Lay Out of Trussed Roofs— Bracing of the Roof and Trusses. Chapter IV. » Open Timber Roofs and Church Roofs. Chapter V. Vaulted and Domed Ceilings ; Octagonal and Domed Roofs. Chapter VI. Coliseums, Armories, Train Sheds, Exposition Buildings, etc. Chapter VII. Computing the Purlin and Truss Loads and Supporting Forces,. ii Chapter VIII. Stress Diagrams and Vertical Loads. BUILDING CONSTRUCTION AND SUPERINTENDENCE. BY F. E. KIDDER, C. E., Ph.D., ARCHITECT. Fellow of the American Institute of Architects. Author of " The Architect's and Builder's Pocket-Book.** REVISED AND ENLARGED BY THOMAS NOLAN, M. S., A. M., Fellow of the American Institute of Architects, Assistant Professor of Architecture, University of Pennsylvania, Part I. NINTH EDITION, REVISED. MASONS' WORK. Illustrations. WILLIAM' T. COy^^^i)CK. , 23 Warren Street. Copyright by F. E. KIDDER 1896, 1897, 1898, 1900, 1902. 1903. ^905, Copyright by KATHERINE E. KIDDER 1906, 1909. Composition: S. L. PARSONS & Co. ,JNC^, Nfiv Vark Presswirk : BdU ■ Ir r'AI^'kl'in ' and fence-boards are nailed horizontally from the corner posts to- each of the other two posts, as illustrated in Fig. 2. These boards, should be long enough to allow both the inside and outside lines of the foundation walls to be marked on them. The stakes should also be braced from the bottom of each corner stake to the top of each of the others. This makes a firm support for the lines and one that need not be moved until the walls are up and ready for the first floor Fig. 2. Stakes and Fence-Boards. Fig. 3. Different Lines Indicated by Saw Marks, Nails and Notches. joists. These boards have the great advantage over single stakes of being more permanent, and of allowing all projections of the walls, such as footings, basement wall and first story wall, to be readily marked on them. It is a good idea to indicate the ashlar line by a saw mark, the basement line by a nail and the footings by a notch, as shown in Fig. 3. In this way no mistake can be made by the workmen. If the tops of all the horizontal boards are kept on a level, it assists a great deal in getting levels for the excavating,, etc. ^ The superintendent will be expected to furnish the contractor with a bench-mark, from which he can get the level for his footings, floor joists, etc. This mark should be put on some permanent object, where it can be referred to after the first floor joists are set in place. In giving such data to the contractor the superintendent must be very careful, as he can be held responsible for any loss resulting from errors which he may make. It is a very safe and good rule to give as few lines, data or measurements as possible to contractors,, requiring them to lay out all the. work themselves and to be alone responsible for the accuracy of their work. FOUNDATIONS. LIGHT BUILDINGS. 3 2. LOT LINES, ETC. — For buildings which are built out to the street line, the lines of the lot should be given by a surveyor employed by the owner, and should be fixed by long iron pins driven into the street, or by lines cut on the curbstone across the street. In building close to the party-lines of a lot it is, of course, of great importance that the building does not encroach upon the adjacent lot, and to prevent this it is always well to set back one inch from the line, thus allowing for any irregularities or projections in the wall. 3. DIAGONALS. — After the batter-boards are in place and properly marked, the superintendent should require the contractor or his foreman to stretch the main lines of the building, and the superintendent should carefully measure the diagonals, as A B and C D, Fig. I, with a steel tape ; if they are not exactly of the same length the lines are not at right angles with each other and should be squared until the diagonals are of equal length. On fairly level ground a building may be accurately laid out by means of a steel tape, using multiples of 3, 4 and 5 for the sides and the hypothenuse of a right-angled triangle. The larger the triangle the more accurate will be the work. 4. STAKING OUT BUILDINGS IN CITIES.— In staking out buildings in cities of the first and second class the building" and property lines should always be obtained from an official survey, furnished at a nominal charge, by the surveyor of the district authorized by the city. It is usual also to have the district surveyor give the street and party-lines at the site of the operation. From these main lines the building may be readily staked out as described above. In reading a survey care must be exercised to determine whether or not the measurements given are in United States standards, as frequently the unit measurements of the city and of the deeds are not standard, and may vary from the tape measurements as muclr as several inches in a hundred feet. 2. FOUNDATIONS. LIGHT BUILDINGS. 5. NATURE OF SOILS.— The architect should in all cases make every endeavor to discover the nature of the soil upon which his building is to be built before he makes his foundation plan. For most buildings a sufficient idea of the nature of the soil may be. 4 BUILDING CONSTRUCTION. ■i (Ch. I) gained by inquiry amongst builders who have put up buildings on the adjacent lots. Many soils, however, vary greatly, even in a distance of lOO feet, owing to a decided dip of the strata, and on all such soils much trouble and annoyance may often be saved by having bor- ings made with a post-auger, showing the composition of the soil of the different strata. If two borings made on different sides of the site show about the same depth and character of soil it may be assumed that other borings would give the same result ; but if the material brought up by the first two borings shows a difference in the character of the soil, or indicates that the strata have a decided dip, then borings should be made all around the foundations. Where the ground has been filled in, or made, a knowledge of the original topography of the soil is always desirable. This information may sometimes be obtained from official county or city maps and is of great assistance in the designing of foundations for important buildings. The data thus obtained should, however, be supplemented by test borings in order to ascertain the character of the original superstratum. For ordinary buildings borings to the depth of 8 or lo feet are generally, sufficient, although a 6- or 8-inch auger may be driven to the depth of 20 or 25 feet by two men using a lever. In soft soils a pipe must first be sunk and the auger. worked inside of it. A smaller auger will answer in such cases. For dwellings built on sand, gravel, clay or rock, an examination of the bottom of the trenches, and a few tests with an ordinary crow- bar or post-auger, will generally be all that is necessary. When borings are deemed necessary the owner should be advised of the fact, and his authority obtained for incurring the expense, which should be defrayed by him. Different soils have not only different bearing or sustaining pow- ers, but also various peculiarities which must be thoroughly under- stood and considered when designing the foundation. An architect who, as a draughtsman, has had several years' expe- rience in one locality before practicing for himself, will naturally have become acquainted with the peculiarities of the soil in that vicinity ; but should his practice extend beyond his own city, he should carefully study the nature and peculiarities of the soil in each different locality where he may have work, and also obtain all the information possible, bearing on the subject, from local builders, as •otherwise he may have serious trouble. FOUNDATIONS. LIGHT BUILDINGS. 5 No part of a building is more important than the foundation, and more cracks and failures in buildings will be found to result from defective foundations than from any other cause ; and for any such defects, resulting from the neglect of usual or necessary precautions, the architect is responsible to the owner, and also for the damage done to his own reputation. The following observations are intended as a general guide in preparing foundations on different soils, although they should be supplemented by the experience of local builders wherever possible. 6. ROCK. — Rock, when it extends under the entire site of the building, makes one of the best foundation beds, as even the softest rocks will safely carry more weight than is likely to come upon them. The principal trouble met with in building on rock is the presence -of water. As the surface water cannot readily penetrate the rock it collects on top of the ledge and in the trenches so that some arrange- ment for draining it away should be provided. If the ledge falls off to one side, a tile or stone drain may be built from the lowest point of the footings to a point near the surface on the slope. If in a sewer district, the water may be drained into the sewer, proper precautions being taken for trapping and ventilation. If there is no sewer and the rock does not fall off, a pit to collect the seepage should be excavated at the lowest part of the cellar and an auto- matic arrangement provided for raising the water into a drain laid above the surface of the rock. Fig. 4. Rock Cut to Level Planes. To prepare the rock for the footings, the loose and decayed por- tions should be cut away and dressed to a level surface. If the sur- face of the rock dips, or is irregular in its contour, the portion under the footings should be cut to level planes or steps, as shown in Fig. 4. In no case should the footings of a wall rest on an inclined bed. This method of filling in the depressions in rock excavation with concrete to a level bed in order to secure a firm footing is the one usually employed in the construction of all large buildings. In Fig. 5 is shown an example of this construction, illustrating the arrange- 6 BUILDING CONSTRUCTION. (Ch. I) ment of a column footing of the New York Times building, one of the heaviest structures in New York. 3i'nJchjral Colo Broken ^one Bed Kock Fig. 5. Filled-in Rock Fissure, New York Times Building. 7. FISSURES AND DIFFERENT LEVELS.— If these are fissures or holes in the rock, they should be filled with concrete, well rammed; or, if a fissure is very deep, it may be spanned by an arch, of brick or stone. In building on rock it is very desirable that the footings shall be nearly level all around the building ; and whenever this is not the case, the portions of the foundation which start at the lower level should be laid in cement mortar and with close joints, as otherwise the foundations will settle unequally and cause cracks to appear above. 8. FOUNDATIONS PARTLY ON ROCK.— Should it be abso- lutely necessary to build partly on rock and partly on soil, the foot- ings on the soil should be made very wide, so that the settlement will be reduced to a minimum. The footings resting on the rock will not settle, and the least settlement in those resting on the soil will be sure' to produce cracks in the superstructure, and perhaps do other damage. Building on such a foundation bed is very risky at best, and if possible should be avoided. FOUNDATIONS. LIGHT BUILDINGS. 7 9. CLAY. — This soil is found in every condition, varying from slate or shale, which will support any possible load, to a soft, damp material, which will squeeze out in every direction when a mod- erately heavy pressure is brought upon it. Ordinary clay soils, however, when they can be kept dry, will carry any usual load without trouble, but as a rule clay soils give more trouble than either sand, gravel or rock. In the first place, the top of the footings must be carried below the frost line to prevent heaving, and for the same reason the out- side face of the wall should be built with a slight batter and per- fectly smooth surface. The frost line varies with different localities, attaining a depth of six feet in some of the Northern States, although between three and four feet is the usual depth reached. The effect of freezing and thawing on clay soils is very much greater than on other soils. The surface of the ground around the building should be graded so that the rain water will run away from the building ; and in most clays subsoil drains are necessary. When the clay occurs in inclined layers, great care must be exercised to prevent it from sliding ; and when building on a side hill the utmost precautions must be taken to exclude water from the soil, for if the clay becomes wet the pressure of the walls may cause it to ooze from under the footings. The erection of very, heavy buildings in such locations must be con- sidered hazardous, even when every precaution is taken. Frequently an excellent foundation soil is found underlaid with a thin stratum of clay. Where such a stratum exists there is little danger in building above it, provided there is no probability of adja- cent excavations being carried below the clay and thus allowing it to be squeezed out by the pressure on the footings. Should it be necessary to carry a portion of the foundations to a greater depth than the rest, the lower portion of the walls should be built as described in Article 7, and care must be taken to prevent the upper part of the bed from slipping. Wherever possible, the footings should be carried at the same level all around the building. 10. FOUNDATIONS IN HEAVY BLUE CLAY.— In Eastern Maine, where the soil is a heavy blue clay, and freezes to the depth of four feet, it is customary to build the foundation walls as shown in Fig. 6, the footings being laid dry, to act as a drain, and the bottom of the trench being slightly inclined to one corner, whence 8 BUILDING CONSTRUCTION. (Ch. I) a drain is carried to take away the water. The portion of the trench outside of the wall is also filled with broken stone or gravel to pre- vent the clay from freezing to the side of the wall. In the better class of work the outside of the wall is plastered smooth with cement. Sometimes a tile drain is laid just outside and a little below the footings. 11. CLAY WITH SAND OR GRAVEL.— If the clay contains coarse sand or gravel its supporting power is increased, and it is less liable to slide or ooze away. In Colorado the top soil consists principally of clay, mixed with fine sand, and as long as it is kept dry it will sustain a great load without settlement. As soon as it becomes wet, however, it turns into a soft mud, which is very compressible and treacherous. For this reason the footings of heavy buildings are carried through the clay to the sand below. A peculiarity of this soil is that, although it freezes, it has never been known to heave. Two-story buildings are therefore often built on top of the ground, and as long as water is kept away from the walls no injury results. 12. GRAVEL. — This material gives less trouble than any other Fig. 6. Foundation in Clay, with Stone Drains. FOUNDATIONS. LIGHT BUILDINGS. 9 as a foundation bed. It does not settle under any ordinary loads, and will safely carry the heaviest of buildings if the footings are properly proportioned. It is not affected by water, provided it is confined laterally, so that the sand and fine gravel cannot wash out. This soil also is not greatly aflfected by frost. 13. SAND. — This material a.lso makes an excellent foundation bed when confined laterally, and is practically incompressible, as. clean river sand compacted in a trench has been known to support 100 tons to the square foot. As long as the sand is confined on all sides, and the footings are all on the same level, no trouble whatever is encountered, unless it is in the caving of the banks while making the excavations. Should the cellar be excavated to different levels, however, sufficient retain- ing-walls must be erected where the depth changes in order to pre- vent the sand of the upper level from being forced out from under the footings; and precautions should be taken in such a case to- prevent water from penetrating under the upper footings. 14. LOAM AND MADE LAND.— N6 foundation should start on loam, that is, soil containing vegetable matter, or on land that has been made or filled in, unless the filling consists of clean beacht sand, which, when settled with water, may be considered equal in resisting power to the natural soil. Loam should alwayS be penetrated to the firm soil beneath, and when the made land or filling overlies a firm earth the footings should be carried to the natural soil. When the filled land is always wet, as on the coast or on the borders of a lake, piles may be used, extending into the firm earth, and having their tops cut off below the low-water mark; but piles should never be used where it is not certain that they will be always wet. 15. MUD AND SILT. — Under this heading may be included all marshy or compressible soils which are usually saturated with water. Foundations on such soils are generally laid in one of the three following ways: i. By driving piles on which the footings are sup- ported. 2. By spreading the footings either by wooden timbers, steel beams or reinforced concrete, so as to distribute the weight over a large area. 3. By sinking caissons or steel wells or cylinders, filled with masonry, to hard pan. As all of these methods are more or less complicated they will be described in Chapter 11. 10 BUILDING CONSTRUCTION. (Ch. I) 16. SOILS OF PECULIAR NATURE.— There are in some localities peculiar conditions in the soil strata with which those engaged in building operations should be familiar. In the anthracite regions, in some localities, the galleries or workings lie near the surface, and it is necessary to locate them with reference to the lines of the building so that the important piers may be extended down through them. In one instance it was necessary to entirely rebuild a portion of a costly building in Scran ton. Pa., because an apparently, solid foun- dation soil was undermined by a subterranean stream which flowed along a shale substratum and then down into an abandoned mine- working. In this way the stream had tunnelled the upper stratum, so that when the weight of the almost completed building was imposed the earth gave way and caused dangerous settlement. 17. BEARING POWER OF SOILS.— The best method of determining the load which a particular soil will bear is the one involving direct experiment; but good judgment, aided by a careful examination of the soil,, and particularly of its compactness and the amount of water it contains, in conjunction with the following table, will enable one to determine with reasonable accuracy its probable supporting power. A mean of the values given below may be con- sidered safe for good examples of the kinds of soils quoted : TABLE 1. Safe Bearing Strengths of Foundation Rocks and Soils. CHARACTER OF SOIL. sq'uTheToT Kock, granite in hard, compact strata . 100 to 200 Rock, limestone 25 to 30 Rock, sandstone 18 to 25 Rock, soft and friable, as shale 5 to 10 Clay, thick beds and dry , 4 to 6 Clay, thick beds and moderately dry 2 to 4 Clay, soft I to 2 Gravel, mixed with sand and well cemented 8 to lo Gravel, coarse and dry, well compacted 6 to 8 Sand, compact and well cemented 4 to 6 Sand, clean and dry and confined in natural beds ; 2 to 4 Quicksand, alluvial soils, etc 0.5 to I In case it is desirable to exceed the maximum loads here given, or in case there is any doubt of the bearing capacity of the soil or a lack of precedent, tests should be made in several places on the FOUNDATIONS. LIGHT BUILDINGS. II bottom of the trenches to determine the actual load required to produce settlement, as described in Article 20. 18. MUNICIPAL REGULATIONS.— While Table I, giving the safe unit-bearing value of different foundation soils, represents conservative engineering practice, the municipal regulations of the locality must usually be observed, as the several cities have estab- lished such values in their building law^. As a rule it is required that these vames shall be used in propor- 1 tioning foundation footings where the soil is not tested; and deviations are allowed from these values when the soil is tested, the test being witnessed by a representative of the building depart- ment and the record of the test being filed with the bureau. The New York building law stipulates that the following loads per superficial foot shall be used in proportioning foundation foot- ings : soft clay, one ton per square foot ; ordinary clay and sand together, in layers, wet and springy, two tons per square foot ; loam, clay or fine sand, firm and dry, three tons per square foot ; very firm, coarse sand, stiff gravel or hard clay, four tons per square foot. The Chicago building ordinance relating to the bearing value of foundation soils deals specifically with the soils underlying the city. These soils are of a clayey nature and the bearing value is limited as given in the following quotation from the ordinance: 'Tf the soil is a layer of pure clay at least fifteen feet thick without admixture of any foreign substance excepting gravel, it shall not be loaded more than at the rate of 3,500 pounds per square foot. If the soil is a layer of pure clay at least fifteen feet thick and is dry and thoroughly compressed, it may be loaded not to exceed 4,500 pounds per square foot. "If the soil is a layer of dry sand fifteen feet or more in thickness, and without admixture of clay, loam, or other foreign substance, it shall not be loaded more than at the rate of 4,000 pounds per square foot. "If the soil is a mixture of clay and sand it shall not be loaded more than at the rate of 3,000 pounds per square foot." 19. EXAMPLES OF ACTUAL LOADS AND TESTS.— On Clay. — The Capitol at Albany, N. Y., rests on blue clay con- taining frorn 60 to 90 per cent of alumina, the remainder being fine sand, and containing 40 per cent of water on an average. The safe load was taken at^2 tons per square foot. A load of 5.9 tons applied 12 BUILDING CONSTRUCTION. (Ch. I) on a surface i foot square produced an uplift of the surrounding earth. The Congressional Library at Washington, D. C, rests on yellow clay mixed with sand. It was found that it required about ly/z tons per square foot to produce settlement, and the footings were proportioned for a maximum pressure of 2^ tons. A hard indurated clay, containing lime, under the piers of a bridge across the Ohio River, at ?oint Pleasant, W. Va., carries approxi- mately 23^ tons per square foot. On Sand. — ''In an experiment in France clean river sand com- pacted in a trench supported 100 tons per square foot. "The piers of the Cincinnati suspension bridge are founded on a bed of coarse gravel 12 feet below water; the maximum pressure is 4 tons per square foot. "The piers of the Brooklyn suspension bridge are founded 44 feet below the bed of the river, upon a layer of sand 2 feet thick, resting upon bed rock; the maximum pressure is about 51^ tons per square foot." * 20. METHODS OF TESTING.— Probably the easiest method of determining the bearing power of the foundation bed is the one involving the use of a platform from 3 to 4 feet square, having four legs, each 6 inches square. The platform should be set on the bottom of the trench, which should be carefully levelled to receive the legs. A level should then be taken from a stake or other bench-mark not liable to be disturbed, to each of the four corners of the platform, and the platform then loaded with dry sand, bricks, stone or pig- iron, as may be most convenient. The load should be put on gradu- ally, and frequent levels taken unttl a sinkage is shown. From one- fifth to one-half of the load required to produce settlement is gener- ally adopted for the safe load, according to circumstances. In testing the ground under the Congressional Library building a travelling car was used, having four cast-iron pedestals, set*4 f^et apart each way, and each measuring i square foot at the base. The car was moved along the trenches, and halted at intervals in such a w-ay as to bring the whole weight of the car and its load upon the pedestals which rested on the bottom of the trench. In this case the car was loaded with pig-lead. By this method, if the legs of the testing apparatus do not settle evenly, it is impossible to tell just what the pressure on the lowest * Ira O. Baker, American Architect, November 3, 1888. DESIGNING THE FOUNDATIONS. corner amounts to ; and it is not safe to consider it more than one-fourth of the whole load. In testing soils by using a small square bearing area, it should be observed that the settlement will be in excess of that which would occur from the same load on a continuous footing. This is. explained by the fact that the square end of the post or pedestal forming the bearing plate of the testing machine has four cutting edges which tend to enter the soil with less resistance than a long footing course having only two edges. 21. SOIL TESTING UNDER NEW YORK STATE CAP- ITOL. — In testing the soil under the State Capitol at Albany, N. Y., the load was placed on a mast 12 inches square, held in a vertical position by guys, and furnished with a cross frame to hold the weights. The bottom of the mast was set in a hole 3 feet deep, iS inches square at the top and 14 inches square at the bottom. Small stakes were driven into the ground in lines radiating from the center of the hole, the tops being brought exactly to the same level, so that any change in the surface of the ground could readily be detected and measured by micans of a straight-edge. In this case there was no change in the surface of the ground until the load reached 5.9 tons, when an uplift of the surrounding ground was noticed. 3. DESIGNING THE FOUNDATIONS. 22. PRELIMINARY DATA.— Knowing the character and sup- porting power of the soil on which he is to build, the architect is prepared to design his foundation plans, but in no case should this be done when the preceding information is wanting. In designing the foundations the first point to be settled will be the depth of the foundations ; the second, whether they shall be built in piers or in a continuous wall ; and the third, the width of the foundations. 23. DEPTH. — For isolated buildings on firm soil, the depth of the foundations will generally be determined by the depth of the basement or by the frost line. Even where there is no frost, and the ground is firm, the footings should be carried at least 2 feet below the surface of the ground, so as .to be below the action of the surface water. In very few soils, however, is it safe to start the foundations at a less depth than 5 feet, thou^i in a temperate 14 BUILDING CONSTRUCTION. (Ch. I) climate, such as that of the Middle States, foundations carried to a depth of 3 feet 6 inches give little trouble. (See Article 10.) The depth of the foundations for city buildings, built near ths lot line, should be governed by the local laws bearing on the sub- ject, by the character of the soil, and by the probable future action of the owners of the adjoining property. In most cities the law provides that any lot owner who excavates below a certain depth, usually about 10 feet, must protect the walls of the adjoining property at his own expense; but that if he does not excavate below that depth, 10 feet, the adjoining owners must them- selves protect their property from falling in. It is, therefore, always wise to provide against any such future expense and trouble by carrying the footings, at least those of the side walls, to the prescribed limit, above which the owner will be responsible, even if the requirements of the soil or building do not necessitate it. This precaution is especially important when the building is erected on sand. 24. CONTINUOUS FOUNDATIONS VERSUS PIERS.— It has been found that when heavy buildings are to be erected on soft or compressible soils greater security from settlement may be obtained by dividing the foundation into isolated piers, as described in Chapter II. When building on firm soils, however, no advantage is gained by pursuing this method, unless the walls of the building are themselves composed of piers with thin curtain-walls between, in which case the foundations under the piers and walls should be built of different widths, and not bonded together, as described in Article 33. When the walls are continuous, however, and of the same thick- ness throughout, the foundation should be continuous. The architect should constantly bear in mind that in all kinds of building construc- tion the simplest methods are almost always the best, and that com- plicated arrangements and the use of iron, etc., in foundations, at least on firm soils, should be avoided. 25. PROPORTIONING THE FOOTINGS. — Whether the foundations are continuous or divided into piers, the, area of the footings should be carefully proportioned to the weight ivliich they support and to the bearing power of the soil. The former is per- haps the most important of all considerations in designing the foot- ings. While th% safe bearing power of the soil ought not to be DESIGNING THE EOUNDATIONS. 15 exceeded, it is, on most soils, not of so much importance as a pro- portioning of the footings, such that the pressure on the soil from every square foot of the footings zvill he the same. If this condi- tion always obtained there would be few cracks in the mason work of buildings, as such cracks are caused, not by a uniform settle- ment of an inch or two, wdiich with most buildings would not be noticed, but by an unequal settlement. In proportioning the area of the footings the architect should carefully compute the w^eights coming upon each pier, and the weight of and the loads supported by the walls, and record the same in a memorandum book or otherwise file for reference. He should then decide, by means of Table I, Article 17, and by an examination of the ground, or, if necessary, by actual tests, the bearing weight which it appears advisable to assume. By dividing the load on the various footings by this assumed carrying load, the proper area of the footings will be found. The pressure under piers supporting a tier of iron columns may be made 10 per cent more than that under a brick v^all, so that the piers may settle a little more to allow for the compression in the joints of the mason work. 26. COMPUTING THE WEIGHT.— /^t computing the zveight to be supported by the footings the live or movable loads and the dead loads should be computed separately. In building on any com- pact soil, the object in carefully proportioning the footings, as has been stated, is not so much to prevent any settling of the build- ing as a whole, but to provide for a uniform settling of all portions of it, so that the floors will remain level and no cracks be developed in the walls. In order to secure this result, it is necessary that the loads for which the footings are proportioned shall agree with the actual conditions as closely as possible.* Thus the dead load under the walls of a five-story building would be a considerable item, while the dead load under a tier of iron columns would be much less in proportion to the floor area supported ; and, as the dead load is always constant and the live load one which may greatly vary, only the amount of the live load that will probably be supported by the footings most of the time should be considered. For warehouses, stores, etc., about 50 per cent of the live load for * Foundations shall be proportioned to the actual average loads they will have to carry in the completec^ and occupied building, and not to theoretical or occasional loads. — Chicago Building Ordinance. i6 BUILDING CONSTRUCTION. (Ch. I) which the floor beams are proportioned should be added to the dead load supported on the footings. ♦ For office buildings, hotels, etc., the weight of the people who occupy them should be neglected altogether in proportioning the footings, and only about 15 pounds per square foot of floor allowed to cover the weight of furniture, safes, books, etc. Actual statistics show that the permanent average loads in such buildings do not exceed the above limit. For theatres and similar buildings some allowance should probably be made for the weight of people, the actual amount depending upon the arrangement of the plan and character of the soil. 27. BUILDING ORDINANCES.— While the data given above represent conservative practice in regard to the percentage of the live load to be assumed in designing foundations, it must be observed that this is regulated by law in the larger cities. Many building codes throughout the country are compiled, with modifications, from the code of the city of New York, so that the following quotation from the portion of the code relating to the proportioning of footings will be found useful here : 'The loads exerting pressure under the footings of foundations in buildings more than three stories in height are to be computed as follows : For warehouses and factories they are to be the full dead load and the full live load established by this code. In stores and buildings, for light manufacturing purposes, they are to be full dead load and 75 per cent of the live load established by this code. The same applies to churches, school-houses and places of public assembly. In oflice-buildings, hotels, dwellings, apartment-houses, tenement-houses, lodging-houses and stables, they are to be the full dead load and 60 per cent of the live load established by this code. The footings must be designed to distribute the loads as uniformly as possible, so as not to exceed the safe bearing capacity of the soil as established by this code." 28. LIVE LOADS AND UNEQUAL SETTLEMENTS.— Almost any soil, after it has been compacted by the dead weight of a building, will carry a shifting load of people without further settle- ment ; while if the footings are computed to carry the full live loads for which the floor beams are designed, it will be found that when the building is finished the actual loads on the footings under the walls will be much greater than under the interior piers; and if DESIGNING THE FOUNDATIONS. 17 the ground settles at all during building the probabilities are that the floors of the building will be higher in the middle than at the walls. 29. CALCULATIONS FOR FOOTING WIDTHS.— Example I. — Assume that a six-story and basement warehouse is to be erected on an ordinary sand and gravel foundation. The building is to be 50 feet wide, with two longitudinal rows of columns and girders. What should be the width of the footings under the walls and columns? Solution. — The load on one lineal foot of footing under the side walls will consist of about 140 cubic feet of brick and stone work, weighing about 17,000 pounds.* One lineal foot of wall will also support about 8 square feet of each floor and the roof. Assume also that the floors are of steel beams and terra-cotta tile, with con- crete filling, weighing altogether 75 pounds to the square foot, and that the roof is of the same material, weighing 60 pounds to the square foot. Then the dead load from the six floors and roof will amount to 4,080 pounds. The first, second and third floors are intended to support 150 pounds to the square foot, and those above 100 pounds to the square foot. The possible weight of snow on the roof will not be taken into account. There miight then be a possible live load on the footing of 6,000 pounds, but as it is improbable that each floor will be loaded all over at the same time, and as some space must be reserved for passages, etc., the actual live load will probably not exceed for any lenglh of time 50 per cent of the assumed load, or 3,000 pounds. Adding these three loads together, the wall loads, floor loads and live loads, there results 24,080 pounds as the load on one lineal foot of footing. By allowing 6,000 pounds, 3 tons, for the bearing power of the soil, and by dividing the load by this amount, the required width of the footing is found to be 4 feet. The load on the footings under the columns will consist only of the weight of the floors, roof and live load, plus the weight of the tier of columns, which will be so small in proportion to the other loads that it need not be considered. If the columns are 14 feet apart longitudinally, each one will support 224 square feet of each floor, so that the total dead load on the footing under the columns will amount to 114,240 pounds, and the possible live load will amount to 168,000 pounds. As it is hardly possible for every square foot of floor in every story to be loaded to its full capacity * For weight per cubic feet of materials, see table in Appendix. i8 BUILDING CONSTRUCTION. (Ch. I) at the same time, it will probably be nearer the actual conditions if only 50 per cent of the total live load, or 84,000 pounds, are taken, making a total load on the footing of 198,240 pounds, which will require 33 square feet in the area of the footing. But as there will be no shrinkage or compression in the iron columns, it will be better to reduce this area 10 per cent, making the footing 5^ feet square, with an area slightly in excess of 30 square feet. The above calculation should be filed, or entered in a memoran- dum book, kept for the purpose, somewhat as follows : DATA FOR FOOTINGS. * UNDER ONE FT. OF SIDE WALLS. UNDER COLUMNS. Cubic feet of brickwork, 108 @ 120—12,960 lbs. Cubic feet of stonework, 28® 150= 4,200 Total weight of wall 17,160 lbs Nothing Floor area supported 8 □ ' 16 x 14= 224 □ Weight of floors per □ ' 75 lbs. "Weight of roof per □ ' 60 lbs. Total for six floors and roof: 510x8= 4,080 510x224=114,240 Live load per □ ' — 1st, 2d and 3d floors, 150 lbs. 3d, 4th and 5th floors, 100 lbs. Total live load, 8 x 750=6,000 750 x 224= 168,000 50^ of this = 3,000 84,000 Total load 24,240 198,240 Assumed bearing load, 6,000 lbs. Width of footings under wall, 4 ft.; under columns, 33 □ ' less 10%, or 5' 6" x 5' 6". The front and rear walls, if continuous, would not have to sup- port any floor loads, and the footings should be reduced in pro- portion. The footings under the piers supporting the ends of the girders should also be separately computed. 30. FOOTING WIDTHS IN GENERAL.— In the case of light buildings it will often be found that the computed width of footings will be less than that required by the building ordinances, in which case it will of course be necessary to comply with such ordinances or building laws. As a rule, the footings under a foundation wall should be at least 12 inches wider than the thick- ness of the wall to give it stability. Even in light buildings the footings under the different portions of them should be carefully proportioned, so that all will bring the same pressure per square foot on the ground. In cases where the width of the footing is regulated by the building law, the pressure per square foot under the footing should be computed, and the footings under all piers, etc., proportioned to this standard. In cases where a high tower DESIGNING THE FOUNDATIONS, 19 adjoins a lower wall the footings under the two portions must be carefully proportioned to the weight on each; otherwise the wall may crack where it is bonded into the tower. 31. CALCULATIONS FOR FOOTING WIDTHS.— £.r- ample II. — To illustrate the manner in which the width of the foot- ings should be proportioned when the pressure under the footings is very light, the following example will be considered : A one-story stone church has side walls 20 inches thick and 22 feet high above the footings and a tower at the corner 60 feet high, the first 22 feet being 24 inches thick and the balance 20 inches thick. The roof is supported by trusses and purlins, so that only the lower 6 feet of the roof rest on the side walls. The side walls also carry 6 feet of the floor. The tower has a flat roof 12 feet square. Solution. — The computations for the widths on the soil under the side walls and under the tower wall will be as follows : UNDER SIDE WALLS. Stonework, 22' x 20" = 36-3 cu.ft. at 150 lbs. per cu. ft., 5,500 lbs. Weight of first floor, 130 lbs. X 6 n '= 780 " Weight of roof below purlin, 40 lbs. X 6 □ '= 240 " UNDER TOWER WALL. Stonework, 22' x 24"= ... 44 cu. ft. 38'X22"= ... 631^ " I07¥x 150= 16,100 lbs. Weight of floor, 130 X 6=. . 780 " Weight of roof, 40 x 6=. . 240 ** Total weight on soil 17,120 Total weight on soil 6,520 " Width of footings, 3 ft. Pressure per □ ' under footings, 2,173 ^bs. Width of footings under tower, 17, i20-f 2,173 = 7.8 ft. In this case the width of the footings under the side wall should be determined by the question of stability, and should not be less than 3 feet. Then if the pressure under the tower is reduced to the same unit per square foot, the tower footings will need to be nearly 8 feet wide. On firm soils, however, such as sand, gravel or compact clay, it will not be necessary to make the footings as wide as this, as the soil will probably not settle appreciably under a con- siderably greater pressure ; so that if the footings of the tower are made 6 feet wide, there will probably be no danger of unequal settlement. Of course the greater the unit pressure on the soil the more exact must be the proportioning of the footings. 32. CENTER OF PRESSURE ' TO COINCIDE WITH CENTER OF BASE.— In order that the walls and piers of a building may settle uniformly and without producing cracks in the superstructure, it is not only essential that the area of the footings 20 BUILDING CONSTRUCTION. (Ch. I) shall be in proportion to the load and to the bearing power of the soil, but also that the center of pressure (a vertical line through the center of gravity of the weight) shall pass through the center of the area of the foundation. ' This condition is of the first importance, for if the center of pressure does not coincide with the center of the base the ground will yield the most on the side which is pressed the most; and as the ground yields, the base assumes an inclined position and carries the lower part of the structure with it, thus producing unsightly cracks, if nothing more. Center of Pressure and Center of I'.ase. Fig. 7. Narrow Offsets. Fig. 8. Wide Offsets. A case in which a violation of this rule cannot w^ll be avoided is the case of a foundation under the side wall of a building, where the footing is not allowed to project beyond the lot line. In this con- struction the center of pressure is indicated by the downward arrow, and the center of base by the upward arrow, Fig. 7. It is evident that the intensity of the pressure is greatest on the portion of the footing to the right of the center of base, and the footing will con- sequently settle obliquely, as shown in the figure, with a tendency to throw the wall outward. This tendency may be counteracted by tying the wall securely to the floor joists, but it is much better to make some arrangement by which the footing will settle evenly. Where it is absolutely necessary to build the footing without pro- jecting beyond the lot line, the former should be carefully built of concrete, dimension stone or hard bricks well grouted in cement mortar, and the footing should be no wider than is absolutely demanded by the nature of the soil. The offsets on the inside of the wall should be so proportioned that a line drawn through their DESlGXrXG THE FOUNDATIONS. 21 edges will make an angle of not less than 60 degrees with the horizontal. The footing shown in Fig. 7 is to be preferred to that shown in Fig. 8. Sometimes the center of pressure or of weight is inside of the center of resistance of the soil, . a result due to the concentration of heavy beam or girder loads toward the inside edge of the wall. Where this condition exists the tendency is to incline the wall inward, and this, instead of diminishing, tends to increase the stability of the structure, as the floor systems, and the opposite and adjacent walls, preclude the pos- sibility of any failure* in this direc- tion. 33. CRACKS IN BUILDINGS.— Fig. 9 illustrates another case in which the center of pressure comes outside of the center of base, and in consequence of which the wall inclines outward, pro- ducing cracks over the opening. This is a very common occurrence in brick and stone walls in which there are wide openings. In such cases the footing under the opening should either be omitted entirely or made narrower there than it is under the pier, and the two footings should not be bonded together. Where several openings occur one above the other, as in Fig. 10, and the footings are con- Fig. 9. Center of Pressure Outside )f Center of Base. Fig. 10. Incorrect Method. Continuous Wall. Fig. IT. Correct Method. Separate Piers and Dwarf Walls. 22 BUILDING CONSTRUCTION. (Cii. I) tinned under the opening, the unequal settlement of the footings will very likely produce cracks over all the openings, the side walls inclining slightly outward. Where the width of the opening is 8 feet or more, and the bottom of the opening is not a great distance above the footings, the latter under the wall on each side should be treated as if they were under piers, as shown in Fig. ii, and the space between the footings should be filled in with a dwarf wall only. If the bottom of the opening is twice its width above the foundation, the wall under it will distribute the weight equally over the footings and the settlement will be uniform. As a rule the foundation of one wall should never be bonded into that of another which is either much heavier or much lighter than itself. The footings should also be proportioned so that the center of pressure will fall a short distance inside of the center of the base, in order to make sure that it will not fall outside of it. Any inward inclination of the wall, as previously explained, is rendered impos- sible by the interior walls and by the floors, while any outward inclination can be conteracted only by anchors and by the bond of the masonry. A slight deviation of the center of pressure outside of the center of base has a rnarked effect, and is not easily counter- acted by anchors. In Chicago an omission of from i to 2 per cent of the weight, by leaving openings, usually causes sufficient inequality in the settlement to produce unsightly cracks.* Where slight dififerences in weight occur, cracks may generally be prevented by building in hoop-iron ties, rods or beams over the openings. It is also a wise precaution, where one wall joins another, either in the middle or at the corner of a building, to tie the walls together by long iron anchors built into the walls about every six feet in height. 34. FOOTINGS AT DIFFERENT LEVELS.— In all cases where the foundations of a new building go down to a greater depth than those of an existing adjacent building care must be taken to prevent the earth from sliding from under the footings of the existing building, and threatening its destruction. Usually the only safe plan is to resort to ''underpinning" as described in Chapter III. * Ira O. Baker in "Masonry Construction." FOUNDATIOXS. SUPERIXTENDEXCE. 23 It should be observed also that many basement plans of impor- tant buildings provide for dififerent floor levels in the several sec- tions of the building. For instance, the boiler-room and engine- room may be carried down in order to provide greater head-room. In such cases the position of each column and wall footing should be examined to see if it is deep enough to prevent the pressure upon it from forcing out the earth into the more deeply excavated doi/er F^oom Fig. \2. Footing's at Different Levels area. This condition is illustrated in Fig. 12, which shows the normal basement level at a, a. and the boiler-room floor level at h, b. At c is shown one of the important column piers of the structure, with its footing near the deeper excavation and at a higher level. The great pressure on the column footing tends to force the earth out from under it, and to overturn the retaining wall at d, and the footing should be carried down to the level indicated by the dotted lines. When the soil is very stable a footing of this nature may generally be considered safe, if the line e, c makes an angle of not more than 30 degrees with the horizontal. It is also necessary in designing foundations to see that column and wall footings are deep enough to permit the installa- tion of engine foundations, tanks or sumps without endangering the footings. 4. SUPERINTENDENCE. 35. MATTERS REQUIRING SPECIAL ATTENTION.— In inspecting the excavation the superintendent should first examine the lines to see that the building has been correctly staked 24 BUILDING CONSTRUCTION. (Ch. I) out, and that the excavation is being carried at least 6 inches out- side of the wall lines, so as to give room for pointing or cementing. If the walls are built against the bank it will be impossible to point up the joints on the outside, and the back of the walls not being exposed, the masons are apt to slight that part of the work to the future detriment of the building; and if the excavation is not made large enough at first, it catises much trouble and vexation, as the work cannot be done as cheaply afterward, and the stone-masons will very likely complain about being delayed. The superintendent should also see that the finished grade is plainly marked on some fixed object and should caution the work- men not to dig the trenches below the levels marked on the draw- ings. If the trenches are excavated below the proper levels, they must not be refilled with earth, as the footings should start on the solid bottom of the trenches ; and as this will require more masonry than the contractor estimated on, he will be c^uite. sure to call for an extra payment for the same from the owner, unless the exca- vating is included in his contract, in which case he will have to settle with the excavator. For this reason it is a good plan to have the excavating included in the contract for the foundation. It is good practice, also, and especially in the construction of heavy buildings, to have the bottom of footing trenches and pier excavations thoroughly rammed so as to further compress the soil before the footings are put in. The superintendent should also examine the character of the soil at the bottom of the excavation, and if he finds that it is not such as was expected, the foundations should be changed or car- ried deeper, as previously described. In case water is encountered in making the excavations, some provision should be made for draining the cellar, either by laying tile drains around the footings, or by laying the bottom courses dry and connecting them with stone drains, as described in Articles 6 and lo. The specifications should provide that the contractor is to keep the trenches free from water while the walls are being built. In places where the water cannot be drained off it must be removed by a pump, either worked by hand or by steam. When the excavation is made close to an adjoining building the superintendent should see that the ' contractor has made proper provision for shoring or otherwise pro- tecting the adjacent walls. Chapter II. Foundations on Compressible Soils 36. COMPRESSIBLE SOILS IN GENERAL.— The soils of this class that are met with in preparing the foundations of buildings are often located along the shores of large bodies of water and hence generally permeated with moisture to within 'a few feet of the surface. For such soils pile foundations are usually the cheapest and most reliable. On a soil like that underlying Chicago, and having a sup- porting power of from i}^ to 2)72 tons per square foot, spread foun- dations may be used with satisfactory and economic results, whereas it would require piles over 40 feet long to reach hard-pan. Occasionally it is necessary to build on ground that has been filled in to a considerable depth, and in which water is not present ; and in that case timber piles cannot be used. In such cases wells of solid masonry with iron casings, or pneumatic caissons, may be sunk to bed-rock or hard-pan, as hereinafter described, or concrete piles may be used. I. PILE FOUNDATIONS 37. OBJECTIONS TO PILE FOUNDATIONS.— When it is necessary to build on a compressible soil that is constantly saturated with water and of considerable depth, the cheapest and generally the best foundation bed is obtained by driving wooden piles. Pile foun- dations cannot always be used without danger to adjoining buildings because the method of driving generally employed is liable to jar and weaken the neighboring walls and foundations. It has also been claimed that driving piles in a soil such as that under Chicago, wdthin a few feet of buildings having spread-foundations, has a tendency to cause the latter to settle so as to necessitate under- pinning. • On driving the first piles for the Schiller building, Chicago, it was found that an adjoining building had settled 6 inches, and it had to be raised on screws. The driving of piles also causes a readjustment of the particles of 25 26 BUILDING CONSTRUCTION. (Ch. II) clay and sand into a jelly, thus greatly diminishing the resisting properties. These objections, however, are not of so much moment when the adjoining buildings are supported by piles. 38. CLASSES OF PILES.— A great many kinds of piles are used in engineering works, but for the foundations of buildings wooden piles are at present used oftener than any other kind. The different conditions under which piles are used for supporting buildings may be classed as follows : 1. When the compressible soil is not more than 40 feet deep and overlies a bed of rock, gravel, sand or clay, long piles should be driven to the rock, or to a distance of from one to two feet into the clay or sand, in which cases they may be considered to act as columns. 2. If the soft soil is more than 40 feet deep, piles varying from 15 to 40 feet in length should be driven, according to the character of the soil, the sustaining power of the piles depending upon the friction between the pile and the surrounding soil. 3. Short piles, from 10 to 15 feet in length, are sometimes driven, particularly in Southern cities, in order to consolidate the soil and to give it greater resisting power. As piles are seldom used in this way, this met*hod of forming a foundation bed will be dismissed with the following quotation : 39. FOUNDATIONS ON SOFT ALLUVIAL SOILS.— 'Tn some sections of the country, especially in the Southern cities, the soil is of a soft alluvial material, and in its natural state is not capable of bearing heavy loads. In such cases trenches are dug as in firm material, and a single or double row of short piles are driven close together, and under towers or other unusually heavy portions of the structure the area thus covered is filled with these piles. The effect of this is to compress and compact the soil between the piles, and to a certain extent around and on the outside, thereby increas- ing its bearing power; whatever resistance the piles may offer to further settlement mav be added, though not relied upon. These piles are then cut off close to the bottom of the trench, and generally a plank flooring is laid resting on the soil and piles, or a layer cf sand or concrete is spread over the bottom of the trench to the depth of 6 inches or i foot, and the structure, whether of brick or stone, commenced on this. There is little or no danger of such structures settling, and if they do the chances are that they will settle uniformly if the number of piles are properly proportioned to the weight di- PILE FOUNDATIONS. 27 rectly above them ; but if the piles are not so proportioned the same number being driven under a low wall as under a high wall, unequal settlement is liable to take place, causing ugly or dangerous cracks in the structure."* A. WOODEN PILES 40. MATERIAL. — Wooden piles are made from the trunks of trees and should be as straight as possible, and not less than 5 inches in diameter at the small end for light buildings or 8 inches for heavy buildings. The woods generally used for piles in the Northern States are spruce, hemlock, white pine, Norway pine, Georgia pine, and occasionally oak, hickory, elm, black-gum and basswood. In the Southern States, Georgia pine or pitch pine, cypress and oak are used. The tougher and stronger woods are the best for timber piles, especially where they are to be driven to hard-pan, and heavily loaded. There is little difference in the durability of these various woods under water. Oak is considered the most durable wood for piles, and also the toughest, but it is too expensive for general use in the Northern States, besides being difficult to obtain in long, straight pieces. Next to oak come Georgia pine, Oregon pine, cypress and spruce, in the order named. Of the 1,700 piles supporting the Illinois Central Railway Station in Chicago, 32 per cent were black-gum, 22 per cent pine, 7 per cent basswood, 21 per cent oak, 15 per cent hickory, with a few maple and elm. A smaller proportion of the hickory piles were broken or crushed than of any other wood. 41. POINTING WOODEN PILES.— Piles should be prepared for driving by cutting off all limbs close to the trunk, sawing the ends square, and removing the bark. The removal of the bark is probably of not very great importance, as many piles are driven with the bark on. The small end of each pile should be sharpened to a point 2 inches square, the bevel being from 18 to 24 inches long. The large end should be cut square to receive the blows from the hammer. Experience has shown that in soft and silty soils the piles can be driven in better line without pointing. A pointed pile," on striking a root or similar obstruction, will inevitably glance off, and no avail- able power can prevent it from doing so, while a blunt pile will cut or break the obstruction without being diverted from its position. * "A Practical Treatise on Foundations." W. M. Fatten. 28 BUILDING CONSTRUCTION. (Ch. II) When driving into compact soil, such as sand, gravel or stiff clay, the point of the pile is often shod with iron or steel, either in the form of a strap bolted to the end of the pile, as at a, Fig. 13, or by a conical cast-steel shoe about 5 inches in diameter, having a 134- in diameter than the head of the pile, and from 2^ to 3 inches wide by ^ of an inch thick. It is better to chamfer the head so that the ring will just fit on than to drive the ring into the wood by the hammer, as the latter method is liable to split long pieces from the pile. 43. PROTECTION OF WOODEN PILES.— Piles that are to be driven in, or exposed to, salt water should be thoroughly im- pregnated with creosote, dead oil of coal-tar, or some mineral poison to protect them from the ''teredo" or ship worm, which will completely honeycomb an ordinary pile in three or four years. 44. DRIVING WOODEN PILES WITH THE DROP-HAM- MER. — The usual method of driving piles is by a succession of blows given with a block of cast-iron called the hammer, which works up and down between the uprights of a frame or machine called a pile-driver. The machine is placed over the pile, so that the hammer descends fairly on its head, the piles always being driven with the small end down. The hammer is generally raised by steam power furnished by a hoisting engine, and is dropped either auto- matically or by hand. The usual weight of the hammers used for inch dowel inches long fit- tins: into a hole in the end of the pile and a ring fitting around the pile, as shown at b, to prevent it from splitting. The latter method should be used in very hard soils. If a strap is used, as at a, it should be 2^ inches wide, an inch thick and 4 feet long. 42. RINGING WOODEN PILES. — When the penetra- Fig. 13. Straps and Shoes for Piles. tion at each blow is less than 6 inches, the top of the pile should be protected from "brooming" by putting on an iron ring about i inch less PILE FOUNDATIONS. 29 driving piles for building foundations is from 1,500 to 2,500 pounds, and the fall varies from 5 to 20 feet, the last blows being given with a short fall. Heavier hammers than these are sometimes, but not often, used, occasionally weighing 4,000 pounds and over. In driving piles care should be taken to keep them plumb, and when the penetration becomes small the fall should be reduced to about 5 feet, the blows being given in rapid succession. Whenever a pile refuses to sink under several blows, before reach- ing the average depth, it should be cut off and another pile driven beside it. When several piles have been driven to a depth of 20 feet or more and refuse to sink more than ^ an inch under five blows of a 1,200- pound hammer falling 15 feet, it is useless to try them further, as the additional blows only result in brooming and crushing the heads and points of the piles, and in splitting and crushing the intermediate portions to an unknown extent. ''Sometimes piles drive easily and regularly to a certain depth, and ♦ then refuse to penetrate farther. This may be caused by a thin stratum of some hard material, such as cemented gravel and sand or a compact marl. It may require many hard and heavy blows to drive through this, thereby injuring the piles, and perhaps getting into a q.uicksand or other soft material, when the pile will drive easily again. If the depth of the overlying soil penetrated is sufficient to give lat- eral stability, or if this can be secured by artificial means, such as throwing in broken stone or gravel, it would seem unwise to endeavor to penetrate the hard stratum, and the driving should be stopped after a practical refusal to go with two or three blows. The thick- ness of this stratum and the nature of the underlying material should be determined either by boring or by driving a test pile, to destruction if necessary. In the latter case the driving of the remaining piles should cease as soon as the hard stratum is reached." * If the hard stratum, however, is only 2 or 3 feet thick, with hard-pan not more than 40 or 50 feet from the surface, the piles should be driven to hard-pan for heavy buildings; but if the soft material continues for an indefinite depth below the hard stratum, the piles should be stopped when the stratum is reached. In such cases, however, the actual bearing power of the piles should be tested by loading one or more of them, as described in Section 50. * "A Practical Treatise on Foundations." W. M. Patton. 30 BUILDING CONSTRUCTION. (Ch. II) 45. DRIVING WOODEN PILES WITH THE STEAM- HAMMER.— There are two other methods of driving piles com- monly employed, namely : with the steam-hammer, and by the water- jet process. By the former method a specially constructed steam- hammer, in contact with or attached to the head of the pile, strikes a rapid succession of blows which cause the pile to penetrate rapidly, because the earth at the penetration point of the pile is not allowed time to compact and readjust itself after each blow. The blows struck are comparatively light, and the head of the pile does not broom and break up as much as under the hammer of the ordinary pile-driver. Because of this the pile used under a steam-power ham- mer may be of poorer quality and softer wood than would ordinarily be used under a drop-hammer, and the pile in driving may be kept more easily in line. 46. DRIVING WOODEN PILES WITH THE WATER-JET. — Piles may be driven by means of a water-jet, and sometimes both the drop-hammer and water- jet are used in conjunction. In using the water-jet for sinking piles a piece of pipe or rubber hose, from 1^/2 to 2^ inches in diameter, is secured to the pile with staples in such a manner that it may be withdrawn after the pile is driven. The piece of pipe or hose passes down to the end of the pile, and is con- nected at the upper end with a pump and provided at the lower end with a nozzle, usually from i inch to J/s of an inch in diameter. Under operation the force of the water scours out and liquefies the soil beneath and around the pile, so that it sinks by its own weight or the weight of the operating platform brought to bear upon it. This method of driving operates the best in soils consisting mostly of sand, soft clay or mud, though it may be used in nearly all soils except hard-pan or rock. Generally the best results are obtained by this process when a considerable volume of water is delivered at a moderate velocity, as the rapid penetration of the pile depends more upon the fluidity created in the surrounding soil than upon the scouring action of the jet. The water- jet process is much used for sinking piles for piers, breakwaters and jetties in sandy beaches, but is not used to such a great extent for building construction as the amount of water used is in most instances objectionable. 47. BEARING POWER OF WOODEN PILES.— When driven in sand or gravel, or to hard-pan, piles will carry to the full extent of the crushing strength of the timber, providing their depth is sufficient to secure lateral stiffness. PILE FOUNDATIONS. ''There are examples of piles driven in stiff clay to the depth of 20 feet that carry from 70 to 80 tons per pile. There are many instances, in which piles carry from 20 to 40 tons under the above conditions. After a pile has been driven to 20 feet in sand or gravel, any further hammering is a waste of time and money, and injurious to the pile itself." * Piles driven from 30 to 40 feet in even the softest alluvial soils should carry by frictional resistance alone from 10 to i2j/4 tons. TABLE II. Safe Bearing Value of Wooden Piles in Different Soils. SOIL. PILE LENGTHS. AVERAGE DIAMETER PENETRA- TION. LOAD IN TO.NS. Ft. Ins. Ins. 40 10 6 Mud 30 8 2 6 Soft earth with boulders or logs 30 8 li 7 Moderately firm earth or clay with 30 8 I 9 30 10 I 9 30 8 1 12 30 8 1 12 20 8 1 4 14 20 8 0 20 20 8 0 20 15 8 0 20 The bearing value of a pile depends upon the distance which it penetrates the soil under the final blows of the hammer; so that, when this distance is known, together with the weight and the height of fall of the hammer, the probable bearing value of the pile may be determined. The values given in Table II, which follows, show the probable penetration of piles of different lengths when driven into the different kinds of soil usually encountered. The safe bearing values in tons, given in the last column of the table, are calculated from the Engineering Nezvs formula, which is explained in the follow- ing article. The values given in the table are for minimum lengths of spruce piles and average penetrations for the last five blows of a 1,200-pound hammer falling 15 feet. When heavier loads than these must be carried, or when the penetration is much greater, the actual bearing power of the piles should be determined by testing, unless it is already known from actual experience. 'A Practical Treatise on Foundations." W. M. Patton. 32 BUILDING CONSTRUCTION. (Ch. II) 48. FORMULA FOR THE SAFE WORKING LOAD ON PILES. — There have been several formulas proposed for determin- ing the safe working loads on piles. Of these, one of the latest, know^n as the Engineering Nezvs formula, is generally considered to be the most reliable. It is claimed for this formula that it sets "a definite limit, high enough for all ordinary economic requirements, up to which there is no record of pile failures, excepting one or two dubious cases where a hidden stratum of bad material lay beneath the pile, and above which there are instances of both excess and failure, with an increasing proportion of failures as the limit is exceeded." The formula is : 2 iif h Safe load in lbs. (I) ^ + 1 in which iv = the weight of hammer in pounds ; h, its fall in feet ; and s, the average set under the last blows in inches. For convenience the following table is given which shows the allowable or safe bearing values for piles, calculated from the above formula, for different penetrations under the blows of a 2,000-pound hammer falling from 3 to 30 feet. TABLE III. Safe Load, in Tons, for Wooden Piles. (Hammer weighing one ton.) Penetra- Drop of the Hammer, in Feet. tion of Pile in Inches. 3 4 5 6 , 8 10 12 14 16 18 20 25 30 0.25 4.8 6.4 8.1 9.7 12.9 16.1 19.4 22.5 25.8 29.1 32.3 0.50 4.0 5.3 6.7 8.0 10.7 13.3 16.1 18.7 21.3 24.0 26.6 33 .3 0.75 3.4 4.6 5.7 6.9 9.2 11.5 13.8 16.1 18.4 20.7 23.0 28.8 34 '5 1.00 3.0 4.0 5.0 6.0 8.0 10.0 12.0 14.0 16.0 18 0 20.0 25.0 30.0 1.25 3.6 4.5 5.4 7.1 8.9 10.7 12.5 14.3 16.1 17.9 22.3 26.7 1.50 3.2 4.0 4.8 6.4 8.0 9.6 11.2 12.8 14.4 16.0 20.0 24.0 1.75 3.G 4.4 5.8 7.3 8.8 10.2 11.7 13.1 14.6 18.2 21.9 2.00 3.3 4.0 5.3 6.7 8.0 9.3 10.7 12.0 13.3 16.7 20.0 2.50 3.4 4.6 5.7 6.9 8.0 9.1 10.3 11.4 14.3 17.1 3.00 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 12.5 15.0 3.50 3.6 4.4 5.3 6.2 7.1 8.0 8.9 11.1 13.3 4.00 3.2 4.0 4.8 5.6 6.4 7.2 8.0 10.0 12.0 5.00 3.3 4.0 4.7 5.3 6.0 6.7 8.3 10.0 6.00 3,4 4.0 4.6 5.1 5.7 7.1 8.6 As the values in the above table vary directly with the weight of the hammer, if the penetration is caused by a 1,000-pound hammer, the bearing value will be one-half of that given, and in this way the table may be used to obtain the bearing value of piles driven by a hammer of any weight. PILE FOUNDATIONS. 33 49. MUNICIPAL REGULATIONS REGARDING WOODEN PILES. — The New York Building Law, 1906, provides that ''Piers intended to sustain a wall, pier or post shall be spaced not more than 36 nor less than 20 inches on centers, and they shall be driven to a solid bearing, if practicable to do so, and the number of such piers shall be suffi- cient to support the superstructure proposed. "No pile shall be used of less dimensions that 5 inches at the small end and 10 inches at the butt for short piles, or piles 20 feet or less in length, and 20 inches at the butt for long piles, or piles more than 20 feet in length. "No pile shall be weighted with a load exceeding 40,000 pounds. 'The tops of all piles shall be cut off below the lowest water line. When required, concrete shall be rammed down in the interspaces between the heads of the piles to a depth and thickness of not less than 12 inches and for i foot in width outside of the piles." The Boston Building Law, 1907, requires that ''All buildings shall, if the commissioner determines that piling is necessary, be constructed on foundation piles which, if of wood, shall be not more than 3 feet apart on centers in the direction of the wall, and the number, diameter and bearing of such piles shall be sufficient to support the superstructure proposed. The commissioner shall determine the grade at which the piles shall be cut. "All wood piles shall be capped with block granite levellers, each leveller having a firm bearing on the pile or piles which it covers, or with first-class Portland cement concrete not less than 16 inches thick, above the pile caps, containing i part of cement to not more than 6 parts of properly graded aggregate of stone and sand, the concrete to be filled in around the pile heads upon the intervening earth." In the Chicago Building Law, 1906, it is required that "The piles shall be made long enough to sustain the required load according to approved formulas for pile driving, and timber piles shall not be loaded more than 25 tons to each pile." The Philadelphia Bureau of Building Inspection stipulates that "Piles intended for a wall, pier or post to rest upon, shall not be less than 5 inches in diameter at the small end, and shall be spaced not more than 30 inches on centers, or nearer if required by the Bureau of Building Inspection, and they shall be^ driven to a solid bearing. No pile shall be weighted with a load exceeding 40,000 pounds. The tops of all piles shall be cut off below the lowest v^ater line where required ; concrete shall be rammed down in the interstices between the heads of the piles to the depth and thickness of at least 12 inches, and for i foot in width outside of the pile. When ranging and capping timbers are laid on piles for foundations they shall be of hard wood t not less than 6 inches thick, and properly joined, and their tops laid below the lowest water line." General William Sooy Smith, in an address delivered March 31. 1892, before the students of engineering of the University of Illinois^ 34 BUILDING CONSTRUCTION. (Ch. II) stated that "A pile at the bottom of a pit 30 feet deep and well into hard-pan, or to the rock where this is within reach, can be safely relied upon to sustain from 30 to 40 gross tons." 50. EXPERIMENTS ON THE BEARING POWER OF WOODEN PILES. — The following description of several tests made to determine the actual sustaining power of piles in various localities gives a good idea of the manner of making such tests, as well as of the loads required to sink the piles : CHICAGO PUBLIC LIBRARY.— To determine the actual resistance of the piles on which it was proposed to erect the Public Library building in Chicago, the following test was made: In order to make the experiment under the same conditions as would exist under the structure three rows of piles were driven into the trench, the piles in the middle row being then cut off below the level at which those in the outside row were cut off, so as to bring the bearing only on four piles, two in each outside row. This gave the benefit arising from the consolidation of the material by the other piles. The piles were of Norway pine, 54 feet long, and were driven about 52^/2 feet, 27 feet in soft, plastic clay, 23 feet in tough, compact clay and 2 feet in hard- pan. They had an average diameter of 13 inches and an area at the small end of 80 square inches. On top of the four outside piles, which were spaced 5 feet apart on centers, 15-inch steel I-beams were placed, and upon these a platform, 7 by 7 feet, com- posed of 12 by 12-inch yellow pine timbers. On this platform pig-iron was piled up at irregular intervals. When 4 feet high the load was 45,200 pounds, and was then continued, until at the end of about four days it was 21 feet high, giving a load of 224,500 pounds. Levels were taken, but no settlement had occurred. By the end of about eleven days the pile of iron had reached the height of 38 feet, giving a load of 404,800 pounds upon the four piles, or about 50.7 tons per pile. Levels were then taken at intervals during a period of about two weeks, and, no settlement having been observed, a load of 30 tons was considered perfectly safe. PERTH AMBOY, N. J., 1873.— Pretty fair mud, 30 feet deep. Four piles, 12, 14, 16 and 18 inches diameter at top, 6 to 8 inches at foot, were driven in a square to depths of from 33 to 35 feet. A platform was built upon the heads of the piles and loaded with 179,200 pounds, or 44,800 pounds per pile. After a few days the loads were removed. The 18-inch pile had not moved, the 12-inch pile had settled 3 inches, and the 14 and 15-inch piles had settled to a less extent.* BUFFALO, N. Y. — In the construction of a foundation for an elevator at Buffalo, N. Y., a pile 15 inches in diameter at the large end, driven 18 feet, bore 25 tons for twenty-seven hours without any ascertainable effect. The weight was then gradually increased until the total load on the pile was 37^ tons. Up to this weight there had been no depression of the pile, but with 37J/^ tons there was a gradual depression which aggregated Y% of an inch, beyond which there was no depression until the weight was increased to 50 * "A Practical Treatise on Foundations." W. M. Fatten. PILE FOUNDATIONS. 35 tons. With 50 tons there was a further depression of % of an inch, making the total depression lYz inches. Then the load was increased to 75 tons, under which the total depression reached 3^ inches. The experiment was not carried beyond this point. The soil, in order from the top, was as follows : 2 feet of blue clay, 3 feet of gravel, 5 feet of stiff red clay, 2 feet of quicksand, 3 feet of red clay, 2 feet of gravel and sand and 3 feet of very stiff blue clay. AH the time during this experiment there were three pile-drivers at work on the foundation, thus keeping up a tremor in the ground. The water from Lake Erie had free access to the pile through the gravel. * "Subsequent use shows that 74,000 pounds is a safe load." — W. M. Patton. PHILADELPHIA.— At Philadelphia in 1873 a pile was driven 15 feet into soft river mud, and five hours after 7.3 tons caused a sinking of a very small fraction of an inch ; under 9 tons it sank >>4 of an inch and under 15 tons it sank 5 feet. "The South Street, Philadelphia, bridge approach fell by the sinking of the foundation piles under a load of 24 tons each. They were driven to an absolute stoppage by a i-ton hammer falling 32 feet. Their length was from 24 to 41 feet. The piles were driven through mud, tough clay, and then into hard gravel. "t The failure in this case may have been caused by vibrations which allowed the water to work its way down the sides of the piles and thus decrease the friction ; or, what is more probable, the last blow may have struck on a broomed head, which would have greatly reduced the penetration and caused the bearing power to be overestimated. When the penetration is very slight or unobservable, and the head much broomed, the broomed portion should be cut ofif and the blows repeated if the full load indicated by the formula is to be put on the piles. 51. ACTUAL LOADS ON WOODEN PILES.— The following examples of the actual loads which are carried by each pile under the buildings named will serve as a guide to architects erecting buildings in these localities : BOSTON. — Under Trinity Church, 2 tons each. CHICAGO. — Public Library building, 30 tons each. Schiller building, estimated load 55 tons per pile; building settled from to 2^ inches. Passenger Station, Northern Pacific Railroad, Harrison Street: piles 50 feet long carry 25 tons each without perceptible settlement. The enormous grain elevators in Chicago rest upon pile foundations. Mr. Adler stated that the unequal and constantly shifting loads are a severer test upon the foundations than a static load of a twenty-story building. NEW ORLEANS. — Piles driven from 25 to 40 feet in a soft, alluvial * "Masonry Construction." Ira O. Baker, t Trans. Am. Soc. of C. E., Vol. VII., p. 264. 3^^ BUILDING CONSTRUCTION. (Ch. II) soil carry safely from 15 to 25 tons, with a factor of safety of 6 to 8. — W. M. Patton. 52. SPACING OF WOODEN PILES.— Wooden piles should be spaced not less than 2 feet on centers, nor more than 3 feet on centers, unless iron or wooden grillage is used. When long piles are driven closer together than 2 feet on centers there is danger that they may force each other up from their solid bed on the bearing straturn. Driving the piles close together also breaks up the ground and diminishes the bearing power. When three rows of piles are used the most satisfactory spacing is 2 feet 6 inches on centers across the trench, and 3 feet on centers longitudinally, provided this number of piles will carry the weight of the building. If they will not, then the piles must be spaced closer together longitudinall}-, or another row of piles driven ; but in no case should two piles be driven closer together than 2 feet on centers, unless driven by means of a water-jet. In all cases, the number of piles under the different portions of a l^uilding should be carefully proportioned to the weight which they have to carry, so that every pile will support very nearly the same load. This precaution is of especial importance when some of the piles must be loaded to their full capacity. 53. CUTTING OFF AND CAPPING WOODEN PILES.— The tops of the piles should invariably be cut off below the low- water mark, as otherwise they will soon commence to decay. The piles are generally cut off with a large cross-cut saw worked by two men. Their tops should be left true and level and on a line with each other. A variation of >4 of an inch in the. tops of the piles may be allowed, but it should not exceed this limit. Three methods of capping wooden piles are commonly employed, using the following materials: i. Granite blocks. 2. Concrete. 3. Timber or steel-beam grillage. 54. GRANITE CAPPING FOR WOODEN PILES.— In this method the piles are capped with blocks of granite, which rest di- rectly on the tops of the piles. If the stone does not fit the surface of a pile, or a pile is a little low, it is wedged up with oak or stone wedges. In capping with stone a section of the foundation should be laid out on the drawings showing the arrangement of the cap- ping stones. A single stone may rest on one, two or three piles, but should not rest on four piles, as it is practically impossible to make the stone PILE FOUXDATIOXS. 37 bear evenly on four piles. Fig. 14 shows the best arrangement of the capping for three rows of piles. Under dwellings and light buildings the piles are often spaced as in Fig. 15, in which case each stone should rest on three piles. After the piles are capped large footing stones, extending in one piece across the wall, should be laid in cement mortar, as shown in Fig .16. '< ■ . 1 — -5— _J r r^— ^ \ ) I 1 / ''1 } Fig. 14. Stone Capping Three Rows of Piles. for Fig. 15. Stone Capping for Piles Under Light Builditigs. Fig. 16. Stone Capping and Wall Footing on Piles. 55. CONCRETE CAPPING FOR WOODEN PILES.— In New York a very common method of capping the piles is to excavate to a depth of i foot below the tops of the piles and i foot outside of them, and to fill solid the space thus excavated' with rich Port- land cement concrete, deposited in layers and well rammed. After the concrete is brought up level with the tops of the piles, additional layers of concrete are laid over the whole foundation until it reaches a depth of 18 inches above the piles. On this foundation bed, the brick or stone footings are laid as on solid earth. Many engineers consider this the best method of capping. There is certainly no question of its durability, and it is believed that the concrete will preserve the heads of the piles from rotting, provided the water is at 38 BUILDING CONSTRUCTION. (Ch. II) all times up to the bottom of the concrete. A concrete beam i8 inches thick would also serve to distribute the pressure over the piles tetter than the stone capping, although not to such an extent as heavy grillage. If the soil is at all firm under the concrete, it will also assist the piles in carrying the load when concrete cap- ping is used. Under very heavy buildings the space between the ''-piles to the depth of i foot should be filled with concrete, \v hatever kind of capping is employed. Concrete cappings in which steel rods or bars are imbedded about 3 inches above the tops of the piles are excellent forms of capping construction, the metal bars giving great transverse strength to the concrete. 56. GRILLAGE CAPPING FOR WOODEN PILES.— In Chi- cago most of the buildings on pile foundations have heavy timber grillage bolted to the tops of the piles, and on these timbers are laid the stone or concrete footings. For building foundations the grill- age usually consists of 12 by 12-inch timbers of the strongest woods available, laid longitudinally on top of the piles, and fastened to them by means of drift-holts, which are plain bars of iron, either round or square, driven into holes about 20 per cent smaller in cross- section than that of a bolt. One-inch round or square bars are gen- erally used, each hole being bored by a ^-inch auger for a round bolt, or by a %-inch auger for a square bolt. The bolts should enter the piles at least i foot. If heavy stone or concrete footings are used, and if the space between the piles and the timbers is filled with concrete brought up level with the top of the timbers, no more timbering is required ; but if the footings are made of small stones, and if no concrete is used, a solid floor of cross timbers, at least 6 inches thick for heavy buildings, should be laid on top of the longitudinal cappings and drift-bolted to them. . Where timber grillage is used, it should, of course, be kept entirely below the lowest recorded water line, as otherwise it will rot and allow the building to settle. It has been proved conclu- sively, however, that any kind of sound timber will last practically forever if completely immersed in water. The advantages of timber grillage are that the timbers are easily laid and efifectually hold the tops of the piles in place. It also tends to distribute the pressure evenly over the piles, as the transverse PILE FOUNDATIOXS. '39 strength of the timber assists in carrying the load over any single pile, which for some reason may not have the same bearing capacity as the others. Steel-Beam Grillage for Wooden Piles. — Steel beams, imbedded in concrete, are sometimes used to distribute the weight over piles, but some other form of construction can generally be employed at less, expense and with equally good results. 57. COST OF WOODEN PILES.— The cost of wooden piles varies with the locality, size of piles and difficulties encountered in driving. Wooden piles of good quality and average size, say 10 inches average diameter and from 15 to 25 feet in length, can be driven for from 20 to 25 cents per foot of length, this price includ- ing the cost of the timber and driving. The variation from these prices may be as much as 25 per cent either way, and where only a few piles are to be driven, the cost will greatly exceed the maximum here given. B. CONCRETE PILES 58. CONCRETE PILES COMPARED WITH WOODEN PILES AND CONCRETE PIERS.— Piles made of concrete have been used in this country since 1902, and they offer several advan- tages over wooden piles. They remain practically uninjured after the operation of driving, they do not decay, and it is not necessary to keep them constantly under water to preserve them, as it is in the case of wooden piles. Consequently, concrete piles can be often used to advantage in place of wooden piles, and frequently may be put in at a lower cost than that of spread-footing construction. They do not, as a rule, require as thick a capping as that required for wooden piles, because they are more readily incorporated with the concrete or masonry of the capping, and not so many of them are required, because they sustain a greater load than wooden piles bear, under similar conditions. In Fig. 17 a comparison is drawn between the method of using concrete piles and the method of penetrating a soft soil by means of wooden sheet piling and a concrete pier. It is frequently found in cases of this kind that the concrete piles are cheaper than the con- crete pier. Another illustration showing some of the advantages gained by the use of concrete piles is given in Fig. 18, (a) and (b). In figure (b) the wooden piles are shown driven deep enough to be below the BUILDING CONSTRUCTION. (Ch. ^80 Tons. ^eo Tons. Fig. 17. Concrete Piles and Concrete Piers Compared. PILE FOUNDATIONS. •41 low-water level. This necessitates a deep foundation wall ; and as the wooden piles will not sustain as great a load as the concrete piles, a greater number of them is required, with a correspondingly ex- Fig. 18. Concrete Piles and Wooden Piles Compared. tended footing. Figure (a) shows the foundation of the same building constructed on concrete piles with much less excavating, and with probably greater permanency. Several types of concrete piles are used, varying in details of con- struction and in manner of driving, and among them may be men- tioned the "Raymond," the ''Simplex" and the "Corrugated." 42 BUILDING CONSTRUCTION. (Ch. II) 59. THE RAYMOND CONCRETE PILE.— This concrete pile is made by driving a collapsible steel core, around which is a sec- tional tank-steel shell, the sections being conical, and fitting closely one within the other. When this core with its outside shell has been driven to the required depth, the core is partially col- lapsed, released from the sectional steel shell, and withdrawn. In this manner a sheet-steel- lined form or mold is made in the ground for casting the pile, the lining acting in the same manner as a caisson in holding back the earth, and in preventing the partial filling of the Fig. 19. The Raymond Concrete Pile. form by loose particles, or its destruction by any pressure on the surrounding soft stratum. After the mold is thus formed it is filled with a good mixture of concrete, which is carefully tamped during the process of filling. Sometimes these piles are reinforced to increase their strength, or to provide anchorage for stacks or tower foundations subjected to PILE FOUNDATIONS. 43 wind-pressure. Such reinforcement is easily put in place during" the process of filling. The form of the ''Raymond" concrete pile and a diagrammatical representation of the method of driving the cone and shell is shown in Fig. 19, (a) and (b). • 60. THE SIMPLEX CONCRETE PILE.— This concrete pile. Fig. 20. The Simplex Concrete Pile. like the ''Raymond," is made in the ground and not driven. The form of the pile differs from the "Raymond," the sides being par- allel instead of tapering, and when finished there is no surrounding steel cylinder. The construction of the "Simplex" pile is shown in Fig. 20, (a) and (b). At (a) is shown an extra heavy steel pipe about 16 inches in diameter, driven into the ground. At the end of the pipe there is a penetration-shoe of cast-iron used to prevent the earth from BUILDING CONSTRUCTION. (Ch. II) filling the pipe while it is being driven. When the steel cylinder reaches the required depth and rests upon hard-pan or penetrates hard gravel, it is filled with concrete as the steel driving form is partly withdrawn, and the penetration-shoe is released and left in the ground. The weight of the concrete causes it to flow out at the lower end of the pipe or driving form and completely fill the hole in the soil. A second method of forming the pile consists in providing an "alligator-jaw" or hinged point at the end of the cylinder, instead of a cast-iron penetration-shoe. This is shown at (b). This jaw is opened to the full extent of the form when the cylinder is with- drawn, allowing the concrete to flow into the hole. As the hole formed by the pipe is not lined with sheet-metal there is a. possibility of some soft earth pressing in upon the concrete before it has set, thus preventing a uniformity of cross-sections. This has not proved a serious trouble, however. Concrete piles are sometimes used in conjunction with timber piles, and when so employed are called "composite piles." These piles are used for driving to a great depth in comparatively soft soil. The concrete pile caps the timber pile and forms an extension to it from below the low-water line, and it is said to afford a cheaper construction under some conditions than longer piles made entirely of concrete. 6i. THE CORRUGATED CONCRETE PILE.— There are several reinforced concrete piles in use, which are first molded to the required shape, and when the concrete has set sufficiently, are driven by a hammer, a water-jet, or a combination of both methods, in much the same manner as wooden piles are driven, about the only difference being the special "driving head" provided to avoid the shock of the hammer. A section through what is known as the "Corrugated Concrete Pile" is shown in Fig. 21. This particular form of concrete pile is made with a vertically corrugated surface, and with a hole left ver- tically through the axis of the pile. It is driven by using the water- jet and hammer together. A hose, or pipe, with water under pressure, is passed down through the hole in Concrete p'iie?'"'''^ the middle of the pile while it is in the machine. PILE FOUNDATIONS. 45 it The force of the water at the lower end loosens the earth and drives it up along the corrugations, and the pile settles under the blows of the hammer on its cushioned head. In one instance it was found that after the concrete had had eight days to set, the piles were not damaged in any way at their upper ends by the action of the hammer. These corrugated concrete piles are reinforced with ''Clinton" electrically welded wire fabric, consisting generally of ^ inch wires^ 3 inches on centers longitudinally, and ]4, inch wires 12 inch on centers around the pile. 62. THE COMPRESSOL SYSTEM.— There is another kind of construction which may be classified with the other types of con- crete pile construction, and that is the "Compressol System of Foun- dation Construction." In this system the ground is mechanically perforated by dropping a pointed weight very similar in form to an enlarged plumb-bob. This pointed weight, dropped rapidly, perfo- rates the ground and compresses it vertically and laterally, and the hole so formed is filled with concrete. The latter is thoroughly tamped, and forms a pillar strong enough to carry from 60 to 90 tons, according to the nature and depth of the soil. The piers of concrete so formed are capped with concrete in a manner similar to that of capping concrete piles. The method used in constructing these piers or cores in the earth is shown in Fig. 22. The weight drops and perforates the soil, the hole usually going down to hard-pan. The falling of the weight compresses the soil on each side of the hole and prevents the per- colation of water into it. Sometimes the hole can be lined with puddle or clay by inserting some of this material under the perforat- ing hammer and allowing it to be carried down to line the hole. When the ground has been perforated as described, a coarse con- crete is tamped into the bottom of the hole, and a hammer shaped as shown in the figure is dropped, striking successive blows as the hole is filled. In this manner the concrete is forced and tamped compactly into the hole, and spread out at the bottom as indicated in the figure at (b) ; so that if the earth were excavated from around the concrete pier, the latter would appear as shown in Fig. 23. The following are some of the advantages claimed for this system of foundation construction : Pillars of concrete can be formed to BUILDING COXSTRUCTION. (Ch. II) PILE FOUXDATIONS. 47 a depth of 50 feet in marshy soils, and even in quicksand ; the sys- tem is economical, as it requires no outlay for excavation, sheet- piling, pumping, etc. ; the work goes on with considerable rapidity, because a pillar strong enough to support 90 tons with safety can be constructed, under favorable conditions, in 4 hours ; the dangers to the workmen in caisson construction are eliminated ; and from the amount of penetration of the conical weight or hammer, the bearing strength of the strata adjacent to the pillars may be approxi- mately determined. An elevation and a cross-section, illustrating Fig. 24. The Compressol System of Concrete Foundation, the use of the Compressol system of foundation construction for a building erected upon soft or unstable soil, are shown in Kig. 24, in which (a) is a side view of an exterior wall, with reinforced con- crete lintels bearing upon the top of the Compressol foundations, supporting their load of brick-work and resting upon the concrete wall piers; and (b) is the same kind of construction supporting an interior column. 63. COST OF CONCRETE PILES.— The cost of concrete 48 BUILDING CONSTRUCTION. (Ch. II) piles is much greater than that of timber piles, but as their bearing strength is on an average twice as great, and as greater dependence . may be placed upon them, the number of piles, and consequently the total cost, may be' reduced. Prices have been quoted for "Simplex" concrete piles at Salem, - Mass. The number of piles was 203 and the length fixed at an average of 17 feet with a total minimum length of 2,000 linear feet. The base price quoted was $1.46 per foot, additional lengths being charged for at 90 cents per foot. For lengths shorter than 17 feet, a deduction was allowed at 90 cents per foot. These piles were 16 inches in diameter and were made of i part of Portland cement, 2]^ parts of sand, and 5 parts of broken and crushed stone. The prices represent a fair average cost of concrete pile construction for a moderate number of piles cast in the ground under average conditions. 2. SPREAD FOUNDATIONS 64. SPREAD FOUNDATIONS IN GENERAL.— Compress- ible soils are often met with which will bear from i to 2 tons per square foot with very little settlement, and, as a rule, this settlement is uniform under the same unit-pressure. When unit-pressure is referred to in connection with foundation soils, the pressure per square foot of bearing surface is usually understood. In such cases it is often cheaper to spread the foundations so as to reduce the unit-pressure to the capacity of the soil than to attempt to drive piles or to use sheet-piles with extensive excavations through soft and wet soils. ''Spread" footings may be built of reinforced con- crete, consisting of concrete with iron or steel tension-bars imbedded therein, of steel beams and concrete, or of timber and concrete. A. REINFORCED CONCRETE FOOTINGS 65. GENERAL DESIGN.— One of the most efficient and eco- nomical^, micthods of constructing spread footings is that of rein- forced concrete, consisting of beds or layers of concrete to which additional resistance to transverse stresses is added by embedding in the concrete, steel or iron rods or bars placed near the bottom sur- faces of the footings, where the tensile stresses are developed. This metal reinforcement consists of plain, round, square, or twisted bars, or of expanded-metal, woven wire, or any of the special patented bars, known as ''deformed bars," now on the market. SPREAD FOUNDATIONS. 49 When a footing is constructed, as shown in Fig. 25, at (a), so that a Hne drawn at an angle of 60° with the horizontal will inter- sect both tli^ lower outside edges of the footing and of the wall, or of the solid base bearing upon the footing, there is little danger of the failure of the footing from bending stresses, whereas there would be danger of such failure if the footing had a considerable / / \- (a) (h) Fig. 25. Footings with Small and Large Projections. projection, as shown in the figure at (b). In the latter illustration the projection x may be great enough to result in causing the up- ward pressure on it from the soil to bend it upward and to cause its failure by stresses developed by flexure, as shown by the fracture at g. This principle of construction is further treated in Chapter III. 66. WALL AND COLUMN FOOTINGS.— Reinforced con- Fig. 26. Concrete Footing with Twisted Reinforcement. Crete spread footings may be used for walls or for piers or columns. Fig. 26 shows the most economical section for a concrete and twisted iron footing. In building the footings with steel beams, the strength of the concrete is practically wasted, while in this method of construction it is all utilized. A large percentage of the tensile strength of the twisted bars can be utilized, and, being held 50 BUILDING CONSTRUCTION. (Ch. II) Typical Reinforced Concrete Foot- ing for Heavy Wall. continuously along their entire length by the concrete as a screw bolt is held by the nut, they neither draw nor stretch, except as the concrete extends with them. ^ Fig. 27 shows a typical spread footing for a heavy wall, resting upon soil of a soft and unreliable nature. Here the bottom of the footing is reinforced with the steel rods, a, to prevent a failure of the projection of this footing by trans- verse or bending stresses. Above the spread footing a deep course of concrete is provided with reinforc- ing rods or bars, h, ex- tending longitudinally or lengthwise of the wall, so so that if the soil is softer in some places than in others, the heavy upper course of concrete will have sufficient strength to span the weak places and thus prevent unequal settlements and un- sightly cracks in the walls. A typical design for a reinforced concrete column footing is shown in Fig. 28. In this illustration the structural steel column a is provided with a heavy structural steel base, designed to transmit the load sustained by the column to the top bed of the concrete foot- ing. The spread footing of reinforced concrete, c, has another block of concrete, b, above it, to lessen the projection of the bottom course. The latter is reinforced with a double layer of rods or bars crossing each other at right angles. As the load ordinarily transmitted by the columns to the reinforced concrete footing is considerable, it is considered good practice to provide, under the bearing-plate of the column, a "mattress" consisting of two layers of reinforcing rods, as shown at d. These rods reinforce the concrete directly beneath the bottom or bearing-plate of the column, and the base is usually proportioned with an area which stresses the concrete up to 500 pounds per square inch. This is the allowable stress for reinforced concrete, adopted by several cities in the compilation of their build- ing laws. In very large and heavily loaded spread column footings it is sometimes necessary to provide vertical reinforcement throughout the body of the footing by introducing stirrups extending up into the SPREAD FOUNDATIONS. 51 body of concrete, so as to provide sufficient bond between the several actual or theoretical layers of the concrete to prevent them from : ■ : ' T • '• M — Fig. 28. Typical Reinforced Concrete Footing for Column. f^rf^orced Comcrets Column Basement Tloor Le^ef slipping one upon the other when they are subjected to transverse stress. An excellent construction for such a column footing is shown in Fig. 29. In this foot- ing the reinforcement consists r-.l. of two layers of what is known as the "Kahn" trussed bar, shown in detail in Fig. 30. In this construction the prongs are partially sheared from the fin of the bar and bent obliquely upward, forming stir- rups, which, besides furnishing additional bond for the rein- forcing rods, provide against any possible failure from the hori- zontal shear between the layers of the concrete. Other deformed bars may be used for spread footing reinforcement, and when stirrups or Kahn Trus^Bar F^ejnjorcemerrh 29. Reinforced Concrete Footing for Heavily Loaded Column. 52 BUILDING CONSTRUCTION. (Ch. II) members to resist horizontal shear are required, they may be made U-form, from ^-inch round bar, or from by i inch flat bar, wired or otherwise secured to the main reinforcing bars or rods. 67. PLACING THE CONCRETE.— In building concrete foot- ings, a layer of concrete from 3 to 6 inches thick, made in the pro- portion of I, 2 and 4, should first be laid, and the iron bars laid on and tamped down into it. Another layer of 4 inches, mixed in the same proportions, should then be laid, after which the concrete may be mixed in the proportions of i, 2^ and 5. Each layer should be laid before the preceding layer has had time to harden ; other- wise they may not adhere thoroughly. 68. STRENGTH OF REINFORCED CONCRETE FOOT- INGS. — In order that reinforced concrete footings may be safely constructed it is necessary to determine the area and spacing of the reinforcing bars or rods at the bottom of the footings, and also to determine whether the concrete in the upper part of the footing has sufficient compressive resistance. It is usual in designing such footings, after the bearing area has been determined by dividing the load upon them by the safe unit bearing value of the soil, to assume or decide upon their thickness, •so that the amount of steel reinforcement required may be found. In Fig. 31, (a), there is represented diagrammatically a reinforced concrete spread column footing. The distance x in the figure rep- resents the projection of the footing beyond the edge of the column base, where the footing tends to fail by flexural stresses, because the greatest bending moment is at that point. The upward pressure of the soil upon this projection is represented by the forces w, w, w, etc., and their sum by W acting at their center of gravity. The dis- tance of this resultant force W from the edge of the column base is the lever arm with which this force tends to bend the footing Fig. 30. Kahn Trussed Bar. Detail. SPREAD FOUNDATIONS. 53 around the edge of the column, and is equal to >^ x. The depth of the footing, or its thickness, is represented by t^, but the theoretical depth for the purposes of calculation is the distance from the middle of the metal reinforcement to the top of the concrete. f Concrete . T^fjng n n n n I n^n n ■605000 R>und5 Load on Column L I 3kel fTeenforcemenf < , Fig. 31. Reinforced Concrete Column Footing. In order to determine the amount of steel reinforcement in a spread footing of reinforced concrete, the following formula may be used, which is calculated to give economical, and at the same time, safe results : IV X ^ 27000 X t (2) In this formula W is equal to the upward pressure of the soil, in pounds, on a strip of the projection of the footing one-foot in width; X is the projection of the footing beyond the edge of the column base, in inches; t is the distance from the top of the concrete footing to the middle of the steel reinforcement, also in inches ; while the term 27,000 is a constant deduced from the usual formula for rein- forced beams of rectangular section, and is based upon a safe unit tensile stress for steel of about 16,000 pounds per square inch. The value a, to be determined by applying this formula, is the area in square inches required for the steel reinforcement for each lineal foot in width of the footing. Besides finding whether there is sufficient steel reinforcement in the footing by determining its area by the above formula, it is neces- sary to ascertain if the concrete in the upper part of the footing is over-stressed by the compressive forces caused by the bending. The maximum safe compressive stress allowed on reinforced concrete in 54 BUILDING CONSTRUCTION. (Ch. II) conservative engineering practice is 500 pounds per square inch ordinarily, and this stress should not be exceeded. To determine the maximum compressive stress on the concrete of the upper part of a reinforced concrete spread footing, the following formula may be used: W X -r In this formula W, x and t represent the same values as given for the foregoing formulas, the constant being 4.59. The value c is the compressive stress in pounds per square inch near the upper surface of the concrete footing at the edge of the column base. These two formulas (2) and (3) are sufficiently correct for all practical purposes and are based on the latest information derived from tests on reinforced concrete beams of rectangular section. They may be expressed by the following rules : Rule I. — To find the area of steel, in square inches, required for each lineal foot in width of a reinforced concrete footing: divide the product of the upward pressure in pounds on the projection of the footing one foot in width and the length of the projection of the footing in inches, by 27,000 multiplied by the distance in inches from the middle of the steel reinforcement to the top surface of the concrete footing. Rule 2. — To find the amount of maximum compressive stress per square inch upon the concrete adjacent to the top surface of the concrete footing: divide the product of the upward pressure in pounds on the projection of the footing one foot in width and the length of the projection in inches, by 4.59, multiplied by the square of the distance from middle of the steel reinforcement to the top surface of the concrete footing. Example. — A reinforced column footing of the design shown in Fig. 31, (&), is subjected to a load from the supported column of 605,000 pounds, and it is desired to determine what amount of steel will be required to reinforce this footing, and also whether the safe compressive stress in the concrete at the point a is exceeded. Solution. — The area of the footing is 11 by 11 feet, or 121 square feet ; so that if the total load on the footing is 605,000 pounds, the load per square foot upon the soil beneath the footing is 605,000 pounds -f- 121, or 5,000 pounds. SPREAD FOUNDATIONS. 55 The projection of the footing measured by the distance x is 4 feet ; so that the total upward pressure on a portion of the footing one foot in width is 5,000 pounds x 4, or 20,000 pounds. Since or the distance from the steel reinforcement to the top surface of the concrete footing, is 24 inches, all of the terms of the second member of formula (2) are known, and the sectional area of steel required for each foot in width of the footing is found as follows : 20,000 X 48 a — — — = 1.40 sq. ms. 27,000 X 24 i The section area of a J^-inch square twisted bar is about .76 square inches, so that if these bars are spaced 6 inches from center to center, each foot in width of the footing will contain two bars hav- ing a total area of 1.52 square inches. Having found the amount of the steel reinforcement for the foot- ing, it is necessary to determine whether tfte concrete of the footing is over-stressed by compression. Formula (3) is used to find the value of c, which must not exceed 500 pounds per square inch. Substituting in the formula, 20,000 X 48 ^ , . c — — = 36^ pounds per sq. m. 4.59 X 24 X 24 ^ ^ ^ From the result of the above calculation it is observed that the value c of 363 pounds per square inch is well within the limit of 500 pounds per square inch, so that the footing as designed may be con- sidered as amply safe ; or the thickness may be decreased, though the saving in concrete will in all probability be less than the additional cost of the steel required for the reinforcement due to the decreased distance * These formulas, (2) and (3), are based upon tests made on reinforced concrete beams, and upon formulas derived from these tests, by Professor A. N. Talbot, of the University of Illinois. In this derivation, consider that the moment-arm for the couple formed by the tension in the steel and the compression in the concrete is 0.87. This is an average value for reinforcement under i per cent. Equating the bending moment to the resisting moment gives: M = 1/2 W X = 0.87 a f t Comparing this with formula (2), / is seen to be about 15,5000 pounds per square inch. In dealing vi^ith the compression, consider that the neutral axis is 0.42 t below the top surface, and use the straitrht line relation. Equating the bending moment and the resisting moment and solving for c gives: W X 4-5 t Professor Talbot states that "it must be borne in mind that footings will be very short beams, and that for short, beams diagonal tension failures, or so-called shearing failures are likely to result. The vertical shearing stress will then be the controlling feature of 56 BUILDING CONSTRUCTION. (Ch. II) 69. TABLE OF STRENGTH AND PROPORTIONS OF FOOTINGS.— The author has prepared Table IV, giving the strength and proportions of reinforced concrete footings, which he beheves have a large margin of safety. While the values given in this table vary slightly from the results obtained from the preceding formulas, the variations are on the side of safety, the values giving an excess of steel v^ithout overstressing the concrete to a great extent. In the table two sizes of bars are given, with the correspond- ing safe loads for the footings, the other measurements applying to both cases. The measurements in the third column refer to the width of the brick or stone footing resting on the concrete. The greater the width of this footing in proportion to the width of the concrete, the less will be the stress in the tension rods. TABLE IV. Proportions and Strength of Concrete Footings with TwifTED Iron Tension Bars. WIDTH OF 1 FOOTING IN FEET. THICKNESS OF CON- CRETE. WIDTH OF STONE FOOTING. DISTANCE BETWEEN CENTRES OF BARS. SIZE OF SQUARE BAR. SAFE LOAD PER LINEAL FOOT. SIZE OF SQUARE BAR. SAFE LOAD PER LINEAL FOOT. 1 Ft. In. Ft. In. Inches. Inches. Tons. Inches. Tons. 20 3 6 6 0 8 2 78 I| 66 18 3 3 5 6 8 2 76 If 56 16 2 10 5 0 7 If 73 li 50 14 2 8 4 8 7 70 If 49 12 2 6 4 4 6 If 65 li 48 10 2 3 4 0 6 li 65 I 42 8 2 0 4 0 6 I 60 3 T 40 6 I 8 3 6 6 f 55 1 29 70. SQUARE TWISTED BARS FOR REINFORCEMENT. • — For some years the use of square twisted bars for reinforcing con- tiie strength of the footing unless some form of web reinforcement is used to overcome this defect. The_ ordinary designer will be likely to overlook this feature. The working stress for the vertical shear for short beatns without efficient web reinforcement should not run more than from 30 to 50 pounds per square inch. Beams with poor concrete fail with values as low as 60 pounds per square inch, and the best ordinary concrete does not run more than 125 pounds per square inch. "Bond stresses may control the footing, and not more than from 50 to 75 pounds to the square inch of surface should be allowed for plain bars. In the case of bars bent up, the bond stress may become the controlling element. It. should be noted also that where 'bending-up' is practiced, the bend should begin at the offset. It may also be suggested that stepped or sloped effects will be of advantage in overcoming the difficulties involved in high shearing stresses." In regard to the form of formulas (2) and (3), and to their "mathematical dimen- sions," the latter will be found to be correct, when the formulas from which they are derived are borne in mind; and the correct resulting dimensions will be given to the 27,000 and to the 4.59 appearaing in the denominators of the second members of the equations. SPREAD FOUNDATIONS. 57 Crete was protected by the patents of Ernest L. Ransome, of San Francisco, Cal., and subsequently by the rights owned by the Ran- some & Smith Co., of New York, Chicago and San Francisco. All patents relating to the use of square twisted bars for reinforced concrete construction have now expired, and many firms are manu- facturing this type of reinforcing bar by both cold and hot twisting. They are now very generally used in reinforced concrete con- struction. f^) (b (c) Fig. 32. different Arrangements of Rods in Reinforced Concrete Footings. 71. PLACING THE RODS IN SPREAD FOOTINGS.-^ There are several ways of arranging rods in reinforced concrete column footings, some of which are shown in Fig. 32 at (a), (b), and (c). The method shown in the figure at (a) is the one com- monly used and consists of two layers of reinforcing rods placed at right angles to each other and spaced an equal distance apart from center to center. Where great economy is required every alternate rod may be shortened somewhat, because the bending moment in the footing becomes smaller toward the outer edge, where it is zero, and consequently less reinforcement is required there. The best practice in the design of reinforced concrete column foot- ings consists in placing several layers of rods, some at right angles with each other and some diagonally, as shown in the figure at (b). Sometimes an effort is made to save concrete by making the foot- ing octagonal in plan, as shown at (c), as the corners of a square footing are considered relatively weak, and hence properly omitted. Where, however, they are reinforced as in the figure at (b), they are ?bout as effective as any portion of the area of the footing, as far as the distribution of the pressure on the soil is concerned. 58, BUILDING CONSTRUCTION. (Ch. II) B. STEEL BEAM FOOTINGS 72. GENERAL DESIGN. — When it is necessary to spread the foundations over 12 or 15 feet in each direction, with a very small height to the footings, as is the case in Chicago, steel beams are used to furnish the necessary transverse strength. For tall buildings, even when constructed on solid ground, it is sometimes found desir- able to use steel-beam grillage footings to distribute the load. Such footings are usually cheaper than massive masonry footings, though they cannot, as a rule, compete in cost with footings of reinforced concrete. The manner of using the beams is shown in Figure 35. In preparing the footings, the ground is first carefully levelled and the bottom of the pier located. If the ground is not compact enough to permit of excavating for the concrete bed without the sides of the pit or trench falling in, heavy planks or timbers should be set up and fastened together at the corners and, if necessary, tied between with rods, to- hold the concrete in place and to prevent its spreading before it has thoroughly set. A layer of Portland cement concrete, made in (he proportion of i, 2 and 4, and from 6 to 12 inches thick, accord- ing to the weight on the footings, should then be filled in between the timbers and well rammed and levelled off. If the concrete is to be 12 inches thick it should be deposited in two layers. Upon this concrete the beams should be carefully bedded in i to 2 Portland cement mortar, so as to bring them nearly level and in line with each other. The distance apart of the beams, from center to center, may vary from 9 to 20 inches, according to the height of the beams, thickness of concrete and estimated pressure per square foot. They must not be so far apart that they will crush through the concrete (see Article 76.), and on the other hand there must be a space of at least 2 inches between edges of the flanges to permit the introduction of the con- crete filling. As soon as the beams are in place the spaces between them should be filled with i, 2 and 4 concrete, the stone being broken into pieces that will pass through a i^-inch ring, and the concrete being well rammed into place, so that no cavities will be left in the center. The concrete must also be carried at least 3 inches beyond the beams on the sides and ends, and kept in place by planks or timbers. 73. CONCRETE BETWEEN LAYERS; BASE-PLATE, ETC. — If two or more layers of beams are used, the top of each layer SPREAD FOUNDATIONS. 59 should be carefully levelled, after the concrete has been put in place, with I to 2 Portland cement mortar, not more than ^ an inch thick over the highest beams, and in this the next layer of beams should be bedded, and so on. The stone or metal base-plate or footing should also be bedded in Portland cement mortar, not more than ^ of an inch thick above the upper tier of beams. After the base-plate or stone footing is in place, at least 3 inches of concrete should be laid above the beams and at the sides and ends ; and when this is set the whole outside of the footings should be plas- tered with I to 2 Portland cement mortar. 74. QUESTION OF PAINTING STEEL BEAMS IN CON- CRETE. — It was formerly the practice to thoroughly clean the beams with wire brushes before they were laid, and, while absolutely dry, to either paint them with iron paint or else to heat and coat them with two coats of asphalt. The protection of steel when imbedded in concrete work seems to be so complete that many engineers are not insisting upon the painting of the grillage beams, as the cem.ent in contact with the steel prevents any serious corrosion. In fact, probably greater strength and continuity of action is secured between the concrete and the steel of the footing when the latter is left unpainted, though such a combined action is not considered in calculating the strength of grillage construction, 75. NUMBER OF LAYERS OF BEAMS.— When iron and concrete foundations were first used in Chicago, railroad rails, on account of their lower cost, were employed to give the required transverse strength. The footings were built up with five or six layers of rails, placed at right angles to each other, each layer diminishing in number until the upper surface was stepped off sufficiently, but not enough to exceed unduly the proper size of the column base As each layer of rails was laid, concrete was filled between and around them, and when completed the footing resembled a simple concrete pier. The footings under the Rand and McNally building, Chicago, erected in l8gi, were of this character, five layers of rails being used in most of the foot- ings. In some of the footings the upper layer consisted of 12-inch beams. Building up footings in successive tiers, however, is not as eco- nomical in the use of the steel as the method of building them up with two layers of deep beams. 6o BUILDING CONSTRUCTION. (Ch. II) 7 Ll It should also be borne in mind that the beams spread the load over the ground only by their transverse strength, and they should, therefofe, be used in the same way that they would be were the foundation re- versed, the wall or column becoming the support and the ground the load, as shown in Fig. 33. 76. NUMBER OF BEAMS IN THE UPPER COURSE.— When sev- eral beams are used in the upper I course or layer, there is a tendency to Fig. 33. Illustration of Flexure in COUCCUtrate the Wcigllt OU the OUtcr Steel Beam Grillage. . beams of the upper layer owmg to the deflection of the beams below. The author therefore advocates the use of as few beams as practicable in the upper course and where the conditions will permit, either a single built-up girder or two heavy beams, and in the lower course the deepest beams consistent with economy. If the beams in the lower course permit of a spacing much greater than their height, a layer of rails should be imbedded in the top of the concrete to prevent the beams from breaking through. The rails, however, would in no w^ay affect the stress or bending action in the beams. For a further discussion of the use of steel beams in foundations, the reader is referred to an article by the author in Architecture and Building of August 24, 1895. Examples of steel-beam and concrete footings are also given, with illus- trations, in the Engineering Record of December 12, 1891, and June i, 1895, and the later issues of the various journals on architecture and engineering contain numerous articles and illustrations of this method of construction. 77. EXAMPLE OF STEEL BEAM GRILLAGE ON SOLID ROCK. — The use of steel beam grillage foundations for tall build- ings has become so universal that numerous accounts and illustra- tions of this type of construction may be found in the current num- bers of the architectural and engineering publications. While the use of grillage foundations is usually confined to com- pressible soils, it is sonietimes employed to distribute the load of the columns over a solid rock foundation. A notable example of the use of grillages of steel beams being used for this purpose is found in the building for the Metropolitan Life Insurance Co., New York. In this structure the tower, which is the highest of all building SPREAD FOUXDATIONS. 6i towers, IS supported upon steel-beam grillage construction as illustrated in Fig. 34. From this figure it will be observed that the main columns are supported upon four tiers of steel beams while the secondary columns rest upon two tiers of beams. The grillage and column base is in each case entirely embedded in concrete. l^'g- 34- Grillage Foundations on Rock. Metrojiolitan Life Insurance Company's Build- ings, New York. 78. METHOD OF DETERMINING THE SIZE OF THE STEEL BEAMS. — As the purpose of the beams is to distribute the load coming from the foundation wall or base-plate evenly over the ground, so that the pressure on each square foot of the soil will be the same, it is obvious that the beams must have sufiflcient trans- verse strength to keep them from -bending, so that they will settle as much at the outer ends as in the middle. The effect on the beams shown in Fig. 35, when resting on a compressible soil and heavily loaded from above, is to cause the ends of the beams to bend up- ward, thus stressing the beams the most in the middle ; the stress in the beams being the same as if they were supported on a pier in the middle and loaded with a distributed load, as shown in Fig. 33. 79. DETAILS OF PROCEDURE AND EXAMPLE. GRIL- LAGE UNDER WALL. — The best method of determining the size of the beams is by computing the maximum bending moments for the steel beams and obtaining the required "section modulus" or "section factor/' by dividing by the safe unit fiber stress of the steel. When the section modulus has been obtained, the corresponding 62 BUILDING CONSTRUCTION. (Ch. II) value may be found in the tables of the steel manufacturers' hand- books, from similar tables given herewith or in Kidder's ''Architects' and Builders' Pocket-Book," and the beam of the required size and weight selected. Cro3:) - Section Side - View Fig. 35. Example of Steel Beam Grillage. The maximum bending moment for a grillage beam may be obtained by the following formula : M=yi,W {L—B) (4) in which M is the maximum bending movement in inch-pounds ; W the load in pounds on one beam of the grillage ; L the length of the grillage beam in inches, and B the width of the upper tier or base in inches. See Fig. 35. When the maximum bending moment M is divided by the safe unit fiber stress of the steel, usually taken at 16,000 pounds per square inch, the section modulus or Q is obtained. Or, this value may be found directly by the formula, Q=^^ (5) 1 28,000 The section modulus and several other properties of rolled steel I-beams of standard section are given in Table V. SPREAD FOUNDATIONS. 63 TABLE V. Section Modulus for Rolled Steel I-Beams of Different Sizes and Weights. Depth of Beam Weight Per Foot Area Thickness of Web Width of Flange Section Modulus Axis Square to Web Depth of Beam Weight Per Foot Area Thickness of Web Width of Flange Section Modulus Asi^ Square to Web Ins. Lbs. Sq. In. Ins. Ins. Q Ins. Lbs. Sq. In. Ins. Ins. Q 20 20 20 20 20 20. 90 85 80 75 70 65 26.4 25.0 NoTE—The above table Is compiled from the Passaic Rolling Mill Go's, hand-hook and agrees closely with the Standard Sections adopted by the American Steel Manufacturers Association. 5 4 4 ' 4 10 ^« 2.9 2.9 2.2 1.8 .21 .39 .20 .18 3.00 2^50 2.19 4.87 3.42: 2 95 2.30 Owing to the tendency of the beams in bending, to concentrate the load on the outer edges of the masonry footing, and thus crush them, which action would have the same effect on the beam as lengthening the arm or projection (see article in Architecture' and Building pre- viously referred to), the author recommends that when the course 64 BUILDING CONSTRUCTION. (Ch. II) above the beams is of stone, brick or concrete, at least one-third the width of the masonry footing he added to the actual projection. The apphcation of the formulas (4) and (5) will be more clearly shown by the following example, the conditions of which are illus- trated in Fig. 35. Owing to the size and to the nature of the material of the bottom course of the wall, the tendency to crush at the outer edge of this course is neglected : Example 1. — A building is to be erected on a soil of which the safe bearing power is but 2 tons per square foot, and the pressure on each lineal foot of wall is 20 tons. It is decided to build the footings as shown in Fig. 35. What should be the dimensions and weight oi the beams? Solution. — As the total pressure under each lineal foot of wall is 20 tons, and the safe bearing power of the soil 2 tons per square foot, the footings must be 20 -f- 2, or 10 feet wide. As 4^feet granite blocks are used for the bottom course of the wall, the value of L — B in formula (5) will be 72 inches; so that if the beams are spaced 12 inches on centers, the load W will be 20 tons, or 40,000 pounds, and 40,000 X 72 • Q — 5 ~, or 22.5. 128,000 From Table (V), giving the Section Modulus for Rolled Steel I-Beams of Different Sizes and Weights, it is found that a lo-inch 25-pound beam is the most economical section to use for the grillage footijig. The beam selected from the table has an. excess of strength as its section modulus is 24.5. This, however, is as close a selection as can usually be made. When there are no values in the table cor- responding closely with the section modulus required, a dififerent spacing should be tried in order to obtain more economical results. 80. TABLE FOR FINDING SAFE LOAD ON GRILLAGE BEAMS. — The use of the above formulas and calculations may be avoided by referring to the following table giving the total safe load in tons of 2,000 pounds on a single beam, for the various sizes of steel I-beams, and for different values of L — B. The values in the table represent the safe load in tons which one beam of the grillage will support throughout its length. By the use of this table, which is compiled from the Passaic Rolling Mill Co.'s hand-book, no calculations are necessary except SPREAD FOUNDATIONS. TABLE VL 65 Safe Load in Tons of 2,000 Pounds on One Beam of Grillage Footings. Beam Projection both sides of Grillage Beam, or L—B, in feet Depth Weight in Pounds Per Foot 80 75 70 65 75 65 60 55 65 60 55 45 42 60 55 45 40 35 40 80 27 25 30 27 25 21 25 20 18 20 15 171^ 12 94. 63.6 53.2 50.0 41.4 39.2 38.0 28.8 27.2 26.2 27.6 26.2 21.8 20.0 19.8 16.0 15.1 14.5 11.3 10.2 7.8 119 111 108 87.5 83.6 78.8 75.6 66.0 52.8 50.8 55.6 53.0 44.2 41.6 34.6 32.8 31.8 24.0 22.6 21.8 23.0 21.8 18.2 16.7 1G.5 13.3 12.6 12.1 9.4 8.5 6.5 102 95 91.2 87.5 92.4 75.0 71.6 68.4 67.6 64.8 56.6 45.4 43.6 47.8 45.6 38.0 35.8 29.6 28.0 27.2 20.6 19.4 18.7 19.7 18.7 15.6 14.3 14.2 11.4 10.8 10.4 8.1 7.3 5.5 83.2 79.8 76.6 80.8 65.6 62.8 59.8 59.2 56.6 49.6 41.8 39 8 33.2 31.3 25.9 24.5 23.8 18.0 17.0 16.3 17.3 16.4 13.7 12.5 12.4 10.0 9.5 9.1 7.1 6 4 4.8 79.8 73.8 71.0 68.2 71.8 58.4 55.8 53.2 52.6 50.4 44.0 35.2 34.0 37.1 35.4 29.5 27.8 23.0 21.8 21.2 16.0 15.1 14.5 15.4 14.6 12.2 11.1 11.0 8.9 8.4 8.1 6.3 5.7 4.3 71.7 66.5 63.9 61.3 64.7 52.5 50.2 47.8 47.3 45.4 39.6 31.7 30.6 33.4 31.8 26.6 25.0 20.7 19.6 19.0 14.4 13.6 13.1 13.8 13.1 10.9* 10.0 8.0 7-6 7.3 5.7 5.1 3.9 &5.2 60.5 58.1 55.7 58.8 47.7 45.6 43.5 43.0 41.2 36.0 28.8 27.8 30.4 28.8 24.2 22.7 18 8 17.9 17.3 13.1 12.4 11.9 12.6 11.9 9.9 9.1 9.0 7.3 6.9 6.6 5.1 12 59.8 55.4 53.2 51.0 53.9 43.8 41.8 39.8 39.4 37.8 33.0 26.4 25.4 26.5 22.1 20.8 17.3 16.4 15.9 12.0 11.3 10.9 11.5 10.9 9.1 8.3 8.3 6.7 6.3 6.1 4.7 13 55.2 51.2 49.1 47.1 49.8 40.4 38.6 3i).8 36.4 34.9 30.5 24.4 23.5 25.7 24.5 20.4 19.2 15.9 15.1 14.7 11.1 10.5 10.1 10.2 10.1 8.4 7.7 7.6 6.1 5.8 14 51.2 47.5 45.6 43.8 37.5 35.8 34.2 33.8 32.4 28.3 22.7 21.8 23.9 22.8 19.0 17.9 14.8 14.0 15 47.8 44.3 42.6 40.9 43.1 35.0 33.4 31.9 31.5 30.3 26.4 21.1 20.4 22.3 21.2 17.7 16.7 13.8 13.1 to determine the difference between the width of the superimposed footing or tier of beams, and the grillage beams. The results obtained by this table should agree with the results obtained from formulas (4) and (5). Thus, in the above example, to use the table, it is simply neces- sary to look down the column headed 6 until the value nearest to 20 tons is found. This will indicate the lightest weight beam that can be used and this beam is found to be a lo-inch 25-pound beam having a strength value of 21.8 tons. A 9-inch 27-pound beam 66 BUILDING CONSTRUCTION. (Ch. II) would also do, but as it weighs more than the previously selected beam there would be no economy in using the shallower beam When there is no value corresponding with the required one it is necessary to use formulas. 8i. EXAMPLE. GRILLAGE UNDER PIER.— In the case illustrated in Fig. 36 the size of both the upper and lower beams are determined in the same way as in Example L, the value of Example II. — The basement columns of a ten-story build- ing, resting on footings as shown in Fig. 36, are re- quired to sustain a permanent load of 400,000 pounds. What should be the size of the beams in the footings, the supporting power of the soil being but 2 tons? Solution. — By dividing the load by the bearing power of the soil the area of the foot- ing is found to be equal to 100 square feet, so that the dimensions of the footing are 10 by 10 feet. The beams are arranged as shown in Fig. 36, and a cast-iron bearing plate 3 feet 6 inches square is used under the column. The dis- tance between the centers of outer beams in upper tier is made 3 feet, thus making the value of L—B for both tiers equal to 7 feet. Considering the upper tier of beams it is evident that, as there are five beams, each one must sustain a load of 400,000 pounds divided by 5 or 3o,ooo pounds, equal to 40 tons. Looking down column headed 7 (Table VI.) the nearest value in the table to 40 tons is 43.6 which indicates a 15-inch 42-pound beam. For the lower tier of beams the load an one beam will be found to equal 400,000-^ ii (the number of beams in the tier) or 36,363 L — B being taken for both tiers. STONE FOOTING Fig. 36. Steel Beam Grillage Footing under Column. SPREAD FOUNDATIONS. 67 pounds. This amount reduced to tons equals 18.18 tons and from the table under column 7 it is found that a lo-inch 25-pound beam has a strength value of 18.7 tons, which though slightly excessive is the economical section. 82. COMBINED FOOTINGS. BASE-PLATES, ETC.— The deepest beam for the weight should always be used, and unless the beams in the upper tier have considerable excess of strength, the two outer beams should be heavy beams. Two Columns Grillage Footing. When the footings carry iron or steel columns in the basement, as is generally the case, a cast-iron or steel base-plate should be used, as shown in Figs. 37 and 38. This plate should be bedded in Portland cement directly above the beams, as described in Article 75. Two and even four columns are often supported on one footing, as shown in Figs. 37 and 38. In such cases the computation becomes more elaborate, and an engineer should be called in con- sultation, unless the architect is himself sufficiently familiar with such calculations. Fig. 39 shows an arrangement in which a built-up base-plate or girder is used in place of the upper tier of beams. The author believes this arrangement much better than that shown in Figs. 36 and 37, though the cost of these heavy structural steel bases is very great and the details of their erection very exacting. In placing the beams, it is essential that they be arranged sym- metrically under the base-plate, as otherwise they will sink more at one side than at the other. When several unequally loaded col- 68 BUILDING CONSTRUCTION. (Ch. II) iinins rest on the same footing-, the ecjual distribution of the weight on the soil becomes a difficnU problem. C. TIMBER FOOTINGS 83. TLAIBER FOOTINGS IN GENERAL.— For biiildincrs of moderate height timber may be used to give the necessary spread to the footings, j>j-ovided that water is always present. The foot- ings should be built by covering the bottom of the trenches, which should be perfectly level, with 2-inch planks laid close together and longitudinally in the direction of the wall. Across these, heavy timbers should be laid, spaced al^out 12 inches on centers, the size Fig. 38. Four Columns on One Grillage Footing. of the timbers being proportioned to the transverse stress. On top of these timbers should be spiked a floor of 3-inch planks of the same width as the masonry footings which are laid upon them. A section of such a fc^oting is shown in Fig. 40. All of the timber work must^be kept below low-water mark, and the space between the transverse timbers should be filled with sand, broken stone or concrete. The best woods for such foundations are oak, Georgia pine and Norway pine. Many of the old buildings in Chicago rest on timber footings. SPREAD FOUXDATIONS. Fig- 39- Built-up Base for Column. X.mck FlanK. Fig. 40. Timber Spread Footing. 70 BUILDING CONSTRUCTION. (Ch. II) 84. CALCULATION FOR THE SIZE OF THE CROSS TIMBERS. — The size of the transverse timbers should be com- puted by the following formula : Breadth m inches = (6) D^XA w representing the bearing power in pounds per square foot ; p, the projection of the beams beyond the 3-inch planks in feet; s, the dis- tance on centers of beams in feet, and D, the assumed depth of the beams in inches. A is the ''constant for strength," and should be taken at 90 for Georgia pine, 65 for oak, 60 for Norway pine and 55 for common white pine or spruce. Example I. — The side walls of a given building impose on the foundation a pressure of 20,000 pounds per. lineal foot ; the soil will support, without excessive settlement, only 2,000 pounds to the square foot. It is decided for economy to build the footings as shown in Fig. 40, using Georgia pine timber. What should be the size of the transverse timbers? Solution. — Dividing the total pressure per lineal foot by 2,000 pounds, we have 10 feet for the width of the footings. The masonry footing we will make of granite or other hard stone, 4 feet wide, and solidly bedded on the planks in Portland cement mortar. The projection p of the transverse beams would then be 3 feet. We will space the beams 12 inches on centers, so that s = i, and we will assume 10 inches for the depth of the beams. Then by formula (6), u ' ■ u 2 X 2000 X 9 X I the breadth m mches = = 4, 100 X 90 or we should use 4 by 10- inch timbers, 12 inches on centers. If common pine timber were used we should substitute 55 for 90, and the result would be 6^ inches. 85. BUILDINGS ON QUICKSAND.— When building on quicksand it is often advantageous to lay a floor of i-inch boards in two or more layers at right angles to each other on which to start the concrete footings. . 86. FOUNDATIONS FOR TEMPORARY BUILDINGS.— When temporary buildings are to be built over a compressible soil, the foundations may, as a rule, be constructed more ■ cheaply of wood than of any other material, and in such cases the durability of the timber need not be considered, as good sound timber will MASONRY WELLS. 71 last two or three years in almost any place if thorough ventilation is provided. The World's Fair buildings at Chicago (1893) were, as a rule, supported on timber platforms, proportioned so that the maximum load on the soil would not exceed 1^4 tons per square foot. Only in a few places over ''mud holes" were pile foundations used. The platform foundations consisted of *'3-inch pine or hemlock planks, with blocking or transverse beams on top, to distribute uniformly over all the planks, the pressure from the loads, and to furnish support for the posts which carried the caps supporting the floor joists and posts of the building. The blocking was well spiked to the platform planks and posts, and the caps and the sills were drift-bolted." Fig. 41. Temporary Timber Column Foundation. World's Fair Buildings, Chicago, 1893. Fig. 41 shows the general arrangement of the blocking under the posts. 3. MASONRY WELLS 87. MASONRY WELLS UNDER CITY HALL, KANSAS CITY, MO. — When it is necessary to support very heavy buildings on compressible or filled-in soil, where piles or spread footings can- not be used, or are not considered desirable, wells of masonry, sunk to bed-rock or hard-pan, will generally prove the method of secur- ing an efficient foundation which comes next in point of economy. 72 BUILDING CONSTRUCTION. (Ch. II) The wells are arranged as isolated piers, and the walls of the super- ^ structure are carried on steel girders resting on these piers. The manner in which such wells or piers should be used can prob- ably be best explained by describing those under the City Hall of Kansas City, Mo., which was one of the first instances in which such wells were used in this country. "The site of the City Hall was formerly a ravine between abrupt bluifs. These had been so cut away and levelled as to leave a 50-foot filling of rub- bish under two-thirds of the building and a solid clay bank under the other third. The fill was made by a public dump. Pile foundations were objection- able on account of the dryness of the fill and the anticipated tendency of the piles to rot therein. Ordinary trenching was considered too expensive and dangerous, therefore a system of piers was chosen, and a cylindrical form was adopted, so that the excavation could be done by a large steam-power auger, followed by a 3/16-inch caisson filled with vitrified brick. The caissons were made in 5-foot lengths of the same thickness throughout, the joints being made with 3"x>^" splice plates, riveted to the inside of the shell. "The piers were of vitrified brick, 4 feet 6 inches in diameter, laid in hydraulic cement mortar, grouted solid in each course, and well bonded in all directions. The piers were sunk to bed rock of oolitic limestone, 8 feet thick, and capped with cast-iron plates (Fig. 42) and steel I-beams, which supported the walls. To the top of the beams was riveted a ^-inch plate of boiler iron, on which the brickwork of the walls was built, as shown in Fig- 43- "Between the beams, and i foot on each side and underneath them, is a concrete filling, so that the beams are entirely encased in masonry. "Piers having excessive loads are reinforced by 12-inch Z-bar columns resting on rock bottom (Fig. 44). These columns pass through the cast-iron caps, so that the loads resting on the columns are separate from those on the brick piers (an essential provision). Essentially the whole system is intended to secure the direct transmission of the entire weight to the solid rock by so arranging the interior construction that each subdivision is carried by an adequate isolated pier. The piers are of uniform size, and their loads are equalized by spacing them at proportionate distances apart." 88. MASONRY WELLS UNDER STOCK EXCHANGE BUILDING, CtllCAGO. — Another instance of the use of masonry wells or deep piers is in the foundation of th% Stock Exchange building in Chicago. "The foundation is generally upon piles about 50 feet long, driven into the hard clay which overlies the rock. Next to the Herald Building, however, which adjoins it, wells were substituted, lest the shock of the pile driver close to its walls should cause settlements and cracks. A short cylinder, * The following description is an abstract of a short paper presented by the architect of the building, Mr. S. E. Chamberlain, of Kansas City, to the twenty-fourth annual con- vention of the American Institute of Architects. The illustrations were prepared in the office of the Engineering Record from the architect's drawings. Several more illustrations are given in the Engineering Record of April 2 and 16, 1892. MJSOXRY WELLS. 73 Figs. 4J, 43, 44. Masonry \\>lls Under City Hall, Kansas City, Mo. 5 feet in diameter, made of steel plate, was first sunk by hand, reaching below the footings of the Herald Building. Then around and inside the base of the cylinder sheet piles, about 35^2 feet long, were driven, and held in place by a ring of steel inside their upper ends. The material inside the sheeting was excavated and a similar steel ring was placed inside their lower ends. By means o*f wedges the lower ends of the sheeting were forced back into the soft clay until another course could be driven outside the lower ring. This operation was repeated unril the excavation had reached the hard clay about 40 feet below the cellar. In this material the excavation was continued with- 74 BUILDING CONSTRUCTION. (Ch. II) out sheeting in the form of a hollow truncated cone to a diameter of feet, and the entire excavation was filled with concrete. The wells are spaced about 12 feet. The loads upon them vary; some of them will carry about 200 tons. "The material excavated was a soft, putty-like clay to a depth of 40 feet, where a firm clay was reached deemed capable of carrying the weight pro- posed."* 4. CAISSON FOUNDATION CONSTRUCTION 89. GENERAL DESCRIPTION.— Caissons are constructed of timber or metal and are made cylindrical, square, or rectangular in section, open at both ends, or closed at the top or bottom. This construction is employed where it is necessary to penetrate a con- siderable depth of soft soil, permeated with water, to the solid rock or hard-pan beneath. Caissons are named after the manner of their use, as "open," ''erect," and "inverted." The "open" caisson is simply a cylinder or open box made of planks, timbers, or sheet- steel, without top and bottom. It is sunk by excavating inside, and allowing it to settle by its own weight, or by a load on a platform constructed upon the top. The sides are made water-tight, and any water coming in around the bottom edge or through the soil at the bottom is pumped out by hand, steam pump, or pulsometer. Caissons constructed with water-tight bottoms are seldom used in building construction, but are frequently employed in building the foundations of bridges or other foundations in water. When so used, they are towed to the desired position, and when properly located, and guided, are sunk by being filled with masonry or con- crete. Such caissons are usually called "erect" caissons. 90. INVERTED CAISSONS.— The "inverted" caissons are the ones most frequently and successfully used in the construction of important foundations carried to hard-pan or solid rock through strata of soft soil. They take the form of water-tight boxes or cylinders. Closed at the top and open at the bottom, they are strongly braced, and are usually made of steel plates, though some- times constructed of heavy timbers. The operation of sinking them consists in building masonry upon the top, and in carrying on the excavation inside and around their cutting-edge. 91. THE VACUUM SYSTEM.— Two systems are successfully * "Foundations of High Buildings." W. R. Hutton. Read before the Congress of Architects at Chicago, 1893. CAISSON FOUNDATION CONSTRUCTION. 75 used in sinking ''inverted" caissons, namely, the ''vacuum" system, and the "plenum" system. In the former the air is exhausted from the interior of the caisson and the excess of atmospheric pressure upon its top assists > in forcing it downward ; while on < ccount of the partial vacuum inside, the water around the excavation flows rapidly under the edge and into the caisson, thus loosening the soil and allowing it to be drawn out with the water. 92. THE PLENUM SYSTEM.— The "plenum" system is the one generally used, however. In this system water is prevented from flowing into the caisson by creating inside of it an air pressure, the excess of which over that of the atmosphere is sufficient to equalize the pressure of the water outside. This air pressure is pro- vided by powerful air-pumps. The workmen enter the caisson through an air-lock, placed in a tube, or cylinder, leading from the caisson, and consisting of an air-tight conipartment with two doors. (See Fig. 49.) In operating the air-lock, the workman enters through the first door, or trap, and closes it, allowing the air under pressure in the caisson to flow in slowly until the pressure in the air-lock is equal to that in the caisson, when the door to the caisson is opened and the workman allowed to enter. If the air were suddenly let into the air-lock, the physical strain upon the men would be severe and dangerous. The material from the excavation is usually hoisted in buckets, operated through air-locks, and the work is carried on in this way until the caisson has reached the required depth, when it is filled with concrete or masonry, and the piers constructed upon the top. 93. CAISSONS IN THE MANHATTAN LIFE INSUR- ANCE CO.'S BUILDING, NEW YORK.— Although caissons have been for some time extensively used in constructing the foundations of bridge piers, they were not, until a relatively recent date, used for the foundations of buildings in this country. The first instance was that of the building for the Manhattan Life Insurance Company, near the foot of Broadway, New York City ; Messrs. Kimball & Thompson, Architects; Charles O. Brown, Con- sulting Engineer. The method there employed proved perfectly satisfactory, and cost only about 8 or 9 per cent of the estimated cost of the building. The following is a short description of the manner in which the founda- 76 BUILDING CONSTRUCTION. (Ch. II) tions were constructed and the superstructure supported thereon, in this early example:'^ "The building occupies an area of about 8,200 square feet, and is seventeen stories high on Broadway and eighteen on New Street. The height from the Broadway curb to the parapet of the main room is 242 feet, and the dome and tower rises 108 feet above the parapet. All the walls, together with the iron floors and roof (which are very heavy), are directly supported by thirty-four cast-iron columns, which sustain an estimated weight of about 30,000 tons. "The great height and massive metal and masonry construction impose enormous loads on the foundations, amounting to as much as 2CO tons for some single columns, and giving about 7,300 pounds per square foot over the whole area of the lot. This enormous weight could not be safely carried on the natural soil, which is essentially of mud and quicksand to the bed rock, which has a fairly level surface about 54 feet below the Broadway street level. Above this rock the water percolates very freely, standing at a level of about 22 feet below the Broadway street line, and therefore making exca- vations below this plane difficult and costly. If piles had been driven as close together as the city regulations permit — /. e., 30 inches center to center over the whole area, about 1,323 might have been placed, and would have carried an average load of 45,300 pounds each, which was inadmissible, the statute laws of New York allowing only 40,000 pounds each on piles 2 feet 6 inches apart and with a smallest diameter of 5 inches. "Special foundations were therefore necessary, and it was imperative that their construction and duty should not jeopardize nor disturb the existing adjacent heavy buildings which stand close to the lot lines. On the south side the six-story Consolidated Exchange building is founded on piles which are supposed to extend to the rock. On the north the foundations of a four-story brick building rest on the earth about 28 feet above the rock, and were especially liable to injury from disturbances of the adjoining soil, which was so wet and soft as to be likely to flow if the pressure was much increased by heavy loading or diminished by the excavation of pits or trenches. "In view of these conditions it was determined to carry the foundations on solid masonry piers down to bed rock. The construction of the piers by the pneumatic caisson process was, after careful consideration by the archi- tects, backed by opinions from prominent bridge engineers as to its feasibility, adopted, "The smaller caissons were received complete and the larger ones in convenient sections, bolted together when necessary, and located in their exact horizontal positions, calked and roofed with heavy beams to form a platform, on which the brick masonry was started and built up for a few feet before the workmen entered the excavating chamber and began digging out the soil. The removal of the soil allowed the caissons to gradually sink to the rock below without disturbing the adjacent earth, which was kept from flowing in by maintaining an interior pneumatic pressure slightly in excess of the * Abstract from a very full description, with ten illustrations, published in the Engineering Record of January 20, 1894. 78 BUILD I KG COXSTKUCTIOX.. (Ch. II) ■outside hydrostatic pressure due io tlie distance of the hottoOT of the caisscyn below the water line. ''The adjacent buildings were shored up at the outset and scrupulouisty watched, observations being made to determine any possible displacemient or injury of their walls, which were not seriously damaged,, though' the pressure they exerted on the yielding soil tended to deflect the caissons which were sunk within a foot of them. They were kept in position by excess of loading and excavating on the edges that tended to be highest.. The caissons encoun- tered boulders and other obstructions, and were sunk through the fine soil and mud at an average rate of 4 feet per day. No blasting was required until the bed rock was reached and levelled off under the edges and stepped intO' horizontal surfaces throughout the extent of the excavating chamber. Usually 'One caisson was being sunk while another was being prepared,, there being only one time when air pressure was simultaneously maintained in two caissons. Generally about eight days were required to sink each caisson." Fig. 46. The Manhattan Life Insurance Building, New York City. Transverse Section. PUBLISHED BY CONSENT 0- THE ENGINEERING RECORD The first caisson was delivered at the site April 13, 1893, and the last pier was completed August 13, 1893. ''After the caissons were sunk to bed rock, and the surface cleared and dressed, the excavating chambers and shafts were rammed full of concrete, made of i part Alsen Portland cement, 2 parts sand and 4 parts of stone, broken to pass through a 2^-inch ring. The superimposed piers were built of hard-burned Hudson River brick, laid in mortar composed of i part Little 'Giant cement to 2 parts sand." Fig. 45 is a plan showing the piers, all of which, except P, which is built on twenty-five piles, are founded on caissons of the same size, and the bol- sters on top of them, together with the girders and the columns, which are indicated by solid block cross sections. CAISSOy FOUKDATIOX COXSTRUCTIOX . 79 "Cylindrical caissons are the most convenient and economical, and would have been used throughout if the conditions had permitted, but the positions of the columns and the necessity of distributing the load along the building lines and other considerations determined the use of rectangular ones, except in four cases." All the caissons were 11 feet high, made of Yi-'mch and •>^-inch plates and 6 by 6-incli angle framework, stiffened with 7-inch bulb- angles, vertical brackets and reinforced cutting edges. The columns supporting the outer side walls of the buildings were located so near the building line that they were near or beyond the outer edge of the foundation piers, as shown in Fig. 45, so that if they had been directly sup- ported thereon they would have loaded them eccentrically and produced unde- sirable irregularities of pressure. This condition was avoided and the weights transmitted to the centers of the piers by the intervention of heavy plate- girders, which supported the columns in the required positions and transferred their weights to the proper bearings above the piers. From these bearings the load was distributed over the whole area of the masonry by special steel bolsters. Fig. 46 is a transverse section at D-H-M, Fig. 45, showing the quadruple girder C, 17-18-19, and the manner in which it supports columns 23 and 33. The cantilever is made continuous across the building, with intermediate supports under columns 21 and 22. Soon after this pneumatic caisson foundations were used in the construction of the American Surety building, Xew York, a full description of which is given in the Engineering Record of July 14,. 1894. Caisson foundations, whether in the shape of wells or in the pneumatic form, should be used only under the advice or direction of a competent engineer. 94. CAISSONS IN THE SINGER BUILDING AND THE UNITED STATES EXPRESS COMPANY'S BUILDING, NEW YORK. — Several interesting examples of recent foundation construction, in which the pneumatic caisson has been successfully employed, are to be found in the Singer building and in the L^nited States Express Company's building, both located in New York City. Beneath the Singer building it was necessary to excavate to bed- rock, found at a depth of 90 feet below the curb. This bed-rock was overlaid with a stratum of hard-pan about 15 feet deep. The foundation plan of the building consists of rectangular and cylindri- cal piers of concrete, arranged as shown in Fig. 47, all of these piers being constructed by means of pneumatic caissons. As the Singer building is 41 stories in height, with a tower 612 feet above the street level, the load upon the foundations is very great,, amount- ing to, approximately, 27 tons per square foot, and including the 8o BUILDING CONSTRUCTION. (Cii. 1. r-r + 4- T 4- + Us.-. © © |h.'--H E^!3 0 ■ft nil a 4- A- + t t + > ;'aV»/' Fig. 47* Plan of Caisson and Pier Foundation, Singer Building, New York. load due to wind pressure, the full dead load and about 6o per cent of the maximum live load. Fig. 48 shows the finished concrete piers constructed by means of the caissons, and supporting the steel frame and curtain-walls of the building along the party-line, with the interior column sup- port carried some distance below the basement floor level. In the construction of the United States Express Company's building, which is a 23-story structure, it was necessary to use* pneumatic caissons on account of the fluid character of the soil, made treacherous by the tidal waters of the Hudson River. The material found on the site of this building consisted of 9 feet of earth, loam and fill, and an average of 18 feet of quicksand over- lying a stratum of hard-pan 14 feet thick; bedrock was found at a depth of 41 feet below the curb, and to this it was necessary to extend the foundations. For the construction of this building, caissons or working cham- bers were provided, consisting of bottomless boxes, rectangular in cross-section and about 6 feet wide, with a minimum length of 35 feet 4 inches, and a width of 6 feet. The walls of these caissons were built up of six courses of timber, which were secured by %-inch drift-bolts 2 feet long, and tied together vertically by i-inch * From Architects' and Builders' Magazine, January, 1907. CAISSOX FOUXDATIOX COXSTRUCTION , 8t Fig. 48* Section of Caisson and Pier Foundation, Singer Building, New York. screw-rods, placed 3 feet apart ; and the cutting edge was provided with a 6 by 4-inch steel angle. The heaviest caisson weighed in the neighborhood of 10 tons, and was large enough for six men to work inside of it; a roof was formed over it with ij^-inch tongued-and-grooved boards, and connected with this was a steel tube or shaft. The shaft was surmounted by what is known as the *'Moran" air-lock. When the shaft or working tube was in place, two lo-feet sections of temporary wooden forms were built upon the top of the caisson, a layer of cement mortar 6 inches thick was spread over the temporary loof, and upon this 24 inches of I, 2 and 4 concrete was placed and allowed to set for 24 hours. This construction formed a concrete slab strong enough to carry the concrete forming the pier. The lo-feet sections were then filled with concrete, and when this had set, additional forms were raised and more concrete put in place. As the caisson was brought *Fro!n Architects' and Builders' Magazine, January, 1907. 82 BUILDING CONSTRUCTION, (Ch. II) to the water level, compressed air was pumped into it, or into the bottom working chambers, to expel the water from the lower or cutting edge, and to allow the work of excavation to proceed inside. Thus undermined, the caisson sank by the great weight of the con- crete above, and where necessary the weight was augmented by piling pig-iron on top. When the caisson reached bed-rock and a pier of concrete extended from its roof to the top of the pier, the interior of the working chamber and the shaft connecting the latter with the outer air were filled with rich concrete. In operating the caisson construction in both this building and the Singer building, the above mentioned Mbran air-lock was employed. This air-lock is illustrated in Fig. 49, and is the inven- o Fig. 49.* Section of Moran Air-Lock, tion of Mr. Daniel C. Moran. In operation it is similar in principle to the ordinary river-lock, in that one door is always closed, thus maintaining the pressure in the working chamber with a minimum of leakage. From the figure it will be observed that the two doors of the air-lock are hinged and counter-weighed, allowing them to be operated readily when the pressure is relieved or equalized ; and they are made air-tight by means of heavy rubber gaskets around the edge. In order to enter the caisson the workman descends the * From Architects' and Builders' Maga::ine, January, 1907. CANTILEVER FOUNDATION CONSTRUCTION. 83 shaft and passes through the upper opening into the chamber or air-lock, when the door is closed and a valve opened, allowing the air to flow from the caisson or lower part of the shaft into the chamber or air-lock, and to thus equalize the air pressure so that the lower door may be opened and access had to the lower part of the tube and thence to the caisson. In hoisting the dirt or silt the process is reversed by hauling the bucket up into the air-lock, the hoisting rope passing through a stuffing-box in the upper door. By closing the lower door the upper one may be opened and the bucket hoisted from the lock and up the shaft. The loss of air in each operation is the volume contained in the air-lock or chamber in the shaft between the two doors. ~ 95. FOUNDATIONS OF HIGH BUILDINGS.— In prepar- ing the foundations for high buildings the same principles apply as for other buildings, except that as the loads on the foundations are so much greater, the footings must be proportioned with the utmost care. When building on firm soils it is only necessary to observe care- fully all the precautions given in Chapter I. ; and when building on compressible soils one of the methods described in this chapter should be employed, always, however, under the advice of an experienced engineer. 5. CANTILEVER FOUNDATION CONSTRUCTION 96. GENERAL DESCRIPTION.— In thickly built-up dis- tricts of cities, where the ground is of great value and where every available square foot of space must be utilized, it is necessary to build close to the party-lines. Frequently the party-walls of the adjoining buildings are entirely inadequate for the support of the floor systems of the newer heavy structure, so that new founda- tions must be provided. If the building to be erected is many stories high, foundations of considerable area are required. Such foundations, under the City Laws and Ordinances, must be entirely within the party-line of the owner's property, unless it is proposed to underpin and shore the old building, and erect a party-wall for both the new and old structure. This is not always desirable, on account of the expense and the likelihood of difficulties with the adjoining owners and tenants. By building the footing entirely inside of the party-line, as shown in Fig. 50, the line of action of the weight JV does not coin- 84 BUILDING CONSTRUCTION. (Ch. II) 1 1 1 1 r J p cide with the Hue of action of the resultant of the pressure P from the foundation soil, so that there is a tendency to throw outward the walls of the building and to cause unequal pressures upon the soil. In order to provide a foundation which will give an equal pressure upon each, square foot of soil, the cantilever system of foundation construction shown in Fig. 51 is used. In this figure the existing wall against which it is desired to build is shown at a, and the wall column and the curtain-wall of the new structure supported by the cantilever beam is indicated at h. By arranging the footing c under the canti- lever beam as shown, the undermining of the old wall of the adjoining building is avoided and a uniform pres- sure is brought to bear on the soil beneath the footing c. As the weight of the curtain-wall, and of one-half of the floor loads of all the stories between columns b and d, is concentrated on the over- hanging end of the cantilever, there is a lifting tendency on the column d ; so that, for stability of construction, the product of the force represented by the weight W by its lever arm x must equal the product of the force represented by the weight ll\ by its lever arm x^. From Fig. 51 it will be observed that the footings are of concrete Fig. 50. Footing In- side of Party Line. Center of Pressure Outside of Center of Base. Fig. 51. Examples of Cantilever Foundation Construction. Loss of Head-room. CANTILEVER EOUNDATIOX COXSTRUCTIOX . 85 and that the weight *is distributed over them by means of the grill- age beams. Usually a heavy cast-iron or structural steel bed-plate or bearing-plate transciiits the load at the overhanging end of the cantilever to the grillage, as at c. The beams marked g are framed in between the several cantilever beams or girders, and support what would in this instance be the basement floor, as there is, with this construction, insufficient head-room below the* bottom of the cantilever beams to form a basement. 97. CANTILEVER CONSTRUCTION WITH EXTENDED HEAD-ROOM.— The type of cantilever foundation just described provides the cantilever beams or girders directly over and not far removed from the foundation footing and immediately under the basement floor. Such construction results in a considerable waste of head-room or vertical distance, which is not always advisable, so that the cantilever construction shown in Fig. 52 is frequently em- ployed. In this illustration the cantilever forms the main supporting member of the first floor construction, and consists of a built-up plate-girder of box section, as at a. Upon the overhang end, where Fig. 52. Example of Cantilever Foundation Construction. Bacenient Head-room Retained. 86 BUILDING CONSTRUCTION. (Ch. II) it is strongly braced against buckling by means of stiffeners or angles, the wall columns and curtain-walls are supported as at b. The cantilever, instead of being supported almost directly upon the foundation, is carried by a structural steel column, some distance inside of the party-line, and this column in turn is supported by the grillage foundation, as at c. The other end of the cantilever girder is secured to the interior structural steel column d. Where the load upon the overhanging end of the cantilever is excessive and the leverage is sufficient to cause too great a lifting tendency upon the interior column d, the latter must be designed with a heavy founda- tion and anchor-bolts, so that there will be sufficient resistance to this upward action. In the illustration, Fig. 52, the bottom of the foundation footing under the wall of the adjoining building does not extend down to the depth of the new basement floor level ; so that, in order to carry on the excavation, steel sheet-piling is driven along the wall line to prevent the earth from sliding from under the old footings, as at e. This sheet-piling is afterwards backed up with concrete,, which is incorporated with the concrete of the grillage footing, and ^ forms an adequate retaining-wall to prevent the earth under the old wall from being disturbed. While the ledge of concrete, as at / in the figure, along the basement wall can hardly be considered as objectionable, this construction may be done away with by under- pinning the old wall. Cantilever foundation construction involving the use of struc- tural steel is always expensive but sometimes unavoidable. In many instances when it must be used, the cost may be materially reduced by using footings and foundation constructions of reinforced con- crete. Chapter III. Masonry Footings and Founda- tion Walls, Shoring and Underpinning ^ I. MASONRY FOOTINGS 98. PURPOSE OF FOOTINGS.— Footings under walls are used for two purposes: i. To spread the weight over a greater area. 2. To add to the stability of the wall. Under buildings of only two or three stories, the latter function is generally the more important. All walls should therefore have a footing or projecting course at the bottom of brick, stone or concrete. The width of the footings should be at least 12 inches wider than the thickness of the wall above, and should also be such that the pressure per square foot under the footings will not exceed the safe bearing power of the soil nor of the material on which it rests. (See Article 17.) 99. CONCRETE FOOTINGS.— For nearly all classes of buildings built on solid ground, cement concrete makes probably the best material for the bottom footing course, especially for the money expended. Concrete possesses the advantage over large blocks of stone of having considerable, transverse strength, so that when fully hardened it is much like a wide beam laid on top of the ground under the walls ; and should a weak spot occur in the ground under the footing, the latter would probably have sufficient transverse strength to span it if it were not very large. Concrete must also necessarily bear evenly over the bottom of the trenches, so that there can be no cavities, as is sometimes the case with stone footings. In localities where large blocks of granite or flagging cannot be cheaply procured, concrete makes much' the cheapest footing. As concrete is now available in all localities, many architects and engineers believe it advisable to use it in place of bricks for foot- 87 * 88 BUILDING CONSTRUCTION (Ch. Ill) ings. While good hard-burned bricks are very durable when used above ground, they are not so durable when used under ground ; and in the latter case there is a tendency to deteriorate, due prob- ably to the continuous saturation and to the action of frost. In stiff soil, trenches for the concrete footings should be dug below the general level of the excavation and of the exact width of the footings, so that when the concrete is put in and tamped it will bear against the sides as well as on the bottom of the trenches. In sandy soils this of course cannot be done, and planks must be set up and held in place by stakes to form the sides of the trenches. After the cement has set, but not before, the planks ma}* be removed. Concrete for footings should be mixed in the proportion of i part of cement to 2 parts of sand and 4 parts of stone for natural cements, and i to 2^ and 5 for Portland cements. The thickness of the concrete should be one-fourth of its width, and never less than 12 inches, except under very light buildings. The concrete should be put in in layers about 6 inches thick. If the footing is considerably wider than the wall it may be stepped in by setting up planks to hold the upper layers of concrete, or a stone footing of proper width may be placed on top of the concrete, as in Fig. 53. The latter is apt to give the best results. Fig. 53. Concrete and Stone Footing. Fig. 54. Two-Course Stone Footing. For the manner of mixing the concrete see Chapter X. For width of offsets see Article 103. 100. BUiLDING LAWS REGARDING CONCRETE FOOT- INGS. — The building laws of several of the principal cities agree closely with the New York building laws in their requirements for concrete footings. In New York concrete for footings must consist' of at least i part of Portland cement to 2 parts of sand and 5 MASONRY FOOTINGS. 89 parts of broken stone, and the stone must be of such a size that it will pass through a 2-inch ring. Clean gravel in the same propor- tions may be substituted for the stone. The footing course must in all cases be at least 12 inches in thickness, and at least 12 inches wider than the bottom width of the wall, or of the piers, columns or posts. Should the projection of the footing be subjected to undue transverse stress, the thickness must be increased so as to safely carry the load. A deviation from the law with regard to the 12-inch thickness may be made, however, at the discretion of the Commissioner of Buildings, where the structure is small or the loads are light. loi. STONE FOOTINGS. — For buildings of moderate height stone footings are generally the most economical, and if they are carefully bedded, answer as well as concrete. If practicable, the bottom footing course should consist of single stones of the full width of the footing, and the thickness of the stones should be about one-fourth of their width, depending much, however, upon the kind of stone. If stone of sufficient width cannot be obtained, the stone may be jointed under the center of the wall, and a second course consisting of a single stone placed on top, as shown in Fig. 54. In order that the projection of a stone in a footing course shall have sufficient transverse resistance, the length of the part of the stone beneath the upper course should be at least twice the pro- jection of the stone; that is, a stone in a footing course should not have a projection greater than one-third of its length. If shorter stones than these are used, the projecting courses of the footings are apt to break off, or to be torn from their beds. It is good practice in the design of stone footing courses to keep the angle between the horizontal and a line drawn through the upper outside edges of the projecting courses not less than 60 degrees, or to make the projection such that it will not be greater than one- half the thickness of the course. Where this rule is followed, the footing is not likely to fail by the cracking or brc::king off of the projection. For light buildings of only one or two stories, used for dwellings or similar purposes, irregular-shaped stones, called "heavy rubble," are generally used, as shown in Fig. 55, which represents a plan of the footing course, the spaces between the larger stones being filled in with smaller stones. Each stone should be laid in cement go BUILDING CONSTRUCTION. (Ch. Ill) mortar and the spaces between the stones sohdly filled with mortar and broken stone. ^ Under heavy buildings the footing stones should be what are called ''dimension stones" ; that is, roughly squared to certain dimensions. Dimension stones for footings may be obtained from 4 to 8 feet in length, according to the kind of stone. The width of the stones, measured lengthwise of the wall, should be at least 2 feet, or two-thirds the wadth of the footings. The best stones for heavy footings are : Granite, bluestone, slate and some hard laminated sandstones and limestones. 102. BEDDING OF FOOTING STONES.— As footing stones are generally very rough, being left as they come from the quarry, they cannot be made to bear evenly on the bottom of trenches with- out being bedded either in a thick bed of mortar, or, if the soil is sand or gravel, by washing the sand into the spaces by means of a stream of water. As a rule, the only safe way is to specify that the stones shall be set in a thick bed of cement mortar and worked around with bars until they are solidly bedded. 103. OFFSETS. — The projection of the footings beyond the wall, or the cours'e above, is a point that must be carefully con- sidered, whatever be the material of the footings. If the projection of the footing or offset of the courses is too great for the strength of the stone, brick or concrete, the footing will crack, as shown in Fig. 56. The proper offset for each course will depend upon the vertical pressure, the transverse strength of the material, and the thickness of the course. Each footing stone may be considered as a beam^ TABLE VII. Safe Offsets for Masonry Footing Courses. KIND OF FOOTING. R. IN LBS. PER SQ. IN.* OFFSET FOR A PRESSURE. IN TON FOOT ON THE BOTTOM OF THE «. PER SQUARE COURSE, OF 0.5 I 2 3 5 10 2,700 3-6 2.6 1.8 1-5 1.2 .8 1,800 2.9 2.x 1-5 Z.3 I •y 1,500 27 1.9 1-3 I.I .6 1.200 2.6 1.8 ■^•3 ID i •s Slate 5,400 5-0 3-6 2-5 2.2 z.a 1,200 2.6 1.8 »-3 I.O .8 •S 150 0.8 0.6 04 80 0.6 0.4 0.3 * Modulus of Rupture, values given by Ira O. Baker in "Treatise on Masonry Construction.' MASONRY FOOTINGS. 91 fixed at one end and uniformly loaded, and in this way the safe projection may be calculated. Table VII gives the safe offset for masonry footing courses, in terms of the thickness of the course, computed with a factor of safety of 10. It should be borne in mind that as each footing course transmits the entire weight of the wall and its load, the pressure will be greater per square foot on the upper courses, and the offsets should be made proportionately less. Fig. 55. Plan of Heavy Rubble Footing Course. Fig. 56. Footing Crack Caused by Too Great Projection. 104. EXAMPLE OF STONE FOOTING COURSE OFF- SETS. — A 4 feet wide footing course of limestone transmits a load of 12 tons per lineal foot or 3 tons per square foot ; the thickness of the course is 10 inches. What should be the width of the course above ? Solution. — From the table under the column headed 3 we find the projection to be i.i times the thickness, or in this case 11 inches. As we would have the same projection each side of the wall, the stone above may be 22 inches less in width, or 2 feet 2 inches wide. Except in cases where it is necessary to obtain very wide footings it is better not to make the offsets more than 6 or 8 inches, and in the case above it would be better to make the upper footing course 3 feet wide. Most building ordinances require the projection of the footings beyond the foundation wall to be at least 6 inches on each side. 105. BRICK FOOTINGS. — On sandy soils brick foundations and footings may be used when good stone cannot be cheaply obtained. In Denver, Col., where the soil is a mixture of sand and clay, very dry and unaffected by frost, brick foundations have been found to answer the purpose fully as well as stone for two and three-story buildings. In building brick footings, the principal point to be attended to is to keep the back joints as far as possible from the face of th-s 92 BUILDING CONSTRUCTION. (Ch. Ill) work; and in ordinary cases the best plan is to lay the footings in single courses, the outside of the work being laid all headers, and no course projecting more than one-quarter brick beyond the one above it, except in the case of unloaded 9-inch walls. The bottom course should in all j^ases be a double one. Figs. 57 to 60 show the proper arrangement of the brick in walls from one to three bricks in thickness. If the ground is soft and compressible, or the wall Fig. 57- «^-2-bks--? HI 1 r Fig. 58. < — - 3 bks: ^ 1 r I ,1 I, r. I r Fig. 59. Fig. 60. Figs. 57-60. Examples of Brick Footings. Proper Arrangement of Bricks. heavily loaded, the footings should be made wider, as shown in Fig. 61. For brick footings under high walls, or walls that are very heavily loaded, each projecting course should be made double, the heading course above and the stretching course below. The bricks used for footings should be the hardest and soundest that can be obtained, and should be laid in cement or hydraulic lime mortar, either grouted or thoroughly slushed up, so that every joint will be entirely filled with mor- tar. The writer favors grouting for brick walls ; that is, using thin mortar for filling the inside joints, as he has always found that it gives very sat- isfactory results. I I * I ^ I * I ' The bottom course of the footing should always be laid in a bed of mortar spread on the bottom of the 1 — n ick Footings for Fig. 61. Wide Br Heavy Walls on CompresS' ible Soils. MASONRY FOOTINGS, 93 trench, after the latter has been carefully levelled. All bricks laid in warm or dry weather should be thoroughly wet before laying, for, if laid dry, they rob the mortar of a large percentage of its moisture, greatly weakening its adhesion and strength. 106. IMPORTANCE OF CAREFUL CONSTRUCTION OF FOOTING COURSES. — Too much care cannot be bestowed upon the footing courses of any building, as upon them depends much of the stability of the work. If the bottom courses are not solidly bedded, if any seams or vacuities are left in the beds of masonry, or if the materials themselves are unsound, the effects of such carelessness are sure to show themselves sooner or later, and almost always when they cannot be well remedied. Nothing is more apt to injure the reputation of a young architect than to have a building con- structed under his direction settle and crack ; and he should see per- sonally that no part of the foundation work is in any way slighted. 107. STEPPED BRICK FOOTINGS ON CONCRETE FOUNDATION. — In the construction of footings under brick walls a bed of concrete is commonly used, and the brickwork off- setted from this bed up to the required thickness for the wall. Such stepped-up brick footings, with concrete beds or footings beneath, are shown in Fig. 62 at (a) and {h) . The illustration represents the vertical cross-section of an exterior wall of a building built close to the street or party-line. In the figure, at (a), the footing is formed by stepping back each course of brickwork, while at (b) the stepping is made at every other course. Either of these methods of building brick footings, with the projections given in the illustration, meets the requirements of the New York building law. 108. INVERTED ARCHES. — Inverted arches are sometimes built under and between the bases of piers, as shown in Fig. 63, with the idea of distributing the weight of the piers over the whole length of the footings. This method is objectionable, first, because it is nearly impossible to prevent the end piers of a series from being 94 BUILDING CONSTRUCTION. (Ch. Ill) Illustration of Inverted Arches. pushed outward by the thrust of the arch, as shown by the dotted line ; and secondly, be- cause it is generally im- possible with inverted arches to make the areas of the different parts of the foundation propor- tional to the load to be supported. It is much better to build the piers with separate footings, projecting equally on all four sides and proportioned to the loads they support. The intermediate walls may be supported by steel beams or arches, as preferred. In some instances, however, when building on comparatively soft soils, and where it is impracticable to use spread footings, inverted arches may be advantageously used, especially when it is necessary to reduce the height of the footing to a minimum. If it is decided to use inverted arches, the foundation bed should be levelled and a footing built over the whole bed to a depth of at least from 12 to 18 inches below the bottom of the arch. Concrete is much the best material for this footing, although brick or stone may be used if found more economical. The uppe;: surface of the foot- ing should be accurately formed to receive the arch, which should be built of hard bricks laid in cement mortar, generally in separate rings or rowlocks, and should abut against stone or concrete skew- backs, as shown in Fig. 64. It is better to build the arches before putting in the skewbacks, and for the latter i to 6 Portland cement concrete possesses special Fig. 64. Details of Footings with Inverted Arches. MASOXRV FOOTIXGS. 95 advantages, as it can be deposited between the ends of the arches and rammed evenly and simuhaneously, giving a sohd and uniform bearing against the ends of the arches, and tending to prevent unequal settlement and cracking. 109. Above the concrete skewback a solid block of stone should be placed if it can be readily obtained. The thickness of the arcli ring should be at least 12 inches, and heavy iron plates or washers should be set in the middle of the concrete skewbacks and connected with iron or steel rods, to take up the thrust of the end arches. The "rise" of the arch, or distance R, Fig. 64, should be equal to from to X) tlie span. The sectional area of the arch should equal the result obtained by the following formula: Section of arch in sq. ins. ^ Total load on arc h_( in lbs.) X span 8X^X10 For wrought-iron tie-rods o - , . . Total load on arch (in lbs.)X span Section ot rods m sq. ms. = q , , p v . o — (8) 8 X X 850 ^ ^ For steel tie-rods . , . . . Total load on arch X span , ^ Section of rods m sq. ins. = ^ — — (q\ ^ SX RX 1050 the span being measured in feet, and the distance R in inches. The load on the arch will be equal to the span multiplied by the pressure per lineal foot imposed on the soil. The latter will be obtained by dividing the load on the piers by the distance betweert centers of piers. no. EXAMPLE IN CALCULATION FOR INVERTED ARCH FOOTINGS. — It is desired to use inverted arches between the piers of a three-story building, resting on a soil whose bearing power cannot be safely estimated at over 3,000 pounds per square foot. The piers are of stone, 4 feet long, 22 inches thick, and 14 feet apart on centers. Each pier supports a total load of 98,00a pounds. What should be the sectional area of the arch, and of the rods in the end spans? Solution. — The span of the arch will be 10 feet, and the distance R about one-fifth of 10 feet, or 24 inches. The load per lineal foot on the soil will equal 98,000^14, or 7,000 pounds. The footings under the arch must therefore be 2 feet 4 inches wide to reduce the pressure to 3,000 pounds per square foot. The width of the arch 96 BUILDING CONSTRUCTION, (Ch. Ill) itself we will make 22 inches, or two and one-half bricks. The tolal load on the arch will equal 10X7,000, or 70,000 pounds. The sectional area of the arch must therefore equal 70000 X 10 . , 5-— — — or 354 square niches. 8 X 24 X 10 ^ As the width is 22 inches, the depth must equal 354-^-22, or 16 inches, which will require four rowlocks or rings. The sectional area of the ties must equal, for wrought-iron, 70000 X 10 . , ■^r— — — T-Ts — or 4-3 square mches. 8 X 24 X 850 ^ ^ ^ In this case it will be better to use two rods of 2.15 square inches in area, or two i^-inch rods. All cast-iron work in the foundation should be coated with hot asphalt, and the rods should be dipped in linseed oil while new and hot and afterward painted one heavy coat of oxide of iron or red lead paint. 2. FOUNDATION WALLS 111. GENERAL DESCRIPTION.— This term is generally applied to those walls which are below the surface of the ground, and which support the superstructure. Walls whose chief office is to withhold a bank of earth, like those around areas, are called retaining-walls. Foundation walls may be built of stone, brick or concrete, the first being the most common. Brick walls for foundations are only suitable in very dry soils, or in the case of party-walls, where there is a cellar or basement each side of them. As the method of building brick foundations is the same as for any brick wall, it will not be described here, but will be taken up in the chapter on Brickwork. For concrete walls see Chapter X. 112. STONE WALLS. — The principal details to be watched in building a stone foundations wall are the character of the stone and mortar, and the bonding, filling of voids and pointing. The best stones for foundations are granites, compact sand- stones, slates and blue shale. The less porous the stone the better it will stand the dampness to which it must be subjected. As a rule laminated stones make the best walls, as they split easily and give flat and parallel beds. If the only stones to be had are boulders FOUNDATION WALLS. 97 or field-stones, they should be split so as to form good bed-joints. Cobble or round stones should never be used for building founda- tion walls, and for all buildings exceeding three stories in height, block stone or the best qualities of laminated stone should be used. The mortar for foundation walls below the grade line should be made either of Portland cement, natural cement, or hydraulic lime, with coarse sand ; while above grade good common lime, or lime and cement, may be used. . The usual practice in building foundations is to use the stone just as it is blasted from the quarry; or, if the building is built on a ledge, the material from the foundation itself, the stone receiving no preparation other than a breaking up with a sledge-hammer, and the squaring of one edge for the face. Too great irregularity and unevenness is overcome by sparing the use of the stone-hammer and by varying the thickness of the mortar joint in which the stones are bedded. The strength of the wall, therefore, depends largely upon the quality of the mortar used. The wall should be levelled off about every 2 feet, so as to form irregular courses, and the horizontal joints should be kept as nearly level as possible. When block stones are used they are generally from 18 inches to 2 feet thick and the full width of the wall. They are commonly roughly squared with the hammer, and but little mortar is used in the wall. Only in a few localities, however, are such stones obtain- able at a price that will permit of their use, so that as a rule stones split from a ledge and called ''rubble" are the materials with which the architect will have to deal. 113. BONDING. — Aside from the quality of the stone and mortar, the strength of a rubble wall depends upon the manner in which it is bonded or tied together by lapping the stones over each other. About every 4 or 5 feet in each course a bond-stone should be used ; that is, a stone that will go entirely through the wall, and, by its friction on the stones below, hold them in place. A stone that goes three-fourths of the way through the wall is called a three-quarter bond. It is customary to specify that there shali- be at least one through-stone in every 5 or 10 square feet of the wall, depending upon the character of the stone and nature of the building. Fig. 65 shows a portion of wall built of square or laminated stones, with through bond-stones at B B, and three-quarter FOUNDATION WALLS. 99 bond-stones 2ii A A. A good three-quarter bond is nearly equal in strength to a through-bond, and when the character of the stone will permit of the wall being built largely of flat stones extending two-thirds of the way through the wall, it will not be necessary to use more than one through-stone to every lo square feet of wall. No stone should be built into the face of a wall with a depth less than 6 inches, although stone-masons will often set a stone on edge, so as to make a good face and to give the appearance of a large stone, when it may be only 3 inches thick. All kinds of stones should always be laid so that their natural bed, or splitting surface, will be horizontal. It is also important that the stones shall break joint longitudinally, as in Fig. 65, and not have several vertical joints over each other, as at A A, Fig. 66. The angles of the foun- dation should be built up of long stones, laid alternately header and stretcher, as shown in Fig. 67 The largest and best stones should always be put in the corners, as these are usually the weakest parts of a wall. 114. FILLING VOIDS.— All stones, large and small, should be solidly bedded in mortar, and all chinks or interstices between the large stones should be partially filled with mortar and then with small pieces of stone, or spalls, driven into the mortar with the trowel, and then smoothed off on top with mortar. Many masons are apt to build the two faces of a wall with long, narrow stones and fill in between with dry stones, throwing a little mortar on top to make it look well. A horizontal section through such a wall would appear as shown in Fig. 68. A wall of this kind would require but little loading to cause the out- side faces to bulge, owing to the lack of strength in its middle portion. The way in which a wall of irregularly shaped stones should be built in order to be as strong as possible is shown in Fig. 69. A wall of this kind requires no more stone than the other, but requires more lifting and a little more work with the hammer, and Fig. 68. Section of Poorly Built Rubble Stone Wall. Fig. 69. Section of Properly Built Rubble Stone Wall. TOO BUILDING CONSTRUCTION. (Ch. Ill) these appear to be the real reasons why better workmanship does not oftener result. 115. WINDOW OPENINGS.— If there should be a window or door opening in the foundation w^all, as in Fig. 70, the stones just below the opening should be laid so as to spread the weight Fig. 70. Stones Under Window Opening. Proper Method. of the wall under it, as shown by the stones A B C. If any great weight is to come upon the foundation it is better not to build the windov/ sills into the wall, but to make their length just equal to the width of the opening. These are called ''slip-sills," and there is no danger of their breaking by uneven settlement. Occasionally some part of the foundation wall of a building goes down much lower than the adjoining portions, and, as there is almost always a slight settlement in the joints of a wall, unless laid in cement the deeper wall will naturally settle more than the other, and thus cause a slight crack. This can be avoided by building the deeper wall of larger stones, so that there will be no more joints than in the other wall, or by making thin joints and using cement mortar. 116. THICKNESS OF FOUNDATION WALLS.— The thickness of a foundation wall is usually governed by that of the wall above, and also by its own depth. Nearly all building regulations require that the thickness of a foundation wall, to a depth of 12 feet below the grade line, shall be 4 inches greater than the wall above for brick and 8 inches RETAIXIXG-WALLS. lor greater for stone ; and that for every additional lo feet, or part thereof in depth, the thickness shall be increased 4 inches. In all large cities the thickness o'f the walls is controlled b}^ law. In cases where the thickness is not so governed the following table will serve as a fair guide : TABLE VIII. Proper Thickness for FoundatiOxN Wall.s. HEIGHT OF BUILDING. DWELLINGS, HOTELS, ETC. WAREHOUSES. BRICK. STONE. BRICK. STONE. Ins. Ins. Ins. Ins. 12 or 16 20 16 20 16 20 20 24 20 24 24 28 24 28 24 28 24 28 28 32 Only block stone, or first-class rubble, with flat beds, should be used in foundations for buildings exceeding three stories in height. The footings should be at least 12 inches wider than the width of the walls. (See Article 98.) In heavy clay soils it is a good idea to batter the walls on the outside, making the wall from 6 inches to a foot thicker at the bottom than it is at the top, and plastering the outside with cement. (See Fig. 6, Article 10.) 3. RETAINING-WALLS 117. GENERAL DESCRIPTION.— A retaining-wall is one that is built to hold up a bank of earth, which is deposited behind it after it is built. The term hreast-zvall or face-wall is used for a similar structure built to prevent the fall of earth which is in its undisturbed natural position, but in which a vertical or inclined face has been left after the excavations. Retaining-walls also differ from foundation walls, in that the latter support superstructures whose weights are generally sufficient to overcome the thrust of the earth against the walls. Retaining-walls depend upon their own stability to resist earth-pressure. Area walls generally serve as retaining-walls, but as they are usually braced by arches or cross walls from the building wall, they do not require the same thickness.as a jetaining-wall proper. 102 BUILDING CONSTRUCTION. (Ch. Ill) Cham^'in^ Jireef' Grade Buu I oj' the Ecirfh Backing ig. 71. Retaining- Wall and Foundation Wall. Poor Construction. Several theoretical formulas have been proposed by writers on engineering subjects for computing the necessary thickness and most economical section for retaining-walls ; but so many varying conditions enter into the designing of such walls, such as the char- acter and cohesion of the soil, the extent to which the bank has been disturbed, the manner in which the material is filled in against the wall, etc., that little confidence is placed in these theoretical formulas, and engineers appear to be guided rather by empirical rules. 118. MANNER OF FAILURE.— Retaining-walls may fail in any one of several ways; by tipping or overturning; by bulging; or by the sliding of the footings. The first is the most common form of failure and is caused by the pressure of the earth backing, overturning the wall about the outside edge of the footing or wall. A retaining-wall may fail also by bulging, caused by filling in back of the wall while the masonry is still green ; by water penetrating back of the wall and freezing; or by a change in the nature of the soil due to heavy rains. While the failure of a retaining-wall by the sliding of the footings is not frequent, it has sometimes occurred where it has been sufficiently heavy to resist overturning, and where the footings have been built on unstable soil, such as slippery clay, or other unctuous material. Ret^jning-walls which .hpld „back ea,rth embankments liable to RETAIN IN G-W ALLS. 103 vibration from passing trains or from heavy street traffic are more likely to fail than walls not subjected to such vibration, and should be made from 25 per cent to 50 per cent heavier. The foundation walls and area walls of buildings are frequently required to act as retaining-walls along railroad sidings and should be carefully designed to meet this condition. The failure of a retaining-wall has been caused by the over- loading of the earth embankment or the backing which it supports. A condition likely to cause failure is shown in Fig. 71, where the footing of an adjacent building is not down to the level of the footing of the retaining-wall required by the changing of the grade of the street. 119. DESIGN AND CONSTRUCTION.— The cross-section that appears to be generally approved for retaining-walls, particu- larly in engineering work, is shown in Fig. 72. The wall may be either built plumb, a-s shown, or inclined toward the bank. The latter method is generally considered to result in greater stability, although it is open to the objec- tion that the water which runs down the face of the wall is apt to penetrate into the inclined joints. Retaining-walls should be built only of good hard split or block stone,* laid in cement mortar and carefully bonded, to prevent the stones from sliding on the bed- joints. Fig. 72. Rctaining-Wall. Generally Ap- The thickuCSS of the Wall at proved Section. the top should be not less than 18 inches, and the thickness, a, just above each step should be from Yz Ys oi the height from the top of the wall to -that point. If the earth is banked above the top of the wall, as shown by the dotted line, Fig. 72, the thickness of the wall should be in- creased. A thickness equal to one-half of the height will generally - CL- — ; * Or of Portland cement concrete with metal reinforcements. I04 BUILDING CONSTRUCTION. (Ch. Ill) answer for a height of embankment equal to one-third the height of the wall. The outer face of the wall is generally battered, or sloped out- ward, about I inch to the foot, Stepping the wall on the back increases the stability by bonding it into the material behind and by increasing the weight by the weight of the soil resting upon the steps. Care should be used in filling in back of a retaining-wall, for the stability varies considerably with the method employed. The sta- bility of the wall is increased if the earth is well rammed in layers inclined down from the wall, whereas if the earth is filled in in layers sloping up toward the wall, it must be made stronger to resist the full pressure of the earth. If built upon ground that is affected by frost or surface water, the footings should be carried sufficiently below the surface of the ground at the base of the wall to insure against heaving or settling. If the ground back of the wall slopes toward the wall a cement gutter should be formed behind the coping and connected with a drain pipe to carry off the surface water. The back of the wall and the tops of the steps should be plastered with cement to the depth of at least 3 or 4 feet. 120. REINFORCED CONCRETE RETAINING-WALLS.— Retaining-walls are now fre- quently constructed of rein- forced concrete, and are built as shown in the section in 73- Such walls depend for their stability rather upon the wide reinforced concrete base than upon the dead weight of the concrete. As a rule, reinforced concrete re- taining-walls are not more than 8 inches in thickness at the top and 18 inches at the bottom. The concrete of the retaining-wall is reinforced so as to resist the pressure of the earth backing, by providing sufficient transverse strength AREA iVALLS. or resistance to bending between the wall and the footing ; and the width of the footing, together with the weight of the earth backing upon it, adds additional stability to the wall. The footing is also reinforced sufficiently to prevent its failing by transverse or bending stresses. In addition to the reinforcing rods, the wall is usually pro- vided with shrinkage rods running horizontally and placed about 2 feet on centers. They are made of from yj-inch to J/^-inch round or square bars. The concrete used in such w'alls is generally made of a I, and 5 mixture of cement, sand or gravel, and broken stone respectively. The exposed face of the wall is molded smooth by the use of planed boards, neatly matched in the construction of the forms ; and is afterwards washed down with a cement wash put on with a soft brush, or is rubbed with carborundum blocks dipped in a cement paint or wash. 4. AREA WALLS 121. GENERAL DESCRIPTION.— Areas are often exca- vated outside the foundation w^alls of buildings to give light or access to the basement, and require surrounding walls to retain the earth and present a neat appearance. Such walls should be built of stone, as stone walls offer greater resistance, when the mortar is green, to sliding on the bed- joints than is offered by brick walls. In making the excavation the earth should be disturbed as little as possible, and in filling against the walls the soil should be deposited in layers and well tamped, and not dumped in carelessly. Either the filling should be delayed until the mortar has had time to harden, or the walls should be well braced. Area w^alls are commonly built like foundation walls with a uniform thickness of about 20 inches for a depth of 7 feet. If more than 7 feet in height the walls should have a batter on the area side and should be increased in thickness at the bottom, so that the average thickness will be at least one-third of the height, unless the walls are braced by arches, buttresses or cross walls. Area walls sustaining a street or alley should be made thicker than those in an open lot. Fig. 74. Area Wall P.racLHl by Arch. io6 • BUILDING CONSTRUCTION. (Ch. Ill) When an area wall is more than lo feet long it is generally prac- ticable to brace it from the basement wall by arches thrown across from one wall to the other, as shown in Fig. 74. When this cannot be done the wall should be stiffened by buttresses about every 10 feet. 5. VAULT WALLS 122. GENERAL DESCRIPTION.— In large cities it is cus- tomary to utilize the space under the sidewalk for storage or other purposes. This necessitates a wall at the curb line to sustain the street and also the weight of the sidewalk. Where practicable, the space should be divided by partition walls about every 10 feet, and when this is done the outer wall may be advantageously built of hard bricks in he form of arches, as shown in Fig. 75. The thickness of the arches should be at least 16 inches for a depth of 9 feet, and the ''rise" of the arch }^ of the span. If partitions are not practicable, each sidewalk beam may be supported by a heavy I-beam column, with either flat or segmental arches between, as shown in Fig. 76^ This latter method is more economical of space than any other, and where steel is cheap is about as economical in cost. Fig. 75. Arched Sidewalk \'ault Walls Fig. 76. Sidewalk Vault Walls with I- with Partition Walls. Beam Columns and Flat Arches. 6. SUPERINTENDENCE OF FOUNDATION WORK. 123. THE FOOTINGS IN GENERAL.— The first work on the foundations is the placing of the footings. If they are of concrete, an inspector should remain on the work during the working hours to see that every batch of concrete is mixed exactly as specified, that the aggregates are broken to the FOOTING DETAILS. 107 proper size and that the cement is all of the same brand and in good condition. There is no building operation that can be more easily "skimped" without detection than the making of concrete, and the only way in which the architect can be sure that his specifications have been strictly followed is by keeping a reliable representative constantly on the ground. The inspector should see also that the concrete is put in to the full thickness shown on the drawings, and that it is levelled and tamped every 6 inches in depth. When water is encountered in the trenches, it should be col- lected in a shallow hole and removed by a pump or drain, as ex- plained in Article 35. Very often, when the foundation rests on the top of a ledge, underlying gravel or clay, running water will be encountered in the trenches in too great a volume to be readily removed. In this case, the flow of water should be intercepted by a drain and cesspool, and a tight drain carried from the latter to a sewer or to a dry well below the foundation of the building. Concrete footings for piers not more than 4 or 5 feet square may be built, where there is running water, by making large bags of oiled cotton, sinking them in the pit and filling the concrete into them immediately. The water will probably rise around the bags, but if the latter keep the water away from the concrete until the cement has had time to set, they will have answered their purpose. Water does not injure concrete, nor mortar made of cement, after they have begun to harden ; but if freshly-mixed concrete is thrown into water, the latter separates the cement from the sand and aggregates, the cement mixing with the water and floating away, while the sand and stone drop to the bottom. For this reason concrete should never be thrown into trenches containing water. 124. DETAILS OF FOOTINGS, WALLS, MATERIALS, ETC. — If the footings are of stone the presence of water does not do as much harm, provided it can be drained so as not to attain a greater depth than 3 or 4 inches. Sometimes the bottom of a wall is used as a drain for collecting the seepage water, and the trench is partially filled with stones laid without rriortar, as explained in Article 10. For heavy buildings, however, the footings should be solidly bedded in cement mortar when the trenches are reasonably dry ; and when this it not the case, in sand or fine gravel. An irregular footing stone can often be bedded more solidly by piling fine sand around it and then washing the sand under the stone with water. io8 BUILBING CONSTRUCTION. (Ch. Ill) than it can by laying it in cement mortar. The former method, however, takes more time, and is seldom employed when mortar can be used with as good results. As stated in Article 105, too much care cannot be bestowed upon the footing courses of any building, and there is no portion of it that needs closer inspection than the footings and foundation. Before the masons commence actual operations the architect should inspect all materials that have been delivered, to see that they are of the kind and quality specified. The mortar, together with the sand, cement or lime, should be particularly examined, to see that it has the proper proportions of cement or lime, and is well worked ; that the cement or lime is fresh and of the kind or brand specified ; and that the sand is clean and sharp. The building of the foundation wall should also be carefully watched to see that the wall is well tied together with plenty of three-quarter and through bond-stones, and that the inside is solidly filled with stone and mortar. The superintendent must also examine the wall occasionally to see that it is built straight and plumb, and that the general bed of the courses is horizontal. When inspecting stonework already built, but which has not had time for the mortar to harden, a light steel rod, about ^/^g inch in diameter and 4 or 5 feet long, will be found useful. If the rod can be pushed down into the center of the wall more than 18 inches or 2 feet in any place it shows that the stones have not been lapped over each other, and if this can be done in several places the in- spector should order the wall taken down and rebuilt. The rod will also indicate to a considerable extent whether or not the stones in the center of the wall have been well bedded, for if this is not the case, they will rock or tip when struck with the rod. The inspection of a foundation wall cannot be too thorough, as there is nothing that causes an architect so much trouble as settle- ments in the foundations of his buildings. 125. FILLING IN. — In buildings, in which the cellar floor is 6 feet or more below the ground level, the trenches behind the walls should not be filled in until the floor joists are on and the walls built 6 feet or more above them, or until the walls are solidly braced with heavy timbers, as otherwise the walls may be sprung by the pressure of loose dirt. In heavy clay soils it is a good idea to fill in back of DAMPXESS IN CELLAR WALLS. 109 the walls with coarse gravel, stone spalls and sand, as frost will not ''heave" them as it does clay. 126. HOLES FOR SOIL-PIPES AND SUPPLY PIPES.— In thick walls built of heavy stone, the architect should locate the position of the soil-pipes and supply pipes, and see that openings are left in the proper places for the pipes to pass through them. 7. DAMPNESS IN CELLAR WALLS 127. GENERAL CONSIDERATIONS.— In many localities it is necessary to guard against dampness in cellar walls, particularly in buildings where the basement is used for living-rooms or for storage. There are several devices for preventing moisture from entering walls, some being applications on the outside and others being constructive devices. Where surface water only is to be provided against, and the ground is not generally saturated with water, coating the outside of the wall with asphalt or Portland cement will, in most cases, prove a preventative against dampness. 128. DAMP-PROOFING CELLAR WALLS.— Asphalt, ap- plied vv'hile boiling hot to the outside of a wall, is generally con- sidered a lasting and durable coating. To insure perfect protection^ the wall should be built as carefully as possible, the joints well pointed and the vvhole allowed to dry before the coating is applied. The asphalt should be applied in two or more coats and carried down to the bottom of the footings. If the soil is wet and generally saturated with water, moisture is apt to rise in the wall by absorption from the bottom. To prevent this, two or three thicknesses of asphal- tic felt, laid in hot asphalt, should be bedded on top of the footings, just below the basement floor, as shown by the heavy line, Fig. 77. Portland cement may be used in place of asphalt if the ground is not exceedingly damp ; but if it is often saturated with water, asphalt should be used. The objections to Portland cement are that it is easily fractured by any settlement of the Fig. 77. Cellar A\'aH, Damp-Proofed and Drained. no BUILDING CONSTRUCTION. (Ch. Ill)' walls, and being to some degree porous, suiters from the action of frost. Common coal-tar also is often used for coating cellar walls. It answers the purpose very well for a time, but gradually becomes brittle and crumbles away. 129, WATERPROOFING BASEMENTS.— It is frequently necessary in cities to construct dry basements in those localities in which water permeates the soil to within a few feet of the sidewalks. In such cases it is necessary not only to make the walls and floors waterproof, but also to give sufficient thickness to the floors that the buoyant force of the water will not cause it to break through. To make the cellar water-tight, its entire area should be covered with concrete from 3 to 6 inches thick, after the footings of the walls and piers are in, so that it will be level with the top of the footings. A narrow course of brick or stone should then be laid along the middle width of the footings to form a break, as shown in Fig, 78. Upon the top of the footings three thicknesses of tarred felt or burlap should then be mopped with hot asphalt, the felt being allowed to project 6 inches on each side. A similar layer of felt and asphalt should be laid over the footings of all piers, 'engine foundations, etc., and allowed to project at least 6 inches on all sides. After the exterior walls are completed, and before ^'filling in," the projecting felting should be turned up against them and mopped with hot asphalt ; and the entire outside surfaces to the sidewalk line should be covered with three thicknesses of felt laid breaking joints in hot asphalt and overlapping the felt coming through the walls. For further protection this covering is also frequently plastered with i to 2 Portland cement mortar. Before the completion of the building the entire cellar floor, also, should be covered with felt in hot asphalt, laid in at least three thicknesses, breaking joint and overlapping the felt first laid. On the top of the felt thus laid there should then be laid Portland A5phalt| Cement^ WalL if" BrcK 'orCoricrete'^ •m footingrg vr Fig. 78. Water-Proofed Basement Wall. DAMPNESS IN CELLAR WALLS. lit cement concrete at least i inch thick, for each 3 inches in depth of the water above the level of the cellar bottom, with a minimum depth of 6 inches. The following description of the waterproofing- of the basement of the Herald building, in New York City, is given as an actual example of the above method :* In this building the printing presses are placed in the basement, and great pains were taken to exclude moisture below grade. The footings and outside basement walls were covered with four-ply burlap mopped on solid,, commencing at the inner edge of sidewalk and back over top of vault and. down the outside of the wall to the bottom of the same, thence through the wall and turned up against same for connection to the waterproof course. Beneath the surface of the entire basement, including floor of vaults, the best four-ply roofing felt was mopped on solid, and similar material was used in connection with all piers, extending in each case through the entire thickness of the pier and beneath the entire surface of foundations for boilers and machinery. The felt was securely lapped and turned up around all walls. Above the felt 4 inches of concrete was laid in the basement and 16 inches in the boiler room. If less expensive, hard bricks laid in cement mortar and at least three courses in thickness, may be used instead of the concrete above the felt. 130. CONSTRUCTIVE DEVICES FOR DAMP-PROOFING FOUNDATION WALLS.— Of the constructive devices, the sim- plest is to make the excavation about 2 feet larger each way than the building, so that there will be about a foot or 10 inches between the bottom of the bank and the wall, as shown in Fig. 77. A V-shaped tile drain should be placed at the bottom of these trenches after the walls are built and connected with a horizontal drain, carried some distance from the building. The trenches should then be filled with cobbles, coarse gravel and sand. If the top, for a distance of about 2 feet from the building, is covered with stone flagging or cement, it will assist greatly in keeping the walls dry. By draining the soil in this way, and by also coating the walls with asphalt or concrete, perfectly dry walls will in most cases be insured. For greater protection of the basement from dampness, the base- ment walls should be lined with a 4-inch brick wall with an air * From the Engineering Record, July i, 1893. 112 BUILDING CONSTRUCTION. (Ch. Ill) space between the main wall and the lining ; or an area should be built all around the outside walls. 8. WINDOW AND ENTRANCE AREAS 131. WINDOW AREAS.— These features, although not strictly •' parts of the foundations, are intimately connected wdth them, and are generally included, in the same contract. The thickness and bracing of area walls has already been con- . sidered (see Article 121). The materials and workmanship of the walls should be the same as in the foundation w^alls. Window areas intended for light and ventilation should be of ample size, so as not to obstruct the light more than necessary. For small cellar windows sunk not more than 2 feet below the grade line, semi-circular areas with 9-inch brick walls give the greatest durability at the least expense. If an area is 3 or 4 feet deep, and as many in length and width, the thickness of its walls should be not less than 12 inches for brick and 18 inches for stone. Area walls should be coped with stone flagging, set in cement, the edge of the flagging projecting i inch over the faces of the walls. If flagging cannot be obtained without great expense the top of the walls should be covered with i to i Portland cement mortar, about ^ of an inch thick. Freestones and all porous stones are not suitable for area or fence copings. An area may be drained as follows : The bottom of the area should be carried at least 6 inches below the window sills and should be formed of stone flagging or of bricks laid in cement. Beneath the bottom a small cesspool or sand-trap, about 8 inches square, should be built, which should be connected by a 3-inch drain pipe with the main drain. A cast-iron strainer or drain-plate should be set over the cesspool, flush with or a little below the paving, so that it can be readily removed and the cesspool cleaned. Where the soil is of gravel or of a sandy nature, a dry drain may be used for an area at little expense. It consists of a vertical piece of salt-glazed tile sewer pipe carried from the cement bottom of the area to a point below the bottom of the footings. The lower end is left open and the upper end is either open or closed with a perfo- rated cover. The bottoiri of the area is graded to the drain, and the surface water is carried away by the pipe and allowed to seep into the soil below the footings, thus causing no damage. WINDOW AND ENTRANCE AREAS. 1^3 The footings of the area walls should be started as deep as the bottom of the cesspool, both being below the frost line. 132. ENTRANCE AREAS.— All area steps, when practicable, should be of stone, or of stone and brick combined.* When the soil is hard and compact and not subject to heaving by frost, a short Fig. 79. Entrance Area. Stone-and-P>rick Steps. run of steps may be economically built by shaping the earth to the rake of the steps and building them directly on the earth, laying two courses of bricks, in cement, for the risers, and covering them with 2-inch stone treads, as shown in Fig. 79. All parts of the steps A. i 1 Fig. 80. Sections Through Area Steps. should be set in cement, and well pointed, and the ends of the treads should be built into the side walls. If an area is 6 feet or more in depth, or if the soil is sandy or a wet clay, then it must be excavated beneath the steps and en- tirely surrounded by a wall. The steps may be formed of 2-inch stone risers and treads, or of solid stone, the ends in either case being supported by the side walls. If of solid stone the front of each step should rest on the back of the stone below it, as shown at A, Fig. 80. If built of treads and risers they may be arranged * Or of reinforced concrete (see Chapters IX and X.) t 114 BUILDING CONSTRUCTION. (Ch. Ill) as shown at either B or C. The arrangement shown at B is stronger than that shown at C. If the steps are more than 5 feet long a bearing wall or iron string should be built under the middle of the steps. Stone steps should always be pitched forward about ]4, of an inch in the width of the tread. In many localities plank steps, supported on plank strings, will last for a long time if the ground is excavated below them and the area walled up all around, and when they decay it is a small matter to replace them. The platform at the bottom of the steps should be of stone or brick, set at least 4 inches below the sill of the door giving entrance to the building, and should be provided with cesspool, plate and drain, as described in Article 131. All outside stone steps, fence coping, etc., should be set on a foun- dation carried at least 2 feet below grade, and in localities affected by frost below the freezing line. 133. CONSTRUCTION OF VAULTS UNDER SIDE- WALKS. — Vaults are often built under entrance steps and porches, the walls of the vaults forming the foundations for the steps and platforms. The roofs of the vaults are generally formed of brick arches, two rowlocks in thickness, with the stone steps set in cement mortar on top of the arches. Vaults under sidewalks may be either arched over with brick, the top of the arches levelled off with sand, cinders or concrete, and the sidewalks laid thereon, or the sidewalks themselves, if of large stone flags, may be made to form the roofs of the vaults. In the latter case the joints of the stone slabs are closely fitted and often rebated, then calked with oakum to within about 2 inches of the top and the remaining space filled with hot asphalt or asphaltic mastic. This makes a tight job for a time, but in the course of two or three years the joints need to be cleaned out and refilled. Any form of fire-proof floor construction may also be used for covering sidewalk vaults and a cement sidewalk may be finished on top of it. Cement makes probably the best walk and the most dur- able construction, with a comparatively slight thickness. In San Francisco it has been customary to build the sidewalks of cement, with steel tension-bars or cables imbedded in the bottom, 9. PAVEMENT VAULTS PAVEMENTS AND SIDEWALKS. so that the same construction answers both for the walk and for the covering of the vauh. If brick arches covered with sand and a stone or brick pavement are used, their tops should be covered with hot asphalt. 134. MUNICIPAL REGULATIONS REGARDING VAULTS. — In many cities the building regulations will not permit vaults to be extended under sidewalks unless certain restrictions are complied with. Generally vaults may be built out to what is known as the "area-line," usually 4 or 5 feet from the building-line, but even then there is sometimes a charge made for this privilege. Where vaults are permitted to be built out to the curbs a consider- able fee is charged by some cities, amounting in some cases to as much as twenty-five dollars a running foot. It is usual also, where vaults extend to the curb line, to restrict their height, keeping their roofs 4 or 5 feet below the pavement. These requirements are made by some municipalities in order to provide against interference with underground service wires, and other city installations. 10. PAVEMENTS AND SIDEWALKS 135. GENERAL CONSIDERATIONS.— Although these do not come under the heading of foundations they are more nearly related to that class of work than to any other, and may therefore be described here. Pavements may be made either of thin slabs of stone, called flag- ging, of concrete, finished with Portland cement, or of hard bricks made especially for the purpose. When large slabs of stone can be economically obtained, they make, in the long run, the most economical and satisfactory pave- ments. Smoother pavements may be made with cement. They are prac- tically imperishable; but should there ever be occasion to cut through them, or to change the grade, the cement and concrete must be destroyed, while the stone flagging can be taken up and relaid, either in the same place or somewhere else. A stone side- walk can be also be repaired more easily than either of the others. Stone Pavements. — As a rule only stones that split with com- paratively smooth and parallel surfaces can be economically used for pavements; for, if the surface of the stone has to be dressed, ii6 BUILDING CONSTRUCTION. (Ch. Ill) Flagging C^ffierit Section Through Stone Pavement. it will generally be more economical to use concrete and cement or hard bricks. For yards and areas, flagging from 2^ to 3 inches thick is com- monly used, the edges of the stones being trimmed so that they will be perfectly rectangular, and the joints between them straight and from % to }i inch in width. The stones should be laid on a bed of sand not less than 2 inches thick, and the edges should be bedded in cement, as shown in Fig. 81, extending 3 or 4 inches under them. On completion the joints should be thoroughly filled with i to i cement and fine sand, and struck smooth with the trowel. In localities where the soil is dry and not afifected by frost, as in Colorado, New Mexico, etc., the cement is generally omitted entirely, the stones being simply bedded in sand and the joints filled with fine sand. This answers very well in those localities ; but since, after a time, grass and weeds commence to spring up through the joints of pavements in yards and private walks, for first-class work, bedding in cement should be specified. Stone sidewalks are generally laid on beds of sand, with the joints in the better class of work bedded in cement. The stones, when 5 feet long, should be at least 3 inches thick, and when 8 feet long, 5 or 6 inches thick. The best sidewalks are laid in one course, unless exceptionally wide. In localities where the ground is affected by frost, as it is in most of the Northern States, the stones, if. merely laid on beds of sand, are sure to become displaced and out of level within one or two years. To prevent this, flagging stones, at least in front of busi- ness buildings, should have a solid support at each end. Fig. 82 shows the manner in which this is generally provided. Section Through Stone Sidewalk and Supports. CEMENT IVAEKS. and also the way in which the curb and gutter is supported. The curbstone should be at least 4 inches thick, and on business streets 6 inches. The dwarf wall should be about 14 or 16 inches thick and carried below the frost line. If the sidewalk is laid in two courses a light wall of brick or stone should also be built under the middle to support the butting ends of the stones, 136. CEMENT WALKS. — Cement walks are extensively laid in the Western States, even in localities where excellent flagging stone is abundant and cement rather dear. They are preferred on account of their smooth and even surface. When properly laid they are also very durable. They should be laid, however, wdiere there is no danger of the grade being altered, and only after the ground has become thoroughly settled and con- solidated. Their durability depends principally upon the thickness of the concrete and the quality of the cement. Only the best Portland cement should be used for the finishing, although natural cements are sometimes used for the concrete. Port- land cement throughout, however, is to be preferred. For first-class work cement walks should be laid as follows : The ground should be leveled off about 10 inches below the fin- ished grade of the walk and well settled by tamping or rolling. On top of this a foundation 5 inches thick should be laid of coarse gravel, stone chips, sand or ashes, well tamped or rolled with a heavy roller. The concrete should then be prepared by thoroughly mixing i part of cement to i part of sand and 3 of gravel, in the dry state, and then by adding sufficient water from a sprinkler to make a dry mortar. The concrete should be spread in a layer from 3 to 4 inches thick, commencing at one end, and should be thoroughly tamped. Before the concrete has commenced to set, the top or fin- ishing coat should be applied, and only as much concrete should be laid at a time as can be covered the same day. If the concrete gets dry on top the finishing coat will not adhere to it. The top coat should be prepared by mixing i part of high grade Portland cement with I part of fine sand, or i part of clean, sharp, crushed granite, the latter being the best. The materials should be thoroughly dry- mixed, and enough water added to give the consistency of plastic mortar. The coat should be applied with a trowel to a thickness ii8 BUILDING CONSTRUCTION. . (Ch. Ill) of I inch and carefully smoothed and levelled on top between- straight-edges laid as guides. Used in the above proportion, one barrel of Portland cement will cover about 40 square feet of con- crete. After the walk is finished it should be covered with straw to prevent it from drying too quickly. For brick paving see Article 331 and "Specifications for Brick- v^^ork" in Chapter XIIL 137. CURBING FOR SIDEWALKS.— Granite or concrete curbs may be used in conjunction with cement sidewalks. Where granite curbs are used they are either 6 inches or 8 inches in thick- ness, and from 24 inches to 36 inches in depth. The top surface and exposed gutter edge are hammer-dressed. It is the best modern practice, however, to provide cement-finished curbs in conjunction with well-constructed cement pavements. These curbs do not as a rule cost any more than granite curbs, and can be protected on the edge with a metal strip. In the illustration, Fig. 83, is shown a concrete curb, the edge being armored with what is known as the ''Wain- wright galvanized-steel cor- ner-bar." It is made with the section shown in the figure, and is tied into the concrete work at intervals with anchors or frogs. A curb of this kind finished, in place, costs from sixty cents to one dollar per lineal foot. Sometimes con- crete curbs are reinforced along the edges with rolled steel chan- nels, the web of the channel beinsf vertical. The channels are with Concrete Sidewalk Cvirb, Corner-Bar. with Steel anchored to the pronged anchors. concrete work at intervals II. SHORING, NEEDLING, UNDERPINNING AND BRACING 138. GENERAL CONSIDERATIONS.— The direction of these operations is generally left to the contractor, as the responsi- bility for the successful carrying out of the work devolves upon him. The architect will be wise, however, when such operations are be- SHORIXG. 119 ing carried on in connection with work let from his office, to see that proper precautions are taken for safety, and that all beams or posts have ample strength for the loads they have to support. When heavy or difficult work has to be done, it should, if possible, be intrusted to some careful person who has had experience in that class of work, as it is a trade by itself. 139. SHORING.— This means the supporting- of a wall of a building by inclined posts or struts, generally from the outside, while its foundations are being carried down, or while its lower portions are moved and girders substituted. The usual method of shorin the walls of buildings not ceeding three stories in he especially when the shorin done for the purpose of holding up the walls wh being underpinned, shown in Fig. 84. The props or shores inserted in sockets cut the wall, with their lower ends resting on timber cribs supported o n the ground. At least two sets of shores should be used, one to support the wall as low down as possible and the other to support it as high, up as pos- sible. . The latter shores should not have a spread at the bottom of more Steel Wedgesc ISectioni ^ ,. ■■ . ■ ■ stone. I ■ 1 Elevation Fig. 84. Shoring or Inclined Bracing and Underpinninj I20 BUILDING CONSTRUCTION. ■ (Ch. Ill) than one-third of their height. The platforms should be made t sufficiently large, so as not to bring too great a pressure on the ground ; and the shores should be driven into place bv oak or steel wedges. The shores should be spaced according to the height and thick- ness of the wall, and all piers and chimneys should be shored. Gen- erally a spacing of 6 feet between the shores will answer. Only a part of the foundation should be removed at a time, and as soon as three sets of shores are in place the wall should be under- pinned, as described in Article 141. As fast as the wall is under- pinned the first set of shores should be moved along, always keeping two sets in place, and working under or with one set. Shoring may often be successfully employed for holding up the corner of a building while a pier or column is being changed ; and sometimes when the lower part of the wall is to be removed and a girder slipped under the upper portion. In the latter case, however, needling is generally more successful and attended with less risk. 140. NEEDLING. — This term is given to the operation of sup- porting a wall, already built, on transverse beams or ''needles" placed in holes cut through it and supported at each end by posts, jackscrews or grillage. At least one end of each horizontal beam should be supported by a jackscrew. Wherever a long stretch of wall is to be built up at one time, and there is working space on each side of it, needling should be em- ployed. The beams must be spaced so near together that the wall will not crack between them, and the size of the beams must be carefully proportioned to the weight of the wall, floors, etc. Fig. 85. Needling. NEEDLING AND UNDERPINNING. 121 In very heavy buildings steel beams should be used for the needles, and thev should be spaced not more than 2 feet apart. In three- or four-story buildings the needles may be of large timbers spaced from 4 to 6 feet apart. Each chimney or pier should have one or more needles directly under it. When the first story walls or supports are to be removed, the beams or needles are usually supported on long timbers having screws under the ends ; or, if the wall is very high or thick, a grillage of timber is built up and the jackscrews are placed on top of the grillage, the ends of the needles resting on a short beam sup- ported by two screws, in the manner shown in Fig. 85. When it is desired fo remove the first story wall of a building for the purpose of substituting posts and girders, or for rebuilding the wall, holes should be cut in the wall from 4 to 6 feet apart, accord- ing to the weight to be supported and the quality of the brickwork or stonework, and at such a height that when the needles are in place they will come a few inches above the tops of the intended girders. Solid supports should then be provided for the uprights, the needles put through the wall, and posts, having screws in the lower ends, set under them, the bases of the screws resting on the solid supports pre- viously provided. If the needles do not have an even bearing under the wall, iron or oak wedges should be driven in until all parts of the wall bear evenly on the needles. The jacks should then be screwed up until the wall is entirely supported by the needles, care being taken, however, not to raise the wall after the weight is on the .needles. The wall below may then be removed, the girders and posts put in place, and the space between the girders and the bottom of the wall built up with brickwork, the last course of brick or stone being made to fit tightly under the old work. The needles may then be withdrawn and the holes filled up. 141. UNDERPINNING. — Underpinning means carrying down the foundations of an existing building, or, in other words, putting new foundations under the old ones. New footings may generally be put under a one or two-story building resting on firm soil without shoring or supporting the walls above, the common practice being to excavate spaces of only from 2 to 4 feet long under the wall, one at a time, sliding in the new footings and wedging up with stone, slate, or steel wedges. Where the underpinning is to be 3 feet or more high, or where i 122 BUILDING CONSTRUCTION. (Ch. Ill) the building is several stories in height, the walls should be braced or supported by shores or needles. The usual method of underpinning the walls of buildings where a cellar is to be excavated on the adjoining lot is shown in Fig. 84. Pits should first be dug to the depth of the new footings, and timber platforms built as shown ; the shores should then be put in place and wedged up with oak wedges. Sections about 3 feet wide between the shores should then be excavated under the wall, new footing stones laid, and the space be- tween the new and old footings filled with brickwork or stonework. Where the height between the new and old footings does not exceed 5 feet, granite posts, if available, offer special advantages for under- pinning. They should be from 12 to 18 inches wide on the face and of a thickness equal to that of the wall ; they should be cut so as just to fit between the new and old work, and with top and bottom surfaces dressed square ; and they should be set in a full bed of Port- land cement mortar, with the top joints also filled with mortar and brought to a bearing with steel wedges. If granite posts are not available, good flat stones, or hard bricks laid in cement mortar may be used instead, and wedged up under the old wall with pieces of slate or steel wedges driven into the upper beds of cement. Under heavy walls the latter wedges only should be used. If the bottom of the old footings is of soft brickwork, pieces of hard flagging, wnth full beds of cement mortar, may be placed under them, and the wedges driven under the flagging so as to bring the latter "hard up" under the old work. The portions of wall between these sections should then be underpinned in the same way and the shores moved along. Where granite posts are used they may be placed 3 feet apart and the space between built up with flat rubble or hard bricks, wedged up under the old wall with slate. If the soil under the old building is sufficiently firm, so that it will not cave or ''run away," and if there is working space beneath the lower floor, the ground may be levelled off, platforms of planks and timbers placed on top of it, and needles used for supporting the wall, as shown in Fig. 85. Where needles are used, all of the underpinning under the portion of wall supported may be put in at the same time. The underpinning should be done as quickly as possible after the shores or needles are in place, so as not to require their support for NEEDLING AND UNDERPINNING. 123 a longer time than necessary. The needles or shores should, how- ever, not be removed until the cement has had time to set. 142. NEW FOUNDATIONS UNDER OLD ONES.— In building modern tall office buildings foundations generally have to go below those of adjacent buildings, and, the ground being com- pressible, new party-wall foundations are almost invariably required. The consequence is that old walls have to be supported while new foundations are being put under them. This is usually done by means of steel needles placed from 12 to 24 inches apart, their ends resting on long beams placed parallel with the wall and supported by jackscrews. Very often an entire wall is supported in this way, several hundred jackscrews being required for the purpose. IS 'brick urati J'^ Floor "Jack Jcreu/s, Columns similar to the/* to be prouided when neu, building is put up on this side of partij u/alL Fig. 86. Wall and Footing, New York Life Insurance Company's Building, Chicago. In erecting buildings of skeleton construction it is often imprac- ticable to remove old walls, and new buildings are supported by iron columns placed against walls and resting on new foundations put in under the old ones. In building the New York Life build- ing in Chicago such was the case, and the adjacent wall, as shown in Fig. 8^, was held up by jackscrews, which were inserted to keep the wall in place during the settlement of the new work. As the new foundations settled the jacks were screwed up, so as to keep the old walls in their original position. In this case the jacks were left in place. 143. EXAMPLE OF HEAVY NEEDLING AND UNDER- PINNING. — An interesting example of foundation construction embodying the use of needle-beams in underpinning, is found in 124 BUILDING CONSTRUCTION. (Ch. Ill) Original 3urfa^^ 6-3k"Bolh Fulcnum Girder -6- 15" ^5'^^^^ Oak ^eparalvrj '(hrfi ^ lever Needles 3-15"!^ £7 ' loncf ^L/ne of Excavation for Underpinning Old South MeeHnghoU3e Bottom cf On^inai Tbunddbn Brjck Uqderpinning I Concrete Invert of Tunnel Bottom of 3tation Eycc^vahon Old^ South l^leeting House I Fig. 87. Heavy Needling and Underpinning, Old South Meeting House and Old South Building, Boston. connection with the construction of the subway tunnel in Boston. The Washington Street tunnel of the Boston Transit Commission Subway is parallel with and close to the front walls of the Old South Meeting-House and Old South building. It extended con- siderably below the foundations of both of these buildings, and it was necessary to provide an entrance to the Subway between their walls. Fig. 87 shows the ingenious construction employed in the opera- tion. To the left of the figure is the Old South building, which is an ii-story and basement office-building, of modern steel con- struction ; to the right of the figure is shown the heavy masonry wall and original foundation of the Old South Meeting House. In proceeding with the operation the earth was excavated between the buildings from the original surface to a depth of 9 feet. It was UNDERPIXXIXG. BRACING. 125 necessary to underpin about 80 feet of the wall of the Aleeting- House, and this was done by cutting holes in the walls at intervals of 15 feet, and inserting needle-beams consisting of three 15-inch I-beams, which projected into the wall of the Old South building, and were supported by the fulcrum girder about 25 feet long, con- sisting of six 15-inch I-beams supported on cribbing at each end. The needle-beams were hung from this girder by eight 3^-inch suspension-bolts, which were drawn up tight until the fulcrum girder had a deflection of about an inch. The weight of the Old South building provided the reaction on the long ends of the needles, which acted as double cantilevers. When the wall was thus sup- ported, the new concrete foundation wall was put in place, restin.^ upon the concrete invert of the tunnel, and the old wall of the Meet- ing-House was underpinned with brick between the top of the con- crete and the bottom of the wall. Each pier of the Old South building was underpinned separately, and was supported on a needle formed of six 15-inch I-beams set close together under the pier, and suspended from a cantilever fulcrum girder, made with nine 15-inch I-beams. In the same way, the Meeting-House wall was utilized fo provide the necessary reaction at the short ends of the cantilevers. After the weight of the pier of the Old South building had been transferred to the needles, a trench 8 feet long, parallel to the build- ing, was excavated under the wall and the fulcrum girders to a depth of 35 feet below the street level, and a concrete footing 13 feet in height was built in. This footing, or pier, was capped with brickwork, and the old foundation wall brought to a bearing with cast-iron plates and iron wedges driven in. After all of the concrete piers were in place the space between was excavated and concrete walls built between. 144. BRACING. — Where buildings have been built with a party-wall, and one of the buildings is torn down, leaving the adjacent walls unsupported, they should be protected from falling by either spreading braces or inclined shores, according to special conditions. Where there is a building on the opposite side of the vacant lot, and less than 40 or 50 feet away, the walls of both buildings may be best supported by spreading braces, in the manner shown in Fig 88. If the distance between the buildings does not exceed 25 feet, the 126 BUILDING CONSTRUCTION. (Ch. Ill) braces may be arranged as shown at A or B. If it exceeds 25 feet, the braces must be trussed in a manner similar to that shown at C Iron or steel rods are preferable for the vertical ties, as they can be screwed up, and any sagging caused by shrinkage in the joints can be overcome. If the buildings are very high every other story should be braced. The ends of the braces or trusses must be supported vertically, so that they will not slip down. When there are offsets in the wall they serve as vertical supports ; when there are no offsets, the braces should be supported by vertical posts, starting from the foundations, or sockets should be cut in the wall with corbels let in and bolted through from the inside. A truss should be placed in line with the fronts, and should be proportioned so as to resist the thrust from any arches there may be there. The braces should be about 8 by 8 or 10 by 10 inches in section, with 6 by 12 uprights against the wall, the ends of the braces being mortised into the uprights. If there is no wall opposite the building to be braced, inclined braces must be used, arranged like the shores shown in Fig. 84, only with a greater inclination. The ends of the braces should^)e brought to a bearing by oak wedges. Fig. 88. Spreading-Braces or Trusses. CHAPTER IV. Limes, Cements and Mortars. I. COMMON LIMES. 145. IMPORTANCE OF THE SUBJECT.— There is hardly any material used by the architect or builder upon which so much depends as upon mortar in its different forms, and it is important that the architect should be sufficiently familiar with the different kinds of limes and cements to know their properties, and to under- stand their adaptation to and suitability for different kinds of work. He should also be able to judge of the qualities of the materials with sufficient accuracy to prevent any which are actually worthless from being used, and he should have some knowledge of mortar mixing. 146. COMMON LIME. — Common lime, sometimes called quick- lime or caustic lime, has a specific gravity of from 2.3 to 3.15, is amor- phous, somewhat spongy, highly caustic, quite infusible, possesses great affinity for water, and if brought into contact with it will readily combine with about 30 per cent of its weight, passing into the con- dition of slaked or hydrated lime (Ca Ho Oo). It is produced by the calcination at moderate heat of limestones of varying composition. This is done by burning the stone in kilns of types varying according to the localities in which they are employed. For example, in the kilns of one type, the ''continuous, vertical, mixed-feed" kilns, the broken stone and fuel (generally coal) are put in in layers, the fire lighted at the bottom', and as the lime drops to the bottom new layers of stone and coal are put in at the top, so that the kiln may be kept burning for weeks at a time. The carbonic acid gas and any moisture in the stone are driven off and allowed to escape. The limestones from which limes and cements are produced differ greatly in their composition, ranging from practically pure carbonate of lime, such as oolitic and coquina limestone, white chalk and marble, to stones containing 10 per cent or more of impurities, such as silica, alumina (clay), magnesia (magnesium oxide), iron, and traces of the alka- lies, soda and potash. The quality of the lime will consequently de- pend much upon the percentage of impurities contained in the stone from which it is made. Strictly sneaking, magnesia should not be classed as an ''impurity," as it. simply se.rves to replace an equivalent 127 128 BUILDING CONSTRUCTION. (Ch. IV) amount of calcium carbonate. Lime is manufactured in nearly every State in the Union, each locahty generally producing its own supply. The only political divisions producing exceedingly small quantities of lime or no lime at all are Delaware, Louisiana, Mississippi, New Hampshire, North Dakota and the District of Columbia. There is considerable difference, however, in the limes of different localities, and before using a new lime the architect should make careful inquiries regarding its quality, and if it has not been much used it would be better to procure a lime of known quality, at least for plastering purposes ; for common mortar it is not necessary to be so particular. For commercial purposes limes have been classified as follows : 'Group A. — High-calcium limes : Limes containing less than 5 per cent of magnesia. The limes of this group differ among themselves according to the amount of silica, alumina, iron, etc., contained. A lime carrying less than 5 per cent of such impurities is a 'fat,' or 'rich' lime, as distinguished from the more impure 'lean' or 'poor' limes." ■^'Group B. — Magnesian limes : Limes containing over 5 per cent {usually 30 per cent or over) of magnesia. These limes are all slower slaking and cooler than the high-calcium limes of the preceding group, and they appear to make a stronger mortar. They are, however, less plastic or 'smooth,' and in consequence are disliked by workmen. As commercially pro- duced, they usually carry over 30 per cent of magnesia." The chemistry of lime-burning, reduced to its simplest terms, may be expressed as follows : 1. — For a limestone, absolutely pure. Limestone (Ca CO3 -j- heat = Ca O (high-calcium lime) -|- CO2 (carbon dioxide). 2. — For limestone containing magnesium carbonate, though other- wise pure: Limestone (Ca CO3, Mg CO3) + heat = Ca O, Mg O (magnesian lime) + CO2 (carbon dioxide). As an example of commercial quantitative values, 100 lbs. of pure limestone will give 56 lbs. of quicklime (CaO) and 44 lbs. of car- bon dioxide (COg) ; and 100 lbs. of limestone consisting of 60 per cent lime carbonate and 40 per cent magnesium carbonate, will give COMMON LIMES. 129 about 34 lbs. of lime (CaO), 19 lbs. of magnesia (MgO) and 47 lbs. of carbon dioxide (COo). In the Eastern cities lime is sold by the barrel, weighing for Rock- land, Me., lime 220 lbs. net; but in many parts of the country it is sold in bulk, either by the bushel or by weight. When shipped in bulk it is generally sold by the bushel of 80 lbs., 2^ bushels or 200 lbs. of lime being considered as equivalent to a barrel. Other weights are 230 lbs. net per barrel, .75 lbs. per bushel, and 64 lbs. per cubic foot. The following are average quantitative equivalents for one barrel of lime : 2^ barrels of paste, mortar silfticient for laying 3 perch of rubble stone or 1,000 to 1,200 bricks, plaster for 28 yards of 3-coat work or for 40 yards of 2-coat work. Lime will keep for a long time in bulk when the climate is very dry, but it soon slakes in damp climates, for example, along the sea coasts, unless enclosed in barrels. 147. CHARACTERISTICS OF GOOD LIME.— Good lime should possess the following characteristics: i. Freedom from cinders and clinkers, with not more than 10 per cent of other im- purities. 2. It should be in hard lumps, with but little dust. 3. It should slake readily in water, forming a very fine, smooth paste, without any residue. 4. It should dissolve in soft water. There are some limes which leave a residue consisting of small stones and silica and alumina in the mortar box, after the lime is drained off. Such limes may answer for making mortar for build- ing masonry, but should not be used for plastering if a better quality of lime can be procured. 148. SLAKING AND MAKING INTO MORTAR.— The first step in the manufacture of lime mortar consists in the slaking of the lime. During the operation of lime-slaking the chemical combina- tion that takes place may be expressed by the formula: Lime (CaO) + water (H2O) — lime hydrate (CaOoHg). Lime hydrate is a fine white powder, with specific gravity of 2.078. When quick- lime is slaked at the building operation, the ordinary practice is to do the slaking either by putting the lime in a water-tight box and adding water through a hose or by pails, or by forming on a plank • floor or on a bed of sand, a circular wall of sand, shovelling into the ring thus formed the lime, and turning on the water from a hose. When the process of slaking is completed the slaked lime is covered with a layer of sand until wanted. Different limes require different I30 BUILDING CONSTRUCTION. (Ch. IV) volumes of water for slaking. The water is rapidly absorbed by the lime, causing a great elevation of temperature, the evolution of hot and slightly caustic vapor, and the bursting of the lime into pieces; and finally the lime is reduced to a powder, the volume which is from two to three and a half times the volume of the original lime. In this condition the lime is said to be slaked and is ready for making into mortar. The best limes slake without leaving a residue. The mortar is made by mixing clean, sharp sand with the slaked lime in the proportion of i part of lime to from 2 to 5 of sand by volume. The New York Building Code requires that not more than 4 parts of safid to i part of lime shall be used. Practically the proportion of sand is seldom, if ever, measured, but the sand is added till the person mixing the mortar thinks it is of the proper proportion. For brickwork over a certain proportion of sand cannot well be added, for if there is too much sand in the mortar it will stick to the trowel and will not work easily. With stonework the temptation is always to add too much sand, as sand is generally cheaper than lime. The architect or superintendent should take pains to make himself familiar with the appearance of good mortar, so that he can readily tell at a glance if it has too much sand. Mortar that contains a large proportion of lime is said to be rich ; if it has a large proportion of sand and works hard it is said to be stiff, and to make it work more readily it is tempered by the addition of water. Tempered mortar looks much richer than stiff mortar, though it may not be so. If the mortar slides readily from the trowel it is of good quality, but if the mortar sticks to the trowel there is too much sand in proportion to the lime. The color of the mortar depends much upon the kind and color of the sand used. Some limes when slaked leave a residue of stones, lumps and gravel, so that instead of mixing the mortar in the same box in which the lime is slaked, a larger proportion of water is added, and the slaked lime and water (about as thick as cream) is run off through a fine sieve into another box, in which the mortar is mixed.. Such lime does not make as good mortar as that which leaves no impuri- ties, but it is sometimes used in ordinary brickwork and stonework. The general custom in making lime mortar has been to mix the sand with the lime as soon as the latter is slaked and to let it stand • until required for use. Much stronger and better mortar will be obtained, however, if the sand is not mixed with the slaked lime until the mortar is needed. COMMON LIMES. 148a. HYDRATED LIME.— When quicklime is slaked on the work, it is usually done by careless laborers in a very indifferent manner, and the slaked lime seldom reaches a condition of theo- retical efficiency. In order to overcome this difficulty, ready-slaked lime, carefully prepared at the lime-plants, has been introduced dur- ing recent years. This is placed on the market under the names of '^new-process lime," ''hydrated lime," *iimoid," etc. Its manu- facture involves the grinding of the lump quicklime to a fairly uni- form, small size ; the thorough mixing of the resulting grains of powder with the proper proportion of water ; and the teduction of the slaked lime to a uniform fine powder by passing it through a sieve or by using other methods. The product is generally sold in either heavy, closely woven bur- lap or duck bags, containing 100 pounds, 20 bags to the ton, or in paper bags containing 40 pounds, 50 bags to the ton. It gains in weight during the process of manufacture, one ton of quicklime (2000 pounds) giving from 2400 to 2600 pounds of hydrated lime. 148b. HYDRATED LIME AND PORTLAND CEMENT MIXED. — Very interesting tests have been made on the strength of a mixture of hydrated lime and Portland cement, and the results show some very interesting data. Up to certain limits the addition of hydrated lime to Portland cement mortar makes the latter easier to work and more plastic ; but the most interesting result noticed is an actual increase in tensile strength when the addition does not exceed 10 or 20 per cent. 149. SAND. — The reason sand is used in mortar is because it prevents excessive shrinkage and reduces the cost of the lime or the cement ; and while its addition to cement mortar always weakens it, its addition to lime mortar in the proportion of i to 2, for example, adds to the latter's strength. Sand is obtained from river beds, from the seashore and from banks or pits. Pit or bank sand, clean, is generally considered the best for mortar. Excellent sand, however, is often obtained from river beds. The objection to sea sand is the alkaline salt it contains, which attracts and retains moisture and causes dampness in walls. The usual specifications for sand used in making mortar require that it shall be angular in form, of various sizes, and absolutely free from all dust, loam, clay, earthy or vegetable matter, and also from large stones. Recent tests and experiments, however, seem to lead engineers to 132 BUILDING CONSTRUCTION. (Ch. the following conclusions : ( i ) It is not necessary to have the grains sharp; (2) the coarseness of the grains governs largely the quality; (3) in mortars loam or clay is sometimes injurious, and sometimes beneficial, at least in cement mortars ; (4) the pouring of water into sand does not accurately determine the voids, which can be found by weighing the sand and finding its moisture; (5) be- cause of the effect of varying degrees of moisture, a study of voids does not result in a method of comparing sands; (6) dry sand meas- ured loose is heavier than moist sand; (7) when mixed with cement coarse sand nfakes a denser mortar and requires less water than fine sand; (8) fine sand with grains of uniform size, and screened coarse sand when dry, have nearly the same weight, but with ordi- nary moisture fine sand is lighter and more porous than coarse sand ; (9) the weight of mixed sand is usually greater and the volume of voids smaller than that of coarse or fine sand. It is generally necessary to pass the sand through a screen to secure the proper degree of fineness. For rough stonework a com- bination of coarse and fine sand makes the strongest mortar. For pressed brickwork it is necessary to use very fine sand. The archi- tect or superintendent should carefully inspect the sand furnished fcr the mortar, and if he wishes to test its cleanliness, a handful put in a tumbler of water will at once settle the question, as the dirt will separate and rise to the top. Another simple method of testing sand is to squeeze some of the moist sand in the hand, and, if upon opening the hand the sand is found to retain its shape, it must contain dirt or loam or clay, but if it falls down loosely it may be considered as clean. Sand containing loam or clay is usually rejected and ordered from the premises, and it is safe for the architect to work on the principle that loam or clay, if in sufiicient quantity to be detected by the touch, or appearance, or* by leaving a stain when rubbed between damp hands, is harmful, and tends to weaken the cementing material in the case of most lime mortars, whatever may be the effect of small percentages in the case of certain cement mortars. As a rule, it is better that the sand should be too coarse than too fine, as the coarse sand takes more lime and makes the stronger mortar. Some masons attempt the use of fine sandy loam in their mortar, as it takes the place of lime in making the mortar work easily ; but it generally tends to weaken the mortar, and it is better not to permit its use. The specific gravity of dry sand may be taken at 2.65. 150. WHITE AND COLORED MORTARS.— White and col- COMMOX LIMES. 133 ored mortars to be used in laying face bri(?lvs should l)c made from lime paste or putty and finely screened sand. After the slaked lime has stood for several days the water evaporates and the lime thickens into a heavy paste, much like putty, from which it takes its name of 'iime putty." By the time the putty is formed the lime should be well slaked and have no tendency to swell or "pop." Colored mortar is made by the addition of mineral colors to the white mortars. Col- ored mortar should never be made with freshly slaked lime, but only with lime putty at least three days old. For IMortar Colors see Articles 216 to 219. Clear lime putty may be kept for a long time in casks, for use in making colored mortar, only a little mortar being made up at a time. Common lime when slaked and evaporated to a paste may be kept for an indefinite time in that condition without deterioration, if pro- tected from contact with the air so that it will not dry up. It is cus- tomary to keep the lime paste in casks or in the boxes in which it was slaked, covered over with sand, to be subsequently mixed with it in making the mortar. 151. SETTING OF LIME MORTAR.— Lime mortar does not set like cement mortar, but gradually absorbs carbonic acid from the air and becomes in time very hard ; the process, however, requires from six months to several years, according to the thickness of the mortar and its exposure to the atmosphere. If permitted to dry too quickly it never attains its proper strength. If frozen, the process of setting is delayed and the mortar is much injured thereby. Alter- nate freezing and thawing will entirely destroy the strength of the mortar. Lime mortar will not harden under water, nor in continu- ously damp places, nor when excluded from contact with the air. In regard to all the phenomena of the process of the setting of lime mortar in their minutest details, there does not seem to be as yet a complete unanimity of opinion on the part of those who have made the subject one of special study. There is a general agreement that the chemical changes take place for the most part at the outer and exposed portion of the lime-mortar joints, and that the mortar in the interior of a wall never acquires what might be called **com- plete hardness," or at least not until after the lapse of long periods of time. Some investigators, for example, emphasize the fact of the prob- able chemical action that takes place between the sand and the lime, and the resulting formation of lime silicates ; while others claim that 134 BUILDING CONSTRUCTION. (Ch. IV) the effect of this is very 'IHght and of Httle engineering importance. One authority, Mr. Edwin C. Eckel,* states that ''the hardening of Hme mortars is a simple process. It may be accepted as proven that lime mortars harden by simple recarbonation, the lime gradually absorbing carbon dioxide from the atmosphere, and becoming, in fact, artificial limestone. As this absorption can take place only on the surface of the masonry, the lime mortar in the interior of a wall never becomes properly hardened. In this process the sand of the mortar takes no active part. It is merely an inert material, added solely in order to prevent shrinkage and consequent cracking." Professor Clifford Richardson, one of the highest authorities on questions of this kind, says : *'The setting of lime mortar is the result of three distinct processes which, however, may all go on more or less simultaneously. First, it dries out and becomes firm. Second, during this operation, the calcic hydrate, which is in solution in the water of which the mortar is made, crystallizes and binds the mass together. Hydrate of lime is soluble in 831 parts of water at 78° Fahr. ; in 759 parts at 32° and in 1 136 parts at 140°. Third, as the per cent of water in the mortar is reduced and reaches five per cent, carbonic acid begins to be absorbed from the atmosphere. If the mortar contains more than five per cent this absorption does not go on. While the mortar con- tains as much as 0.7 per cent the absorption continues. The resulting carbonate probably unites with the hydrate of lime to form a sub- carbonate, which causes the mortar to attain a harder set, and this may finally be converted to a carbonate. The mere drying out of mortar, our tests have shown, is sufficient to enable it to resist the pressure of masonry, while the further hardening furnishes the necessary bond." Mr. C. F. Mitchellf gives a simple statement of the chemistry of lime mortar setting, as follows : ''The setting of lime depends on the absorption of CO2 from the atmosphere by the particles of slaked lime in solution in the mortar, the carbon dioxide being soluble in water. The CaO and CO2 com- bine to form crys.tals of CaCOg, these being deposited, and giving up the H2O, which combines with the next particle, forming it into a saturated solution, rendering it into the necessary condition to take up another molecule of CO, ; this in its turn crystallizes and * "Cements, Limes and Plasters." Edwin C. Eckel. + "Building Construction." Charles F. Mitchell. COMMOX LIMES. 135 is deposited ; this process is repeated till the whole has set. The crystals always have a tendency to adhere to something rough and hard, such as sandy particles or the surfaces of bricks ; for this reason the addition of sand up to a certain ratio increases the strength of the mixture, the best ratio being one part pure lime to one of sand, the maximum being one of pure lime to three parts of sand. long time elapses before pure limes harden, owing to their depending upon external aid to attain this state. If lime alone were used the surface would set and form an impervious layer, and so check the CO2 from acting on those particles below the surface, the moisture in which evaporates and leaves the same in the state of a powder; and even when a large proportion of sand is used and the mass made porous, the supply of COg must necessarily be small, and a long time elapses before the material hardens. Pure lime mortar built in thick walls never hardens nor sets, but crumbles into a friable powder. 'Tor this reason pure limes should be avoided for constructional work, and a lime or cement which does not depend on external aid to set be used." 152. PRESERVING LIME.— Fresh burned lime will readily absorb moisture from a damp atmosphere, and will in time become slaked, thereby losing all of its valuable qualities for making mortar. It is therefore important that great care should be taken to secure freshly burned lime and to protect it from dampness until it can be used. If the lime is purchased in casks it should be kept in a dry shed or protected by canvas, and if it is bought in bulk it should be kept in a water-tight box built for the purpose. On no account should the superintendent permit the use of air- slaked lime, as it is impossible to make good mortar with it. 153. DURABILITY OF LIME MORTAR.— Good lime mortar, when protected from moisture, has been considered by many archi- tects to have sufficient strength for ordinary brickwork above ground, except when heavily loaded, as in piers. It continues to grow harder and stronger for many years after it is in place. The writer knows of old walls in which the lime mortar was as strong as the bricks, and where the adhesion of the mortar to the bricks was greater than the cohesion of the particles of the bricks. A specimen of mortar, supposed to be the most ancient in exist- ence, obtained from a buried temple on the island of Cyprus, was 136 BUILDING CONSTRUCTION. (Ch. IV) found to be hard and firm, and upon analysis appeared to be made of a mixture of burnt lime, sharp sand and gravel, some of the frag- ments being about ^ an inch in diameter. The lime was almost completely carbonized."^' Lime mortar, however, attains its strength slowly, and where high buildings are built rapidly the mortar in the lower story does not have time to get sufficiently hard to sustain the weight of the upper stories, and for such work cement should be added to the lime mortar. Some cities limit the use of lime mortar to the brickwork of chim- neys in frame buildings, but the building laws of many cities allow its use in all but fire-proof buildings. The allowable stress, however, is limited, for example, in the case of brick piers in one case, to seven tons per square foot. For the brickwork of ordinary buildings, and for light rubble foun- dations, lime and natural cement mortar forms a suitable and fre- quently used mixture ; and when a still superior quality and strength are wanted, lime and Portland cement mortar is used. Beyond these come the natural and Portland cement mortars without the lime. 2. HYDRAULIC LIMES. 154. GENERAL DESCRIPTION.— Hydraulic limes are those containing, after burning, enough lime to develop, more or less, the slaking action, together with sufficient of such foreign constituents as combine chemically with lime and water, to confer an appreciable power of setting under water, and without access of air. The process of setting is entirely different from that of drying, which is produced simply by the evaporation of the water. Setting is a chemical action which takes place between the water, lime and other constituents, causing the paste to harden even when under water. Hydraulic lime or cement should not be used after it has com- menced to set, as the setting will not take place a second time and the strength of the mortar will be lost. In the hydraulic limes used for making mortar, the constituent which confers hydraulicity is clay, or more correctly, the silica con- tained in the clay. Mr. Edwin C. Eckel statesf that "theoretically the proper compo- sition for a hydraulic limestone should be calcium carbonate 86.8 ♦William Wallace, Ph.D., F. R. S. E., in London Chemical Nervs, No. 281. t "Cements, Limes and Plasters." Edwin C. Eckel. HYDRAULIC LIMES. 137 per cent and silica 13.2 per cent. The hydraulic limestones in actual use, however, usually carry a much higher silica percentage, reaching at times to 25 per cent, while alumina and iron are commonly present in quantities which may be as high as 6 per cent. The lime content of the limestones commonly used varies from 55 per cent to 65 per cent." The same authority gives'^ another definition of hydraulic limes as follows : "The hydraulic limes include all those cementing materials (made by burning siliceous or argillaceous limestones) whose clinker after calcination contains so large a percentage of lime silicate (with or without aluminates and ferrites) as to give hydraulic properties to the product, but which at the same time contains normally so much free lime (CaO) that the ma^s of clinker will slake on the addition of water." Commercial as well as theoretical differences make it convenient to divide the true hydraulic limes into two groups, the classification depending upon the extent to which the so-called impurities of the limestone are present, reduce the slaking action, and confer upon the lime the property of setting under water. These groups are 1. Eminently hydraulic limes. 2. Feebly hydraulic limes. . During the calcination of the eminently hydraulic limes a by- product is produced. This is usually put on the market separately, and is known as ''grappier cement." By treating the feebly hydraulic limes with sulphuretic acid accord- ing to the formulas of a special process developing new properties, a secondary product results, which also is marketed separately as ''selenitic lime," or ''Scott's cement." This cement cannot compete with the excellent natural cements of the United States. The following is an analysisj of a typical hydraulic lime, after slaking : Silica (Si O^) 22.0 Alumina (Al^ O3) 2.0 Iron Oxide (Fe^ O3) 2.0 Lime (Ca O) 62.0 Magnesia (Mg O) 1.5 Sulphur trioxide (S O3) 0.5 Carbon dioxide (C O^) 0.0 ) Water lo.o f 100.0 * American Geologist, March, igo-', p. 152. t Le Chatelier, Trans. Am. Inst. Min. Engrs., vol. 22, p. 16. 138 BUILDING CONSTRUCTION. (Ch. IV) Artificial hydraulic lime can be manufactured by mixing together, in proper proportions, soft chalk or thoroughly slaked common lime . and unburnt clay, then burning and grinding in much the same manner as in the manufacture of Portland cement ; but as the process of manufacture is nearly as expensive as for making Port- land cement it is more profitable to make cement, on account of its superior hydraulic energy. A very simple experiment will determine if a lime is hydraulic or not : Make a small cake of the lime paste, and after it has com- menced to stiffen in the air, place it in a dish of water so that it will be entirely immersed. If it possesses hydraulic properties it will gradually harden, but if it is not hydraulic it will soften and dissolve. Limestones with a composition suitable for making hydraulic lime are very common in England and on the Continent of Europe, the siliceous and argillaceous limestones of Teil, in France, being among the most noted. As hydraulic limes are usually only feebly hydraulic when compared with good natural cements or Portland cements, and as the United States is rich in materials suitable for the manufacture of natural cements, these hydraulic limes have never been manu- factured in this country and they have never been known as an article of commerce, although the importations each year are considerable. 155. LAFARGE CEMENT. — Among the non-staining cements, the Lafarge Cement is the best known, and has been on the American market for many years. It is a grappier cement of very satisfactory composition, made at Teil, France, and belongs in the class of emi- nently hydraulic limes. These latter and the grappier cements have a relatively small percentage of iron and soluble salts, and besides being light colored, do not stain masonry, built, for example, of marble, limestone and other porous stones. They are unlike Portland and Rosendale cement in this respect, and hence are especially desir- able in setting such stones. This non-staining property is possessed also by some of the foreign Puzzolan cements. For setting large stones, mix i part by volume of lime paste to 4 parts of the cement, to retard the setting of the cement until the stones are well bedded. NATURAL CEMENTS, 139 The following are the analyses of two typical Lafarge cements* : (I) (2) Silica (Si O^) 3110 27.38 Alumina (Al^ O3) (4.43 2-6i Iron Oxide (Fe^ O3) ( 2.15 1.02 Lime (Ca O) 58.38 58.38 Magnesia (Mg O) 1.09 0.46 Alkalies (K^ O, Na^ O) 0.94 n. d. Sulphur trioxide (S O3) 0.60 0.43 Carbon dioxide (C O^) j 1.28 j n. d. Water ( n. d. ( n. d. 156T NON-STAINING CEMENTS IN GENERAL.—The following is a typical specification for these cements: "Non-stain- ing cement n^ust be of a brand that has been in use for at least two years to test its non-staining qualities, have a specific gravity of not less than 2.75, contain not more than 2 per cent of sulphuric acid, nor more than 3 per cent of magnesia, be of such fineness that 85 per cent will pass through a No. 100 standard sieve, and in bri- quettes of neat cement, when tested as usually specified for Port- land cement, have a tensile strength of 200 pounds per square inch. All cement must be of uniform quality, and when delivered must be in original packages with the brand and maker's name marked thereon, and must be kept dry." 3. NATURAL CEMENTS. 157. -CLASSIFICATIONS OF CEMENTING MATE- RIALS. — Cementing materials in general may be classified as I, Common Limes; 2, Hydraulic Limes; 3, Natural Cements; 4, Portland Cements ; 5, Puzzolans or Slag Cements. They also naturally fall into two groups; non-hydraulic cement- ing materials and hydraulic cements. To the first group belong Plaster of Paris, Keene's Cement, cement plaster, common lime, etc., and to the second group belong all but the first of the above men- tioned five subdivisions. Having considered the common limes and the hydraulic limes, the natural cements will be considered in the next article. A" comparison of the compositions of the different cementing materials, excluding the plasters, will aid in making the basis of the classification clear, and the following is a tablef giving some typical analyses: * (i.) C. F. McKenna, analyst, 1897. *(2.) Engineering News, vol. 47, p. 23., Jan. 9, 1902. t "Concrete, Plain and Reinforced." Taylor and Thompson. I40 BUILDING CONSTRUCTION. (Ch. IV) TABLE IX. Typical Analyses of Cements. Portrnd Cement 'Si Silica (Si Oa> Alumina (AI2 O3) Iron Oxide (Fe^ O3) Calcium Oxide (Ca O) Magnesian Oxide (Mg O), Sulphuric Acid (S O3) Loss on Ignition Other Constituents 31.31 2.53 62.89 2.64 1.34 1.39 0.75 Natural Cement American c3 O 21.931 5.98 2.35 62.92 1.10 1 54 2.91 18.38 15.20 - a5.84 14.02 0.93 3.73 11.46 ^3 Eng French 20.42 4.76 3.40 46.64 12.00 2.57 6.75 3.74 25.48 10.30 7.44 44.54 2 92 2;6i 3.68 1.46 2^.60 8.90 5.30 52.69 1.15 3.25 6.11 26.5 2.5 1.5 63.0 1.0 0.5 5.0 28.95 .40 .54 .29 .96 If 21.70 3.19 0.66 60.70 0.85 .37 0.60 .39 13.20 .30 0.10 1. W. F. Hildebrand, Society of Chemical Industry, 1902, Vol. XXI. 2. W. F. Hildebrand, Journal American Chemical Society, 1903, 25, 1180. 3. Clifford Richardson, Brickbuildcr, 1897, p. 229. 4. Stanger & Blount, Mineral Industry, Vol. V, p. 69. 5. Candlot, Ciments et Chaux Hydrauliqu^s, 1898, p. 174. 6. Le Chatelier, Annales des Mines, September and October, 1893, p. 36. 7. Report of the Board of U. S. Army Engineers on Steel Portland Cement, 1900, p. 52. 8. Candlot, Ciments et Chaux Hydrauliques, 1898, p. 24. 9. Rockland-Rockport Lime Company. 10. Western Lime and Cement Company. 158. DEFINITION OF NATURAL CEMENT.— Natural cement is the product resulting from the burning and subsequent pulverization of a natural clayey limestone containing from 15 to 40 per cent of silica, alumina and iron oxide. There is no prelimi- nary mixing and grinding. The temperature of the burning is about that of the ordinary lime-kiln, and not sufBcient to cause vitrifica- tion. Almost all ' of the carbon dioxide is driven ofif, there is a combination of the lime with the silica, alumina and iron oxide, and the formation of a mass containing silicates, aluminates and ferrites of lime ; or in case the original rock contains magnesium carbonate, the formation of magnesia and magnesian compounds. As this resulting mass, as it comes from the kiln, will not slake if water be poured on it, it is ground into a fine powder, which, when mixed with water, hardens or sets rapidly either in air or in water. The property of hydraulicity, as in the case of all silicate cements, is due principally to the formation of tricalsic silicate (3CaO, Si02). NATURAL CEMENTS, 141 159. EARLY USE OF NATURAL CEMENTS.— Cements in general have been used from the earhest known civiHzations. The Egyptians, Carthagenians and Romans knew their properties and employed them in their works. Recent discoveries seem to point to a practical knowledge of their value possessed by the ancient peoples of Mexico and Peru. After an apparent general loss of the art of their manufacture during the Middle Ages and early modern times, it appears to have been rediscovered about the middle of the eighteenth century, on the occasion of the build- ing of the Eddystone lighthouse, when John Smeaton, the en;^ineer in charge, produced a good hydraulic lime or natural cement from argillaceous limestones. In England, again, just at the beginning of the nineteenth century, the so-called "Roman Cement," a natural cement made by calcining and grinding nodules of clayey lime car- bonate, called "septaria," found in the clay, was introduced by Joseph Parker. About this time natural cement was manufactured in France. The first natural cement made in the United States was that manufactured for use in the building of the Erie Canal. It came from a natural rock in New York State, Madison County, and was introduced by, Canvas White in 1818. The increase in its use was steady from that time until about 1900, since which date there has been a decline in the output, caused by the reduction in cost and consequent increase in use of American Portland cement. The pro- duction of natural cement in 1906 was 4,055,797 barrels, valued at $2,423,170, and declined as compared with the output of the pre- ceding year. The industry fluctuated between a production of 7,000,000 and 8,000,000 barrels from 1900 to 1904, when it fell to a little more than 4,500,000 barrels. In 1905 it decreased to a little less than 4,500,000 barrels. 160. DISTRIBUTION OF NATURAL CEMENTS IN THE UNITED STATES. — "In no other country in the world is there to be found cement rock formations which are at all to be compared with those so well distributed throughout the United States. . . . Here we have immense beds of cement rock absolutely free from any extraneous substances, perfectly pure and clean, with layer upon layer, extending for thousands of feet without appreciable variation in the proportion of the ingredients."* There is a very wide distribution throughout the United States, geologically and geographically, of clayey limestones whose chemical * TJriah Cummings in the Brickbuilder. BUILDIXG COXSTRUCTION. (Ch. IV) composition is such that they may be used in the manufacture of natural cement, and this product has been made, in small or large amounts, and at different periods, in almost every State in the Union. But in order that a natural cement industry may become well estab- lished in any given locality, the rock maist be fairly steady in chem- ical composition throughout the strata, the material must be cheaply mined or quarried, the cost of fuel must not be too high, freight must be reasonable and a steady local demand prevail. It is the absence of these requisites in many districts where there are valuable natural cement rock deposits which explains the reason for the relatively few localities in which this industry has become concen- trated. The cement is commonly known by the name of the place from which the stone is obtained, although, as there are often several manufactories in the same locality, there may be several brands of cement made from the same rock. The difference in the quality of such brands is often due to the care exercised in their manufacture. The principal localities arranged by States in which natural cements are made in the United States are as follows : Nezv York. — "In the State of New York natural cement is manufactured in four localities. In the order of their importance they are: (i) the Rosen- dale district in Ulster County, (2) the Akron-Buffalo district in Erie County, (3) the Fayetteville-Manlius district, for the most part in Onondaga County, .and (4) at Howe's Cave in Schoharie County." The term, "Rosendale Cement," has been heard in New York and New England more frequently than the term "Natural Cement," because Rosendale, Ulster County, N. Y., was one of the towns in which this cement was first made. As a matter of fact, for a time, all natural cements in the United States were called "Rosendale Cement." Owing to the length of time for which it has been used, and the special advantages enjoyed for transportation and nearness to the great building centers of the country, Rosendale cement has perhaps been more widely known than any other of the natural cements. The New York cements are generally of a very good quality and well suited for building operations. Indiana-Kentucky.— 'The. plants of the 'Louisville district' are for the most part located in Indiana, though one or two mills are in operation on the Kentucky side of the Ohio River." It is probably the leading natural cement beyond the Alleghenies, the product being exceeded only by the production from New York State. There are several brands of this cement in the market, and they find their way as far west as the Rocky Mountains. Illinois.— NesiT Utica, La Salle County, Illinois, a natural cement has * For a very complete account of the distribution of the American Natural-cement Rocks, and detailed analyses of the same, see "Cements, Limes and Plasters," by Edwin C, Eckel. NATURAL CEMENTS. 143 been manufactured since 1838. This cement has always stood well in public favor, and is largely used throughout the West. Wisconsin. — "Two plants in Wisconsin are engaged in the manufacture of natural cement from a clayey magnesian limestone, located north of Mil- waukee, near the Lake." Minnesota. — A cement rock of good quality exists at Mankato, and the manufactured product has obtained a foothold in the markets of the Northwest. There is a second plant located at Austin. Georgia. — "Two natural cement plants are located in Northwest Georgia, but they use cement rocks from two different geological formations, and their raw materials and products differ widely in composition." The cement manu- factured from stone quarried at Cement, Bartow County, "probably has no^ superior in this country. Used as an exterior plaster on a house in Charleston in 1852, the stucco still remains unimpaired, while the sandstone lintels over the windows have long since been worn away." Kansas. — A natural cement has been manufactured near Fort Scott since 1867. A bed of natural cement rock, feet thick, outcrops at this place. It is a dark-colored, fine-grained, compact limestone of the Carboniferous age, and extends for a considerable distance throughout the State. North Dakota. — A lo-foot bed of soft, chalky limestone rock of the Cretaceous age is being mined for a natural cement plant located in Cavalier County. Ohio. — At different points in Ohio, notably at Defiance and New Lisbon, there are some small natural cement plants. At the former plant a black calcareous shale of the Devonian age is used, and in regard to this Mr. Edwin C. Eckel states in his "Cements, Limes and Plasters" that if published analyses be correct, this rock is by far the most argillaceous material used anywhere for this purpose. Texas. — Two natural cement plants have been started in Texas, but the analyses published would seem to show that the product obtained by burning a rock of the chemical composition indicated would be a weak hydraulic lime and not a true natural cement, according to the classifications at present in use. An extended description of the natural cements manufactured in this country prior to 1895 was given in a series of articles by Uriah Cummings in the Brickbuilder for that year. 161. EUROPEAN NATURAL CEMENTS.— These are man- ufactured in almost all the countries of Europe, but as the products are inferior to the little less costly Portland cement, the latter are gradually driving them out of the market. They also have to compete with the better class of hydraulic limes. European natural cements may be divided into two classes, . called respectively (i) ''Natural Portland Cements" and (2) **Roman Cements." 144 BUILDING CONSTRUCTION. (Ch. IV) (1) The European natural Portland cements are made from a natural rock and have a small percentage of magnesia. They are burned at a fairly high temperature, and as regards their physical properties and chemical analysis, they are somevv^hat similar to the true Portlands. But as they are not very carefully and finely ground artificial mixtures made before burning, and will not pass any but the low-grade Portland tests, they cannot be classed with the true Portland cements. (2) The Roman cements form a second class of European natural cements, and they usually, although not always, have a rela- tively low percentage of magnesia in their chemical composition. In some respects these products approach the best of the American natural cements, at least as far as their ''cementation index" is concerned. In Belgium a quick-setting cement, called a ''Roman Cement," is one of the especial products of the immense quarries in the calcareous district of Tournai. In England, stones which burn naturally to cements are to be found to a large extent in certain districts, notably as rounded lumps or nodules of clayey lime carbonate, and called "septaria." T^ese nodules are embedded in the clay of the south of England, in the shale beds of the Lias formation, and along the coast where they have been washed out of the beds. The Roman cement sets very rapidly, usually in about fifteen minutes after mixing ; has about one-third the strength of true Portland cement ; and is much weakened by the addition of sand, which should never be used in a greater ratio than i to i. In speaking of the subject of American and European "Natural Cements," Professor J. B. Johnson in his treatise on "The Materials of Construction" says : "There are few suitable rocks in Europe for making this cement. It is extremely irregular in composition, and not to be compared with the very uniform beds found in inex- haustible quantities in the United States. If such natural cement rocks as we have had been common in England and on the Con- tinent, it is almost certain that the artificial Portland cement would never have been discovered." 162. CHEMICAL ANALYSIS OF SOME AMERICAN NATURAL CEMENTS.— The following table, giving the chemi- cal constituents of some of the American -natural cements, will be found useful in comparing the products from different localities': NATURAL CEMEXTS, TABLE X. Table of Analyses — Natural Rock Cements. NUMBER. SILICA. ALUMINA. IRON OXIDE. LIME. MAGNESIA. POTASH AND SODA. CARBONIC ACID, WATER. 24-3^ 2.61 6.20 39-45 6.16 5-30 15-23 34.66 5.10 I .00 30.24 18.00 6.16 4.84 3 23. i6 6.33 I. 71 36.08 20.38 5.27 7.07 4 26.40 6.28 I .00 45.22 9.00 4.24 7.86 5 25.28 7-85 1-43 44.65 9-50 4-25 7.04 6 30.84 7-75 2. II 34-49 17-77 4.00 3 04 7 27.30 7.14 1 .80 35-98 18.00 6.80 2.98 8 28.38 II. 71 2.29 43-97 2.21 9.00 2-44 9 27.69 8.64 2.00 42. 12 14-55 2.00 3-00 24-34 8.56 2.08 61 .62 0.40 2.00 0.80 23.32 6.99 5-97 53-96 7.76 2.00 27.60 10.60 0.80 33-04 7. 26 7-42 2.00 13 33-42 10.04 6.00 32.79 9-59 0.50 7.66 14 22.58 7-23 3-35 48. 18 15.00 3.66 15 26.61 10.64 3-50 42. 12 13. 12 2.00 2.01 I6 25.15 8.00 3.28 49-53 13-78 0.26 REFERENCE. 1. Buf¥aIo Hydraulic Cement, Buffalo, N. Y. 2. Utica Hydraulic Cement, Utica, 111. 3. Milwaukee Hydraulic Cement, Milwaukee, Wis. 4. Louisville Hydraulic Cement, 'Tern Leaf," Louisville, Ky. 5. Louisville Hydraulic Cement, "Hulme," Louisville, Ky. 6. Rosendale Hydraulic Cement, "Brooklyn Bridge," Rosendale, N. Y. 7. Rosendale Hydraulic Cement, "Hoffman," Rosendale, N. Y. 8. Cumberland Hydraulic Cement, Cumberland, Md. 9. Akron Hydraulic Cement, "Cummings," Akron, N. Y. 10. California Hydraulic Cement, South Riverside, Cal. 11. Fort Scott Hydraulic Cement, "Brockett's Double Star," Fort Scott, Kansas. 12. Utica Hydraulic Cement, La Salle, 111. 13. Shepherdstown Hydraulic Cement, Shepherdstown, W. Va. 14. Howard Hydraulic Cement, "Howard," Cement, Ga. 15. Mankato Hydraulic Cement, Mankato, Minn. 16. James River Hydraulic Cement, Balcony Falls, Va. 163. THE MANUFACTURE OF NATURAL CEMENT.— From a mechanical standpoint, the manufacture of natural cement is a comparatively simple process, and especially when compared to that of Portland cement. It involves only two general opera- tions, burning and grinding. 146 BUILDING CONSTRUCTION. (Ch. IV) It is not the province of a work on Building Construction to go into detail regarding the manufacture of building materials, and for full descriptions of the processes of cement burning and grind- ing the reader is referred to the many recent treatises on Limes, Cements, Mortars and Concretes. At this point, however, a very brief enumeration of the steps followed in making natural cement may be useful. The limestone is usually stratified, the strata varying somewhat in chemical composition, but the rock, in its natural state, con- tains the proper ingredients for natural cement. For any given brand of cement it is usual to mix several strata, so that in case there is too much silica in one layer, it will be corrected by another containing a surplus of lime or magnesia. The principal steps in order in the process of manufacture are as follows : 1. Quarrying the rock, (a) in open cuts, or {b) by mining in tunnels and chambers. 2. Breaking the rock into sizes conveni^t for handling. 3. Running the rock through an ordinary rock-crusher, and breaking it into pieces varying in size up to six inches, greatest dimension. 4. Carrying the rock, generally by tramway, to the platforms at the top of the kilns, which are usually of the 'Vertical continuous mixed-feed, type," avera^ng 45 feet in height and 16 feet in diameter, and built either (a) of masonry lined with fire-brick, or {b) of an iron shell, -lined with fire-brick. 5. Spreading the rock and fuel in the kiln in alternate layers, the fuel being {a) anthracite coal, or {b) a good quality of bituminous coal. 6. Burning the rock and fuel, the temperature being ''somewhat greater than that used for burning lime, but below the point of incipient fusion reached in burning Portland cement." '7. Sorting out and throwing away the underburnt and over- burnt clinker, necessitated by the inevitable non-uniform burning, and resulting in a "probable average loss of about 25 per cent." 8. Conveying the sorted calcined rock to crushing machines, usually "pot-crackers." 9. Conveying the crushed material to screens which separate the coarse particles from the cement that is fine enough to pack. 10. Grinding the coarser particles in the fine grinding machines, NATURAL CEMENTS. 147 usually either (a) "edge-runners," or (b) ball or tube-mills, or (c) ordinary mills, or (d) emery-faced stones. 11. Passing the product through the mixers to obtain greater uniformity. 12. Conveying the product by. chutes to the packing rooms, and packing it in bags and barrels. 164. THE USES OF NATURAL CEMENTS.— As the use of lime mortar is confined to dry places where it is exposed to the air, being usually employed only in the construction of thin walls above ground and in the foundation coats of plaster ; and as it loses its binding properties when exposed to dampness, as in base- ment walls, and when excluded from contact with air, as in thick walls ; and as it sets too slowly to bear any immediate heavy weight ; cements have to be added or cement mortars substituted to meet these conditions. In mortar, natural cement is adapted to ordinary brickwork not subjected to high water pressure or to contact with water until about one month after laying; and for ordinary stone masonry v^here the chief requisites are weight and mass. Natural cement mortar or concrete should never be allowed to freeze, should never be laid under water, nor in very exposed situa- tions, nor in marine construction. Natural cement may be substituted for Portland in concrete, if economy demands it, for dry unexposed foundations where the load in compression can never exceed about 75 pounds per square inch (5 tons per square foot) and will not be exposed until three months after placing; for backing or filling in massive concrete or stone masonry where weight and mass are the essential elements; for subpavements of streets and for sewer foundations. Messrs. Taylor and Thompson in their treatise on concretes state that ''mixtures of natural and Portland cements, unless mixed at the factory and sold as improved natural hydraulic cements, are not advised under any conditions. ''Mixtures of natural cement and lime mortar are suitable for ordinary building brickwork, for light rubble foundations and for building walls."* "Natural, quick-setting cements are used for reinforced concrete only in special forms of construction, viz., in repair work, as when quick setting is necessary in order to enable the structure to sustain * "Concrete, Plain and Reinforced." Taylor and Thompson. 148 BUILDING CONSTRUCTION. (Ch. IV) moderate loads or enable its use within a few hours ; in hydraulic work, as in the construction of reservoirs and conduits ; and in the construction of reinforced pipe. They are, however, extensively used for plain concrete work. Sometimes, when quick setting with great strength is desired, a mixture of natural and Portland cements is employed."* ■''While the better grades of natural cement are quite sufficient in strength for nearly all kinds of engineering works, the want of uniformity in their hardening properties is a serious objection to their use."t ''Natural cement mortar is used in the construction of ordinary walls, sewers, foundations for roadways, etc., when Portland is considered too expensive. "J 165. CHARACTERISTIC PROPERTIES AND REQUIRE- MENTS OF NATURAL CEMENTS.— Facy^a-^^.— Natural cement as well as Portland cement is usually packed in strong cloth or canvas sacks, except in cases where it is to be stored in damp places or near the sea, when it should be packed in well-made wooden barrels lined with paper. Field Inspection. — A general field inspection often enables a cor- rect judgment to be formed of the condition of the cement, which is generally stored temporarily on raised platforms at the site of the construction, in ord^r that the necessary tests may be made. The general condition and marking of the packages should be observed. Sampling. — For the purpose of testing, samples are taken from the packages at random. There are different methods of sampling. Sometimes each sample from each package is tested separately, and sometimes small samples are taken from each of a number of packages, mixed together, and then separated again into convenient sample lots for testing. Color. — The color of cement is no criterion of quality. In a natural cement it may indicate the uniformity or non-uniformity of a given brand or grade, or differences in the composition of the rock used, or in the degree of burning. There is a great variation in color among the natural cements, and they run from a light yel- low to a dark gray and sometimes to a chocolate-brown. The color gives no clue to the cementitious value, since it is due chiefly to ♦ "Concrete, and Reinforced Concrete Construction." Homer A. Reid. t "The Materials of Construction." J. B. Johnson. % "Civil Engineering." C. J. Fiebeger. NATURAL CEMEXTS. 149 oxides of iron and manganese, which bear no direct relation to the cementing properties. A very light color often may indicate, however, an inferior underburned natural cement. Weight. — The specifications of the American Society for Test- ing Materials require the packing in bags of 94 pounds, net, three bags constituting a barrel of 282 pounds. A cement bag weighs about one pound. In different localities, however, different stand- ards of weight prevail. The standard barrel of natural cement weighs about 320 pounds gross or 300 pounds net in the Rosen- dale, Howe's Cave, and Akron districts ; 300 pounds gross and 280 pounds, net, in the Lehigh district of Pennsylvania ; and 280 pounds gross or 265 pounds, net, in the Louisville, Utica, Milwaukee, Fort Scott and other western districts. Again, these rules have excep- tions, the Howard cement of Georgia, for example, weighing only about 240 pounds to an Eastern natural cement barrel, and the Pembina cement of North Dakota weighing 380 pounds net per barrel. The latter cement is packed at about the regular Portland cement weight. The average weight of Louisville or Rosendale cement is, per cubic foot, loose, 50 to 57 pounds; and per cubic foot, packed, from 74 to 80 pounds. Specific Gravity. — The specific gravity of a cement in general gives an indication of the thoroughness of burning,^as it is lowered by underburning and raised by overburning. It is also lowered by hydration and adulteration. This test supplements the chemical analysis, since the latter does not indicate the degree of calcination. The specific gravity of natural cement is generally no criterion of its quality, but, to some degree, may be regarded as a measure of the uniformity of a single grade. The usual specification requires that the specific gravity of the natural cement thoroughly dried at ICQ degrees Cent. (212 degrees Fahr.) shall be not less than 2.8. Very few American natural cements ever fall as low in specific gravity as 2.8, and they range between 2.8 and 3.2, thus overlapping the lower limit given for Portland cement. Activity, or Time of Setting.— When water is added to cement, making a paste, the latter gradually hardens, and the rate of hard- ening is called the "activity" of the cement. The time when the mass begins to harden is called the "initial set,-" and the time when the mass has become so hard that it cannot be distorted or penetrated without rupture is called the "final set" or "hard set." BUILDING CONSTRUCTION. (Ch. IV) Certain definite limits must be fixed for the time of setting, and for natural cement it is usually specified that it shall develop initial set in not less than ten minutes, and hard set in not less than thirty minutes, nor in more than three hours. For full descriptions of the * apparatus and methods used to determine the time of set, the reader is referred to the treatises on Cement Testing, especially to "Prac- tical Cement Testing," by W. Purves Taylor. The natural cements are generally much quicker in setting than the Portland cements, although slow-setting natural cements are occasionally met with, and a rapidity of set may be changed by aeration, by the addition of gypsum or plaster, etc. In case the necessary laboratory apparatus for testing the activity is not at hand, for practical purposes the setting qualities of the cement or mortar may often be examined in ordinary construction, by making up pats from a number of the packages and by the pressure of the thumb testing their hardening. When the surface can no longer be indented, the paste or mortar may be considered to have reached the stage of the final set. Soundness or Constancy of Volume. — It is the purpose of this test to determine in advance whether or not the cement is apt to disintegrate, to crumble, expand or contract and thus cause crack- ing or distortion in the masonry. The term ''deformation" is em- ployed in France. A cement is said to be ''sound" when it does not expand or contract or check in setting. The principal causes of unsoundness are improper mixing, faulty processes of manufacture, excess of lime, insufiicient grinding, underburning, the presence of sulphides, an excess of magnesia or of the alkalies, an excess of clay and insufficient age. Tests for soundness are of two kinds : (i) The Normal test, a pat being immersed in water at 70 degrees Fahr. for 28 days, and a similar pat kept in air at ordinary tem- peratures and observed at intervals, and (2) the Accelerated test, a pat being exposed in any convenient way in an atmosphere of steam above boiling water, in a loosely closed vessel, for 5 hours. This test is usually considered as a corroborative test only, and not as final. Tests made on pats of neat cement paste kept in air and water under normal conditions are considered to be the only conclusive ones for natural cements. In both natural and Portland cements similar phenomena are noticed in regard to excessive expansion, NATURAL CEMENTS. checking or disintegration on normal pats. For natural cements the accelerated test has not proved successful. The usual requirements for constancy of volume of natural cement are as follows: Pats of neat cement about 3 inches in diameter, one-half inch thick at the center, and tapering to a thin edge, shall be kept in moist air for a period of 24 hours. (a) A pat is then kept in air at normal temperature. (b) Another pat is kept in water maintained as near 70 degrees Fahr. as practicable. These pats are observed at intervals for at least 28 days, and to satisfactorily pass the tests should remain firm and hard and show- no signs of distortion, checking, cracking or disintegration. Fineness. — The finer a cement of any class is ground the better its quality. The following requirement for the ^'fineness" of natural cement is taken from the Standard Specifications of the American Society for Testing Materials : *Tt shall leave by weight a residue of not more than 10 per cent on the No. 100, and 30 per cent on the No. 200 sieve." The following are some opinions of different engineers and authorities on fineness requirements of cements : *Tt is generally accepted that the coarser particles in cement are practically inert, and it is only the extremely fine powder that possesses adhesive or cementing qualities. The more finely cement is pulverized, all other conditions being the same, the more sand it will carry and produce a mortar of a given strength. "The efifects of grinding upon cements are to make them, (1) Stronger when tested with sand; (2) Weaker when tested neat; (3) Quicker setting; (4) Capable of producing a larger volume of paste; (5) Less affected by free lime. "With the same proportions of sand higher tensile and compres- sive strength is obtained from finely ground than coarsely ground cements. Conversely,, a larger proportion of sand can be used with fine-ground than with coarse-ground cement, with the same result- ing strength."* "The degree of fineness to which a natural cement is ground depends both upon the composition of the material and the process of grinding used. At times the percentage which will pass a No. * "Concrete, Plain and Reinforced." Taylor and Thompson. BUILDING CONSTRUCTION. (Ch. IV) 200 sieve will approximate that for Portland cement. Fine grind- ing is, however, not as essential in the manufacture of natural as in Portland cement, as the amount of free lime present is much- less. If the requirements are such that 85 per cent or more must pass a No. 100 sieve, and 70 per cent or more must pass a No. 200 sieve, a good quality of natural cement should result."* ''Until quite recently the grinding of an American natural cement was rarely carried further than was necessary to pass 95 per cent of the material through a 50-mesh sieve. In only a few cases was a greater fineness demanded than 85 per cent through a lOO-mesh sieve. The average requirements, then, were low, and the average cement just about passed requirements. "Within the past few years some natural cement manufacturers have realized that if the natural cement industry is to be main- tained in the face of competition from Portland cement the product must be improved. One of the easiest methods of doing this is to increase the fineness of the grinding. This has the effect of mak- ing the cement more sound and of increasing its sand-carrying capacity, and therefore its strength when tested as mortar. "There are differences in the fineness requirements of ' several important standard specifications. The requirements of the Ameri- can Society for Testing Materials (90 per cent through lOO-mesh, 70 per cent through 200-mesh) are high, and probably cannot be economically attained unless modern grinding machinery is in use at the mill. With tube mills, however, this fineness can be readily reached, and the tensile strength of the cement is greatly im- proved."t 166. STRENGTH TESTS. — For Natural Cements. — A discus- sion of the various tests for the strength of different kinds of cements is taken up in the subdivision of this chapter devoted to that subject. At this point, however, it will be well to give some of the standard and recent usual requirements for the tensile strength of natural cements. (See Articles 191, 197 and 208.) The paragraph relating to the tensile strength of natural cements, in the Standard Specifications of the American Society Testing Materials, is as follows : The minimum requirements for tensile strength for briquettes * "Concrete, and Reinforced Concrete Construction." Homer A. Reid. t "Cements, Limes iSfid Plasters." Edwin C. Eckel. NATURAL CEMENTS, 153 I inch square in cross-section shall be within the following limits, and shall show no retrogression within the periods specified. Age. Neat Cement. Strengtfi. 24 hours in moist air , 50-100 lbs. 7 days (i day in moist air, 6 days in water) 100-200 lbs. 28 days (i day in moist air, 27 days in water) 200-300 lbs. I part Cement, 3 Parts Standard Sand. 7 days (i day in moist air, 6 days in water) 25- 75 lbs. 28 days (i day in moist air, 27 days in water) 75-150 lbs. The tensile strength required for natural cements is highly vari- able in specifications for even large and important works, and these variations are illustrated in the following table :* TABLE XL NATURAL CEMENTS. Strength Required by Various Specifications. Neat I : I I Day 7 Days 28 Days 7 Days 28 Days 65 lbs. 100 " 60 " 25-75* " 125 lbs. 150 " 150 " 75-150*" Engineer Corps, U. S. A.. . . SO-ioolbs. 125 lbs. 90 " 100-200" 200 lbs. 200 *' 200-300" *In this specification the mortar mixture is i cement, 3 sand. The following tests belong to a fuller discussion of the whole subject of strength tests of cements and cement mortars: Com- pressive strength, relation of compressive to tensile strength, trans- verse or flectural strength, relation of flectural fiber stress to tensile stress, adhesive strength, abrasive or wearing resistance, shearing strength and coefficient of elasticity. 167. SPECIAL TESTS OF CEMENTS AND MORTARS.— The most important tests for comparing the qualities of different cements and for determining their practical value have been men- tioned or discussed in the preceding articles. There are certain other tests, which may be merely mentioned here, and which are sometimes made to investigate special qualities of a cement or mortar, or for scientific research. Such, for example, are the tests which are made for porosity, permeability, yield of paste and ♦"Cements, Limes and Plasters." Edwin C. Eckel. 154 BUILDING CONSTRUCTION. (Ch. IV) mortar, rise of temperature while setting, homogeneity (micro- scopical) and decomposition. As compared with the standard tests, such as chemical analysis, specific gravity, fineness, activity or time of setting, tensile strength and soundness or constancy of volume, the special tests above men- tioned are usually of minor importance, and for full descriptions of them the reader is referred to the treatises on cement testing. i68. SPECIFICATIONS FOR NATURAL CEMENTS.— Specifications for the cement for any particular operation are based upon the architect's or engineer's own practice, supplemented by a careful study of the model specifications of other recent important works. There is considerable variation in the requirements on vari- ous points, and it is useful to compare these dififerent demands, and thus determine the average of good and safe practice. Several dififerent sets of specifications for natural cements are given in Chapter XIII, "Specifications." One excellent set is given here, the specifications for natural cement based upon the practice of Engineers F. W. Taylor and S. E. Thompson, supplemented by their careful study of the speci- fications of the following : American Society for Testing Materials, American Railway Engineering and Maintenance-of-Way Associa- tion, City of Philadelphia, United States Army, United States Navy, Massachusetts Metropolitan Commissions, New York Rapid Transit Commission, and others. 1. Packages. — Cement shall be packed in strong cloth or can- vas sacks. t Each package shall have printed upon it the brand or the name of the manufacturer. Packages received in broken or damaged condition may be rejected or accepted as fractional pack- ages. 2. Weight. — Three bags shall constitute a barrel, and the aver- age net weight of the cement contained in one bag shall not be less than 94 pounds, or 282 pounds net per barrel. A cement bag may be assumed to weigh one pound. The weights of the separate packages shall be uniform. 3. Requirements.^ — Cement failing to meet the seven-day re- quirem'ents may be held awaiting the re&u-lt of the twe-nty-eight- day tests before rejection. * Paragrapbs designated by an asterisk are quoted from the Standard Specifica'tions of the American Society for Testing Materials. tif the cement is to be stored in a damp place or near the sea, it must be packed in well-made wooden barrels lined with paper. NATURAL CEMENTS. 155 4. Tests."^ — All tests shall be made in accordance with the methods proposed by the Committee on Uniform Tests of Cement of the American Society of Civil Engineers, presented to the Society January 21, 1903, and amended January 20, 1904, with all subse- quent amendments thereto. 5. Sampling. — Samples shall be taken at random from sound packages, and the cement from each package shall be tested separ- ately. •6.'*' The acceptance or rejection shall be based on the following requirements : 7. Definition of Natural Cement.'^ — This term shall be applied to the finely pulverized product resulting from the calcination of an argillaceous limestone at a temperature only sufficient to drive off the carbonic acid gas. 8. Specific Gravity."^ — The specific gravity of the cement thor- oughly dried at 100 degrees Cent. (212 degrees Fahr.) shall be not less than 2.8. 9. Fineness."^ — It shall leave by weight a residue of not more than 10 per cent on the No. 100, and 30 per cent on the No. 200 sieve. 10. Time of Setting."^ — It shall develop initial set in not less than ten minutes, and hard set in not less than thirty minutes, nor more than three hours. 11. Tensile Strength. — Briquettes one inch square in section shall attain at least the following tensile strength and shall show no retrogression within the periods specified. NEAT CEMENT. Age. Strength.t 24 hours in moist air 50 lbs. 7 days (i day in air, 6 days in water) 100 lbs. 28 days (i day in air, 27 days in water) 200 lbs. ONE PART CEMENT, THREE PARTS STANDARD SAND. Age. Strength.t 7 days (i day in air, 6 days in water) 25 lbs. 28 days (i day in air, 27 days in water) 75 lbs. 12. Constan'cy of Volume.'^ — Pats of neat cement about 3 inches *Paragraphs designated by an asterisk are quoted from the Standard Specifications of the American Society for Testing Materials. fThe American Society for Testing Materials gives minimum requirements as follows: Neat Cement — 24 hrs., 50-100 lb.; 7 days, 100-200 lb.; 28 days, 200-300 lb.; 1:3 mortar — 7 days, 25-75 lb.; 28 days, 75-150 lb.; the exact values to be fixed in each case by the consumer. 156 BUILDING CONSTRUCTION. (Ch. IV) in diameter, one-half inch thick at the center, and tapering to a thin edge, shall be kept in moist air for a period of 24 hours. {a) A pat is then kept in air at normal temperature. . {h) Another pat is kept in water maintained as near 70 degrees Fahr. as practicable. These pats are observed at intervals for at least 28 days, and to satisfactorily pass the tests should remain firm and hard and show no signs of distortion, checking, cracking or disintegration. 169. MISCELLANEOUS DATA AND MEMORANDA, PRINCIPALLY ON NATURAL CEMENTS.— "Cement is shipped in barrels or in cotton or paper bags. The usual dimen- sions of a barrel are : length, 2 feet 4 inches ; middle diameter, i foot 4^ inches ; end diameter, i foot 3^ inches. *The bags hold 50, 100 or 200 pounds. "A barrel weighs about as follows : Rosendale, N. Y 300 lbs. net. Rosendale, Western 265 lbs. net. Portland 375 lbs. net. "A barrel of Rosendale cement contains about 3.40 cubic feet and will make from 3.70 to 3.75 cubic feet of stiff paste, or 79 to 83 pounds will make about one cubic foot of paste. "A barrel of cement measured loosely increases considerably in bulk. The following results were obtained by measuring in quan- tities of two cubic feet: I bbl. Norton's Rosendale gave 4.37 cu. ft. I bbl. Anchor Portland gave 3.65 cu. ft. I bbl. Sphinx Portland gave 3.71 cu. ft. I bbl. Buckeye Portland gave 4.25 cu. ft. **The weight of cement per cubic foot is as follows : Portland, English and German 77 to 90 lbs. Portland, fine-ground French 69 lbs. Portland, American 92 to 95 lbs. Rosendale 49 to 56 lbs. Roman 54 lbs. ''A bushel contains 1.2/^4 cubic feet. The weight of a bushel can be obtained sufficiently close by adding 25 per cent to the weight per cubic foot."* * "Inspector's Pocket Book." A. T. Byrne NATURAL CEMENTS. 157 The following data bearing upon the above, and showing slight variations, are taken from another authority Portland cement weighs per barrel, net 376 lbs. Portland cement weighs per bag, net 94 lbs. Natural cement weighs per barrel, net 282 lbs. Natural cement weighs per bag, net 94 lbs. Cement barrel weighs from 15 to 30 lbs., averaging about 20 lbs. Portland cement is assumed in standard proportioning to weigh per cubic foot 100 lbs. Packed Portland cement, as in barrels, averages per cubic foot about 115 lbs. Packed Portland cement, based on 3.5 cubic feet barrel contents, weighs per cubic foot 108^ lbs. Loose Portland cement averages per cubic foot about 92 lbs. Volume of cement barrel, if cement is assumed to weigh 100 lbs. per cubic foot 3.8 cu. ft. American Portland cement barrel averages between heads about.. 3.5 cu. ft. Foreign Portland cement barrel averages between heads about... 3.25 cu. ft. Natural cement barrel averages between heads about 3.75 cu. ft. The additional data in this article, useful in estimates of cement work, are added with the accompanying explanatory note if "The following estimates of quantities are simply approximate and may be exceeded or not attained, according to the local cir- cumstances. While most of them are the results of actual experi- ment under practical conditions, the writer has checked but few of them in his practice, and presents them as being correct under a single set of conditions only, and approximately so in others. For rough estimates they will answer satisfactorily. Each engineer or contractor is soon able to estimate his own quantities under the conditions of the methods he adopts better than he can from any statements of average results. Packing and Shipping Cement. Cement is packed in barrels, cloth sacks or paper bags, as ordered. •A barrel of Portland cement weighs about 400 pounds gross, and should contain 380 pounds net of cement. Portland cement, loose, weighs 70 to 90 pounds per cubic foot; packed, about no pounds per cubic foot. A barrel of eastern natural hydraulic cement weighs about 320 pounds gross and should contain 300 pounds net of cement. A barrel of western natural hydraulic cement weighs about 285 pounds gross and should contain 265 pounds net of cement. * "Concrete, Plain and Reinforced." Taylor and Thompson, t "Handbook for Cement Users." Charles C. Brown. 158 BUILDING CONSTRUCTION. (Ch. IV) Natural hydraulic cement, loose, weighs about 50 to 57 pounds per cubic foot; packed, about 80 pounds per cubic foot. Weights of - cement and volumes of barrels are not uniform. Nearly all natural hydraulic cement is sold in sacks. Slag cement weighs about 350 pounds gross, or 330 pounds net. - Cloth sacks ordinarily contain one-third of a barrel of natural hydraulic cement. The standard for Portland cement is one-fourth of a barrel. Paper sacks contain one-fourth of a barrel. The following on cement packages is from a circular issued by a firm of general agents for cement : Four paper bags or four cloth bags constitute one barrel or 380 pounds of Portland cement. The paper bags are charged to the cus- tomer at 2^ cents each or 10 cents per barrel, and are of no further value. They have served their purpose in carrying the cement to destination and have given you service that is worth 10 cents per barrel. The cloth bags are charged at 10 cents each or 40 cents per barrel, and are worth 10 cents each or 40 cents per barrel if returned and received, freight paid, in good condition at the mill. Here has been the misleading part to the consumer. While a few paper bags are liable to be broken in transportation with a corre- sponding loss of cement, the minimum loss of cement in a cloth bag is one pound to the sack or four pounds to the barrel. This amount remains unshaken from the bag. We have seen laborers so careless as to waste 3 per cent of their cement in this manner. A paper bag is more easily handled — can be emptied with absolutely no loss of cement. It takes time to untie a cloth bag and time costs money. A paper bag can be cut open with a hoe instantly. The manufacturers and the railroads require bags returned to be freight prepaid. The minimum expense of such transportation from this district is cents per barrel, which you pay. Use paper and save it. The table on page 159 from The Engineering News gives an idea of the variation in size of cement barrels. The first three brands named are American and the other two foreign Portland cements. A carload of Portland cement usually means 100 barrels (40,000 pounds) ; 75 barrels is the minimum carload, or the same quantity by weight in cloth or paper bags. When cement is ordered in cloth sacks the sacks are charged at cost, viz. : 10 cents each, in addition to the cost of the cement ; but when the sacks are returned to the works in good condition, freight NATURAL CEMENTS. r TABLE XII. Table Showing Variations in Sizes of Cement Barrels. (I) (2) (3) Difference Difference Portland Capacity Actual Volume between betweei\ . cement of bbl. contents. when (I) (2) brand cubic packed dumped and and feet measure loose (2) (3) Giant 3.5 3-35 4.17 4% 3-45 3.21 3-75 • 4" 3-15 4.05 3" 30'^ 3. 16 4.19 2" 33" 312 3-03 4.00 3" 33" prepaid, 10 cents is allowed for each, with a deduction of 2 cents for wear and tear in some cases. For paper bags there is no charge, as they are not apt to be re- turned. Empty sacks to be returned should be safely tied in bundles of ten or fifty, giving the name of the sender." 170. THE CHOICE OF CEMENTS, AND THE SELECTION OF BRANDS. — The question often arises as to whether natural cement or Portland cement is the more desirable from an economic standpoint, aside from considerations of strength and other prop- erties. Local conditions generally decide the question. There are some general rules of good engineering practice which have beem formulated, and which relate to the classes of construction for which different kinds of cement and lime are best adapted. These classes have already been mentioned in regard to the uses of natural cement mortar, for example, under that heading. (See Article 164.) If the architect or engineer decides that in a certain structure either natural cement or Portland cement may be used, the relative cost decides the choice, and the cost in turn depends upon the pro- portions of cement and sand that may be adopted in either case. The usual proportions for natural cement mortar are i :2, that is, one part of cement to two parts of sand, by volume, while in Portland cement mortar the sand is, up to a certain point, only limited by practical considerations, such as the handling of the cement with the trowel, and goes to the proportions i 13 and 1 14. After assuming the proportions of the two classes of mortar, tbe relative cost is governed principally by the nuantity of cement in a cubic yard of mortar. Tt can he sho- - '^-^t Portland cement i6o BUILDING COXSTRUCTION . (Ch. IV) mortar made of one 'part cement to four parts sand is equivalent in cost to natural cement mortar made of one part cement to two parts sand, when Portland cemert delivered on the job costs 68 per cent more than natural cement, or when the former, for example, costs $1.68 per barrel, and the latter $i.oo per barrel. About lo per cent more of bricks can be laid in a given time with natural cement mortar when the proportions ' are 1:2 than with Portland cement mortar with the proportions, for example, of 1 13 ; 'Consequently when the cost of Portland and natural cement is the same, the natural cement produces the brickwork for less money. It has been estimated that in some cases there is a difference of 30 •cents per barrel of cement corresponding to the difference in the labor of laying bricks ; and it has also been shown that Portland ^cement mortar can seldom be substituted for natural cement mortar without an increase in the cost of the work. In regard to the selection of any particular brand from a number of different brands of the sam.e class of cements, such as natural cements, for example, the architect or engineer m.ust be guided by experience, by the history and reputation of that special brand, or \>y thorough laboratory tests. Between two cements which are ■''sound," and which set properly, the choice can usually be made by selecting the one which shows the greater fineness when tested with two sieves, as already described. The stronger mortar is usually produced by the finer cement. The cheapest cement is not always the most economical. Tables have been made to show the relative economy of cements offered by bidders at different prices, especially for government work. The final selection is made after careful consideration of all the data referring to each brand, such as the relative tensile strength of the mortars of certain proportions of cement to sand, the products of the relative strength by the relative cheapness, the soundness, the volumes of the barrels, their gross net weights, the percentages of water used in mixing the pastes and mortars, the timie of setting of the mortar, and the strength and relative economy of mortars with sand proportioned to the price of each cement.* 'The difficulties which are encountered in the attempt to discuss the natural cements as a class, laying emphasis upon the points of resemblance of the various brands and disregarding for the time *For a full discussion of the subjects of "The Choice of Cement," and "The Selection of the Brand," see "Concrete, Plain and Reinforced," by Taylor and Thompson. PORTLAND CEMENTS. i6i their many points of difference, are greater than the reader, at first sight, may imagine ; for few engineers reaUze what a heterogeneous collection of products is included under the well-known name of ^natural cement.' The cause for this lack of knowledge is not far to seek. Natural cements are too low in value to be shipped, under ordinary circumstances, far from their point of production. The natural cement made at any given locality has usually, therefore, a well-defined market area within which it is well known and sub- ject to little competition. The engineer practicing within such an area naturally forms his idea of natural cements in general from what he knows of the brands encountered in his work, and as all the brands from one cement-producing locality are apt to resemble one another quite closely, he is likely to conclude that natural cements are quite a homogeneous class, with many points of resem- blance and few of difference. The truth is, on the contrary, that there may be far greater differences of strength, rate of set, chemical composition, etc., between the natural cement made in two different localities than between any given brand of natural cement and a Portland cement."* See also Art. 182, ''The Choice of Portland Cement, and the Selection of Brands." 4. PORTLAND CEMENTS. 171. PLACE OF PORTLAND CEMENT IN THE CLASSI- FICATION. — The classification of cementing materials has already been considered under that heading in Article 157, and Portland cement is the fourth of the five divisions mentioned. It belongs to the group of hydraulic cements, and is perhaps now the most impor- tant of the cementing materials. Having considered the common limes, the hydraulic limes and the natural cements, the Portland cements will be considered in the fol- lowing articles. Reference to Table IX, in Art. 157, will make clear the position of Portland cement in the classification, and show the comparison of this with other cementing materials in the typical analyses given. 172. DEFINITIONS OF PORTLAND CEMENT.— The fol- lowing is the definition given in the Standard Specifications of the American Society for Testing Materials : "This term applies to the finely pulverized product resulting from the calcination to incipient fusion of an intimate mixture of properly proportioned * "Cements, Limes and Plasters." Edwin C. Eckel. BUILDING CONSTRUCTION. (Ch. IV) argillaceous and calcareous materials, and to which no addition greater than 3 per cent has been made subsequent to calcination." The term ''argillaceous" means clayey, and ''calcareous" means consisting of lime or calcium. The definition in the specifications of the Engineer Corps, U. S. Army, 1902, is as follows : "By a Portland cement is meant the product obtained from the heating or calcining up to incipient fusion of intimate mixtures, either natural or artificial, or argillaceous with calcareous substances, the calcined product to contain at least 1.7 times as much of lime, by weight, as of the materials which give the lime its hydraulic prop- erties, and to be finely pulverized after said calcination, and there- after additions or substitutions for the purpose only of regulating certain properties of technical importance to be allowable to not exceeding 2 per cent of the calcined product." Another definition is: "Portland cement is a hydraulic cementing material with a specific gravity of not less than 3.10 in the calcined condition, and contain- ing not less than 1.7 parts by weight of lime to each one part of silica + alumina + ii'on oxide, the material being prepared by inti- mately grinding the raw ingredients, calcining them to not less than clinkering temperature, and then reducing to proper fineness." Mr. Edwin C. Eckel, of the U. S. Geological Survey, believes that the following definition will be found more satisfactory than those now in use for insertion as a preliminary requirement in cement specifications : "By the term Portland cement is to be understood the product obtained by finely pulverizing clinker produced by burning to semi- fusion an intimate artificial mixture of finely ground calcareous and argillaceous materials, this mixture consisting approx-imately of three parts of lime carbonate (or an equivalent amount of lime oxide) to one part of silica, alumina and iron oxide. The ratio of lime (Ca O) in the finished cement to the silica, alumina and iron oxide together shall not be less than 1.6 to i, or more than 2.3 to i." The question of the definition of Portland cement for specifica- tions is an important one, as there has been only a partial and not a complete agreement as to what is to be understood by the term. The principal difference of opinion is in regard to the question of including or not including among the true Portlands those cements made by burning a natural rock without previous mixing* and grind- PORTLAND CEMENTS. 163 ing, and any definition based upon such criteria would exclude some products manufactured in France and Belgium called ''natural Port- lands." Also, in regard to American-made Portland cements, it is considered by some of the highest authorities a serious error to omit from specifications the requirement relating to the pulverizing or artificial mixing of the materials prior to burning, because at present there are no true Portland cements manufactured in America from natural mixtures without such preliminary pulverizing and artificial mixing. 173. THE EARLY HISTORY AND USE OF PORTLAND CEMENT. — Joseph Aspdin, a brickmaker of Leeds, England, invented Portland cement and took out a patent in 1824 on the manu- facture of a product resulting from the calcination of an artificial mixture of pulverized limestone and clay. It was first patented as an ''artificial stone." To this product was given the name "Port- land," from a fancied, though really slight resemblance of the cement after it has set to the noted oolitic limestone from the Isle of Port- land, a peninsula on the south coast of England, in Dorset, near Weymouth. This stone, well known to all English architects and engineers as "Portland Stone," was much used in England at that time, and a recent prominent example of its use is the London West- minster Cathedral, where it appears in bands in the red brickwork. It was not until about twenty years after the discovery by Aspdin that the Portland cement industry was developed to any great extent, when J. B. White & Sons, in Keiit, England, began its manufacture, and when a little later Mr. John Grant, an eminent English engi- neer, made irnportant tests and used the cement extensively on the London drainage works. In France the first manufactory for producing Portland cement was established at Boulogne-sur-Mer toward the middle of the last century. In Germany, soon after the first production of the cement in France, the first factories were built for the production of the Stettin brands. Although for a time England led in^he manufacture of Portland cement, Germany afterward took the lead, and with such success that for a while it was the foremost country in the amount produced, in 1900 passing all other countries. The United States during the past few years has surpassed all other countries in the manufacture of Portland cement. Mr. David 164 BUILDING CONSTRUCTION. (Ch. IV) O. Saylor, of Coplay, Pa., in the Lehigh Valley, was the founder of this industry in America. He made his first discoveries in 1874 and 1875, built his first factory in 1878. During the first fifteen years the development of the industry was exceedingly slow, but about the year 1890 it took a new start and since then has been very rapid. 174. THE PRESENT USE OF PORTLAND CEMENT.— Good Portland cement is constantly finding wider and wider fields of application. It has been said that it has already worked a revolu- tion in engineering and architectural construction nearly equal in significance to that following upon the general use of the Bessemer and open-hearth processes of making steel. In its production its quality is being constantly improved, a result largely due to. the excellent systems of testing, and to the consequent necessity of employing at the works the most competent scientific supervision. It is now made on a gigantic scale in the United States, Germany, Belgium, the United Kingdom and France. In 1890 only 335,500 barrels of Portland cement were manu- factured in the United States ; but since that time the development of the industry has been so rapid that in 1905 the number of barrels reached a grand total of 35,246,812, and of this total over one-half was produced in the Lehigh district of Pennsylvania and New Jer- sey. In 1906 the output was 46,463,424 barrels, valued at $52,- 466,186, and the estimated output for 1907 is 48,000,000 barrels. Existing American plants have now (1908) a total capacity of about 60,000,000 barrels a year. The wonderful rapidity of the development of the manufacture of Portland cement, and the increase in the amount of this cement produced from about the year 1880 to the present time, may be best understood by an examination of the tables compiled and published by the government and by the most recent treatises on building materials of this nature. It is not possible in this brief chapter to insert these tables, and the reader is referred to such authoritative data as, for example, the annual reports on the ''Mineral Resources of the United States," issued by the United States Geological Sur- vey, and to various compilations made from these reports, found in recent exhaustive works on limes, cements, mortars and concretes. Such are the tables on "Total Production of Portland Cement in the United States from 1870 to Date," "Production of Portland Cement PORTLAND CEiMEXTS. 165 in the United States for the Different Years by States," "Distribution of the Manufacture of Portland Cement and the Development in the Various Regions," ''Portland Cement Production of the Lehigh District of Pennsylvania-New Jersey," "Imports of Cement into the United States by Years, and by Countries," "Total Consumption of Natural Cement, Imported Portland Cement, Domestic Portland Cement and Puzzolan Cement in tjie United States in Barrels, and the Annual Percentages of Each Class," "Consumption of Cement in the United States per Capita of Population," "Exportation of Cement from the United States," and "Diagrams Showing Graphic- ally Changes in Percentages of Natural Cement and Imported and American Portland Cement Used Each Year." 175. CHEMICAL ANALYSIS OF PORTLAND CEMENTS. — The definitions of Portland cement have already, been given in Article 172. A Portland cement mixture, when ready for burning, should contain about 75 per cent of lime carbonate (CaCOg), and about 20 per cent of silica (SiOg), alumina (ALOg) and iron oxide (FcgOg) together, the remaining 5 per cent or so containing any magnesia, sulphur and alkalies that may be present. There is an abundant and wide distribution in nature of lime, silica, alumina and iron, which occur in various kinds of rocks in different forms. Mr. Edwin C. Eckel analyzes the various raw materials available for use in Portland cement manufacture as follows : He states that as to composition, they may be (a) purely calcareous, (b) a mixture TABLE XIII.* Character of Portland Cement Materials. Natural Artificial Hard Soft Unconsolidated Unconsolidated Calcareous (CaCOg over 75%) Pure hard limestone Pure soft limestone or pure., chalk Pure marl Alkali waste Argillo-calcareous (CaCOg 40 to 75%) Hard clayey • limestone (cement rock) Soft limestone or clayey chalk Clayey marl Blast-furnace slag Argillaceous (CaCOg less than 40% ) Slate Shale Clay * "Cements, Limee and Plasters." Edwin C. Eckel. BUILDING CONSTRUCTION. (Ch. IV) of calcareous and argillaceous elements, or (c) almost purely argil- laceous; as to physical character they may be (a) hard and massive, like the hard limestones and slates, (b) soft, like the chalks and shales, or (c) granular or unconsolidated, like the marls, clays, alkali waste and granulated slag. As to origin, they may be (a) natural, like limestones, marls, slates, clays, etc., or (b) artificial, like alkali waste and furnace slag. The same writer in various valuable papers published at different times has grouped, under six heads, the various combinations of raw materials at present used in the United States in the manufacture of Portland cement: (1) Argillaceous hard limestone (cement rock) and pure lime- stone. (2) Pure hard limestone and clay (or shale (3) Soft (chalky) limestone and clay (or shale). (4) Marl and clay (or shale). (5) ^ Alkali waste and clay. (6) Slag and pure limestone. The materials vary with the locality. In the Lehigh district the chief raw materials used are cement rock and limestone, and the Virginias, Alabama, Colorado and Utah have similar formations ; in the New York State Eastern cement region and in California and occasionally in the Central States, limestone and clay; in Western New York and in the Middle West, marl and clay; and in the States bordering the Mississippi River on the west and in Texas and Arkansas, chalk and clay. Slag and limestone are little used in the United States, although extensively employed in Europe. In Germany the Alsen and Stettin brands are made from chalk and clay; the Mannheimer and Dyckerhoff brands from limestone and clay ; while the Hannover and Germania manufactories use marl and clay. In England chalk and clay principally are the raw materials. In Belgium chalk and clay are used by the manufacturers, and a natural rock also is used for the production of a Portland cement. In France, marl and clay, and chalk and clay, constitute the prin- cipal constituents for true Portland cements. The ordinary composition of a good Portland cement should PORTLAND CEMENTS. 167 approximate the following limits given by H. Le Chatelier, the emi- nent authority : p^^^^^^ Silica 21 to 24 Alumina 6 to 8 Iron Oxide 2 to 4 Lime , 60 to 65 Magnesia 0.5 to 2 Sulphuric Acid 0.5 to 1.5 Carbonic Acid and Water i to 3 For a comparison of the chemical composition of the different kinds of cements and of limes, see Table IX, "Typical Analyses of Cements," in Article 157, on the ^'Classification of Cementing Materials."* ^ There is a large mass of literature on the subject of "The Con- stitution of Portland Cement," as it has grown rapidly in importance during recent years. f 176. THE MANUFACTURE OF PORTLAND CEMENTS. — The process of manufacturing Portland cement from rock, or rock and clay mixtures, consists essentially of (a) crushing the materials, either separately or after mixing them, (b) drying, (c) grinding, (d) calcining, (e) cooling, (f) grinding to powder and (g) packing. There is greater variety in the methods employed for producing Portland cement than for natural cement. Portland cement clinker is not as readily powdered as the burnt natural cement rock, but grinding machinery similar to that used in Portland cement plants is now used in the newer natural cement mills. The methods of mixing the materials in preparation for their introduction into the kilns has led to a classification of the processes into A, the dry process, and B, the wet process. In these processes either i. Stationary kilns, or 2, Rotary kilns, are used. The stationary kilns may be either (i) Intermittent kilns, or (2) Continuous kilns. A. — The dry process was first used in Germany, when limestone * For a very interesting and complete table giving the analyses of 80 of the most prominent American Portland Cements, see the article on the "Composition of American Portland Cements." Table 221, in "Cements, Limes and Plasters," by Edwin C. Eckel. + Bonnami. H. Fabrication et controle des chaux hydrauliques et des ciments. 8vo. 276 pp. Paris, 1888. Le Chatelier, H. Tests of hydraulic materials. Trans. Arrffcr. Inst. Mining Engineers, vol 22, pp. 3-52. 1894- Newberry, S. B. and W. B. The constitution of hydraulic cements. Journ. Soc. Chem. Industry, vol. 16, pp. 887-894. 1897. Richardson, C. The constitution of Portland cement. Cement, vols. 3, 4, 5. 1903-1905. Richardson, C. The constitution nf Portland cement from a physico-chemical stand- point. i2mo, 20 pp. Long Island City, N. Y., 1904. Richardson, C. The setting or hydration of Portland cement. Engineering News, vol. 53. PP- 84-85. Jan. 26, 1905. i68 BUILDING CONSTRUCTION. (Ch. IV) was substituted for the chalk of England. In the early days of the industry all cement was burned in stationary kilns. They are still occasionally used in the United States, and to a large extent in Germany and France. They are of two general types, intermit- tent kilns, which are completely charged and then burned, and continuous kilns, in which there is a continuous maintenance of the fire, and in which the raw materials are dried and heated by the exhaust heat before they are burned. There has been a universal introduction of rotary kilns into new cement plants, and a gradual substitution of them in the older mills for the stationary kilns. The typical method for the manufacture of Portland cement may be considered to be the dry process with rotary^kilns. In the dry process the ingredients are ground and mixed in a dry state. For stationary kilns the mixed materials are moistened with enough water to make plastic bricks, afterwards dried. For rotary kilns there is no addition of water, and the mixture of dry materials passes, after grinding, directly into the kiln. The following is a brief description of a rotary kiln used for calcining dry materials and of the process of manufacture of the cement from the time of entering the kiln to the packing ready for shipment *'The rotary kiln is a steel cylinder, varying in length from 40 to 150 feet and from 4^ to 9 feet in diameter, lined with from 6 to 12 inches of fire-brick, with its axis inclined 8 or 10 degrees to the hori- zontal, and arranged to rotate at a speed averaging about one turn per minute. The raw materials are introduced at the upper end in form of powder, and in passing through are calcined to a clinker, which leaves the kiln at the lower end in small balls, ranging from to inches in diameter. Finely pulverized gas-slack coal is generally used for fuel, although both gas and oil have been em- ployed, but with poorer results. The coal is blown into the lower end of the kiln, and instantly ignites, forming a flame reaching from 15 to 25 feet into the kiln, and producing a temperature of from 2,600 to 3,000 degrees Fahrenheit. The coal is pulverized in the same manner, and to about the same degree of fineness as the raw mate- rials. The temperature and time of burning vary with the nature of the raw materials. ''The clinker as it leaves the kiln is sprayed with a small stream of water, which cools and makes it more easy to pulverize. It then * "Concrete, and Reinforced Concrete Construction." Homer A. Reid. PORTLAND CEMENTS. 169 passes through coolers, which reduce it to a normal temperature. From the coolers the clinkers pass to the pulverizing and grinding machines, which are similar to those for reducing the raw material. The finished cement from the grinding machines is conveyed to the stock house, often being stored for a time tq give it a chance to 'season' somewhat. It is then packed in bags or barrels for ship- ment." ♦ B. — The wet process is employed with soft or wet materials, such as chalk and clay, and marl and clay, and may be used with either the stationary or rotary kilns. The latter was first used in England on wet materials. In the United States it is usually only employed by the mills in which the raw material used is marl, although it is adapted to chalk or other materials, which are easily reduced when in a wet condition. The carbonate of lime and the clay are mixed in a vat or wash- mill with a large excess of water, the lumps are broken up by agita- tors which reduce the particles to so fine a condition that the water holds them in suspension and they flow off over the top of the vat. The material then settles -in another receptacle, the water is drawn off, and the ''slurry" becomes hard enough to handle in barrows and then form into bricks to be dried. This is the process for the stationary kilns, in which these bricks are calcined. Regarding the wet process with rotary kilns, it may be said that these kilns, almost universally adopted in the United States for calcining dry materials, have more recently had their use extended to handling the slurry, of a thick creamy consistency, and drying it with the same flame used for calcination. The wet slurry is pumped into the upper ends of the rotary kilns, which are usually somewhat longer than those employed in the dry process. After calcination the treatment is similar to that in mills where dry materials are used. Silica-Portland Cement, or Sand-Portland Cement. — This is a mixture of true Portland cement and siliceous sand ground together into an impalpable powder in a tube-mill. A mixture of equal parts of sand and cement thus ground together possesses about the same strength as ordinary Portland cement alone. '*A mixture of silica-cement, i part cement and i part sand, with 3 parts unground sand, has the same composition as i part cement BUILDING CONSTRUCTION. (Ch. IV) and 7 parts sand ; but possessing the strength of a mixture of I part cement and 3 parts sand.* The siHca-cement process was first introduced into Denmark and has the special advantage of making mortar that is impermeable to moisture and able to ^resist the action of the elements. Eight thousand barrels of silica-cement were used in the founda- tion of the Cathedral of St. John the Divine, New York City. 177. THE USES OF PORTLAND CEMENTS.— Portland cement is by far the most useful and valuable of all the cements. If quick setting is not necessary, but great ultimate strength required, this cement should be adopted. It is used in almost all kinds of masonry construction, but chiefly in foundations in wet places, in subaqueous work of all kinds, for important structures where great strength is required, and in plain and reinforced concrete work. It is also used in the more exposed parts of ordinary structures, such as the copings of walls and the tops of chimneys, for protecting the outer faces of walls and buildings from the weather, for thin walls where extra strength is required, for pointing and filleting, and for arches, piers and other important parts of buildings and engineering works. Portland cement, as it has been said elsewhere, has worked a revo- lution in engineering construction, and is still finding wider and wider fields of application. In discussing the choice of cements, Messrs. Taylor and Thompson statef that ''Portland cement should be used in concrete and mortar for structures subjected to severe or repeated stresses; for structures requiring strength at short periods of time ; for concrete building construction ; for work laid under water or with which water will come in contact immediately after placing; for thin walls subjected to water pressure ; for masonry exposed to wear or to the elements ; and for all other purposes where its cost will be less lhan that of natural cement concrete, or mortar of similar quality." Mr. Homer A. Reid, in discussing^ the properties of cement and methods of testing, states that ''Portland cement is used for rein- forced concrete construction almost to the exclusion of other cements. Its great strength, uniform composition and the regularity of its properties eminently fit it for this class of work." * Addison H. Clark, in "Architects' Handbook of Cements." t "Concrete, Plain and Reinforced." Taylor and Thompson. ^"Concrete, and Reinforced Concrete Construction." Homer A. Reid. PORTLAND CEMENTS. 171 Professor C. J. Fiebeger in writing of limes and cement mortars* says, with reference to engineering works in particular, ''Portland cement mortar is employed in structures in which great strength is required, as in masonry dams and masonry arched bridges ; where the surface is exposed to mechanical wear, attrition, or blows, as in sidewalks and fortifications ; and takes the place of natural cement whenever the cost of the work is not thereby increased." ''The cement should be suited to the work in which it is to be used. This will decide whether natural, hydraulic, puzzolan or Port- land cement shall be used, and the grade of the latter. Economy should be one of the elements considered and may turn the decision to a natural cement in one locality, while some grade of Portland cement would be used in another. For external work the conditions of variation in temperature, drainage, possibility of shocks, blows and abrasions, and appearance determine the grade of Portland cement to be used."t 178. CHARACTERISTIC PROPERTIES AND REQUIRE- MENTS OF PORTLAND CEMENT.— Packages, Field Inspection and Sampling. — The statement made in regard to these particulars under natural cement in Article 165 apply also to Portland cement. Color. — As was said under this subdivision for natural cement, the color of a cement is no criterion of its quality. It 'may show, however, too large an amount of some ingredient, and for some particular brand, differences in shade may be an index of variations in the composition of the rock from which the cement was made, or of the degree of burning. "Portland cement should be a dull gray. Bluish-gray probably indicates an excess of lime ; dark green, a high percentage of iron ; brown, an excess of clay ; and a yellowish, shade indicates overburning.":|: "The chemical composition of Portland cement made by different processes is so uniform that the color of different brands varies less than that of natural cements. "The color of Portland cement is described as cold blue gray. The dark color of the coarser particles of a Portland cement left as residue on a screen is due simply to the fact that cement clinker is * "Civil Engineering." C. J. Fiebeger. t "Handbook for Cement Users." Charles C. Brown. Published by Municipal Engi- neering Company, Indianapolis and New York. $ "Concrete, and Reinforced Concrete Construction." Homer A. Reid. 172 BUILDING CONSTRUCTION. (Ch. IV) black, and pieces which are not finely ground retain the color of the clinker."'^ Mr. David B. Butler saysf that a brownish color denotes insuffi- ■ cient calcination or the use of unsuitable clay or possibly excess of clay. The origin of the name "Portland Cement," from a fancied resemblance in its color to the English Portland stone, has already been referred to. Mr. Austin T. Byrne saysj that the color of Portland cement should be a dull bluish or greenish gray, caused by the dark ferru- ginous lime and the intensely green manganese salts ; that any variation from its color indicates the presence of some impurity; and that blue indicates an excess of lime, dark green a large per- centage of iron, brown an excess of clay and a yellowish shade an underburned material. Weight. — The quality of a cement is not indicated by the weight alone. If weight is considered it must be taken in conjunction with fineness. Either a fine grinding or an underburning may cause a light weight. Until recently specifications required a standard weight per struck bushel or per cubic foot, the idea being that, other conditions being equal, a cement thoroughly burned is heavier than one underburned. But when it was discovered that the degree of fineness, much more than any difiference in calcination, affects the weight, the weight requirements were omitted, and tests for specific gravity substituted. Experiments have shown that the weight of a cement decreases with age. According to the specifications of the American Society for Test- ing Materials, Portland cement should be packed in bags of 94 pounds net weight, four of which make a barrel of 376 pounds net. Some other specifications require a barrel of 375 pounds net. For convenience in ordinary calculations it is often assumed that a barrel of Portland cement weighs 400 pounds gross or 380 pounds net. In standard proportioning it is assumed to weigh 100 pounds per cubic foot. Packed in barrels it averages 115 pounds per cubic foot. Packed Portland cement based on 3.5 cubic feet barrel contents weighs 1085^ pounds per cubic foot. * "Concrete, Plain and Reinforced." Taylor and Thompson. t "Portland Cement." David B. Bvtler. t "Inspector's Pocket Book." Austin T. Byrne. PORTLAND CEMENTS, 1/3 Loose Portland cement averages about 92 pounds per cubic foot. Specific Gravity. — Under this heading, in discussing the properties of natural cements, the significance in general of the specific gravity tests for cement was explained. With Portland cements the specific gravity is of little importance in itself, although it will serve to detect underburned or adulterated cement. A well-dried sample of Portland cement will have a specific gravity which is seldom lower than 3.10, while a natural cement, or a slag cement, or a Portland cement adulterated with slag will have a specific gravity which is rarely higher than 3.00. It must be admitted, however, that there are a few American natural cements showing a specific gravity of 3.00, and reaching as high as 3.2. The standard specifications of the American Society for Testing Materials require that the specific gravity of Portland cement, thor- oughly dried at 100° Cent. (212° Fahr.), shall be not less than 3.10. Mr. Homer A. Reid says* ''the specific gravity of Portland cement varies from 3.00 to 3.25, but for the higher grades of American cements it is usually found to be between 3.10 and 3.25." Activity, or Time of Setting. — A brief general description of the use and significance of the tests for this property has already been given under natural cements. The specifications of the American Society for Testing Materials require that Portland cement shall develop "initial set" in not less than thirty minutes, but must develop "hard set" in not less than one hour nor in not more than ten hours. Portland cements are generally much slower in setting than natural cements. There are, however, as was mentioned under natural cements, a few of the latter which are slow-setting. Soundness, or Constancy of Volume. — The purpose and general description of the test was described under natural cements, and those phenomena common to both natural and Portland cements were mentioned. The soundness tests are of greater importance than any other, and are often the only ones necessary. An unsound cement is likely to go to pieces on the work. The following are the requirements in the specifications of the American Society for Testing Materials for Soundness or Constancy of Volume of Portland Cement : Pats of neat cement about three inches in diameter, one-half inch * "Concrete and Reinforced Concrete Construction." Homer A. Reid. 174 BUILDING CONSTRUCTION. (Ch. IV) thick at the center, and tapering to a thin edge, shall be kept in moist air for a period of twenty-four hours. (a) A pat is then kept in air at normal temperature, and observed at intervals for at least 28 days. (b) Another pat is kept in water maintained as near 70° Fahr. as practicable, and observed at intervals for at least 28 days. (c) A third pat is exposed in any convenient way in an atmos- phere of steam, above boiling water, in a loosely closed vessel for five hours. These pats to satisfactorily pass the requirements shall remain firm and hard and show no signs of distortion, checking, cracking or disintegration. Engineers are pretty well agreed that it is safe to adopt the fol- lowing conclusion: ''If a Portland cement passes the hot test it may be used immediately with reasonable certainty of its ultimate soundness. If it fails to pass, it should be regarded with sus- picion and thoroughly tested." The following are useful and simple directions for soundness test- ing for small purchasers of Portland cement : "Take about ^ pound, or one cupful, of Portland cement and mix by kneading minutes with sufficient water to form a paste of a consistency like putty. Press portions of the paste onto 3 pieces of window glass 4 inches square, so as to make 3 pats each about 3 inches in diameter and 3^ an inch thick at center, tapering to a thin edge, and place in moist air for 24 hours. Then keep one pat in air at moderate temperature (about 60° or 70° Fahr.) for 28 days, keep second pat in water for 28 days, and place third pat in loosely closed vessel over boiling water and keep there for five hours. Reject cement if any pats show radial cracks or curl or crumble. The air pat should not change color. Portland cement may be accepted on the steam test alone if time is limited. Natural cements should be subjected to water and air but not to steam."* Fineness. — The general significance of the fineness tests for all cements was explained under this subdivision in treating of natural cements. The following are the requirements for the fineness of a Portland cement, taken from the standard specifications of the American Society for Testing Materials "It shall have by weight a residue of * "Concrete, Plain and Reinforced.". Taylor and Thompson, PORTLAND CEMENTS. not more than 8 per cent on the No. loo, and not more than 25 per cent on the No. 200 sieve." The fineness requirements of some other specifications for Port- land cement used in important works are as follows : (1) Rapid Transit Subway, New York City, 1900-1901 : ''Ninety-eight per cent shall pass a No. 50 sieve and 90 per cent a No. 100 sieve." (2) New York State Canals, 1896: "Portland cement must be of such fineness that 95 per cent of the cement will pass through a sieve of 2,500 meshes to the square inch, and 90 per cent through a sieve of 10,000 meshes per square inch." (3) Department of Bridges, New York City, 1901 : "Cement must be ground so fine that 90 per cent of it will pass through a sieve of 10,000 meshes per square inch." (4) Engineer Corps, U. S. Army, 1902: "Ninety-two per cent of the cement must pass through a sieve made of No. 40 wire, Stubbs' gauge, having 10,000 openings per square inch." (5) U. S. Reclamation Service, 1904: "Ninety-five per cent by weight must pass through a No. 100 sieve having 10,000 meshes per square inch, the wire to be No. 40 Stubbs' wire gauge ; and 75 per cent by weight must pass through a No. 200 sieve having 40,000 meshes per square inch, the wire to be No. 48 Stubbs' wire gauge." (6) Canadian Society of Civil Engineers, 1903 : "The cement shall be ground so fine that the residue on a sieve of 10,000 meshes to the square inch shall not exceed 10 per cent of the whole by weight, and the whole of the cement shall pass a sieve of 2,500 meshes to the square inch." The following is a simple test for the fineness of a cement : "Sift 5 ounces of dry cement containing no lumps through a sieve about 6 to 8 inches diameter with 100 meshes per linear inch. Not more than y2 ounce of either Portland or natural cement should remain on sieve. To compare quality of two brands otherwise similar, sift through a 200-mesh sieve and choose the finer cement."* 179. STRENGTH TESTS FOR PORTLAND CEMENTS.— * "Concrete, Plain and Reinforced." Taylor and Thompson. 176 BUILDING CONSTRUCTION. (Ch. IV) As was stated under this subdivision of natural cements, a brief description of the manner of applying strength tests to cement is - given in division 6, of this chapter, entitled ''Strength Tests for Cements." A standard requirement, however, will be given here. The requirements for tensile strength of Portland cement, as given in the specifications of the American Society for Testing Ma- terials, 1904, are as follows : "The minimum requirements for tensile strength for briquettes one inch square in section shall be w^ithin the following limits, and shall show no retrogression in strength within the periods specified: Age. NEAT CEMENT. Strength. 24 hours in moist air 150-200 pounds. 7 days (i day in air, 6 days in water) 450-550 pounds. 28 days (i day in air, 27 days in water) 550-650 pounds. ONE PART CEMENT, THREE PARTS SAND. 7 days (i day in air, 6 days in water) 150-200 pounds. 28 days (i day in air, 27 days in water) 200-400 pounds." The tensile test is the one most commonly applied strength test, because it is difficult to make an accurate compressive test. The ratio between compressive and tensile strength is quite uniform, and is aboiit 10. For a list of other "Strength Tests of Cements and Cement Mortars," and a list of the "Special Tests of Cements and Mortars" see Articles 166 and 167 under the subject "Natural Cements." 180. SPECIFICATIONS FOR PORTLAND CEMENTS.— As was stated under this heading for natural cements, the specifica- tions for the cement for any operation are' based upon the result of tests, upon experience and practice, and upon the study of model requirements for the most recent and approved modern works. The set of specifications given under natural cements and the fol- lowing set here are sufficient to indicate the general form, the details of the requirements, of course, differing for Portland cement. It is not possible here to give the dififerent specifications for the latter, and the reader is referred to various treatises on cements, and to the bibliographies of cement specifications published here and else- where. One most excellent set is given, however, the specifications for Portland cement, based upon the practice of Engineers F. W. Taylor and S. E. Thompson, supplemented by a careful study of the specifications of the following: American Society for Testing Ma- PORTLAND CEMENTS. ^77 terials, American Railway Engineering and Maintenance-of-Way Association, City of Philadelphia, United States Army, United States Navy, Massachusetts Metropolitan Commissions, New York Rapid Transit Commission, and others. 1. Packages. — Cement shall be packed in strong cloth or canvas sacks. t Each package shall have printed upon it the brand and name of the manufacturer. Packages received in broken or damaged con- dition may be rejected or accepted as fractional packages. 2. Weight. — Four bags shall constitute a barrel, and the average net weight of the cement contained in one bag shall be not less than 94 pounds or 376 pounds net per barrel. A cement bag may be assumed to weigh one pound. The weights of the separate packages shall be uniform. 3. Requirements.^ — Cement failing to meet the seven-day re- quirements may be held awaiting the results of the twenty-eight-day tests before rejection. 4. Tests."^ — All tests shall be made in accordance with the meth- ods proposed by the Committee on Uniform Tests of Cement of the American Society of Civil Engineers, presented to the society Jan- uary 21, 1903, and amended January 20, 1904, with all subsequent amendments thereto. 5. Sampling. — Samples shall be -taken at random from sound packages, and the cement from each package shall be tested sep- arately. 6. * The acceptance or rejection shall be based on the following requirements : 7. Definition of Portland Cement.^ — This term is applied to the finely pulverized product resulting from the calcination to incipient fusion of an intimate mixture of properly proportioned argillaceous^ and calcareous§ materials, and to which no addition greater than 3 per cent has been made subsequent to calcination. 8. Specific Gravity."^ — The specific gravity of the cement, thor- oughly dried at 100° Cent. (212° Fahr.), shall be not less than 3.10. 9. Fineness."^ — It shall leave by weight a residue of not more *Paragraphs designated by an asterisk are quoted from the Standard Specifications of the American Society for Testing Materials. +If the cement is to be stored in a damp place or near the sea, it must be packed in well-made wooden barrels lined with paper. If stored in a dry place to be used immediately, it may be packed in stout cloth or canvas bags which are of course cheaper than barrels. % Clayey. § Consisting chiefly of lime or calcium. 178 BUILDING CONSTRUCTION. (Ch. IV) than 8 per cent on the No. loo, and not more than 25 per cent on the No. 200 sieve. 10. Time of Setting."^ — It shall develop initial set in not less than thirty minutes, but must develop hard set in not less than one hour nor more than ten hours. 11. Tensile Strength.^ — Briquettes one inch square in section shall attain at least the following tensile strengths and shall show no retrogression within the periods specified: Age. NEAT CEMENT. Strength.f 24 hours in moist air 175 lbs. 7 days (i day in air, 6 days in water) 500 lbs. 28 days (i day in air, 27 days in water) 600 lbs. ONE PART CEMENT, THREE PARTS STANDARD SAND. Age. Strength.f 7 days (i day in moist air, 6 days in water) 150 lbs. 28 days (i day in moist air, 27 days in water) 200 lbs. 12. Soundness or Constancy of Volume. — Pats of neat cement about three inches in diameter, one-half inch thick at the center, and tapering to a thin edge, shall be kept in moist air for a period of twenty-four hours. {a) A pat is then kept in air at normal temperature, and observed at intervals for at least 28 days. (b) Another pat is kept in water maintained as near 70 de- grees Fahr. as practicable, and observed at intervals for at least 28 days. (c) A third pat is exposed in any convenient way in an atmos- phere of steam, above boiling water, in a loosely closed vessel for five hours. These pats to satisfactorily pass the requirements shall remain firm and hard and show no signs of distortion, checking, cracking or disintegration. 13. Sulphuric Acid and Magnesia. — The cement shall not con- tain more than 1.75 per cent of anhydrous sulphuric acid (SO3), nor more than 4 per cent of Magnesia (MgO). In writing on "Specifications for Portland Cement," Mr. Edwin *Paragraplis designated by an asterisk are quoted from the Standard Specifications of the American Society for Testing Materials. tThe American Society for Testing Materials gives minimum requirements as fellows- Neat Cement — 24 hours, 150-200 lb.; 7 days, 450-550 lb.; 28 days, 550-650 lb. 1:3 mortar— 7 days, 150-200 lb.; 28 days, 200-300 lb.; the exact values to be fixed in each case by the consumer. PUZZOLAN CEMENTS. 1/9 C. Eckel"^ has collected and published various specifications, and states that they are of interest partly for comparison and partly to show the growth of intelligent treatment of the subject. He also states that the specifications of the American Society for Testing Materials will probably become the standard in this country. 181. MISCELLANEOUS DATA AND AIEMORANDA ON PORTLAND CEMENTS.— Reference should here be made to the corresponding Article, 169, under Natural Cements, as occasional data these are for Portland Cements, The following are some useful notes compiledt to show the weights and measurements of contents of a barrel of Portland cement. (See also Article 178.) A barrel of Portland cement weighs about 380 pounds net. A barrel of Portland cement weighs about 400 pounds gross. A barrel of Portland cement contains about 3.40 cubic feet packed. A barrel of Portland cement contains about. 4. 25 cubic feet loose. A barrel of Portland cement contains about 2.73 bushels packed. A barrel of Portland cement contains about 3.61 bushels loose. 182. THE CHOICE OF PORTLAND CEMENTS, AND THE SELECTION OF BRANDS.— The reader is here referred to Article 170, under Natural Cements, wuich considered the ques- tion of deciding between the two classes of cements in any case, and also the question of the selection of some particular brand of either. 5. PUZZOLAN CEMENTS. 183. CLASSIFICATION. — The puzzolan cements belong to the silicate division of the complex cementing materials. They differ from the other three classes of the silicate cements, the hydraulic limes', natural cements and Portland cements, as their raw materials are not calcined after mixture. 184. DEFINITION OF PUZZOLAN CEMENT.— Puzzolan cement is a mechanical mixture of certain natural or artificial * "Cements, Limes and Plasters." Edwin C. Eckel. The following is the list of these specifications: 1. New York State Canals. 1896. 2. Rapid Transit Subway, New York City. 1900-1901. 3. Department of Bridges, New York City. 1901. 4. Engineer Corps. U. S. Army. 1902. 5. U. S. Reclamation Service. 1904. 6. Canadian Society of Civil Engineers. 1503. i 7. Cohcrete-Steel Engineering Company. 1903. .8. British Standard Specifications. 1905. , 9. American Society for Testing Materials. ' 1904. t "Handbook for Superintendents of Construction." H. G. Richey. i8o BUILDING CONSTRUCTION. (Ch. IV) products, such as volcanic ash or blast-furnace slag, with powdered slaked lime. The term piiz::olan has been adopted by many authori- ties and is now in general use. The material was first obtained near the town of Pozzuoli, a few miles west of Naples, from which place the Italian poz:::iiolana takes its name. 185. THE CHEMICAL ANALYSIS OF PUZZOLAN CEMENTS. — In Article 157 on the "Classification of Cementing Materials," in Table IX, "Typical Analyses of Cements," the average chemical analysis is given. The puzzolanic materials in composi- tion are made up largely of silica and alumina, and usually with more or less iron oxide ; and some of these materials, such as the slags used in cement-manufacture, contain in addition notable per- centages of lime. 186. THE MANUFACTURE OF PUZZOLAN CEMENTS.— Puzzolanic materials include the (i) natural and (2) the artificial materials. To the first class belong the direct products of volcanic action, and to the second class the blast-furnace slag and some other artificial materials, such as burnt clay. In using the natural materials, they are dug out from the deposits, screened and ground and occasionally slightly roasted to increase their hydraulic properties. In using the artificial materials, as blast-furnace slag, no kilns are used, and the molten slag coming from the furnace is chilled and granulated by a stream of cold water, and separated from most of its sulphur. It is then dried and may or may not have a pre- liminary grinding before the addition of the slaked lime. The production of puzzolan cement in the United States in 1906 was 481,224 barrels, valued at $412,921. An advantage of this industry lies in the fact that it utilizes and consumes a product of steel and iron foundries which has for years been troublesome to dispose of and regarded as a waste product. 187. THE USES OF PUZZOLAN CEMENTS.— The follow- ing are the generally accepted conclusions regarding the proper uses of puzzolan cement : ( 1 ) It never becomes extremely hard, like Portland cement. (2) Puzzolan mortars are tougher or less brittle than Portland cements. (3) It is well adapted for use in sea-water. (4) It is well adapted for use in all positions constantly exposed to moisture. PUZZOLAN CEMEXTS. i8i (5) It is suitable for use in foundations of buildings in damp places. (6) It may be used in sewers, drains and in underground works generally. (7) It may be used in the interior of heavy masses of masonry or concrete. (8) It is not suitable for use in any positions subjected to mechanical wear, attrition or blows, and it should not be employed in places where it is liable to be exposed for long periods to dry air, even after it has reached its hardest set. (9) It has a tendency to change to a whitish color and to dis- integrate, on account of the oxidation of its sulphides at and near the surface, when exposed to dry air as mentioned in (8). 188. CHARACTERISTICS AND PROPERTIES OF PUZ- ZOLAN CEMENTS. — Color. — Puzzolan cement made from slag can usually be distinguished from Portland cement bv its decidedly lighter color and slightly different tint, and from natural cements by a marked difference in tint. The color varies from bluish-white to lilac. This cement is also characterized by the intense bluish- green color in the fresh fracture after long submersion in water, diie to the presence of sulphides, which color fades after exposure to dry air. Slag cements do not stain masonry. Weight. — Slag cement weighs about 350 pounds gross, or 330 pounds net, per barrel. Specific Gravity. — The slag cements are lighter than the Portland cements, and for the same weight more bulk is obtained. The usual range of variation in the specific gravity of the slag cements is from 2.7 to 2.9, as compared with the fair average 3.15 for good Portland cement. Activity or Time of Setting. — Slag cements are generally slower setting than Portland cements. The use to which the cement is put determines whether or not slow set is desirable. Rapidity of set varies decidedly with the amount of alumina in the slag. Burned clay, active forms of silica, slags high in alumina, etc., when added hasten the set. Alkalies a||felerate the set. Soundness or Constancy of Volume. — To test the soundness, pats of* neat cement mixed for five minutes with 18 per cent of water by weight are made on glass, each pat about 3 inches in diameter and an inch thick at the center, tapering thence to a thin edge. They are kept under wet cloths until finally set, when they are placed in l82 BUILDING CONSTRUCTION. (Ch. IV) fresh water. They should not show distortion or cracks at the end of twenty-eight days. Fineness. — Ninety-seven per cent of the puzzolan or slag cement should pass through a sieve made of No. 40 wire, Stubbs' gauge^ having 10,000 openings per square inch. 189. STRENGTH OF PUZZOLAN OR SLAG CEMENTS.— Slag cements approximate in tensile strength similar mixture of Portland cements. In compressive strength, however, their resist- ance is less, the' ratio of compressive to tensile strength being about from 5 to 7 to I for slag cements, and from 9 to 11 to i for Portland cements. Slag cements also often give nearly as great tensile strength in 3 to i mixtures as in neat briquettes, this being due to the fact that they are ground very fine. 190. SPECIFICATIONS FOR PUZZOLAN CEMENTS.— Detailed specifications for puzzolan cements have been prepared and published by the Engineer Corps, U. S. Army, and are to be found in most of the treatises on limes, cements, mortars and concretes.* 6. STRENGTH TESTS FOR CEMENTS. 191. STRENGTH TESTS IN GENERAL.— The object of strength tests for cement mortars is to determine their strength in actual work. As it is easier to make the test for tension than for compression, shear, flexure, adhesion, etc., and as the tensile strength bears a generally constant relation to these other stresses, it is the tension test that is usually made. The tests are made on neat cement and on cement mixed with varying proportions of sand. The former indicate the character and quality of the material, the latter the strength under actual conditions. (See also Articles 166 and 208.) For Portland cement, sand mixture tests, i part by weight of cement to 3 parts of sand are used ; and for natural and slag cements, i to i and i to 2. The briquettes are broken at periods of 24 hours, 7 days, and 28 days for neat tests, longer periods being necessary for special experimental purposes. 192. NORMAL CONSISTENCY^. OF MORTAR.— This means the use of a proper percentage of water in making the pastes for the pats, briquettes, etc. Various methods are followed for making this determination. A simple method is to mix the cement * Among other books in which these specifications are published is "Cements, Limes and Plasters," by Edwin C. Eckel. STRENGTH TESTS FOR CEMENTS. 183 1 — i i 1 1 1 1 1 ♦ • 1 Fig. 89. Standard American Form of Cement Briquette. paste to such a degree of plasticity that when a ball of the paste 2 inches in diameter is dropped upon a hard surface from a height of 2 feet it will not crack or flatten more than half its original thick- ness. 193. FORM OF BRIQUETTE.— The standard American form of briquettes, with which the tensional tests are usually made, is shown in Fig. 89. This is the form adopted by the Special Com- mittee on Uniform Tests of Cement of the American Society of Civil Engineers. The minimum cross-sectional area is one square inch. The molds are made of brass, and are either single or in gangs of three or four, as shown in Fig. 90. In making the tests a solid metal clip of the form shown in Fig. 91 is used without -cushioning at the points of contact. The bearing is % of an inch i84 BUILDING CONSTRUCTION. (Ch. IV) wide, and the distance between centers of contact on same clip should he i}i inches. 194. METHOD OF MIXING.— A careful determination by weight of the proportions of cement, sand and water is made, the sand and cement mixed dry, and the water added all at once. A rapid and thorough mixing of the mortar then follows, and when it is stiff and plastic it is pressed firmly into the molds with a trowel, without ramming, and struck off level. The mixing is done Fig. 90. Gang-Mold for Cement Briquettes. FORM OF CLIP. Fig. 91. Standard Metal Clip for Testing Cement Briquettes. Upon a glass or slate slab, the hands being protected by rubber gloves. 195. STORING THE BRI- QUETTES OR TEST PIECES. During the first 24 hours after molding, the test pieces are stored in a damp atmosphere to prevent them from drying out. They are then immersed in water until tested. 196. TESTING MACHINES. — There are many testing ma- chines in use, all of them rather expensive. When properly used, any one of them will give satis- factory results. These machines and their detailed operation are discussed and illustrated in the treatises on these subjects. A home-made testing machine of low cost is shown in Fig. 92. It can be made by an ordinary mechanic at small expense. It is not as convenient nor quite as STRENGTH TESTS FOR CEMENTS. 185 accurate as the more elaborate machines, but it is sufficiently accurate for all practical purposes. "The machine consists essentially of a counterpoised wooden lever, 10 feet long, working on a horizontal pin, between two broad uprights, 20 inches from one end. Along the top of the long arm runs a grooved wheel carrying a. weight, W. The distances from the fulcrum in feet and inches are marked on the surface of the lever, and also the corresponding effect of the weight at each point. The clamp for holding the briquette is sus- pended from the short arm, 18 inches from the fulcrum. The clamps are of wood and are fastened by clevis points to the lever* ^ arm and bed-plate respectively. The pin is iron and the pin holes are reinforced by iron washers. When great stresses are required extra weights are hung on the end of the long arm. Pressures of 3,000 pounds have been developed with this machine." Fig. 92. Simple Machine for Approximate Cement Tests. In applying the load on the briquette it is recommended that it start at o and be increased regularly at the rate of 400 pounds per minute for neat Portland cements, and 200 pounds per minute for natural cements and mortar. A rough test may be made by suspending the clamps from a beam or trestle and hanging a bucket or box from the lower clamp, into which sand is run until the briquette breaks, when the sand is weighed. 197. TENSILE STRENGTH OF CEMENT MORTARS.— Tests of tensile strength are made to determine the strength which w'lW develop in a certain time, and the ultimate strength. A cement should never decrease in strength. The usual stipulations are that the materials must pass a minimum strength acquirement at 7 and 28 days. The sand test is the true criterion of strength, and there should be no acceptance of any cement failing to satisfactorily pass it, even though the neat tests have not failed. Cement and cement mixtures attain a strength not differing greatly from the ultimate strength within a period of three months BUILDING CONSTRUCTION. (Ch. IV) from the time of setting, and practically within a month or so after this period no appreciable change of strength takes place.* The following tablet gives the approximate values for the tensile strength of first-class Portland, natural and slag cements in neat and sand tests : TABLE XIV. Tensile Strengths of Portland, Natural and Slag Cements. PORTLAND CEMENT. Age. Neat. Strength. 24 hours (in moist air) • 175 lbs. 7 days (i day in moist air, 6 days in water) 500 lbs. 28 days (i day in moist air, 27 days in water) 600 lbs. Age. One Part Cement, Three Parts Sand. Strength. 7 days (i day in moist air, 6 days in water) 170 lbs. 28 days (i day in moist air, 27 days in water) 240 lbs. NATURAL CEMENT. Age Neat. Strength. 24 hours (in moist air) 40 lbs. 7 days (i day jn moist air, 6 days in water) 125 lbs. 28 days (i day in moist air, 27 days in water) 225 lbs. Age One Part Cement, Two Parts Sand. Strength. 7 days (i day in moist air, 6 days in water) 75 lbs. 28 days (i day in moist air, 27 days in water) 140 lbs. SLAG CEMENT. Age Neat. Strength. 7 days (i day in moist air, 6 days in water) 350 lbs. 28 days (i day in moist air, 27 days in water) 500 lbs. Age. One Part Cement, Three Parts Sand. Strength. 7 days (i day in moist air, 6 days in water) 140 lbs. 28 days (i day in moist air, 27 days in water) 220 lbs. 198. COMPRESSIVE STRENGTH- OF CEMENT MOR- TARS. — Compression tests of cement are not generally made in the United States, although they are made in Europe. When they are made the ends of the specimens broken in tension are often used in making the test. The ratio of the compressive to the tensile strength, in natural cements and slag cemicnts, seems to be lower than in Portland cements, in which latter it may be taken as 10. For natural cem.ent the average ratio is 4.9, and for slag cements 5.3, as determined by a series of tests. See also Article 208, * See "Cements. Mortars' and Concrete." Myron S. Falk. + "Concrete and Reinforced Concrete Construction." Homer A. Reid. STRENGTH TESTS TOR CEMENTS. 187 "Strength of Mortar," and Article 189, ''Strength of Puzzolan or Slag Cements." 199. OTHER STRENGTH PROPERTIES.— rra;zj^'rr^^ or Flexure Tests have been made on beams and prisms of cement mor- tars, but are now seldom used. Their principal value is in compar- ing the direct tensional stress with the tensile fiber stress due to flexure. A relation has been determined between the ultimate tensile and Hexiiral fiber stresses of cement mortar briquettes, and the tensile flexural fiber stress has been found from several series of careful experim.ents to be 1.9 times the simple direct tensile stress of the same material.* Tests have been made to determine the adhesive strength of cement m.ortars. There is a great variation in the adhesive strength of mortars made from dififerent cements. The adhesion of mortar to a stone or brick surface depends upon the state of the surface and the nature of the cement used. It is less than the tensile strength of the mortar. f The adhesion increases as the surface receiving the mortar becomes more porous. Irregu- larities of the surface of stone do not seem to afifect the adhesive strength, but with iron, roughening the surface increases the adhesion of the mortar. A dirty surface or insufiicient moistening of the surface lowers the adhesion. The average ultimate adhesive strength of cement mortar to brick surfaces may be taken at from 25 to 85 pounds per square inch. In the use of iron or steel for reinforcement, and the setting of bolts in mortar and concrete, the whole question of the adhesion of mortar to iron or steel is one of great importance, but belongs to discussions in connection with reinforced concrete. From 200 to 500 pounds per square inch may be taken as average figures for the ultimate adhesive strength of cement mortar to iron rods or bolts imbedded in it. See also in Article 209, 'The Adhesion of Mortars." Shearing tests have been made upon dififerent mortars, and the shearing resistances for Portland cement mortars found to be very much less than the compressive resistance. 4: * M. Durand-Claye in "Commission des Methodes d'Essai des Materiaux de Construc- tion," 1895, Vol. IV, p. 211. + "A'lechanics of Materials." Mansfield Merriman. % For a comparison of Flexural, Tensional, Compressive and Shearing Strength of Portland Cement Mortars, see very comprehensive tables in Chapter IX of "Concrete, Plain and Reinforced," by Taylor and Thompson. 188 BUILDING CONSTRUCTION. (Cii. IV) . The coefficient of elasticity of American natural cements has been found to vary from 500,000 to 1,800,000 pounds per square inch, and of American Portland cements from 2,300,000 to 4,500,00a pounds per square inch. 7. CEMENT MORTARS. 200. USE. — Cement mortar should be used for all mason work which is below grade, or situated in damp places, and also for heavily loaded piers and arches of large span. It should be used for setting coping stones, and wherever the mason work is especially exposed to the weather. For construction under water, and in heavy stone piers or arches, and for concrete, Portland cement should be used ; elsewhere natural cement mortar will answer. See also the articles relating to the *'Uses" of the various cements. 201. MIXING THE MORTAR.— The following are directions for hand mixing cement mortar for ordinary masonry : Spread about half the sand required for mixing evenly over the bed of the mortar box (which should be water-tight), and then spread the dry cement evenly over the sand and spread the remaining sand on top. Thoroughly mix the dry sand and cement with a hoe or shovel, as this is a very essential part of the process. Shovel the dry mixture to one end of the box and pour water into the other end. ("Cements vary greatly in their capacity for water, freshly-ground cements re- quiring more than those that have become stale. An excess of water is, however, better than a deficiency, particularly when a very ener- getic cement is used, as the capacity of this substance for absorbing water is great.") Draw down with a hoe the sand and cement in small quantities and mix with the water until enough has been added to make a good stiff mortar, taking care not to get it too thin. Work the mortar vigorously with a hoe for five minutes to get a thorough mixture. The mortar should leave the hoe clean when drawn out of it, very little sticking to the steel. But a very small quantity of cement mortar should be mixed at a time, particularly that made of nat- ural cements, as mortars made from these cements soon commence to set, after which they should not be used. As a rule natural cement mortars should, not be used after they have been mixed two hours, and Portland cement mortars after four hours (for best work not over one hour). CEMENT MORTARS. 189 t The sand and cement should not be mixed so as to stand over night, as the moisture in the sand will destroy the setting qualities of the cement. Mechanical mixtures are frequently used in large operations, with a lessening of the labor of manipulating the materials, and, when employed with great care, with a uniformity of good work. The principal objection to these mixer^ is the failure to thoroughly inter- mix the dry cement and sand, and the temptation to lighten the labor of the wet mixing by giving an overdose of water. 202. KEEPING CEMENT MORTARS MOIST.— ''Hydraulic cements set better and attain a greater strength under water than in the open air ; in the latter, owing to the evaporation of the water, the mortar has a tendency to dry rather than to set. This difference is very marked in hot, dry weather. If cement mortar is to be ex- posed to the air it should be shielded from the direct rays of the sun and kept moist." 203. PROPORTION OF SAND.— "A paste of good hydraulic cement hardens simultaneously and uniformly throughout the mass, and its strength is impaired by any addition of sand." As mortar is never used by itself, however, but as a binding material for brick and stone, and there can obviously be no advantage in making the strength of the mortar joints greater than that of the bricks or stones they unite, sand is always added to the cement in making mortar. Sand also generally reduces the tendencies to shrink and crack, especially in lime mortar. As cement is much more expensive than sand, the larger the proportion of sand in the mortar the less will be its cost. The proportion of sand should vary according to the kindfDf cement and the kind of work for which the mortar is to be used. For natural cements the proportion of sand to cement by measurement should not exceed 3 to i, and for piers and first- class work 2 to I should be used. Portland cement mortar may- contain 4 parts of. sand to i of cement for ordinary mortar, and 3 to I for first-class mortar. For work under water not more than 2 parts of sand 'to i of cement should be used. When cheaper mortars than these are desired it will be better to add lime to the mortar instead of more sand. The following are the proportions of cement and sand generally used for some specific purposes: , For masonry and brickwork, i part cement to 2, 3, or 4 parts of sand, according to strength required and purposes for which the igo BUILDING CONSTRUCTION. (Ch. IV) . mortar is to be used. For some special purposes 5, or even 6, parts of sand have been used. For face brickwork, i part cement to 2 parts of sand. For backing and in ordinary masonry foundations, i part cement to 3 parts of sand. For brick piers and first-class brickwork, not more than 2 parts of sand to i of natural cement should be used, and i or 1^2 parts of sand will make a still stronger mortar. For cement plastering, equal parts of natural cement and sand. For rubble stonework under ordinary conditions, i part Portland cement to 4 parts of sand are frequently used and found to satisfy every condition. For top surfaces of floors and walks, i part Portland cement to from I to parts of sand. The superintendent should see that the cement and sand for each batch of mortar are carefully measured to get the right proportions. To mortars composed of the same cement with different propor- tions and sizes of sand two fundamental laws* of strength may be applied. The first law is that with the same aggregate — that is, the inert material, such as sand, broken stone, etc., with which the cement or other adhesive material is mixed to form mortar or concrete — the strongest and most impermeable mortar is that containing the largest percentage of cement in a given volume of the mortar. The second law is that with the same percentage of cement in a given volume of mortar, the strongest, and usually the most impermeable, mortar is that which has the greatest density ; that is, the mortar which in a unit volume has the largest percentage of solid materials. Plastering mortar, for stucco work or waterproofing, should be made of i part cement and i part sand. For lining cisterns 2 parts of natural cement or i of Portland cement should be used. The following tablef shows the comparative strength of English Portland cement mortar, with different proportions of sand and at different ages: • "Concrete, Plain and Reinforced." Chapter IX. Taylor and Thomp?on. _ t This table shows the comparative ultimate tensile strengths of some English neat cements and sand mixtures. The reader is referred to the numerous and detailed reports of recent tests made on American cement mortars of all kinds, and printed in various bulle- tins and treatises on these subjects. « CEMENT MORTARS, TABLE XV. Strength of English Portland Cement Mixtures, AGE AND TIME IMMERSED. PROPORTION OF CLEAN PIT SAND TO I CEMENT. Neat cement. I to I. 2 to I. 3 to I. 4 to I. 5 to I. 445 o 679-9 877-9 978.7 995-9 1,075-7 152.0 326.5 549-6 639.2 718.7 795-9 64-5 166.5 451-9 497-9 594-4 607.5 44-5 91.5 305-3 304-0 383.6 424-4 22.0 71.5 153-0 275-6 49.0 123.5 218.8 215.6 Twelve months 317.6 P. 177, " Notes on Building Construction," Part III. The values in the table represent the breaking strength in pounds on a sectional area of 2^4 square inches. See also the various tables and specifications given in other articles of this chapter, showing the decrease in strength due to larger proportions of sand. 204. PORTLAND AND ROSENDALE CEMENT, MIXED, — "Mixtures of Portland and natural cements, unless mixed at the factory and sold as Improved Natural Hydraulic Cements, are not advised under any conditions."* 205. CEMENT-LIME MORTARS.— Some constructions re- quire quick-setting mortars, but do not need the strength nor war- rant the expense of a i to 2, 3 or 4 mixture of cement and sand. A I to 5 or more mixture would give ample strength, but would work "short" ; that is, it would not work easily, rapidly and smoothly on the trowel. It would not adhere perfectly to the stone or brick, and could not be safely used. The addition of a limited quantity of slaked or hydraulic lime corrects these faults, results in a cheaper mortar, and gives a mixture suited to a great variety of uses. It permits the use of Portland cement mortar for very many purposes. The following are the principal advantages of Portland cement- lime mortar: ■ (i) Cheapness in comparison with other hydraulic materials. (2) Rapidity of setting and hardening. (3) Marked hydraulic properties. *See Taylor and Thompson in "Concrete, Plain and Reinforced," in the discussions on "The Choice of Cement" and "The Class of Cement." T92 BUILDING CONSTRUCTION. (Cii. IV) n {4) Great strength on exposure to air. (5) Remarkable resistance to the weather. In making cement-lime mortar the sand and cement arc thoroughly mixed dry, the lime putty is mixed with water and screened into a mortar box, and the whole is then thoroughly mixed and worked together until a proper consistency is obtained. The following are mixtures by measure that have been used with excellent results : Cement i part, sand 5 parts, lime paste part. Cement i part, sand 6 to 7 parts, lime paste, i part. Cement i part, sand 8 parts, lime paste 13^ parts. Cement i part, sand 10 parts, lime paste 2 parts. In regard to the strength, a mixture of Portland cement i, lime paste I, sand 6, is as good as a mixture of Portland cement i, sand 3, in this case one-half the cement being replaced without loss of strength. Portland cement-lime mortar is very much stronger, and little or no more expensive than natural cement-lime mortar. 206. GROUT. — This is a very thin liquid mortar sometimes poured over courses of masonry or brickwork in order that it may penetrate into empty joints left in consequence of bad workman- ship. It is also sometimes necessary to use it in deep and narrow joints between large stones. The mortar may be neat or have vari- ous proportions of sand added, say from ^ to 2 parts to one part of cement. Its use is not generally recommended by writers on mortars, and the author believes that it should not be used in stone- work where it can be avoided. For brickwork, however, the author feels convinced that walls grouted with a moderately thin mortar every course makes a solid job. If the bricks are well wet before laying, and every joint slushed full of stiff mortar, it is impossible to get anything stronger; but in most localities it is difficult to get such work without keeping an inspector constantly on the ground, and when the walls are grouted the joints are sure to be filled. In his own practice the author always specifies grouting for all brick footings and foundation walls. Many of the largest buildings in New York City have grouted walls. ''Grouting is not now considered a first-class method of con- struction. It has, however, been used successfully in many cases, and will at times prove useful when, on account of local conditions, * CEMENT MORTARS. 193 other methods cannot be used. It has been successfully used for subaqueous foundation work by English engineers, both in India and Europe."'^ ^ The usual method of mixing is as follows : The cement is mixed, on a flat platform or ordinary mixing board, to the consistency of stiff paste, and then placed in a tub and slightly thinned down by the addition of water in small quantities. It is then stirred until the paste is reduced to a thick grout, just soft enough to leave the bucket. It is poured rapidly ; the faster the pouring and the more continuous the flow the better the results obtained. (See Chapter VII, Article 342, ''Grouting Brick Walls.") 207. DATA FOR ESTIMATES.— The following memoranda, made up from data given by Prof. Ira O. Baker, will be found useful in estimating the amounts of materials required in making any given quantity of mortar: Lime Mortar. — The weight of a barrel of lime is often taken at about 230 pounds net ; a bushel .of lime at 75 pounds. At these weights one barrel (or three bushels) of lime and i yard of sand will make i yard of i to 3 lime mortar, and will lay about 80 cubic feet of rough brickwork or common rubble. The following data are given by Mr. H. G. Richey : "i barrel of lime will make 2^ barrels of paste. I barrel of lime will lay 3 perches of stone rubble. I barrel of lime will lay 1,000 to 1,200 bricks. I barrel of lime will plaster 28 yards of 3-coat work. I barrel of lime will plaster 40 yards of 2-coat work. I barrel of lime equals 3 bushels of 80 pounds each."t Cement Mortar. — 1.8 barrels, or 540 pounds, of natural cement and .94 cubic yard of sand will make i cubic yard of i to 3 mortar ; two barrels, or 675 pounds, of Portland cement and .94 cubic yard of sand will also make i cubic yard of i to 3 mortar; 1.7 barrels, or 525 pounds, of Portland cement and .98 cubic yard of sand will make I cubic yard of i to 4 mortar ; i cubic yard of mortar will lay from 67 to 80 cubic feet of rough rubble or brickwork, from 90 to 108 cubic feet of brickwork with ^ to ^-inch joints, and from 324 to 378 cubic feet of stone ashlar. A cubic foot of common brickwork contains about eighteen bricks. See also Articles 169 and 181. * "Concrete, and Reinforced Concrete Construction." Homer A. Reid. + "Handbook for Superintendents of Construction." H. G. Richcy.' 194 BUILDING CONSTRUCTION. (Ch. IV) The following are useful data which have been compiled by Mr. H. G. Richey to show "What a Barrel of Portland Cement Will Do." A barrel of Portland cement will make about 3.15 cu. ft. of neat mortar. A barrel of Portland cement will make about 5.4 cu. ft. of mortar mixed I to I. A barrel of Portland cement will make about 8.5 cu. ft. of mortar mixed I to 2. A barrel of Portland cement will make about 10.7 cu. ft. of mortar mixed i to 3. A barrel of Portland cement will make about 13.5 cu. ft. of mortar mixed I to 4. A barrel of Portland cement will make about 23 cu. ft. of concrete mixed I, 3, 5- A barrel of Portland cement will make about 26 cu. ft. of concrete mixed I, 3, 6. A barrel of Portland cement will make about 29 cu. ft. of concrete mixed I, 3, 7. A barrel of Portland cement will make about 30 cu. ft. of concrete mixed i, 3, 8. A barrel of Portland cement (neat) will cover about 40 sq. ft. i in. thick. A barrel of Portland cement to i of sand will cover about 65 sq. ft. I in. thick. A barrel of Portland cement to 2 of sand will cover about 92 sq. ft. I in. thick. . A barrel of Portland cement to 3 of sand will cover about 128 sq. ft. I in. thick. A barrel of Portland cement to 2 of sand will lay about 750 bricks with ^-inch joints. A barrel of Portland cement to 2 of sand will lay about 1,050 bricks with 54-inch joints. A barrel of Portland cement to 3 of sand will lay about 900 bricks with ^-inch joints. A barrel of Portland cement to 3 of sand will lay about 1,350 bricks with J4-inch joints. A barrel of Portland cement to 3 of sand will lay about 2 perches of rubble stonework. 208. STRENGTH OF MORTAR.— This subject has been treated also in the articles relating to the strength of the different kinds of cement. The exact strength of mortar to resist compres- sion is not of very great importance, as it seldom, if ever, fails in this way. The tensile and adhesive strength of mortar is more important, particularly the latter, as whenever a building has fallen from using poor mortar it has generally been on account of the failure of the mortar to adhere to the bricks or stones. Whatever CEMENT MORTARS. 195 kind of mortar is used, it should be made rich and well worked, as the saving by using more sand is but a small percentage at most, and it is never safe for an architect to allow poor mortar to be used in his buildings. The safe crushing strength of Portland cement, natural cement and lime mortar used in ^-inch joints should equal the following values in tons per square foot : Portland cement mortar, i to 3, 3 months, 40 tons; i year, 65 tons. Natural " i to 3, 3 months, 13 tons; i year, 26 tons. Lime mortar i to 3, 3 months, 8.6 tons ; i year, 15 tons. From these values we see that for granite piers, heavily loaded, only Portland cement mortar should be used. For all piers loaded with over 10 tons per square foot, and not exceeding 20 tons, natural cement mortar may be used. (See also Article 198, "The Compressive Strength of Cement Mortars.") Lime mortar alone should never be used where any but moderate loads are to bear upon the work ; nor where the full loading is to be applied before the mortar has had time to harden. 209. THE ADHESION OF MORTAR.— "The adhesion of mortars to brick or stone varies greatly with the different varieties of these materials, and particularly with their porosity. The adhesion varies also with the quality of the cement, the character, grain and quantity of the sand, the amount of water used in tem- pering, the amount of moisture in the stone or brick, and the age of the mortar." Mortar adheres to both stone and brick better when they are wet (unless the temperature is below the freezing point), and the archi- tect should always insist on having the bricks well wet down with a hose before laying. Dry bricks absorb the moisture from mortar so that it cannot harden properly, and also destroy its adhesive prop- erties. The wetting of the bricks is fully of as much importance as the quality of the mortar in the brickwork. The adhesive strengths of cement mortars and lime mortars are as a rule proportional to their tensile strengths. Therefore where great adhesive strength is required to prevent sliding, as in arches, etc., either Portland or natural cement should be used, according to the importance of the work and stress to be resisted. Some years ago the walls of a brick building in New York City were pushed outward by barrels of flour piled against them, so that they suddenly fell into the street. [An examination of the mortar showed that it was of poor quality, 196 BUILDING CONSTRUCTION. (Ch. IV) with little adhesion to the bricks. If good mortar had been used, and if the bricks had been well wet, the failure (it should not be called an accident) would not have occurred. The adhesive and tensile strength of mortar is of great importance also in resisting wind pressure and vibration. 210. MORTAR IMPERVIOUS TO WATER.— The follow- ing proportions may be used for making a water-tight mortar, pro- vided the water is not moving, not too cold and not impregnated with acids : Cement. Lime Putty. Sand. I part. part. i part. I part. I part. 3 parts. I part. 1V2 parts. 5 parts. I part. 2 parts. 6 parts. A frequent cause of the failure of masonry is the disintegration of the mortar in the outside of the joints, although this does not take place to such an extent in buildings as in engineering works. "Or- dinary mortar, either lime or cement, absorbs water freely, com- mon lime mortar absorbing from 50 to 60 per cent of its own weight, and the best Portland cement mortar from 10 to 20 per cent, and consequently they disintegrate under the action of the frost. Mortar may be made practically non-absorbent by the addi- tion of alum and potash soap. One per cent, by weight, of pow- dered alum is added to the dry cement and sand and thoroughly mixed, and about i per cent of any potash soap (ordinary soft soap made from wood ashes is very good) is dissolved in the water used in making the mortar. The alum and soap combine and form com- pounds which are insoluble in water. These compounds are not acted upon by the carbonic acid of the air, and add considerable to the early strength of the mortar and somewhat to its ultimate strength."''' The alum and soap are comparatively cheap and can be easily used.f The mixture could be advantageously used in plastering base- ment walls and on the outside of buildings, and would add greatly to the durability of mortar used for pointing. 211. PLASTER OF PARIS IN MORTAR.— The imperme- ability of Portland cement mortar is increased by the addition of puzzolan cement. Plaster of Paris, which is sulphate of lime, when * "Treatise on Masonry Construction." Ira O. Baker. t For the effect of alum and soap in diminishing the permeability of mortars, see also results of experiments by Mr. Edward Cunningham, and Prof. W. K. Hatt in Trans. Am. Soc. of Civil Engineers, Vol. LI, pp. 127 and 128. CEMEXT MORTARS. 197 added to either lime or cement mortar in quantities not exceeding 5 per cent, accelerates the setting and also increases the early and the ultimate strength of mortar. Lime mortar to which plaster of Paris had been added is called "gauged" mortar. Selenetic lime, known as "Scott's cement" or "Selenetic cement," much used in England, is made by combining plaster of Paris and hydraulic lime, in the proportion of three pints of the plaster to a bushel of un- slaked lime. The addition of the plaster of Paris to lime appears to increase the strength of the mortar from two to three times. 212. SUGAR IN MORTAR.— Sugar has been employed for centuries in India as an ingredient of common lime mortar, and adds greatly to the strength of the mortar. An addition of sugar or syrup equal to one-tenth of the weight of the unslaked lime, to lime mortar, adds 50 per cent to the strength of the mortar and will cause the mortar to set more quickly. The addition of sugar to lime mortar is especially beneficial when used in very thick walls, as the lime mortar thus placed is never fully acted upon by the carbonic acid of the atmosphere. Sugar added to natural and Portland cement mortars in the proportion of 3^ to ^ per cent in weight of the cement increases the strength of the mortars about 25 per cent. Experiments made to determine the effect of sugar upon Port- land cement showed that an addition of from j/g to 2 per cent of sugar added to Dyckerhoff's German Portland cement increased considerably its strength after three months. While the sugar retarded the setting, and favorably assisted the perfecting of the chemical changes, more than 2 per cent of it rendered the cement useless. As the combination of sugar and lime is soluble in water, sugar should not be added to mortar that is to be used under water. Experiments have been made also to show the effect on the strength and other properties of mortars of various other admix- tures, such as alcohol, clay and loam, glycerine, lime, peat, plaster, salt, sawdust, soda, tallow, etc.* 213. EFFECT OF TEMPERATURE ON MORTARS.— Very hot weather is apt to injure mortar by causing its water to evaporate too rapidly, and thus interfere with the normal setting or hardening. Stones and bricks should be well moistened in such * For a short bibliography of papers relatiriP' to these tests see "Concrete, Plain and Reinforced," Taylor and Thompson. Chap. XXIX, "References to Concrete Literature." 198 BUILDING CONSTRUCTION. (Ch. IV) weather before bedding them so that the mortar may not dry out too fast and be reduced to a powder by the materials absorbing its moisture. Freezing does not appear to injure Hme mortar if the mortar remains frozen until it has fully set. Ahernate freezing and thawing materially damages the strength and adhesion of lime mortar, and as this is generally what happens when mortar is laid in freezing weather, it is much the safer rule for the architect to specify and see that no masonry shall be laid with lime mortar at such times. Very cold weather retards the setting or hardening of cement mortar, and the freezing and expansion of its water tend to disin- tegrate it. If the temperature of mortar can be kept above the freezing point long enough to allow it to set with sufficient strength to resist the disruptive effect of frost, it may be used in freezing weather. Quick-setting Portlands are used, or hot water, or salt put in the water used in making the mortar, or the stones or bricks or sand additions are heated, or the masonry is carefully covered immediately after laying with straw or canvas or manure, etc. Most natural cement mortars are ruined by freezing. They ex- pand by the frost, and a settlement results with the thawing. Portland cement mortars have their setting retarded, and their strength at short periods lowered, by freezing, but have their ulti- mate strength but slightly, if at all, affected. The setting of cement mortars is hastened, and the action of frost retarded, by heating the materials. Salt lowers the freezing point of mortar, and does not seem to affect the ultimate strength of cement mortar, where used in quan- tities up to 10 per cent of the weight of the water. "Mortar composed of i part Portland cement and 3 parts of sand is entirely uninjured by freezing and thawing, and mortar made of . natural cement, in any proportion, is entirely ruined by freezing and thawing."* 214. SALT IN MORTAR.— When it is desfred to use natural cement mortar in freezing weather the mortar should be mixed with water to which salt has been added in the proportion of one pound of salt to eighteen gallons of water, when the temperature is at 32 degrees Fahr., and for each degree of temperature below 32 degrees add three additional ounces of salt. Mortar mixed with * Trans. Am. Soc. of C. E., Vol. XVI., pp. 79-84. MORTAR COLORS AND STAINS. 199 such a solution does not freeze in ordinary winter weather, and hence is not injured by frost. Builders sometimes advocate the addition of hme to natural cement mortars in cold weather to ^ivarm them. There would be no heating effect of the lime, however, as heat is generated in lime only when it slakes. If natural cement mortars must be used in freezing weather, the only safe way of using them is by the addition of salt, as described on opposite page, otherwise the mortars will be com- pletely ruined by freezing. 215. CHANGE OF VOLUME IN SETTING.— Cement mor- tars diminish slightly in volume during the early periods of setting in air, and expand in like manner but in a less degree when under water, but the expansion and contraction are not sufficient to injuri- ously affect building construction. The contractions and expan- sions are greatest in neat cement mortars. 8. MORTAR COLORS AND STAINS. 216. THE USE OF MORTAR COLORS.— The natural color of the cement, sand and stone or gravel used affects the color of a mortar or concrete, and these separate ingredients of the complex mixture also modify the final shades even after the addition of coloring matters. Mortars and concretes of different shades can be made by vary- ing the amount of water used. Sands of different colors give different final colors to mortars and concretes, the color of the other ingredients remaining the same ; and the results obtained in this manner are usually far more permanent and satisfactory than those obtained from the use of artificial coloring matters. The use of artificial coloring in mortars, however, has been in vogue, more or less, for two thousand years, but the general use of colored mortars dates from a comparatively recent period. The object aimed at in using colored mortars in brickwork or stonework is either to get the effect of a mass of color, by conceal- ing the joints, or else, by using a contrasting color, to emphasize the joints. Rougher bricks may also be used with nearly as good effect by using a mortar of the same color as the bricks. Chipped or uneven edges -do not show as plainly with mortar of the same color as the bricks as they do when laid with white mortar. Coloring matter is added also to cement and concrete surfaces of 200 BUILDIXG COXSTRUCTION. (Ch. IV) all kinds, either to obtain a color effect in the cement in concrete itself, or to imitate stone of various kinds. I 217. OBJECTIONS TO MORTAR COLORS.— The objec- tion is sometimes made to the use of colored mortars that they are not as strong as white mortars and that the color always fades. These objections undoubtedly have much truth in them when cheap colors are used and the mortar is not properly mixed, but there are better grades of mortar colors now on the market which affect the strength of the mortar to a very slight extent, and some of them, when properly mixed, hold their color fairly well. 218. KINDS OF COLORS.— Most, if not all, of the coloring materials sold under the name of ''mortar colors," or stains, consist of mineral pigments put up either in the form of a dry powder or in the form of a pulp or paste. Pulp colors are thought by some to lend themselves more readily than the dry colors to a uniform mixing with the mortar, and they are sometimes preferred for the better grades of work. Paste or pulp stains should not be allowed to freeze, and should be kept moist by covering with water. A great deal of colored mortar is made by using common lamp- black and Venetian red, or the cheap grades of mineral paints for the coloring matter. These are very apt to fade and run and also tend to weaken the mortar, and the cheaper grades of mineral colors are not much better. Red lead, for example, is said to be injurious, even in very small quantities. The cost of the coloring matter is so small an item that only the very best grades should be used. The principal colors used are red, brown, buff and black, although green, purple, gray, drab and other mortar colors are made. For different grades of gray the proper kind of lampblack is used in varying proportions. The proportions used for the dry mineral colors vary from 2 to 10 per cent of the amount of cement, according to the shade desired. No injurious effects appear to result from the use of Prussian blue, ultramarine blue (in small quantities), burnt umber, red iron ore, yellow ochre and boneblack lampblack. Among the lampblacks the ''Germantown lampblack" is consid- ered a desirable coloring- material, on account of the small quan- tities necessary to obtain a good color. It is stated that even as , small an amount as i per cent of red lead works more or less injury MORTAR COLORS AND STAINS. 20 1 to cement mortar and concrete, and that it is not advisable to use it in larger amounts. Only moderate quantities of colors other than those mentioned should be used. Red oxide of iron, if it contains sulphuric acid, may cause swell- ing. Peroxide of manganese is sometimes used to produce shades of black and bluish gray ; the best raw iron oxide to produce red ; caput mortuum (expensive) to produce bright red; Venetian red Xo produce a cheaper red ; the best roasted iron oxide to produce brown ; and ochre to produce buff. The following are useful data''' compiled by Mr. Charles Carroll Brown, and bearing upon this subject: "Cement manufacturers recommend the following quantities per 100 pounds of cement : Black, 2 pounds excelsior carbon black. Blue, 5 to 6 pounds ultramarine. Brown, 6 pounds roasted iron oxide. Gray, ^ pound lampblack. Green, 6 pounds ultramarine. Red, 6 to 10 pounds raw iron oxide. Bright red, 6 pounds Pompeiian red. Yellow or bu0, 6 to 10 pounds yellow ochre. "It is said that unfading colored cement can be made by mixing with the raw materials before burning chromic oxide for green, oxide of copper for a blue-green, and equal parts of oxides of iron, manganese and cobalt for a black color. Such cements are not on the general market, however. Finely ground oxide of manganese added to the mortar will give a black color and not weaken the concrete. Venetian red and lampblack will fade. "White cements are often asked for. There is some difference in shade of Portland cements and puzzolan cements are usually the lightest. They are not satisfactory for greatly exposed work.. An English patent makes a white cement by mixing one part of kaolin, a clay without iron, three to five parts of white chalk, and two to five per cent of gypsum, or three to five per cent of magnesium chloride. The mixture is burned as any other cement is burned. The resulting cement would probably not stand severe exposure to the weather. Lafarge, a French "grappier" cement, is very light * "Handbook for Cement Users." Edited by Charles Carroll Bro\^m. Published by Municipal Engineering Company, Indianapolis and New York. 202 BUILDING CONSTRUCTION. (Ch. IV) colored. The use of a white marble dust in place of sand and puz- zolan or lighter cements produces the best results yet obtained. Sul- phate of barium, oxide of zinc and sulphate of lead produce a grayish white color, but their permanence is not guaranteed." The following table* is given by Mr. Lewis Carlton Sabin, and shows the colors given to Portland cement mortar containing two parts yellow river sand to one part cement. TABLE XVL Colors for Portland Cement Mortars. Cost of Coloring Matter per lb. ct. Dry material used Weight of Dry Coloriijg Matter to 100 Pounds of Cement ^ pound I pound 2 pounds 4 pounds 15 Lamp Light Light Blue Dark Blue Black Slate Gray Gray Slate 50 Prussian Light Green Light Blue Blue Bright Blue Blue Slate Slate Slate Slate 20 Ultramarine Light Blue Blue Bright Blue Blue Slate Slate Slate 3 Yellow Light Light Ochre Green • Buff 10 Burnt Light Pinkish Pinkish Dull Laven- Chocolate Umber Slate Slate der Pink Venetian Slate, Bright • Light Dull Red Pink Tinge Pinkish Slate Dull Pink Pink 2 Chattanooga Light Pinkish Dull Light Light Iron Ore Slate Pink Terra-Cotta Brick Red Red Iron Pinkish Dull Terra- Light Ore Slate Pink cotta Brick Red Mr. Homer A. Reid has compiled a listf of the usual proportions by weight of different coloring matters to be added to i sack of cement and 2 cubic feet of sand (a i to 2 mixture) to secure dif- ferent colored mortars. The list gives the weight of coloring matter to i sack of cement for a I to 2 mixture, and is as follows : FOR WHITE STONE: White Portland cement, i part; Pulverized lime, 54 part; # Pulverized marble, part; Light-colored sand, i part. On account of the inferiority of white Portland cement, the above is seldom used. * "Cement and Concrete." Lewis Carlton Sabin. + "Concrete, and Reinforced Concrete Construction." Homer A. Reid. MORTAR COLORS AND STAINS. FOR BLACK STONE: 3 lbs. Excelsior carbon black, or II lbs. manganese dioxide. GRAY STONE: I lb. Excelsior carbon black, or ^ lb. Germantown lampblack (boneblack). BROWN STONE: 4 to 5 lbs. brown ochre, or 6 lbs. roasted iron oxide, best quality. BUFF STONE: 4 lbs. yellow ochre. RED STONE: 5 lbs. violet iron oxide (raw). BRIGHT RED STONE: From 5^ to 7 lbs. English or Pompeiian red. YELLOW STONE: 5>4 lbs. ochre. GREEN STONE: 6 lbs. of greenish blue ultramarine blue. BLUE STONE: 2 lbs. ultramarine blue. DARK BLUE STONE: 4 lbs. ultramarine blue. PURPLE STONE: 5 lbs. Prince's metallic. VIOLET STONE: 5^ lbs. violet oxide of iron. In the construction of six emplacements at Fort Wadsworth, New York, the exterior surface was coated with colored mortar mixed according to the following formulas: FOR GREEN COLOR: Cement, i bbl. ; Sand, 2 bbls. ; Ultramarine blue, 50 lbs.; Yellow ochre, 73 lbs. ; Soft soap, 7 lbs. ; Alum, 7 lbs. FOR SLATE COLOR: Cement, i bbl.; Sand, 2 bbls. ; Lampblack, 50 lbs. ; Ultramarine blue, 35 lbs.; Soft soap, 7 lbs. ; Alum, 7 lbs. After completion of the batteries, the color became much lighter with age. It was found that spraying with linseed oil very materi- ally deepened its shade. 204 BUILDING CONSTRUCTION. (Ch. IV) 219. MIXING. — Mortar colors, whether in dry or paste form, should not be mixed with lime until the latter has been slaked at least forty-eight hours, and the best way is to keep a lot of lime putty on hand and mix the color with it as needed. Mortar colors should never be mixed with hot lime. For coloring lime mortar the colors should first be mixed with dry sand, then the cold slaked lime added and again mixed thor- oughly. It is very important that the colors be uniformly mixed. For cement and concrete work the stain should be thoroughly mixed with the cement, the sand then added, and the whole thor- oughly mixed dry. When gravel or stone is used it should be mixed dry with the sand and coloring matter, and then the whole should be thoroughly mixed until the color of the mass is uniform. After this the water should be gradually added as needed, and the mixing continued until the requisite consistency is obtained. The color of the mortar looks different in the bed than when dry. To get the final color of the mortar a little should be taken from the bed and permitted to dry thoroughly, when the permanent color may be seen. The gloss of the water makes the mortar look darker. The amount of coloring matter required to stain a given quantity of mortar varies with the different colors and brands. The follow- ing quantities may be taken as the average amounts required in laying one thousand bricks with spread joints: Red, buff or brown, 50 pounds. Black, from 40 to 45 pounds. When buttered joints are used: Red, buff or brown, 40 pounds. Black, from 25 to 35 pounds. The following additional data* give the weight of coloring matter to I barrel of cement, advised by good authorities : GRAY, use 2 pounds of Germantown lampblack to a barrel of cement. BLACK, use 45 pounds of manganese dioxide to a barrel of cement, BLUE, use 19 pounds of ultramarine to a barrel of cement. GREEN, use 23 pounds of ultramarine to a barrel of cement. RED, use 22 pounds of iron oxide to a barrel of cement. BRIGHT RED, use 22 pounds of Pompeiian or English red to a barrel of cement. VIOLET, use violet oxide of iron 22 pounds to a barrel of cement. YELLOW and BROWN, use 22 pounds of ochre to a barrel of cement. * "Handbook for Superintendents of Construction." H. G. Richey. Chapter V. Building- Stones. I. INTRODUCTORY. 220. THE SUBJECT IN GENERAL.— It is important that an architect should have some knowledge of the nature of the different kinds of stone in order that he may know what kind it is best to use or not to use under any given circumstances. While he is not expected to possess the special knowledge of a geologist, a mineral- ogist or a chemist, nor to determine the exact composition of a stone, he is supposed to know enough of the subject to specify stones which jiave sufficient strength and durability, and which will not become discolored by chemical changes in their constituents. This general knowledge of building stones requires not only a study of their mineral constituents and of their structure, but alsa much accurate observation and experience. 221. PRODUCTION AND VALUE OF DIFFERENT KINDS OF STONE.— The following table* shows the value of the different kinds of stone produced in the United States from 1896 to 1906, inclusive : TABLE XVII. Value of the Different Kinds of Stone Produced in the United States, 1896- 1906. Year 1900. 1903. 1904. 1905. 1906. Granite Trap rock Sandstone Bluestone Marble Limestone Total $7,944,994 8,905,075 9,324,406 10,343,298 10.969,417 14,266,104 16,083.475 15,703,793 17,191,479 17,563,139 18,569,705 $1,275,041 1,706,200 1,710,857 2,181,157 2,732,294 2,823,546 3,074,554 3,736,571 $4,023,199 4,065,445 4,724,412 ^4,910,111 45,272,865 46,974,199 49,430.958 49,482,802 48,482,162 48,075,149 47,147,439 ^$750,000 ■ Chaniplain ' ) Glacial, or Drift i Age of Mammals |- Tertiary Cretaceous. Age of Reptiles \ Jurassic Triassic, Carboniferous Age Devonian, or Age of Fishes Silurian, Age of Invertebrates Cambrian, or Primordial Upper Silurian Lower Silurian J Upper ) \ Middle V, ) Lower ) Permian Carboniferous Subcarbonif erous . Catskill Chemung Hamilton Corniferous Oriskany Lower Helderberg Salina Niagara. Trenton . . Canadian. Archae.m, Pr - -am- brian Pliocene Miocene Eocene Laramie Upper Middle Lower Wealden Upper oolite Middle oolite Lower oolite LTpper Lias Marlstone Lower Lias Keuper Muschelkalk Bunter Sandstone Permian Upper Coal-measures Lower Coal-measures Millstone Grit Upper Lower Catskill Chemung Portage Genesee Hamilton Marcellus Corniferous Schoharie Cauda-galli Oriskany Lower Helderberg Salina Niagara Clinton Medina Cincinnati Utica Trenton Chazy Quebec Calcif erous Potsdam Georgian St. John's Huronian Laurentian contains a large proportion of quartz it is very hard and difficult to work, but when there is a considerable proportion of feldspar it works more easily. and Francis B. Lans^y with the collaboration of George P. Merrill, Ikilletin No. 2, North Carolina Geological Survey, 1906. "The Fire-Resisting Qualities of Some New Jersey Building Stones," by W. E. Mc- Court, in Annual Report of the State Geologist, 1907. "The Granites of Maine," by T. Nelson Dale, with an introduction by Geo. O. Smith, Bulletin No. 313, United States Geological Survey, 1907. "The Building and Decorative Stones of Maryland," by E. B. Mathews and Geo. P. Merrill. Vol. II, Special Publications, Geological Survey of Maryland, 1898. "The Chief Commercial Granites of Massachusetts, New Hampshire and Rhode Island," by T. Nelson Dale, Bulletin of the United States Geological Survey, 1908. "The Granites of Vermont," by T. Nelson Dale, Bulletin of the United States Geological Survey, 1908. "The Granites of Connecticut," by T. Nelson Dale. To be published in 1909. BUILDING STOXES—GRAKITE. 215 The color of a granite is determined principally by the color of the feldspar, but the stone may also be light or dark, from the light or dark mica in it. The usual color of granite is either light or dark gray, although all shades from light pink to red are found in different localities. The light fine-grained stones are the strongest and most durable, although almost every granite has sufficient strength for ordinary building construction. It generally breaks with regularity and may be readily quarried, but it is extremely hard and tough and works with great difficulty, so that it is a very expensive kind of stone to use for cut work. It is impossible to do fine carving on most of the granites. They rank among the best stones for foundations, base- courses, water-tables, etc. ; for columns and all places where great strength is required ; and for steps, thresholds and flagging, for which last-mentioned purpose they can often be split. Excellent varieties of granite may be obtained from any of the New England States, from most of the Southern States, from the Rocky Mountain region, and from California and Minnesota. As a rule granite can be quarried in any size required. Stones from new quarries should be analyzed to see if they contain iron, in which case it is dangerous to use them for ornamental pur- poses until their weathering qualities have been thoroughly tested by exposing them for a long time to the weather. If the iron is a sulphurate it is quite sure to stain them. Gneiss (pronounced like ''nice") has the same composition as granite, but the ingredients are arranged in layers which are approx- imately parallel. For this reason the rocks split so as to give parallel flat surfaces, making the stones valuable for foundation walls, street paving and flagging. Gneiss is often mistaken for granite, and is frequently called by quarrymen stratified or bastard granite. Syenite also is a rock resembling granite, but containing no quartz. It is a hard, durable stone, generally of fine grain and light gray color. The principal syenite quarries in this country are near Little Rock and Magnet Cone, Arkansas.* * In many books and papers treating on granite, syenite is described as a rock con- sisting of quartz, feldspar and hornblende, the latter taking the place of the mica in the true granites. According to the modern methods of classification such rocks are called "hornblende granite." "The name 'syenite' takes its origin from Syene, Egypt, but the stone from which it was named has been found to contain more mica than hornblende. According to recent lithologists the Syene rock is a hornblende-mica granite, while true syenite, as above stated, is a quartzless rock." — Merrill. 2l6 BUILDING CONSTRUCTION. (Ch. V) All three of the above-mentioned kinds of stone are badly affected by fire, large pieces breaking off and the stone cracking badly. Fox Island, Me., Groton, Conn., Woodstock, Md., St. Cloud, Minn., and Nova Scotia granites are spoiled at 900° Fahr. Hallowell, Me., Red Beach, Me., Oak Hill, Me., and Quincy, Mass., granites are spoiled at 1,000° Fahr. The granites standing the highest fire tests are those from Barre, Vt., Concord, N. H., Ryegate, Vt., Mt. Desert, Me. 230. DESCRIPTION OF SOME IMPORTANT GRAN- ITES.— Maine. The quarries of Vinalhaven and Hurricane Islands. Knox Co., Maine. — These and the adjacent islands have been knov^n collectively as the Fox Islands and their granite as Fox Island granite. These quarries are the most extensive in the country; texture of stone rather coarse ; color, gray ; stone contains a small amount of hornblende. It takes a good and lasting polish, and is well adapted to all kinds of ornamental work and to general building purposes. It has been used extensively all over the country for building and monumental purposes. The product is used for docks, bridges, piers, buildings and monuments. The thin sheets and much of the waste are made into paving blocks 12 by 4 by 7 to 8 inches. The principal markets are New York, Philadelphia and Washington. Specimen structures in which Vinalhaven granite was used are: The new post-office building, Washington, D. C. ; Masonic Temple, Philadel- phia ; savings-bank building, Wilmington, Del. ; new Board of Trade building, Chicago; new post-office and custom-house, Brooklyn, N. Y. ; Manhattan Bank building. New York. These quarries furnished also the stone for the new custom-house in New York, for the Altman building. Thirty-fourth street and Fifth avenue, and for the West street office-building. West, Cedar, and Albany streets, New York, and for some docks in the same city. These quarries supplied also 8 columns, 51^ to 54 feet long by 6 feet in diameter, for the Cathedral of St. John the Divine in New York. It was intended that they should each be of one piece, but as both the direction of the rift at the quarry and architectural principles required that they be cut with their long axes at right angles to the rift, the stress in the great lathe came upon the weakest part of the stone. However, as the first stone put into the lathe broke with a long diagonal fracture, it became evident that the chief difficulty was that the stone had been subjected to too great a torsional stress by the application of rotary power from one end only. It therefore became jiecessary to make each column in two sections, each about 26 feet long. Specimen buildings in which granite from the Hurricane Islands quarries was used are : The Suffolk County court-house in Boston ; the St. Louis post-office and custom-house ; two buildings for the Naval Academy at Annap- olis, Md. ; the United States custom-house. New York ; Pennsylvania Rail- road station and base course of Bulletin building, Philadelphia. Other Knox Co. quarries are as follows: The High Isle quarry; granite BUILDING STO.XES— GRANITE. slightly pinkish, medium gray, and of medium to coarse, even-grained texture ; used in new Wanamaker stores, Philadelphia. The Dix Island quarries ; granite somewhat dark gray shade, and of medium to coarse, even-grained texture; used in United States Treasury De- partment extension at Washington, basement of Charleston, S. C, custom- house, the New York and Philadelphia custom-houses. The Sprucehead quarry; granite with conspicuous black and white par- ticles, and of medium to coarse even-grained texture; used in Carnegie Library building, Allegheny, Pa., new post-office and custom-house at Atlanta, Ga., the Mutual Life Insurance Company's building. New York. The Clark Island quarry; granite bluish gray, fine to medium texture; used in Hartford, Conn., and Buffalo, N. Y., post-offices, and Standard Oil Company's building, New York. The Long Cove quarry; granite bluish gray; used in Albany, N. Y., post- office, and Bates building, Philadelphia. Hallozvell, Kennebec Co., Maine. — This stone is celebrated for its beauty and fine working qualities, and is in great demand for monuments and statuary. It is a fine light gray rock, comparatively pure, the principal con- stituents being quartz, feldspar and mica. Has been used extensively all over the country. About seven-eighths of the product go into building and one-eighth goes into carved work. The principal markets are Chicago and New York. Speci- men buildings: Albany, N. Y., Capitol; Hall of Records (including its statuary). New York; Brooklyn Savings Bank building. New York; Masonic Temple, Boston ; academic and library buildings at tfflited States Naval Acad- emy, Annapolis, Md. ; Illinois Trust Company's building, Chicago; North- western Insurance Company's building, Milwaukee; post-office at Allegheny, Pa.; American Surety Company's building. New York; Shawmut Bank build- ing, Boston; Marshall Field building, Chicago. Hallowell granite is of fine texture, and especially suited to building work, lending itself remarkably well to statuary and delicate ornamental carving. The quarry consists of three principal openings, the largest being 800 feet long, 400 feet wide and 60 feet deep, and is an excellent example of the gradual increase in thickness of sheets of granite, as they vary from 6 inches at the top to 14 feet at the bottom, permitting the quarrying of stones of all shapes and sizes. Among the largest stones quarried have been the following: I piece /3f% by 4>2 by 50 feet long, weighing 100 tons in the rough, 8 pieces 4>^ " 4K " 36 " " 72 " 16 " aVz " 3-S " 36 " " " 60 " 1 piece 18 " 18 " 2,0 " " " 64 " " 2 pieces 8 " 18.6 " 3.10 " " " 55 " 1 piece 8,9 " 6.6 " 5,8 " " " 34 " 2 pieces 32.7 " 7.3 " 14 " " " 3^ I piece 13.5 " 10. II " 2.1 " " " 30 " The crushing strength of this granite is about I7*,500 pounds per square inch. 2l8 BUILDING CONSTRUCTION. (Ch.V) Cumberland Coiiniy. Maine, Quarries. — Brunswick; medium gray; fine, even-grained; used in chapel of Bowdoin College, Brunswick, Me., and First Parish Church, Portland, Me. Freeport ; medium gray, slight bluish tinge, fine even grain ; monumental work. Pownal ; light gray, fine even grain, used in chapel at corner of Seventieth street and Central Park, New York; Van Norden Trust Co.'s building. Six- tieth street and Fifth avenue, New York, and building corner Eighty- first street and Ninth avenue. New York. Franklin County, Maine, Quarries. — The Maine and New Hampshire Granite Corporation quarries are at North Jay. The granite is of very light gray shade, "white granite," and of fine, even-grained texture. Specimen structures: General Grant's tomb. New York; Richard Smith Soldiers' and Sailors' Memorial gateway, Fairmount Park, Philadelphia; Chicago and Northwestern Railway building, Chicago ; Western German Bank, Cincinnati ; Union County Court House, Elizabeth, N. J. ; Bowling Green building. New York; etc. The American Stone Company's quarry also is at North Jay. The granite is identical with that of the preceding, and was used in all but the basement of Senator W. A. Clark's residence on Seventy-seventh street and Fifth avenue. New York. Hancock County, Maine, Quarries. — Bluehill. Medium gray, coarse, even- grained; specimen buildings: Woman's Hospital, New York; Mercantile Trust Company's and C^edonia Insurance Company's buildings, St. Louis; part of extension to House of Representatives; part of District of Columbia n.unicipal building; First Day and Night Bank, New York; Delamar and Brokaw residences. New York; chemical laboratory of Pratt Institute, Brook- Ivn, N. Y. ; chemical laboratory of Stevens Institute of Technology, Hoboken, N.J. Mount Desert. Light grayish buff, coarse even-grained; specimen build- ings : United States Mint, Philadelphia ; basement of the custom-house, New York ; new bridge over the Potomac River, Washington. Light grayish pink ; the Crocker residence. Darlington, N. J. ; Danforth Library, Paterson, N. J. ; First National Bank building, Baltimore, Md., Phoenix National Bank, Hart- ford, Conn. Crotch Island. Lavender medium gray, coarse even-grained; specimen buildings : Post-office, Lowell, Mass. ; court-house, Delham, Mass. ; cadet armory, Boston, Mass. ; Public Library, Laconia, N. H. ; Ninth Regiment armory. New York; approaches to East River bridge. No. 3, New York; trimmings for University Heights bridge, New York. Moose Island. Lavender medium gray, coarse, even-grained ; specimen buildings : Gate-house at Central Park, and steps of Columbia University, New York; trimmings of Hampton Dormitory, Cambridge, Mass. There are other quarries in Hancock County, in the towns of Bluehill, Brooksville, Delham, Franklin, Long Island, Mount Desert, Sedgwick, Ston- ington, Sullivan, Swans Island and Tremont, which have supplied granite for important structures. BUILDING STONES— GRANITE. 219 Lincoln County, Maine, Qiiarries.-trThtso. quarries are in the towns of Bristol, Waldoboro and Whitefield. The granite from the Waldoboro quarry is of a medium gray color, and of fine, even-grained texture. Specimen buildings : Buffalo, N. Y., Savings Bank; armory, boat-house and cadets' quarters. United States Naval Acad- emy, Annapolis, Md. ; Chemical National Bank, New York. Oxford County, Maine, Quarries. — These quarries are in the towns of Fryeburg, Oxford and Woodstock. The color of the granite is medium gray and medium cream gray, and specimens of the material may be seen in the public library at Conway, N. H. ; the Roman Catholic Church, Berlin, Me.; the McGillicuddy block, Lewiston, Me.; all bridges and stations of the Grand Trunk Railway. Penobscot County, Maine, Quarries. — These quarries are in the town of Hermon, and produce a black granite, described as "an altered diabase por- phyry of dark green color and fine texture, with porphyritic crystals of black hornblende up to three-fourths inch in diameter." Piscataquis County has a quarry in the town of Guilford, producing a light gray granite. Somerset County has quarries in the towns of Hartland and Norridge- wock producing granite of medium and light gray color. Waldo County, Maine, Quarries. — These quarries are in the town of Frankfort, Lincoln and Swanville. The color of these granites is medium and light gray, and also black and dark gray, that from Swanville being the darkest of the fine-textured granites of the State. The grays have been used in the post-office at Lynn, Mass., post-office, Chicago, 111. ; post-office, Mil- waukee, Wis. ; post-office, Indianapolis, Ind. ; United States Mint, Philadel- phia, Pa. Washington County, Maine, Quarries. — These quarries are located in the towns of Addison, Baileyville, Calais, Jonesboro, Jonesport, Marshfield and Millbridge. Addison and Baileyville quarries produce dark gray and black shades. Calais quarries produce dark grays, blacks, dark reddish-greenish grays, dark reddish shades, bright pinkish shades, red shades and pink shades. The Maine Red Granite Company's granite works are in Calais, and include the most extensive plant for polishing granite in the State. Specimens of polished work are seen in the four fluted columns, 22 by 3 feet, of Shattuck Mountain red granite for the court-house at Marquette, Mich., and balusters of gray granite for the court-house at Kansas City, Mo. The Redbeach Granite Company's quarry, in the town of Calais, furnished the granite, of a bright pinkish color, for the two corner wings of the American Museum of Natural History, in New York. The Bodwell-Jonesboro quarries furnished a grayish pink colored granite for the "Bourse, Philadelphia; for the West End Trust Co.'s building, New York; for the custom-house and post-office at Buffalo, N. Y. ; for the Metho- dist Book Concern building, and for the Havemeyer residence. New York; for the custom-house and post-office at Fall River, Mass. ; for the town 220 BUILDING CONSTRUCTION. (Ch.Y) buildings at Peabody, Mass., and for the Western Savings Bank building, Philadelphia. The Jonesport quarries furnished a dark reddish gray granite for the Colorado building, Fourteenth and G streets, Washington, D. C. ; State armory, Providence, R. I. ; pov^er-house of the Metropolitan Street Railway, Interurban, Ninety-fifth to Ninety-sixth streets and First avenue to East River, New York. These quarries also furnished the dark reddish gray gran- ite, known commercially as "Moose-a-bec red," for the wainscoting and stairway in main entrance to Suffolk County court-house, Boston, Mass. ; for the American Baptist Publication Society building, in' Philadelphia, Pa., and 25 columns in the Roman Catholic Cathedral in Newark, N. J. York Comity, Maine, Quarries. — These quarries are in the towns of Alfred, Berwick, Biddeford, Hollis, Kennebunkport and Wells, and pro- duce granites of greenish dark gray, very dark olive brownish, light gray, medium gray pinkish buff, and light gray shades. VERMONT. Barre, Vt. — These granites are light and dark gray, clean, fine-grained stones, and may be had in almost any practicable size, free from all blemishes and defects. Among other granites of importance may be mentioned those found in Brunswick, Essex County ; Morgan, Orleans County ; Rycgate and St. Johns- bury, Caledonia County; Bethel, Windsor County, and Woodbury, Washing- ton county; and those at Windsor and West Dummerston. Woodbury, Vt. — The granite from these quarries is a light gray, fine- grained stone, suitable for all kinds of buildings and constructive work. It was used in the following recently constructed buildings : Public buildings : Pennsylvania State Capitol, Harrisburg, Pa. ; Cook County court-house, Chicago, 111. ; Kentucky State Capitol, base-course and interior polished columns, Frankfort, Ky. ; Iowa State Capitol, steps and platforms, Allentown Hospital, Allentown, Pa. ; Syracuse, N. Y., University library; Syracuse, N. Y., University gymnasium; post-office, Providence, R. I.; post-office, Hamilton, Ohio; post-office, Des Moines, Iowa. Bank and office-buildings : Commonwealth Trust Co., Pittsburg, Pa. ; Machesney building, Pittsburg, Pa. ; Bank of Ohio Valley, Wheeling, W. Va. ; Schmul- bach building. Wheeling, W. Va. ; Peoples' Savings Bank, Toledo, Ohio. Hotels : Hotel Knickerbocker, New York City ; National Hotel, Rochester, N. Y. ; Hotel Pontchartrain, Detroit, Mich. Monumental work : Archway at Port Huron, Mich. ; Soldiers' and Sailors' monument, Scranton, Pa. ; Con- federate monument. Springfield, Mo. Miscellaneous : Northern avenue bridge, Boston, Mass. ; Mortuary Chapel, Schenectady, N. Y. ; crematory, Linden, N. J. Bethel, Vt. — The granite from these quarries is a very choice and beau- tiful stone, ranking among the very whitest, and showing a very fiigh com- pressive strength, running up to 33,150 pounds per square inch. It has been used in the following buildings : Wisconsin State Capitol, Madison, Wis. ; Title Guarantee and Trust Com- BUILDING STOXES—^ GRANITE. 22L pany building, 176 Broadway, New York City; Importers' and Traders* National Bank, 247 Broadway, New York City; Essex County court-house, base and approaches, Newark, N. J. ; American Bank Note Company build- ing, Broad and Beaver streets, New York City ; Harry Payne Whitney resi- dence, Seventy-ninth street and Fifth avenue, New York City; Union Station, in part, Washington, D. C. Windsor, Vt. — At Windsor are operated quarries on Mount Ascutney, from which is produced a dark bronze green granite, used for polished columns and other work of similar character. This granite was used for the sixteen polished column shafts in the interior of the library building of Co- lumbia University, New York. They are 24 feet inches long and .'! feet and 7 inches in diameter. It was used also for thirty-erght large columns for the office of the Bank of Montreal, Montreal, Canada. West Dummcrston, Vt. — The granite from these quarries come in shades^ of white and blue. It has been used in the Royal Baking Company's office-building, New York ; for the interior columns in Cathedral, Newark,, N. J.; in the Kellogg-Hubbard Library, Montpelier, Vt. ; the Patten resi- dence, Evanston, 111. ; Thames Loan and Trust Company's building, Norwich, Conn.; First National Bank building, Spring Grove, Pa. MASSACHUSETTS. Quincy, Mass. — The Quincy granite quarries are among the oldest in the country. The product is, as a rule, dark, blue-gray in color, coarse-grained and hard. Composition : quartz, hornblende and feldspar. It has been used in many buildings, among which may be mentioned : JThe United States custom-houses at Boston, Providence, Mobile, Savannah, New Orleans and San Francisco ; Masonic Temple and Ridgeway Library buildings, and polished stairways and pilasters of the city-hall, Philadelphia. Gloucester, Cape Ann; and Rockport, Peahody, Wyoma, Lynn and Lynn- Held, Mass. — These quarries produce hornblende granites, of a gray or green- ish color. The material was used in the post-office and in several churches and private buildings in Boston, Mass., and in the Butler house on Capital Hill at Washington, D. C. ; in the towers and superstructure work for the new Cambridge Bridge between Boston and Cambridge, Mass. ; in Blackwell's Island Bridge, New York, Manhattan and Queens approaches, and in the Registry of Deeds and Probate court-house at Salem, Mass. Mil ford, Brockton, North Easton, Mass. — These quarries produce granites of mellow tints of light creamy pink, with lively black spots. Among speci- men buildings in which they were used, may be mentioned the following : Allegheny County court-house and jail, Allegheny, Pa.; Chamber of Com- merce buildings in Boston, Mass., and Cincinnati, Ohio : the polished columns of the Madison Square Garden and of the New York Herald building in New York; city-hall, Worcester, Mass.; University Club, New York; Union Railroad station, Albany, N. Y. ; Pennsylvania Railroad terminal station. New York ; Public Library building, Boston, Alass. ; John Hancock Mutual Life Insurance Co.'s building, Boston, Mass.; Pennsylvania building, Phila- 222 BUILDING CONSTRUCTION. (Ch. V) delphia, Pa. ; Hanover National Bank building, New York ; Columbia University Library building, New York ; New York Insurance Company's building, New York, and Continental National Bank building, Chicago, 111. A polished sphere, five feet in diameter, of this granite surmounts the column of Stony Creek, Conn., reddish granite, in the battle monument at West Point, N. Y. Framingliam, Leominster, Fitehburg, Clinton, Fall River and Freetown, Mass. — These quarries produce coarse gray, strong and durable granites. Dedhani, Mass. — Fine-grained, light pink granites from these quarries were used in Trinity Church building, Boston, Mass. Westford, West Andover, Lawrence, Lozvell, Ayer, Becket, N orthiield, Monson and towns in Worcester County, Mass. — These quarries produce fine-grained very light gray, sometimes pinkish gneiss of good quality. Among specimen buildings in which the material from the Monson quarries was used may be mentioned the following: Hall of Records, Springfield, Mass. ; St. Francis Xavicr's Church, New York ; St. Leonard's Church, Brook- lyn, N. Y., and monastery at Hunt's Point, N. Y. CONNECTICUT. Roxhury and Thomaston, Litchfield County; on Long Island Sound, Fairfield County; Ansonia, Bradford, Leetes Island, and Stony Creek, New Haven County; Haddam, Middlesex County, and Lyme, Niantic, Groton and Mason's Island, New London County, Conn. — At all of these places there are located extensive quarries of granite and gneiss, which are generally fine- grained in texture and light gray in color. Stony Creek, Conn. — These granites are known also as ''Branford Gran- ites," the quarries being located in Stony Creek, in the township of Branford, Conn. These were. opened and developed by Norcross Brothers in 1887, and contain practically inexhaustible deposits of reddish colored stone, well adapted for constructive, decorative or ornamental work. Some of the more important work in which this granite has been used is as follows : South Terminal station, Boston, Mass. ; Exchange building, Boston, Mass. ; in several buildings at Columbia University, New York; Connecticut River Bridge, Hartford, Conn. ; St. Gaudens' equestrian statue of General Sherman at en- trance to Central Park, New York ; the polished column for the battle monu- ment at West Point, N. Y., a monolithic shaft, 41 feet long by 6 feet in diameter; the monument commemorating the fiftieth anniversary of the opening of the canal at Sault Ste. Marie, Mich., a shaft 4 feet 5 inches square at the base and 45 feet long; Broad vvay Chambers, New York; New York Central post-office and office-building, Lexington avenue. New York; Belle- vue Hospital, New York, and the McKinley monument, near the city-hall, Philadelphia, Pa. Waterford, Conn. — The quarries at this place produce granites of fine v/liite texture and of a light color, well suited to work of a monumental char- acter. Recent work in which this stone is used is represented by the sculp- tured monument to the soldiers and sailors in the town of Northbridge, BUILDING STONES— GRANITE. 223 Mass., at Whitinsville ; and the Williamsburg and Greenpoint Savings Bank, New York. NEW HAMPSHIRE. Concord, N. H. — A fine-grained granite, light gray in color, with a silver lustre; well-developed rift and grain, and remarkable for the ease with which it can be worked. Constituents : opaque quartz, soda-feldspar and white mica. Well adapted for statuary and monumental purposes, as well as for general building. The stone is eminently durable, the New Hampshire State House, built of this stone in 1816-19, being still in an excellent state of preservation. From the list of specimen buildings in which granite from the Concord quarries was used may be mentioned the following : Congressional Library and new Senate office building, Washington, D. C. ; Union Trust building, Pittsburg, Pa. ; Camden County court-house, Camden, N. J. ; Tradesman Trust Company's building and Alta Friendly Society's building, Philadelphia, Pa. ; Standard Oil Company's building. Western National Bank building. First Church of Christ Scientist, New York; and Blackstone Library build- ing, Chicago, 111. Marlboro and FitzwilUam, N. H. — These quarries produce light gray, fine, close-grained granites, and the following is a list of some of the important buildings in which they have been used : Clark University buildings, and resi- dence of Jonas G. Clark, Worcester, Mass. ; First Church of Christ Scientist, Somerset hotel, and Buckminster Chambers, Boston, Mass. ; Vanderbilt Memorial Hospital building, Newport, R. L ; city-hall, Newark, N. J. ; Indus- trial Trust Company's building, Pawtucket,. R. I.; Marshall Field building-, Chicago, 111. ; and armory for the Lawrence Light Guard, Medford, Mass. Troy, N. H. — These quarries produce a fine-grained gray granite, of pro- nounced whitish effect after it is cut. Specimen structures in which it has^ been used are : Cathedral of the Sacred Heart, Newark, N. J. ; Pittsburg Bank building, Pittsburg, Pa. ; the approaches to the Library of Congress, Washington, D. C. ; and the Hanna mausoleum, Cleveland, Ohio. Redstone, N. H. — The two quarries at this place are adjacent, yet dis- tinct. One produces granite of a warm pink shade, the other a granite of a mottled green color. The following are specimen buildings in which the pink granite was used : Russia stores, Boston and Maine union station, Boston, Mass. ; Leiter block, W. C. T. U. temple, Michael Reese Hospital, Chicago, 111. ; Brooklyn Real Estate Exchange, power station, 59'th street. Franklin Savings Bank, New York; Fidelity Mutual Life Association build- ing, Philadelphia, Pa. ; Todd building, Louisville, Ky. ; Cleveland Chamber of Commerce, Cleveland, Ohio ; First and Fourth National Bank buildings, Cin- cinnati, Ohio; Equitable Insurance Company's building, Des Moines, la.; Memphis Trust Company's building, Memphis, Tenn. ; Bank of British North America, Winnipeg, Canada ; Richardson and Tuck Halls, Dartmouth College, Hanover, N. H. ; Erie Public Library, Erie, Pa.; State Library, Concord, N. H. ; and Memorial Library, Lowell, Mass. 224 BUILDIXG COXSTRUCTION. (Ch.V) Specimen buildings in which the green granite was used are : Northwest- ern Guaranty Loan building, Minneapolis, Minn. ; J. P. Maginnis' residence, Chicago, 111.; Portland Savings Bank building, Portland, Me.; and building at 777 Broadway, New York. RHODE ISLAND. Westerly, R. /.—Granite of fine grain and even texture and of excellent quality. Constituents: quartz, feldspar and mica, with some hornblende. Color, rich light gray or pink, with a distinct tint of brown when polished. Among the specimen buildings in which the Westerly, R. I., "red granites" have been used are the following: American Tract Society buildings, Wash- ington Life Insurance Company's building, American Exchange Bank build- ing. New York; Travelers' Insurance Company's building, Hartford, Conn.; Colonial Trust Company's building and Arrott building, Pittsburg, Pa. NORTH CAROLINA. The granites of North Carolina are distributed over about one-half the total area of the State, but the productive part of the area is considerably less. Openings from which more or less granite has been quarried in the past have been made in the majority of the counties in which granites occur, but in 1906 less than a dozen quarries were being systematically worked, .The prevailing color is light gray, with a pinkish cast, and there are also delicate shades. From the quarries at Granite Quarry in Rowan County come the Belfour pink granites, especially superior stones for statuary and finely 'carved work, for mausoleums and monuments. Neighboring quarries produce also a gray granite which is similar in all its properties to the pink, except in color. These granites are of uniform color and texture and take an excep- tionally high polish. For very complete and reliable data on the subject the reader is referred to "The Building and Ornamental Stones of North Carolina," by Thomas L. Watson and Francis B. Laney, with the collaboration of George P. Merrill, Bulletin No. 2, of the North Carolina Geological Survey. Raleigh, N. C, 1906. GEORGIA. The granites of Georgia are distributed over all of the State north of a line drawn from Augusta, through Macon to Columbus, with the exception of the extreme northwestern portion of the State. Of this section granites and gneisses have been quarried only in those counties comprised within the limits of what is known as the "Piedmont Plateau." Up to 1902 less than a score of these counties included the entire granite industry in Georgia; but recently quarry developments have been rapid. The State has enormous ■quantities of superior stone. The prevailing colors are light gray, dark gray ,and dark blue-gray. In DeKalb County are situated the Stone Mountain, Pine Mountain and Arabia Mountain granite quarries. The Stone Mountain granite was used in the following buildings taken from a larger list: LTnited States post- •office, Wheeling, W. Va. ; court-house and city-hall, New Orleans, La. ; BUILDING STONES— GRANITE. 225 terminal station, New Orleans, La. ; Fulton County court-house annex and Fulton County jail, North Avenue Presbyterian Church, First Methodist Church, First Baptist Church, and St. Mark's Methodist Church, United States Federal prison, and the United States post-office building, Atlanta, Ga. For extended data the reader is referred to "A Preliminary Report on a Part of the Granites and Gneisses of Georgia," by Thomas L. Watson, Assist- ant Geologist, Bulletin No. 9 — A, of the Geological Survey of Georgia, Altanta, Ga., 1907. MISSOURI. The major part of the granite works of Missouri arc in an area of about 110 to 120 square miles, and confined to nine counties in the southeastern part of the State. In color the granite varies from light gray through different shades of reddish pink to brownish red. The stone has been used in many important buildings in St. Louis, Kan- sas City, Chicago and other cities. For further recent detailed data the reader is referred to "The Quarrying Industry of Missouri," by E. R. Buckley and H. A. Buehler, Vol. II, 2d Series, Missouri Bureau of Geology and Mines, Jefferson City, Mo., 1904. WISCONSIN. The following are the areas from which granites have been quarried dur- ing the past few years : Montello, Berlin, Waushara, Utley, Marquette, Granite City, Waupaca, Wausan and Amberg, and situated generally in the north-central part of the State. The quarries furnish granites of colors vary- ing from brilliant red to dark gray. From the Montello quarries, situated in the central part of Marquette County, come the dense, fine-grained, uniform bright red and grayish gran- ites. They rank among the most durable granites, though necessarily diffi- cult to cut and to dress. It was from these that the stone was selected for the sarcophagi for General and Mrs. Grant at Riverside Park, New York. These granites were used also in the McKinley monument at Canton, Ohio. For further detailed data the reader is referred to "The Building and Ornamental Stones of Wisconsin," by Ernest R. Buckley, Assistant Geologist, Wisconsin Geological and Natural History Survey, Bulletin No. IV, Madi- son, Wis., 1908. OTHER STATES AND SECTIONS. Maryland. — Maryland granites are better adapted to general construc- tional work than to monumental purposes, and are light to dark gray in color, and medium fine-grained in texture. New Jersey. — But few granite quarries have been opened, yielding mostly gneiss, used almost exclusively for heavy construction work. Neiv York. — Notwithstanding the reported recurrence of gneisses and granites, suitable for general economic purposes, over various portions of the eastern and northeastern sections of the State, the granite industry of the State of New York is comparatively small. From the quarries situated on the north end of Picton Island, three miles from Clayton, N. Y., comes the medium-grained granite called "Picton Island 226 BUILDING CONSTRUCTION. (Ch.V) Red Granite." It is a bright and handsome stone, well suited to building pur- poses, and adapted to taking a high polish, j^^mong the buildings in which, it has been used may be mentioned the American Museum of Natural History, New York, and 25 decorative polished columns in the Maryland Institute building in Baltimore, Md. Pennsylvania. — This State furnishes nothing in the way of granite rocks to the markets, outside of its own limits. The granitic stone quarried is gneiss, with the qdarries grouped and in close proximity to Philadelphia. Delaware. — The production of granite rocks in Delaware is very limited, the only locality where quarries have been opened being near Wilmington. The rock is a dark gray augite-hornblende gneiss, used for general building purposes. South Carolina. — A fine and even-textured, gray biotite granite, of excel- lent quality, is quarried near Winnsboro, Fairfield County, and a granite of slightly pinkish hue occurs in the same county. Granite is found in six other counties also, Tennessee. — Scarcely anything in the line of granite rock is quarried *m this State. Virginia. — The principal quarries are located near Richmond and Peters- burg, those near Richmond having produced a large supply of stone, mar- keted in all States south of New England. The War, State and Navy building in Washington, D. C., was constructed of the Virginia granite. The Virginia granites are generally medium coarse-grained and light gray in color, and are said to correspond very closely to those of New England. Minnesota. — The granites of this State are very similar to those of Wis- consin. They are excellent granites of the gray and red, fine and coarse- grained varieties, carrying hornblende and biotite as the chief accessory min- erals. At St. Cloud, Minn., both gray and red granites are quarried, the latter greatly resembling the Scotch granite in color, grain and polish. The gray granite is about one-third quartz and two-thirds feldspar. Western States. — The granites of the Western States have been only sparingly quarried. While the rock abounds in both quantity and quality throughout various portions of the West, quarrying is limited almost ex- clusively to California, Colorado, South Dakota, Montana and Oregon ; and it is carried on sparingly in Utah, Idaho, Nevada, Washington and Wyo- ming. The granites of this section of the country range in color from light gray to red, and in texture from fine to coarse grain. In Colorado the principal quarry is at Gunnison, which produces a blue- gray granite, which may be seen in the Colorado State House. 3. LIMESTONES. 231. GENERAL DESCRIPTION.— This name is commonly used to include all stones which contain lime, though differing from each other in color, texture, structure and origin. All lime- stones used for building purposes contain one or more of the fol- BUILDING STONES— LIMESTONES. 22y lowing substances, in addition to lime : Carbonate of magnesia, iron, silica, clay, bituminous matter, mica, talc and hornblende. There are three varieties of limestone used for building purposes, viz.: Oolitic liniestoiie, niagncsian limestone and dolomite. Oolitic limestones are made up of small rounded grains resem- bling the eggs of a fish, that have been cemented together with lime to form solid rocks. Magnesian limestones include those limestones which contain lo per cent or more of carbonate of magnesia. Dolomites are crystalline granular aggregations of the mineral dolomite, and are usually whitish or yellowish in color. They are generally heavier and harder than limestones. Almost all varieties of limestone contain more or less pulverized shells, corals and fossils of marine animals. A limestone can be identified by its effervescence when treated with a dilute acid. Many of the finest building stones are limestones, but as they are less easily and accurately worked than sandstones they are not so largely used as the latter, except in the localities where the best varieties are found. The color of limestone is generally light gray, sometimes deep blue, and occasionally cream or buff. The light gray varieties often resemble the light, fine-grained granites in general appearance. Most of the granular limestones take a high polish. Good limestone should have a fine grain and weigh about 145 pounds per cubic foot. Many of the limestones described below are very durable, but the light-colored stones are apt to become badly stained in large cities, especially where soft coal is used. All kinds of limestone are destroyed by fire, although some varie- ties will stand a greater degree of heat without injury than others. 232. DESCRIPTION OF SOME IMPORTANT LIME- STONES. — The limestones most extensively used for building purposes come from the States of Illinois, Indiana, Ohio, New York and Kentucky. The most celebrated American Hmestone is that quarried at Bedford, Indiana. It is a light-colored oolite, consisting of shells and fragments of shells so minute as to be scarcely discernible to the naked eye and cemented together by carbonate of lime. This stone is most remarkably uniform in grain and texture, is exceed- ingly bright and handsome in color, and is less liable to discolor than most light stones. 2^8 BUILDING CONSTRUCTION. (Ch.V) It has about the same strength in vertical, diagonal and horizontal direc- tions, and when first quarried is so soft that it can be easily worked with saw or chisel. It hardens, however, on exposure, and attains a compressive strength of from 10,000 to 12,000 pounds per square inch. Owing to its fine and even grain and to the ease with which it can be cut in any direction, it is especially suitable for fine carving and is also very durable. On account of its many excellent qualities it was selected by the architect for Mr. George W. Vanderbilt's palatial residence at Biltmore, N. C. It was also used in the following buildings : The Auditorium building, Chi- cago ; the Manhattan Life Co.'s building, New York; the mansion of Mr. C. J. Vanderbilt on Fifth avenue. New York; the State Capitols at Indianapolis, Ind., Jackson, Miss., Frankfort, Ky., and Atlanta, Ga. ; Walters art gallery, Baltimore, Md. ; Public Library and Museum building, Milwau- kee, Wis. ; State Historical building, Madison, Wis. ; court-house, Hunting- ton, Ind. ; Catholic Cathedral, Pittsburg, Pa. ; Trinity building and Boreel annex, New York City, N. Y. ; Federal building, Indianapolis, Ind. ; St. Paul's Cathedral, Pittsburg, Pa. ; all the buildings for the University of Chicago, Chicago, 111. ; main art palace. World's Fair, St. Louis, Mo. ; First National Bank, San Francisco, Cal. ; all buildings for the University of Iowa, both at Iowa City and Ames, Iowa ; Union Club, New York City, N. Y. ; Yacht Club, New York City, N. Y. ; the Handley Library at Winchester, Va. In the residence of E. G. Fabri, New York City, Bedford stone was used for both exterior and interior work. Bedford stone is of the same geological age as the famous Portland stone of England, out of which St. Paul's Cathedral of London is constructed. Below is given a comparative analysis : Portland Stone. Bedford Stone. Carbonate of Lime 95- 16 97.26 Silica 1.20 1.69 Oxide of Iron 50 .49 Magnesia 1.20 .37 Water and loss 1.94 .19 100.00 100.00 Regarding the crushing strength, a test made by the United States Gov- ernment gives the crushing strength of Bedford stone at about 135,000 pounds per square foot. That this enables it to sustain an enormous weight ic shown by the following table of maximum weights borne by the piers and masonry of some well-known structures : Pounds per sq. foot. Piers of St. Peter's Rome 33,ooo Piers of St. Paul's, London 39,ooo Piers of Brooklyn Bridge S7,ooo Granite Masonry of Washington Monument 45,000 Reliable sustaining weight of Bedford stone 135,000 BUILDIXG STOXES—LIMIISTOXES. 229 Indiana limestone, or Bedford stone, is not as porous as Portland stone, the English product. It is more easily worked, responding readily to mailer and tool in the hands of workmen, and it can also be planed or turned by- machinery, which advantage adds to its desirability, as ft minimizes the cost of preparing it. The oolitic belt of Indiana extends over a portion of the counties of Lawrence and Monroe, and is about thirty miles in length and about six miles in width. It is a homogeneous limestone, the upper ledges of which are light buff in color. At a depth of about 30 feet the stone in most places changes abruptly to a decided blue shade. The texture and other chemical properties remain the same from the point wliere the color changes to a depth of about 30 feet more, at which point the stone becomes very coarse, and seems to be of a shelly formation. Alabama has a dark compact limestone, some of it closely resembling • the Bedford, Indiana, stone. Arkansas produces a durable, oolitic limestone suitable for building, and also a cream-colored magnesium limestone of good quality. Colorado furnishes a coarse, reddish limestone, and also a compact, finely crystalline black stone. In Florida there is a loose and porous oolitic limestone at Key West, and the coarse, porous shell limestone called "Coquina" quarried at Anastasia Island. In Illinois almost the entire building stone product is limestone or dolomite, with a few sandstone quarries. The most notable of the limestones is the fine-grained, very light colored Niagara stone from near Lemont and Joliet. There are many other localities in the State which furnish excellent varieties of building stone. There are large quarries of limestone also at Grafton and Chester, and from the quarries at East Fort Madison, Hancock County, 111., come the "Appanoose Dolomite Stone," a strong and durable stone. lozL'a abounds in limestones and dolomites, which, however, so far enjoy only a local reputation. There are numerous small quarries, producing, how- ever, many good building stones. Kansas has limestones and dolomites of generally light color, and of soft and porous texture, although there are some exceptions, several varieties having a firm and compact texture and acquiring a good surface and finish. There are large quarries of limestone in the vicinity of Topeka. This stone can be worked almost as easily as wood, and yet becomes hard and durable when placed in a building. There are also several small quarries which supply the local demand in various parts of the State. Kentucky has limestones of the finest quality and in inexhaustible quan- tities, the oolitic limestones being without superiors, if indeed they have equals. But these building stones are almost unknown in the principal mar- kets, and such as are quarried have only a local reputation. The best known of the Kentucky limestones is probably the Bowling Green oolitic stone quarried at Memphis Junction. This stone is almost identical in composition with the celebrated "Portland" stone of Great Brit- 230 BUILDING CONSTRUCTION, (Ch. V) ain. Its color is light gray. It is as readily worked as the Bedford stone, is very durable, and is pre-eminent in its resistance to the discoloring influences of mortar, cement and soil. The "Green River Stone" comes from the quarries at Hadley, Warren County, Ky., which produce a stone dark in color -when first quarried, but bleaching out white upon exposure to the weather. The stone is similar to the Bedford stone, being a close-grained oolitic limestone. It was used in the Pennsylvania State Library building, Harrisburg, Pa., the residence of S. B. Elkins, Philadelphia, Pa., and the Daviess Company Bank building, Owens- boro, Ky. Maine has little if any limestone that is well adapted for building stone, as it is generally blue or blue-black, veined with white, a combination thought to be not desirable, Michigan has limestones and dolomites suitable for building stones, but they have been but comparatively little quarried. Minnesota furnishes limestones and dolomites generally of a light buff, drab or blue color, fine-grained and compact. Missouri's limestones and sandstones from all formations have been used to some extent in buildings. A majority of the quarries in the sedi- mentary formations are engaged exclusively in producing stone to supply the local market. At Carthage, Jasper County, Missouri, there are extensive quarries of limestone, which produce large quantities of both quicklime and building stone. The stone is coarse-grained and crystalline, takes a good polish, and is well adapted to exterior finishing. Excellent quarries of limestone exist also at Phoenix, Missouri, the stone being shipped to St. Louis, Kansas City and Omaha. Nebraska has carboniferous limestones in several counties of such quality as to render them suitable for building purposes; but few if any of them are in demand outside the limits of the State. New York has several limestones belonging to seven or eight different geological formations. A gray limestone is quarried at Lockport and Roches- ter, N. Y., which is extensively used for trimmings in that State and in some parts of New England. The limits of this chapter will not permit any con- sideration of these several building stones, and the reader is referred to the various publications bearing upon the stones of New York State. North Carolina. — On account of the lack of a large enough market and of transportation facilities, the limestones and dolomites, although of very good quality for building purposes, are not extensively quarried. Ohio. — The limestones and dolomites of Ohio, while in many instances used locally for building purposes, are employed chiefly for rough founda- tion work, street paving and flagging and for making quicklime. This is because they are generally of a dull and uninteresting color, and not well suited for any kind of fine building or ornamental work, although often strong and durable. There are large quarries of limestone at Dayton and Sandusky. BUILDING STOXES— MARBLES. 231 Pennsylvania. — Formations in Montgomery, Lancaster and Chester Coun- ties furnish gray or bluish gray limestone, used for general building. Other localities furnish calcareous dolomites, limestone, breccias, etc., none of which possesses such characteristics as would make it of more than local value. From the Avondale, Chester County, Pa., quarries comes the "Avondale Limestone," varying in color from white to light brownish gray. It has been used in many churches and other buildings in Philadelphia, Pa., and in buildings in neighboring cities and towns. Tennessee. — None of the limestones are quarried for anything more than local use. Texas. — Near Austin, and also in Burnett County, are respectively found light-colored, fine-grained limestones, and dark mottled limestones ; and near San Saba, compact, fine-grained cretaceous limestones of poor quality. Iflseonsin. — A large part of the State is immediately underlain by lime- stone, the suitability of which for building, purposes is widely different, in different localities. The colors range from buff or straw yellow to dark bluish gray. In some parts of the State the limestone is closely compacted and crystalline, often resembling marble. In other places it has a loose, open texture. Bridgeport, Trempealeau and Maiden Rock furnish mag- nesian limestone suitable for all ordinary purposes. The Trenton forma- tion, on which many of the important cities of the State are located, furnishes a blue limestone extensively used locally for buildings. It has proven satisfactory where there is no danger from freezing. At Watwatosa, Lannan, Genesee, Marblehead, Sturgeon Bay and Knowles there is a good limestone generally siiited to building purposes, 4. MARBLES. 233. GENERAL DESCRIPTION.— Marble is simply a crys- tallized limestone, capable of taking a good polish. The scarcity and constant expense of good marbles have in the past prevented them from being used in constructional work, except occasionally for columns. Most of the marbles obtained from the older quarries also stain so easily that they are considered unde- sirable for exterior work. Since the rapid development of the Georgia and Tennessee quar- ries, however, the marbles taken from them have been much used for exterior finish, and even for the entire facing of the walls. They will probably be more extensively used for exterior work in the future, as they are exceedingly strong and durable and do not readily stain. Nearly all varieties of marble are wprked with comparative ease, and the fine-grained varieties are especially adapted to fine carving. They generally resist frost and moisture well, they are admirably 232 BUILDING CONSTRUCTION. (Ch. V) suited for interior decoration, sanitary purposes, etc., and in clear, dry climates make splendid material for exterior construction. The compressive strength of marble varies from 5,000 to 20,000 pounds per square inch, but it is only when used for columns that this strength need be considered. For the composition and strength of various marbles see the tables in the Appendix. 234. PRODUCTION OF MARBLE IN THE UNITED STATES. — The marble output in the United States in 1906 was valued at $7,582,938. Vermont produces the greater part of the marble of the United States, the output of this State representing 60.36 per cent of the total output of the country in 1906, and amounting to about 1,400,000 cubic feet. In that year Georgia ranked second in the marble-producing States, its value of output representing 12.12 per cent of the total of the United States, and amounting to 875,000 cubic feet. TABLE XXII. Distribution and Value of Output of Marble^ 1902- 1906, FOR Various Uses. Use 1902 1903 1904 1905 1906 Sold by producers in rouj^h state Ornamental purposes Dressed for monumental work . Interior decoration in buildings Total $2,275,429 1,038,802 7,300 956,870 679,913 86,368 $2,454,263 1,111,072 51,359 1,062,339 663.558 20,100 $2,599,052 988.671 21,554 1,211,389 1,257,96:3 219,206 $2,987,542 1,168,450 13,643 1,170,279 1,682,651 106.506 $1,795,169 1,559,925 44,523 2,214,872 1,722.445 246,(X)4 $5,044,182 $5,362,686 $6,297,835 $7,129,071 $7,582,938 In 1906 the next States and territories in order of output were Tennessee, New York, Massachusetts, Maryland, Pennsylvania, California, Alabama, Washington, Arkansas, Nevada, Utah, Wyoming, New Mexico, Missouri and Alaska. In Pennsylvania's output is generally included a production of serpentine from Northampton county, and small quantities of ser- pentine are also generally included in the Georgia outputs. The outputs of California, New Mexico, Utah and Wyoming often include small quantities of onyx. The greater part of the marble output is for building and monu- mental work, the values for the two being nearly equal in 1906. BUILDING STOXES— MARBLES. 233 Table XXII shows the various uses to which the marble quarried in 1902, 1903, 1904, 1905 and 1906 was put. From this table it appears that while the rough .marble sold to manufacturers, dealers and contractors decreased in value, the dressed stone of all kinds sold by the quarrymen increased. 235. DESCRIPTION OF SOME IMPORTANT AMERI- CAN MARBLES. — Great quantities of white and black marble are quarried in this country, but nearly all of the beautiful streaked and colored marbles are imported. Vermont Marble. — This State is the greatest producer of marble of any State in the Union, the total product in 1906 amounting to $4,576,913, more than the combined value of all other marbles quarried in the country. The largest quarries are at West Rutland and Proctor. Among other towns in which the marble quarrying industry has been par- ticularly active may be mentioned Dorset, East Dorset, Wallingford, Pitts- ford, Brandon and Middlebury, In texture Vermont marble is, as a rule, fine-grained, although some of it is coarse-grained and friable. In color it varies from pure snowy white through all gradations of bluish, and sometimes greenish shades, often beautifully mottled and veined, to deep blue-black, the bluish and dark vari- eties being, as a rule, the finest and most durable. These marbles are used principally for monumental and statuary work, and for decorative work, sanitary fittings, tiling, etc., in buildings. At Proctor the stone is very massive, and large blocks are taken out for general building purposes. Vermont marble has been used for the exterior and interior of innu- merable buildings. Merel}^ as illustrations the following specimen buildings in which it has been used may be mentioned : Church of our Lady of Good Council, East 9th street, and Church of the Ascension, 107th street. New York; United States post-office and court-house, Worcester, Mass.; water tower, Fort Ethan Allen, Essex, Vt. ; Hart Memorial Library, Troy, N. Y. ; Clio Hall, Princeton College, Princeton, N. J. ; Metropolitan Club, Ne\\^ York; Second National Bank building, Paterson, N. J.; Knickerbocker Trust Company's buildings and Engineers' Club, New York; United States post- office building, Waterloo, Iowa; court of new Federal building, Cleveland, Ohio ; public library, Atlantic City, N. J. ; Tufts College Library building. Georgia. — This State contains extensive beds of marble, which of late years have come into very general use. The quarries, which are situated in the northern part of the State, produce : 1st. A clear white marble, bright and sparkling with crystals. 2d. A marble with a dark mottled white ground, with dark blue mottlings ; and also one with a light blue and gray ground, with dark mottlings. 3d. A white marble, with dark blue spots and clouds, and a bluish-gray marble, with dark spots and clouds. 4th. Pink, rose- tinted and green marbles in several shades. The appearance of the Georgia marbles is quite different from that of the marbles from the other States. 234 BUILDING CONSTRUCTION. (Ch. V) The stone is an almost pure carbonate of lime, free from foreign or hurtful ingredients. It is remarkably non-absorbent, and absolutely impervious to liquids, including even ink; and it is not subject to discoloration, atmos- pheric changes or decay. If soiled by dust or smoke it can be easily cleaned by washing with clean water alone, so as to look as bright as when first finished. Georgia marble has been extensively used for monuments and for the interior finish of buildings, notably in the Congressional Library building at Washington, D. C. It is also used more and more every year for exterior construction, either for trimmings or for the entire walls. It may be seen on the exterior of the following buildings, given as illustrations : St. Luke's Hospital building, New York ; post-office, Tampa, Fla. ; Century building, St. Louis, Mo.; Bank of Montreal, Winnipeg, Canada; Equitable building, Atlanta, Ga. It may be seen on the exterior and interior of the following: Girard Trust and Banking Company, Philadelphia, Pa. ; Royal Bank of Canada, Montreal, Canada; Century building. Atlanta, Ga. It may be seen in the interior of the following: Terminal station, Atlanta, Ga. ; Kentucky State Capitol building, Frankfort, Ky. ; Wilson build- ing, Dallas, Texas ; House of Representatives office-building, Washington, D. C. ; court-house, Mendon, Neb. ; Marion hotel, Little Rock, Ark. ; Patten hotel, Chattanooga, Tenn. 'Tennessee. — Marble has been quarried in this State since 1838, the prin- cipal quarries being in the vicinity of Knoxville, in East Tennessee. The varieties of marble produced from these quarries include grays, light pinks, dark pinks, buffs, chocolate and drabs. Only the pinks and the grays, how- ever, are suitable for general building purposes, the darker colors being con- fined principally to furniture and interior work. The stone is 98 per cent carbonate of lime. The pink and gray varieties are well adapted to building purposes, their density and resistance to crushing being equal to that of any other marbles in the world. They also offer great resistance to moisture, and are practically imper- vious to the staining or discoloring agencies of the atmosphere, except, per- haps, those which are found in large manufacturing centers. Under favorable conditions there appears to be no reason why they should not last for ages on the exterior of buildings. The highly colored varieties are among the hand- somest produced in this country. Neiv York. — There are several quarries of gray, blue and white marble just north of New York City which furnish good building marble, but not quite good enough for decorative work. Much of it has been used for building purposes in New York City, and the best yet obtained from this series of deposits are those of Tuckahoe and Pleasantville in Westchester County. At Gouverneur, in St. Lawrence County, there is a very coarsely crystal- line light gray magnesian limestone, which, while too coarse for carved work, answers well for massive structures, and acquires a good surface and polish. BUILDING STONES— MARBLES. 235 In Clinton County are found excellent fine-grained colored marbles of gray and gray-and-pink shades, known as "Lepanto" and "French Gray," and very extensively used for general interior work. The best quality of black marble is quarried at Glens Falls, on the Hudson River. Massachusetts. — In Berkshire County arc medium fine-grained white or gray marbles used for general building. At Egremont are coarsely crystal- line white and gray limestones from which were obtained the large Corin- thian columns of Girard College, Philadelphia. From the Lee quarries came the marble used in the Capitol extension in Washington, D. C, and in the city buildings in Philadelphia. Pennsylvania. — In this State are several quarries of a granular white and mottled marble, which have furnished a great deal of this stone for Phila- delphia buildings. Maryland. — Baltimore County is the important marble-producing center of the State, and contains the white stone of the Beaver Dam quarries, from which the 26-foot monoliths used in 1859-61 in the National Capitol were obtained. Nearby are the coarsely crystalline white limestones from which the material was obtained for the lower 150 feet of the Washington monu- ment, in Washington, D. C. Colorado. — This State contains beautiful varieties of marble, which it is thought in time may take the place of much of the foreign marble now imported. At present only a few quarries are worked. In Gunnison County, on the Yule Creek and Crystal River, there is a belt of white marble appar- ently superior in quality to anything found elsewhere in the United States. This marble belt is about 100 feet in thickness and not less than six miles in length. The prevailing colors are pure white, creamy white, and white slightly clouded with gray. Other States and Territories. — The other States and territories men- tioned in Article 234 have valuable marbles which are quarried in smaller and various quantities, and used for rough and dressed work, for general building purposes, for monumental and ornamental work and for interior decoration. 236. ONYX MARBLE. — The composition of these stones is the same as that of the common marbles, but they vv^ere formed by chemical deposits instead of in sedimentary beds crystallized by the action of heat. ''They owe their banded structure and variegated colors to the intermittent character of the deposition and the pres- ence or absence of various impurities, mainly metallic oxides. The term onyx as commonly applied is a misnomer, and has been given merely because in their banded appearance they somewhat resemble the true onyx, which is a variety of agate." Owing to their translucency, delicacy and variety of colors, and to the readiness with which they can be worked and polished, the onyx marbles are considered the handsomest of all building stones, and they bring the highest price also; the cost per square foot for 236 BUILDING CONSTRUCTION. (Ch.V) slabs I inch thick varying from $2.50 to $6. Their use is confined to interior decoration, such as wainscoting, mantels, lavatories, and to small columns, table tops, etc. Most of the onyx marble used in the United States is imported from Mexico, although considerable onyx is quarried at San Luis Obispo, California ; and quarries of very beautiful stone have recently been opened near Prescott, Ari- zona. The Mexican onyx presents a great variety of colors, such as creamy white, amber-yellow and light green, each generally more or less streaked or blotched with green or red. Some of the light stones have beautiful translucent clouded effects. When cut across the grain the stone often presents a beautifully banded struc- ture like the grain of wood. Cutting the stone across the grain, however, reduces its strength greatly, so that it is necessary to back it with slabs of some stronger marble. The San Luis Obispo stone is nearly white, finely banded and- translucent, and it takes a beautiful surface and polish. The Arizona stone presents a greater variety of coloring, ranging from milky white to red, green, old gold and brown, the colors inter- mingled in every possible way. Up to the present time a compara- tively small amount of this stone is on the market, but farther developments will probably result in the production of large quan- tities of it. 5. SANDSTONES. 237. GENERAL DESCRIPTION.— ^'Sandstones are composed of rounded and angular grains of sand so cemented and compacted together as to form a solid rock. The Cementing material may be silica, carbonate of lime, an iron oxide or clayey matter." They include some of the most beautiful and durable stones for exterior construction ; and on account of the ease with which they can be worked, and because of their wide distribution throughout the country, they are used more extensively than any other stones for exteriors. The grains of sand themselves are nearly the same in all sand- stones, being generally pure quartz ; the character of the stone depends principally upon the cementing material. If the latter is composed entirely of silica, the rock is light-colored and generally very hard and difficult to work. When the grains have been cemented together by fusion or by the deposition of silica between the granules, and the whole hardened under pressure, the rock is BUILDING STONES—SANDSrONES. 257 almost the same as pure quartz and is called quartaite, one of the strongest and most durable of rocks. *'If the cementing material is composed largely of iron oxides the stone is red or brownish in color and usually not too hard to work readily. When the cementing material is carbonate of lime the stone is light-colored or gray, soft and easy to work." Such stones do not as a rule weather well, as the cementing material becomes dissolved by the rain, thereby caus- ing a loosening of the grains and allowing the stones to dis- integrate. Clay is still more objectionable than lime as a cementing" material, as it readily absorbs water and renders the stones liable to injury by frost. In several sandstones some of the grains consist of feldspar and mica, which have a tendeifty to decrease the strength. Sandstones have a great variety of colors; brown, red, pink, gray^ buff, drab or blue, in varying shades, being common varieties. The color is due largely to the iron in the composition. The oxides of iron do no harm, but no light-colored sandstone should be used for exterior work which contains iron pyrites, or sulphate of iron, as it is almost sure to cause stain or rust. Sandstones vary in texture from almost impalpable fine-grained Stones to those in which the grains are like coarse sand. All other conditions being the same, the fine-grained stones are the strongest and most durable and take the sharpest edge. Sandstones being of a sedimentary formation, are often laminated, or formed in layers; and if they set "on edge," or with the natural bed or surface par- allel to the face of a wall, their outside face is quite sure to dis- integrate or peel off in time. All laminated stones should always be laid on their natural bed. When freshly quarried, sandstones gener- ally contain a considerable quantity of water, which makes them soft and easy to work, but at the same time very liable to injury by freezing if quarried in winter weather. Many Northern quarries cannot be worked in winter on this account. Almost all, if not all, sandstones harden as the quarry-water evaporates, so that many of them which are very soft when first quarried become hard and dur- able when placed in a building. Such stones, however, should not be subjected to much weight until they are dried out. There is a great abundance of fine sandstone of all colors dis- tributed throughout the United States, so that it is not difficult to get first-class stone for any building of importance. Most of the sandstones in the Eastern part of the country are either red or 23B BUILDING CONSTRUCTION. (Ch.V) brown in color, there being no merchantable light sandstones east oi Ohio. 238. PRODUCTION OF SANDSTONE.— In 1906 Pennsyl- vania, New York, Ohio and California, with values of $1,346,140, $724,164, $659,611, $400,083 respectively, were the ranking States in the building-sandstone output. 239. DESCRIPTION OF SOME IMPORTANT SAND- STONES. — The following are some of the best-known sandstones in this country, any of which are good building stones : Connecticut brozvnstonc includes all the dark brown sandstones quarried in the neighborhood of Portland, Conn. It is a handsome dark brown stone, tinted slightly reddish, has a fine even rift, is easy to work, and gives a bea-jtiful surface when rubbed. This stone "ts decidedly laminated, and the surface will soon peel if the stone is set on edge. When laid on its natural bed, however, it is very durable. This was the first sandstone quarried in the country, and great quantities of it have been used in New York City. The following is a brief resume of the properties of Connecticut brown- stone and a list of some of the recent buildings in which it was used : Color. — Brown, evenly laminated, uniform and permanent. No discolor- ation appears after many years' exposure to the weather. Texture. — Sandstone, triassic, fine and even-grained. Easy "to work. Free from clay, marl or gravel. Uses. — Used for exterior and interior of churches, college buildings, public buildings, private houses, apartment-houses and all kinds of buildings ; also for bridge masonry, retaining-walls, foundations, rubble masonry, pier, dyke and dock construction. Strength. — Crushing strength from 13,330 to 15,020 pounds per square inch. Chemical Properties. — Chemical analysis shows them to be as follows : The following is a short list of some recent buildings erected of this stone: Wesleyan University, Middletown, Conn., North College dormitory ; Wesleyan University, Middletown, Conn., Fisk Hall; U. S. Government post-office, New Bedford, Mass. ; U. S. Government post-office, Hoboken, N. J. ; U. S. Government post-office, Bridgeport, Conn.; lining of chancel, St. Mark's Episcopal Church, Evanston, 111.; Episcopal Church, Troy, N. Y. ; Univer- salist Church, Meriden, Conn.; Caldwell H. Colt Memorial building, Hart- Silica Alumina Iron Oxide Manganese Lime Magnesia Soda, Potash, etc 70.11 1349 - 4-85 •35 2.39 1.44 7-37 100.00 BUILDING STONES—SANDSTONES. fcrd, Conn.; High Schoo' building, Hartford, Conn.; John H. Hall Memorial building, Portland, Conn.; Packer Institute, .Brooklyn, N. Y. ; residence of Governor Murphy, Newark, N, J.; Canadian Bank of Commerce, Toronto, Canada. Longmcadow Stone. — This is a reddish brown sandstone quarried prin- cipally at East Longmeadow, Mass. It is an excellent building stone, without any apparent bed, and may be cut in any way. It varies from quite soft to very hard and strong stone and should be selected for good work. It has been largely used throughout the New England States for the past, twenty- five years. The following are some of the specimen buildings in which the Long- meadow stone was used : Sever Hall, Harvard College, Cambridge, Mass. ;. Osborn Memorial Hall, Yale College, New Haven, Conn. ; Marshall Field building, Chicago, 111. ; Trinity Church, Youth's Companion building,. Mechanics' Arts high-school, Boston, Mass. ; Waldorf-Astoria hotel. Teachers' College, New York ; Commencement Hall and Library building, Princeton College, Princeton, N. J. ; South Unitarian Church, Worcester, Mass. Potsdam Red Sandstone, from Potsdam, N. Y., is a quartzite and one of the best building stones in the country, being extremely durable and equal tO' granite in strength. It was used in All Saints' Cathedral, Albany, N. Y., and m the Dominion Houses of Parliament, in Ottawa, Canada. There are three shades, chocolate, brick-red and reddish cream. Hummelstozvn Browiistone, from Hummelstown, Pa., is a medium fine- grained stone, bluish brown or slightly purple in color, the upper layers being more of a reddish brown and much resembling the Connecticut stone. The stone compares very favorably with the other brownstones mentioned, and is in very general use in the principal Eastern cities. The following is a short list of recent buildings constructed of this stone: North American building. Broad and Sansom streets, Philadelphia, Pa. ; Emory M. E. Church, Pittsburg, Pa. ; Corpus Christi R. C. Church, Buffalo, N. Y. ; Market and Fulton National Bank, New York City ; Wyatt building, 14th and F streets, Washington, D. C. ; Arcade building, Cleveland, Ohio; court-house, Orlando, Fla. ; First Universalist Church, Watertown, N. Y. ; .National Exchange Bank, Hopkins place, Baltimore, Md. ; M. J. Heyer office-building, Wilmington, N. C. North Carolina, West Virginia and Indiana contain quarries of brown- stone which supply the local demaiid and the stones from which are worthy of a wider distribution, particularly those of North Carolina. Fond dii Lac, Minnesota, furnishes a reddish brown sandstone which closely resembles the Connecticut brownstone, but which is much harder and firmer. "The stone consists almost wholly of quartz cemented with silica and iron oxides." Kettle River Sandstone. — At Banning, Minnesota, are quarries from which this stone is taken. It is a siliceous sandstone, and of a uniform light salmon color. It was used in the Main Library building. University of Illinois, Urbana, 111. ; in the interior of the United Presbyterian Church, at Worcester, Mass. ; Spokane Club building, Spokane, Wash. ; Public Library, 240 BUILDING CONSTRUCTION. (Ch. V) building, Des Moines, Iowa ; court-houses at Elk Point, S. D. ; Crookston, Grand Rapids and Benson, Minn. Lake Superior Sandstones. — These are brown and red sandstones of the Potsdam formations. There are quarries at Portage Entry and Marquette, Mich., producing the red and brown shades, respectively, and at Port Wing, Wis., producing the brown shades. The Portage red sandstone was used in the Waldorf-Astoria hotel, Manhattan Savings Institution, Altman's new stores. New York ; Board of Trade building, Toronto, Canada ; Carnegie office-building, Pittsburg, Pa. ; city-hall, Omaha, Neb. The Port Wing brown sandstone was used in the new armory building, St. Paul, Minn,; Carnegie Public Library building, Duluth, Minn. Ohio Stone. — The finest quality of light sandstone in the United States is quarried in the towns of Amherst, Berea, East Cleveland, Elyria and Inde- pendence, Ohio, and is commonly known as "Ohio stone" or "Berea stone.'* It is a fine-grained, homogenous sandstone, of a very light buff, gray or blue- gray color, and is very evenly bedded. The stone is about 95 per cent silica, the balance being made up of small amounts of lime, magnesia, iron oxides, alumina and alkalies. There is but little cementing material, the various particles being held together mainly by cohesion induced by the pressure to which they were subjected at the time of their consolidation. They are very soft, work readily in every direction, and are especially fitted for carving. "Unfortunately the Berea stone nearly always contains more or less iron pyrites and needs to be selected with care. Most of the quarries, however, have been traversed by atmospheric waters to such a degree that all processes of oxidation which are possible have been very nearly completed."* The stone can be furnished in blocks of any desired size and uniform color. It is shipped to all parts of the' country, and is in great demand for fine buildings. Mr. H. H. Richardson, the celebrated architect, often used it in contrast with the Longmeadow sandstone for trimmings and decorative effects. It contains from about 6 to 8 per cent of water when first taken from the quarry, and about 4 per cent when dry. It cannot be quarried in winter on account of the splitting of the stone caused by the freezing of the water contained in it. There are some fourteen or fifteen different companies that quarry this stone for the market. The following are some representative buildings in which this Ohio sand- stone has been used : Calvary M. E. Church, Allegheny, Pa., gray "Canyon" stone; Sixth United Presbyterian Church, Pittsburg, Pa., buff Amherst stone; Jewish Synagogue, Washington, D. C , Berea stone ; Masonic Temple, Minne- apolis, Minn., Berea stone ; Planters' hotel, St. Louis, Mo., Berea stone ; the Canadian Bank of Commerce, Winnipeg. Canada, gray "Canyon" stone ; State Historical Library, Minneapolis, Minn., buff Amherst stone; O. N. G. armory, Cleveland, Ohio, Berea stone ; city-hall, Milwaukee, Wis., Berea stone ; city-hall, St. Louis, Mo., buff Amherst stone ; city-hall, Davenport, Iowa, Berea stone; Taber opera-house, Denver, Col., buff. "The Waverly sandstone comes from Southern Ohio. This is a fine- grained homogenous stone of a light drab or dove color, which works with * "Stones for Building and Decoration." George P. Merrill. BUILDIXG STONES—SLATES. 241 facility, and is very handsome and durable. It forms the material of which many of the finest buildings in Cincinnati are constructed, and is, justly, highly esteemed there and elsewhere."* Ohio is the largest producer of sandstone of any State in the Union. At Warrcnsburg, Mo., there is quarried a gray sandstone which has been used in many important buildings in Kansas City. The Rocky Mountain region also furnishes great quantities of fine sand- s<'l)nes. In Aricona there is quarried a very fine-grained chocolate sandstone, which t^kes a fine edge and is excellently adapted for rubbed and moulded work. A considerable quantity of it is used in Denver, Col., on account of its pleasing color, and it is also shipped east of the Missouri River. At Manitou, Col., there are inexhaustible quarries of a fine red stone, much resembling the Longmeadow stone of Massachusetts, but of a lighter red color. It has no apparent bed and weathers well. It has sufficient strength for ordinary purposes. At Fort Collins, Col., there is quarried a much harder and slightly darker stone, which is excellent for almost any purpose. It has sufficient strength for piers and columns, and is hard enough for steps and thresholds. It is much harder to cut than the Manitou stone, and hence is more expensive; but it is at the same time more durable. This stone has been shipped as far East as New York City. Colorado also contains an inexhaustible supply of sandstone flagging, admirably adapted for founda- tions and sidewalks ; it is as strong as granite, and may be quarried in slabs of almost any size or thickness. A red and buff sandstone is quarried at Glcnrock, Wyoming, which has been used in Omaha, Nebraska. The Rawlins, Wyoming, gray sandstone has been used in the following- buildings : The Wyoming State Capitol and the United States post-office at Cheyenne, Wyo. ; the State University at Laramie, Wyo. ; court-house, school-house and State Penitentiary at Rawlins, Wyo. ; residence cf John F. Campion, Denver, Col. ; court-house at Beatrice. Neb. ; opera-house, Kearney, Neb. ; public park building and several store buildings at San Francisco, Cal. California has many quarries of sandstone, the larger number of which are in Santa Clara County. Stanford University is built of a light-colored sandstone quarried at San Jose, Cal. Owing to the sparsely settled condition of the country and the lack of railroad facilities, the building stones of the Western portion of the United States have been but little developed, but with the building up of that part of the country the quarrying industry will undoubtedly become one of great importance. 6. SLATES. 240. GENERAL DESCRIPTION.— Although slate is not strictly a building stone, it is largely used for covering the roofs of buildings, for blackboards, sanitary purposes, etc., and the archi- tect should be familiar with its qualities and characteristics. Ira Raker, "Masonry Construction." 242 BUILDING CONSTRUCTION. (Ch.V) The ordinary slate used for roofing and other purposes is a com- pact and more or less metamorphosed siHceous clay. Slate stones originated as deposits of fine silt on ancient sea bottoms, which in the course of time became covered with thousands of feet of other materials and finally turned into stone. ''The valuable constituents in slate are the silicates of iron and alumina, while the injurious constituents are sulphur and the can^ bonates of lime and magnesia." One of the most valuable characteristics of slate is its decided tendency to split into thin sheets, whose surfaces are so smooth that they lie close together, thus forming a light and impervious roof covering. These plans of cleavage are caused by intense lateral pressure, and are generally at very considerable though varying angles with the ancient bedding. The most valuable qualities of slate are its strength, its tough- ness and its non-absorptive character. 241. USES OF SLATE. — Slate is used principally for roofing purposes, but it is used also for billiard table tops, mantels, floor tiles, steps, flagging, fittings for toilet-rooms, school blackboards, school slates and pencils, electrical supplies and for numerous other purposes. 242. PHYSICAL FROFERTIES.— Strength and Hardness.— From various tests that have been made on the quality of slate, it appears that, in general, the strongest specimens are the heaviest and softest, as they are also the least porous and corrodible. "The tests for strength and corrodibility are probably those of greatest importance in forming an opinion regarding the value of the slate under actual conditions of service." * Mr. Mansfield Merriman suggests that specifications should require roofing slates to have a modulus of rupture for transverse strength greater than 7,000 pounds per square inch. If the slate is too soft the nail holes will become enlarged and the slate will get loose. If it is too brittle the slate will fly to pieces in the process of squaring and holing, and will be easily broken on the roof. "A good slate should give out a sharp metallic ring when struck with the knuckles ; should not splinter under the slater's axe ; should be easily 'holed' without danger of fracture, and should not be tender or friable at the edges." * Mansfield Merriman in Stone, April, 1895. B UILDING STONES—SLA TES. The surface when freshly spHt should have a bright metallic luster and be free from all loose flakes or dull surfaces. Color. — The color of slate varies from dark -blue, bluish black and purple to gray and green. There are also a few quarries of red slates. The color of slate does not appear to indicate its quality. The red and dark colors are generally considered the most effective in appearance, while the greens are used principally on factories, storehouses and buildings where the appearance is not of so much importance. Some slates are marked with bands or patches of a different color, and the dark purple slates often have large spots of light green upon them. These spots do not as a rule affect the durability of the slates, but detract greatly from their appearance. As a rule the dark color of slates, particularly that of the slates of Maine and Pennsylvania, appears to be due to particles of car- bonaceous matter contained in them. "The red slates of New York are made up of a ground mass of impalpable red dust in which are imbedded innumerable quartz and feldspar particles." Absorption. — A good slate should not absorb water to any per- ceptible extent, and if a slate is immersed in water half its height the water should not rise in the upper half ; if it does, it shows that the slate is not of good quality. *Tf, upon breathing upon a slate, a clayey odor be strongly emitted, it may be inferred that the slate will not weather." Grain. — Good slates have a very fine grain. They should be cut lengthwise of the grain, so that if they break on the roof they will not become detached, but will divide each into two slates, each held by a nail. Market Qualities. — The market qualities of slate are classed according to their straightness, smoothness of surface, fair, even thickness, and also according to the presence or absence of dis- coloration. 243. PRODUCTION OF SLATE.— There were 9 States re- porting a commercial output of slate in the United States in 1906 — Pennsylvania, Vermont, Maine, Virginia, Maryland, California, New York, Arkansas and Georgia, named in the order of value of output. Besides these States Arizona, New Jersey, Tennessee 244 BUILDING CONSTRUCTION. (Ch.V) and Utah have deposits more or less developed. The production for 1906 was reported as valued at $5,668,346. There has been a gradual decrease in the number of squares of slate made in this country, due to a decrease of export trade, the English market, where American slates found considerable sale for several years, being now supplied either from the Welsh quarries, in consequence of the settlement of strikes in these quarries, or by small-sized, cheaper French roofing slates. The decrease is also due to labor troubles in the building trades for the last four or five years, to strikes in the slate quarries, and to the fact that the present building conditions in large cities do not call for slate roofs, the roofs being more nearly fiat, and the large number of patent- roofing processes and tiles being cheaper and more convenient than the slate. This condition is, however, ofifset outside of cities, espe- cially in the vicinity of quarries, by the high price of wooden shingles and the great durability of slate roofing., The scarcity and high price of labor has also been a factor in the decreased output. During the last five years smaller sizes of slate have been sold, making the average value lower. The roofing slate in 1906 was reported as 1,214,742 squares, valued at $4,448,786. Average value per square, $3.66 in 1906. • This table gives the number of "squares" of slate and the values of same, by States, for 1906 : Squares. Value. California 10,000 $80,000 * Georgia 1,000 5,000 Maine 18,498 100,916 Maryland 25,288 129,965 New York 10,788 60,000 Pennsylvania 755,966 2,710,249 Vermont 354-134 1,189,799 Virginia 39»o68 172,857 Total 1,21 4,742 $4,'448,786 A ^'square" of slate is the number of slates required to lay 100 square feet of roof, allowing a 3-inch lap. The estimated weight of roofing slate of ordinary thickness is 650 pounds to the square, and the slate is generally shipped in carload lots of from 50 to 90 squares per carload. The following shows the average price of roofing slate per square BUILDING STONES- —SLATES. 245 from 1901 to 1906 for the entire country: 1901, $3.15; 1902, $3.45; 1903, $3.88; 1904, $3.78; 1905, $3,69; 1906, $3.66. There is practically no slate imported into the United States. In 1906 the importations were valued at $9,471, of which only $228 was for roofing slate. The value of roofing slate exported from the United States in 1906 was $255,785, the chief slate export trade being to the United Kingdom, Canada and British Australasia.''' 244. TRADE CLASSIFICATION OF SLATE.— Slates are classified in the trade by the name of the region in which they are quarried, some regions extending into two or more States. Several regions are contained in the State of Pennsylvania. The product from each region is more or less- distinctive from that of other regions. .The more important producing regions are: Vermont and New York region ; Bangor region. Pa. ; Lehigh region, Pa. ; Pen Argyl region. Pa.; Maine region; Northampton hard-vein region, Pa.; Peach Bottom region, Md. and Pa. ; Virginia region. The slates of the Bangor, Pen Argyl and Lehigh regions and the Northampton hard-veined slates are found in the extensive slate formation known as the Hudson River Division of the lower Silurian deposits ; while the sl5te formations of Vermont, New York and Maine, and the Peach Bottom region, probably belong to the Cam- brian Division, whose place in the geological series is lower and older than the Silurian rocks. . ''The slates of the Cambrian formation are usually regarded as better in respect to strength and weathering qualities than those of the Silurian age, the market price of some varieties of the former being, indeed, more than double that of the common kinds of the latter." 245. DESCRIPTION AND LOCAL PRODUCTION OF SLATES FROM DIFFERENT STATES AND REGIONS.— VERMONT AND NEW YORK REGION.— In the western portion of Vermont there are extensive quarries of slate, the product being used for all the different purposes for which the material is adapted. Vermont ranks next to Pennsylvania in slate production, both in quan- tity and value of roofing slate, producing in 1906 29.15 per cent of the quantity of roofing slate. Almost the entire output is from Rutland County, in the vicinity of Castleton and West Castleton, Poultney. Fair Haven, North * For further data regarding the production of slate in the United States see "Min- eral Resources of the United States," calendar year 1906, from which much of this article is taken. 246 BUILDING CONSTRUCTION. ' (Ch. V) and South Poultney, Hydeville, Wells, Pawlet and West Pawlet, with a small output from Northrteld, Washington County. The stone is soft and uniform in texture, and can be readily planed or sawed like wood with a circular steel saw. The slates from this region vary greatly in color, and are classified and sold under the following names : "Sea-green," "unfading green," "uniform green," "bright green," "red," "bright red," "purple," "variegated" and "mottled." The true "sea-green" slate is found in this State, but it fades and changes color badly. Red Slate. — Nearly all the red slate used in the United States is quarried in the neighborhood of Granville and Middle Granville, Washington County, near the Vermont line, in New York State. "The slates of this formation are of a brick-red and green color, both varieties often occurring in the same quarry." The slate is of good quality and is used almost entirely for roofing purposes, its color making it especially desirable for fine residences and public buildings. Owing to the limited quantity, this slate brings about three tij-nes the price of the dark slates. MAINE REGION. — The quarries in this region are located at Monson, Elanchard and Brownville, Piscataquis County. The stone is of a blue-black color, of excellent quality, being hard, yet splitting readily into thin sheets with a fine surface. The slates are not subject to discoloration, and give forth a clear ringing sound when struck. The Brownville slate is said to be the toughest in the world. Slate from this quarry, after fifty years* exposure, looks as bright and clean as when new. • The Maine quarries furnish nearly all the black slates used in New England. The product is also extensively used for school slates, blackboards and sanitary purposes. PENNSYLVANIA SLATES.— Pennsylvania, from the three producing counties, Northampton, Lehigh and York, produced in 1906 62.13 per cent of the slate output of the United States. Of the roofing slate the number of Squares produced in Pennsylvania represented 62.34 P^r cent of the quantity of roofing slate produced in the United States. Northampton County pro- duced 71.16 per cent of the Pennsylvania output and 44.28 per cent of the total for the United States ; Lejiigh County 27.32 per cent of the Pennsylvania output and 17 per cent of the total, and York County 1.52 per cent of the Pennsylvania output and 0.94 per cent of the total. The number of squares and values of same for 1906 by counties are as follows : York County Lehigh County Northampton County Squares. 11,468 206,505 537,993 Value. $59,833 741 933 1,908,483 Totals 755,966 $2,710,249 Bangor Region. — This region is entirely within Northampton County, and is the most important, in point of production, in the country. The princioal BUILDING STONES— MISCELLAX ROUS, quarries are at Bangor, East Bangor and Slatington. The color is a uniform dark blue or blue-black. This slate is used very extensively for blackboards and school slates, as well as for roofing purposes. -The average modulus of rupture is 9,810 pounds per square inch. The Lehigh region includes all of Lehigh County, a few quarries in Berks and Carbon Counties and regions opposite Slatington in Northampton County. The product is similar to that of the Bangor region. The Pen Argyl region embraces quarries at Pen Argyl and Wind Gap in Northampton County. The Northampton hard-vein region includes the Chapman, Belfast and other quarries, all in Northampton County. This region is distinguished on account of the extreme hardness of the slate as compared with that pro- duced in other regions of the State. The product is considered the best of the Silurian slate, its extreme hardness being generally considered an advantage, rendering it durable and non-absorbent. It is especially suitable for flagging. The average modulus of rupture is about 8,480 pounds per square inch. PEACH BOTTOM REGION.— The celebrated "Peach Bottom Slate" is taken from a narrow belt scarcely 6 miles long and a mile wide, extending across the southeastern portion of York County and into Harford County, Maryland. The Maryland slate is produced at Cardiff, Harford County, a continuation of the "Peach Bottom" region at Delta, York County, Pa. The stone is tough, fine and moderately smooth in texture, blue-black in color, and does not fade on exposure, as has been proven by seventy-five years' wear on the roofs of buildings. It also ranks very high for strength and dura- bility, and is generally considered equal, if not superior, to any slate in the country. The average modulus of rupture of twelve specimens was 11,260 pounds, the lowest value being 8.320 pounds per square inch. THE NORTHERN PENINSULA OF MIGHT GAN contains an inex- haustible supply of good roofing slate, and quarries were at one time worked about 15 miles from L'Anse and about 3 miles from Huron Bay. No slate " has been produced from there, however, since 1889. "The stone here is sus- ceptible of being split into large, even slabs of any desired thickness, with a fine, silky, homogenous grain, and combines durability and toughness with smoothness. Its color is an agreeable black and very uniform." * VIRGINIA.— A good blue-black roofing slate is quarried commercially at Arvonia, Ore Bank and Penlan, Buckingham County. GEORGIA. — Quarries in Polk County, Georgia, furnish most of the roofing slates for Atlanta and neighboring towns. OTHER STATES. — Good roofing slate is found also in other States, but the quarries have not been recently worked, or not opened at all, or not worked commercially to any great extent. 7. MISCELLANEOUS BUILDING STONES. 264. LAVA STONE, TUFFS OR TUFA.— Near Castle Rock, in Colorado, is quarried a soft, very light gray and pink stone * "Stones for Building and Decoration." George P. Merrill. 248 BUILDING CONSTRUCTION. (Ch.V) of volcanic origin, which is commonly called ''lava stone." It is extremely light, weighing only from 75 to no pounds per cubic foot, and it can be cut with a knife. It weathers better than the soft sandstones, and its color makes it very suitable for rock-faced ashlar. It is difficult to obtain in large blocks, and is full of clay or air holes and often of invisible cracks, which render it dangerous for use in heavy buildings; but for dwellings it makes a very cheap, durable and pleasing stone. Owing to the small air holes which it contains it does not receive a finished surface, and is most effective when used in rock-faced work. There are a great many houses and several public buildings in Denver built of this stone. A similar stone occurs in the vicinity of the Las Vegas Hot Springs and Albuquerque, New Mexico. 247. BLUE SHALE. — This is a variety of sandstone that is dark blue in color, quite dense and hard, and makes a fair material for foundations. As a rule it does not work readily and often con- tains iron pyrites, which render it unsuitable for ashlar or trim- mings. 248. TRAP. — The only stone in many localities is a hard, igne- ous rock, called trap, which is suitable for foundations, but cannot be cut easily. Such stones are used for local purposes only, and when none other can be obtained except at great expense. 249. SOAPSTONE. — Although not properly a building stone, soapstone is used more or less in the fittings of buildings, especially for sinks and wash-trays. It is a dark bluish gray rock, composed essentially of the mineral talc. It is soft enough to be cut readily with a knife, or even with the thumb nail, and has a decided soapy feeling, which gives it its name. Although so soft, it ranks among the most indestructible and lasting of rocks. At present its chief use is in the form of slabs about inches thick, for stationary wash-tubs and sinks, for which it is one of the best materials. Soapstone also offers great resistance to heat, and is often used for lining fireplaces. At one time it was extensively used in New England in the manu- facture of heating- or warming-stones. Considerable quantities of powdered soapstone are used for making slate-pencils and crayons, as a lubricant for certain kinds of machinery, and in the finishing coat on plastered walls. BUILDING STONES—SELECTION. The principal quarries producing block stone are situated in the States of New Hampshire, Vermont and Pennsylvania. The State of North Carolina produces most of the powdered soap- stone, which is quarried in small pieces and ground in a mill.. 8. SELECTION OF BUILDING STONES. 250. GENERAL CONSIDERATIONS.— The selection of stones for structural purposes is a matter of the greatest impor- tance, especially when they are to be used in the construction of large and expensive buildings. The cities of Northern Europe are full of failures in the stones of important structures, and even in the cities of the northern portion of the United States the examples of stone buildings which are falling into decay are only too numerous. 'The most costly building erected in modern times, the Parlia- ment House in London, was built of a stone taken on the recom- mendation of a committee representing the best scientific and tech- nical skill of Great Britain. The stone selected was submitted to various tests, but the corroding influences of a London atmosphere were overlooked. The great structure was built of magnesian limestone, and now it seems questionable whether it can be made to endure as long as a timber building would stand, so great is the effect of the gases of the atmosphere upon the stone." * Stone should be studied with reference to its hardness, durability, beauty, chemical composition, structure and resistance to crushing. 251. NEW STONES. — If, in selecting a building stone, it is deemed advisable to use one from a new quarry, and if its weather- ing qualities have not been tested by actual use in buildings, the architect should insist upon a chemical and microscopic test by an expert to see if there is anything in its composition or structure which would render it unsuitable for building purposes. If the .report is favorable, and if the stone meets the tests described in the following sections, he may then use it with a free conscience. An architect cannot be too careful about using a new stone, or one that has not been used under circumstances similar to the new ones ; and whenever he is obliged to use such stone he should take pains to obtain as much information in regard to it as possible front all practical sources. The writer has known of a case in which a certain kind of stone, * Ira O. Baker in "Masonry Construction." 250 BUILDING CONSTRUCTION. (Ch.V) which had for a long time been used for making ashlar, was used in the piers under a seven-story building. The piers commenced to crack under only about one-one-hundredth part of the breaking strength as given in a published report of strength tests, and it cost nearly $200,000 to repair the damage and to substitute other stone. It was a lava stone, and its failure was supposed to be due to fine cracks produced in blasting out the stone from the quarry. It will not always do, either, to rely upon the past reputation of a stone for durability, as the quality of one building stone may differ from that of another from the same quarry. 252. CLIMATE AND LOCATION.— In selecting a building stone the climate, together with the location, with especial reference to the proximity to large cities and manufacturing establishments, should be first considered. There are many porous sandstones or limestones which could endure an exposure of hundreds of years in a climate like that of Florida, New Mexico, Colorado or Arizona, but which would be sadly disintegrated at the end of a single sea- son in one of the Northern States. The climate of our Northern and Eastern States, with an average annual precipitation of from 30 or 40 inches and with a variation in temperature sometimes reaching 120 degrees Fahr., is very trying to stonework; and unless the stones used are suited to the conditions in which they are placed, they are liable to decay and utter failure. 253. EFFECTS OF CHANGES IN TEMPERATURE.— The most trying conditions to which building stones are subject are the ordinary changes of temperature which prevail in the Northern and Eastern States. "Stones, as a rule, possess but a low conducting power and slight elasticity. They are aggregates of minerals, more or less closely cohering, each of which possesses degrees of expan- sion and contraction of its own. As temperatures rise each and every constituent expands more or less, crowding with resistless force against its neighbor; as the temperatures decrease a corre- sponding contraction takes place. Since the temperatures are ever changing, often to a considerable degree, so, within the mass of the stone, there is continual movement among its particles. Slight as these movements may be they can but be conducive of one result, a slow and gradual weakening and disintegration." * This is sup- posed to be the chief cause of the disintegration of granites. There are several examples of old stonework in New York City * "Stones for Building and Decoration." George P. Merrill. BUILDING STONES— SELECTION. 25t in which the stone has begun to decay on the south and west sides, where the sun shines the longest, but in which it has not begun to decay on the north and east sides. The efforts of moderate tem- peratures upon stones of ordinary dryness are, however, shght compared with the effects of freezing upon stones saturated with moisture. The pressure exerted by water in passing from a Hquid to a soHd state amounts to not less than 138 tons to the square foot; and it is, therefore, evident that any porous stone exposed to heavy rains and to a temperature several degrees below the freezing point must be seriously damaged by a single season's exposure. It is also evident that the more porous a stone is the greater will be the deterioration ; and as sandstones are the most porous of all building stones, they suffer the most from this cause and granites suffer the least. Granite is, accordingly, the best stone for a base-course '^r for vmderpinning. For the effect of absorption on the durability of stones see Article 263. 254. DURABILITY OF DIFFERENT STONES.— The dur- ability of a stone is naturally of the first importance ; for unless it lasts a reasonable length of time, the money spent on a structure will be largely wasted. All public buildings should be built of materials practically imperishable. Table XXIII, taken from the Report of the Tenth Census, 1880, Vol. X, p 391, gives the number of years that different stones have been found to last in New York City, without discoloration or disintegration to the extent of necessitating repairs : TABLE XXIII. Durability of Different Stones. c Coarse brownstone. . Fine laminated brownstone Compact brownstone Bluestone (sandstone), untried , Nova Scotia sandstone, untried Ohio sandstone (best siliceous variety), 5 to 15 , 20 to 50 100 to 200 Probably centuries .Perhaps 50 to 200 Perhaps from one to many centuries Coarse fossiliferous limestone.. Fine oolitic (French) limestone. Marble, coarse dolomite Marble, fine dolomite Marble, fine Granite Gneiss 50 years to many centuries 60 to 80 50 to 100 75 to 200 20 to 40 30 to 40 ' 40 252 BUILDING CONSTRUCTION. (Ch.V) There are many circumstances and conditions, aside from the quaHty of the stone, that affect the durabihty of exposed stone- work, the more important of which are heat and cold, composition of the atmosphere, position of the stone in the building, and manner of dressing the stone; 255. EFFECT OF ATMOSPHERIC ACTION ON BUILD- ING STONES. — The chemical action of the gases of the atmos- phere, when brought by rain in contact with the surfaces of certain ston'es, seriously affects their durability. The most important changes produced by these agencies are (i) oxidation and (2) solution. (1) Oxidation. — The process of oxidation is, as a rule, confined to those stones which contain some compound of iron, and par- ticularly that known as pyrite or iron disulphide. If the iron exists in the latter form it generally combines with the oxygen of the air, forming the various oxides and carbonates of iron, such as are popularly known as ''rust." ^Tf the sulphide occurs scattered in small particles throughout a sandstone the oxide is disseminated more evenly through the mass of the rock, and aside from a slight yellowing or mellowing of the color, as in certain Ohio sandstones, it does no harm. Indeed, it may result in positive good, by supplying a cement to the individual grains and thus increasing the tenacity of the stone."* If the pyrite exists in pieces of any size, however, it is almost sure to oxidize and stain the stone so as to ruin its appearance, # especially if it is of a light color. In all stones other than sandstones the presence of any pyrite is a very serious defect, as it is almost sure to rust them and may also render them porous and more liable to the destructive effects of frost. (2) Solution. — The worst effect of the action of the gases of the atmosphere in connection with rain is the dissolving of certain constituents of stones, thereby causing their decomposition. Pure water alone is practically without effect on all stones used for build- ing, but hi large cities, and particularly in those in which a great deal of coal is consumed, the rain absorbs appreciable quantities of sulphuric, carbonic and other acids from the air, conveys them into * "Stones for Buildins: and Decoration." George P. Merrill. BUILDING STONES— SELECTION. 253 the pores of the stones and very soon destroys those whose con- stituents are Hable to be decomposed by such acids. Carbonate of h'me and carbonate of magnesia, the principal con- stituents of ordinary marbles, limestones and dolomites, are particu- larly affected by the solvent action of these acids, even when they are present only in very minute quantities ; and on this account these stones are extremely perishable in large cities and manufacturing towns. Of course in dry climates the acids are not conveyed into the stone to any great extent, and the stones last much longer than, they do in a damp climate. The less absorbent a stone is the less • will be the solvent action of the acids, and the longer it will last. Dolomites are in this respect more durable than limestones. Sandstones, whose cementing material is composed largely of iron or lime, are also subject to rapid decay through the solvent action of the acidulated rains. The feldspars of granites and other rocks are also responsive to the same influence, though in a less degree. 256. METHOD OF FINISHING BUILDING STONES.— This also has a great deal to do with the durability of a stone. As a rule, the less jar from heavy pounding that the surface is sub- jected to the more durable will be the surface, for the reason that the constant impact of the blows tends to destroy the adhesive or cohesive power of the grains, and thus renders the stone more sus- ceptible to atmospheric influences. This applies particularly to granites and limestones. Only granites and the hardest sandstones should be pene- or bush-hammered ; all others, if dressed, should be cut with a chisel. Sandstones may afterward be finished with a crandall, if desired. For granites a rock-face surface is probably the most durable, since the crystalline facets thus exposed are best fitted to shed moisture and the natural adhesion of the grains is not disturbed. For ail other stones, however, a smoothly sawn, rubbed or polished surface seems best adapted to a variable climate. 257. MANNER OF SETTING STONES.— When a stone is built into the wall of a building in such a way that the natural lay- ers of the stone are vertical, or on edge, the water penetrating the stone and freezing there causes its surface to exfoliate or peel off much more quickly and to a much greater extent than is the case when it is laid with its natural bed horizontal. Stones also so placed in a building that rain strikes them and washes over them, such as sills, belt-courses, etc., decay sooner than 254 BUILDING CONSTRUCTION. (Ch.V) the ashlar forming the face of the wall, and should be of the rnosf durable material. 258. THE COLOR OF STONES.— The great governing point with an architect in selecting a building stone is generally its color. In this again he is limited to a choice between those stones which come within the limit of cost. But the question of durability should always be borne in mind. Architects, owners and contractors should always keep in mind not only how a building will look when just completed, but how it will appear at the end of a few years, and, again, at the end of half a century. And probably it is better to accept shades of color which may be a little harsh and inharmonious at first, if durability is gained thereby, than to use the most pleasing color only to see it entirely changed at the end of a year, and crumbled to pieces at the end of a decade. A durable stone of any color generally tones down and becomes more pleasing at the end of a few years, while one that is not durable and permanent in color very soon becomes an eyesore. In the country and in small towns where there is no manufactur- ing, and where little bituminous coal is used, light-colored stones may be used with the prospect of having their color remain un- changed ; but in large cities and manufacturing towns, and particu- larly in those in which bituminous coal is the principal fuel, light stones should be avoided. For the last-mentioned localities red or brown siliceous sandstones are the most enduring and permanent, and next to these come the granites. In cities like Chicago, St. Louis, Pittsburg, Cincinnati, etc., the darker the stone used the more permanent will be its color, that is, in the central portions of the cities, as both brick and stone assume a dirty, dark bronze color in a few years, and in such localities deli- cate colors and fine carving are out of place. In climates like that of Colorado, Arizona and New Mexico, where there is a very bright sun and almost no rain, the light stones, and particularly the marbles, are most effective, as the shadows on such stones are very marked, and all kinds of ornament are made much more prominent than on red or dark stones. Any compact stone will last for centuries above the ground. As a rule, other things being equal, those stones which hold their native color the best will be the most beautiful in a building; and BUILDING STONES— SELECTION. 255 of the stones which do change color, those will be the most desir- able which change the least and the most evenly. 259. THE COST OF BUILDING STONES.— This has often more to do with the choice of a building stone by the owner than the architect wishes. The cost of a stone when cut depends not only upon the cost of the rough stone delivered at the site, but also upon the ease with which it may be worked ; upon whether it is to be smooth or rock-face ; plain or moulded ; and also, to some extent, upon its weight. One stone may be cheaper than another « in the rough, but the extra labor of cutting may make it the more expensive when built into the wall. The heavier a stone is the greater will be the cost of setting and of transportation. 260. THE HARDNESS OF 'BUILDING STONES.— For many purposes the hardness of a stone must be considered, as, for example, when it is to be used for steps, door sills, paving, etc. Granites, quartzites, or siliceous sandstones, and bluestones are the ■ best for this purpose. 261. THE STRENGTH OF BUILDING STONES.— When- ever any kind- of stone is to be used for foundations, piers, lintels, or bearing-stones, etc., its strength should be considered, and if this has not been demonstrated to be sufficient by practical use under similar circumstances, cubes of the stone measuring about 6 inches on a side should be carefully tested for the crushing strength. If it has every appearance of being a first-clasS stone of its kind, its strength may be assumed to be equal to the average strength of stones of that kind. The safe working strength for piers, etc., should not exceed one-tenth of the crushing strength. Tables giving the crushing strength of many well-known stones and the safe working strength for stone' masonry are given in the Appendix. The method according to which a stone is quarried sometimes has much to do with its strength. If it is quarried by means of explosives it may contain minute cracks, which cannot . be dis- covered until it receives its load, when their presence is unpleasantly manifested. Such an occurrence could take place only in some stone like a lava or a conglomerate. The cracking and splitting of stones in buildings are due more often to imperfect setting than to lack of strength in the stones themselves. All stones that will meet the requirements for durability will have sufficient strength for all pur- poses, except when they are in the positions mentioned above. 256 BUILDING CONSTRUCTION. (Ch,V) 262. FIRE RESISTANCE OF BUILDING STONES.^— The property in a stone of resisting the action of fire is often of much consequence, especially when there is exposure to fire risks on all sides, as is the case with most business blocks. Of the different kinds of stone used for building, the compact, fine-grained sand- stones withstand the action of fire the best ; limestones and marbles suffer the most, being calcined by an intense heat; and granites are intermediate in regard to injurious effects. The best sandstones generally come out uninjured, with the exception of the discolora- tion caused by smoke. Granites do not always collapse, but the face of the stone generally splits off and flies to pieces, often with ex- plosive violence. 9. TESTING OF BUILDING STONES. 263. GENERAL CONSIDERATIONS.— Every stone intended for building purposes that does not come from some well-known quarry should be tested by chemical analysis and the results com- pared with the analysis of well-known stones of the same kind ; and if found to differ materially in those constituents which are soluble in water or attacked by sulphuric or carbonic acids it should be rejected. The presence also of iron pyrites should lead to the re- jection of the stone if it is intended for exterior use. If. the build- ing is one of importance the architect should insist on the owners getting the opinion of some expert chemist or mineralogist on the durability and weathering qualities of the stone in question. As a rule, however, most buildings are now built with stone which is taken from well-known quarries, and whose weathering qualities have been tested ; so that if the quality is equal to the best that the quarry will supply, the ston-e will prove all that was expected of it. The fact, however, that certain quarries have furnished good material in the past is no guarantee of the future output of the * For recent and valuable data on the fire resistance of building stones the reader is referred to the very interesting paper by W. E. McCourt, on "The Fire-Resisting Quali- ties of Some New Jersey Building Stones, Part I," in "The Annual Report of the State Geologist for 1906." Mr. McCourt collected a number of samples of New Jersey stones during the summers of 1904 and 1905, under the direction of the State Geologist, and these were tested in the Geological Laboratory of Cornell University, in connection with work for advanced degrees. The object of the investigation was to ascertain the relative tendency of various stones to withstand extreme heat, and to determine, as far as possible, the criteria which control the refractory properties. The report includes an outline of earlier investigations, observations on burned build- ings, methods of making the fire tests, samples tested, general summary of results with granites and gneisses, diabases, sandstones, limestones and argillite, and a detailed state- ment of experiments, with nnmerous illustrations. The reader is referred also to the Appendix. f BUILDING STONES— TESTING. 257 entire quarry. This is especially true regarding rocks of sedimen- tary origin, like the sandstones and limestones, different beds of which will often vary widely in color, texture, composition and dur- ability, although lying closely adjacent. In many quarries ^f cal- careous rocks in Ohjo, Iowa and neighboring States the product is found to vary at different depths, all the way from pure limestone to magnesian limestone and dolomite, and in many cases an equal variation exists in point of durability.* The architect should, therefore, make a careful examination of the stone as it is delivered on the ground, or in the yard and before it is cut, to see that the quality of the stone is up to the standard re- quired ; and in large buildings in which a great quantity is required .it is advisable to visit the quarry and to determine from what part of it the stone shall be taken. The following rules and tests will enable one to judge if a stone is of good quality and likely to prove durable : Compactness. — As a general rule, in comparing stones of the saifle class, the least porous, most dense and strongest will be the most durable in atmospheres which have no special tendency to attack their constituent parts. Good building stones should also give out a clear, ringing sound when struck with a hammer. Fracture. — A fresh fracture, when examined through a powerful magnifying glass, should be bright, clean and sharp, with the grains well cemented together. A dull, earthy appearance indicates stone likely to decay. Absorption. — One of the most important tests for the durability of stone is that of the porosity or degree to which it absorbs mois- ture ; since, other things being equal, the less moisture it absorbs the more durable it will be. To determine the absorbent power the specimen is thoroughly dried in a temperature of about 100 degrees Fahr., and carefully weighed ; then soaked for at least twenty-four hours in pure water ; then removed from the water, and the surface allowed to dry in the air ; and then weighed. The increase in weight is the amount of water absorbed, and stands, although not absolutely correct, as an expression of the stone's absorbent power. This test is extremely simple, and when done with care gives very practical results. Any stone which absorbs 10 per cent of its weight of water dur- * "Stones for Building and Decoration." George P. Merrill. 258 BUILDING CONSTRUCTION. (Ch.V) ing twenty-four hours should be looked upon with suspicion until, by actual experiment, it shows itself capable of withstanding, with- out harm, the different effects of the weather for several years. Half %i this amount may be considered too large when the stone contains any appreciable amount of lime or clayey matter.* The porosity of a stone also has an effect upon its appearance when in a building. A non-absorbent stone is washed clean by each heavy rain, and its original beauty is retained ; while a porous stone soon fills with dirt and smoke and looks little better than a stone plastered with cements. Even in stones for interior decoration absorption should not be overlooked, as ink, oils or drugs may ruin expensive furnish- ings if the stones used are porous. Acid Test.-\ — Simply soaking a stone for some days in dilute solutions containing i per cent of sulphuric acid and hydrochloric acid will afford a rough idea as to whether or not it will stand a city atmosphere. A drop or two of acid on the surface of the stone will create an intense effervescence if there is a large proportion present of carbonate of lime or carbonate of magnesia. Test for Solution —The following simple test is useful for deter- mining whether a stone contains much easily dissolved earthy or mineral matter: Pulverize a small piece of the stone with a hammer, and put the pulverized portion into a glass filled about one-third with clear water, and let it remain undisturbed for at least half an hour. Then agitate the water and broken stone by giving the glass a circular motion with the hand. If the stone is highly crystalline, and the particles well cemented together, the water will remain clear and transparent ; but if the specimen contains uncrystallized earthy powder the water Vv^ill present an appearance more or less turbid or milky, depending upon the quantity of loose matter contained in the stone. 10. SEASONING OF STONE. 264. GENERAL CONSIDERATIONS.— All stone is better for being exposed to the air before it is set until it becomes dry. This gives a chance for the quarry water to evaporate, and in nearly all * "Stones for Building and Decoration." .George P. Merrill, t "Notes on Building Construction," Part III, p. 11. BUILDING STONES—SEASONING— PROTECTION 259 cases renders the stone harder, and prevents it from spHtting from the action of the frost. Many stones, particularly certain varieties of sandstones and lime- stones which are quite soft and weak when first quarried, acquire considerable hardness and strength after they have been exposed to the air for several months. The following is supposed to be the cause of this hardness. The quarry-water contained in the stone holds in solution a certain amount of cementing material, which, as the water evaporates, is deposited between the particles of sand, binding them more firmly together and forming a hard outer crust to the stone, while the inside remains soft, as at first. On this account the stone should be cut soon after it is taken from the quarry, and if any carving is to be done it should be done before the stone becomes dry, otherwise the hard crust will be broken ofif and the carving will be on the soft interior, and consequently have its durability much impaired. II. PROTECTION AND PRESERVATION OF STONEWORK. 265. GENERAL CONSIDERATIONS.— There are a great many preparations that have been used for preventing the decay of building stones, but all are expensive, and none have proved entirely satisfactory. Paint. — One material very generally used for preserving stone- work is lead and oil paint. This is effectual for a time, but the paint is destroyed by the atmospheric influences, and must be renewed every three or four years. It also spoils the beauty of the stone. The White House at Washington is built of a porous red sand- stone, which has been painted white for many years. Oil. — Boiled linseed oil is sometimes used on stonework, but it always discolors a light-colored stone, and renders a dark-colored one still darker. "The oil is applied as follows : The surface of the stone is washed clean, and, after drying, is painted with one or more coats of boiled linseed oil, and finally with a weak solution of ammonia in warm water. This renders the tint more uniform. This method has been tried on several houses in New York City, and the waterproof coating thus produced found to last about four or five years, when it must be renewed. The preparation used in coating the Egyptian obelisk in Central Park is said to have consisted of paraffine containing creosote dissolved in turpentine, the creosote 26o BUILDING CONSTRUCTION. (Ch.V) being considered efficacious in preventing organic growth upon the stone. The melting point of the compound is about 140 degrees Fahr. In applying the preparation the surface to be coated is first heated by means of specially designed lamps and charcoal stoves, and the melted compound applied with a brush. On cooling it is absorbed to a depth dependent upon the degree of penetration of the heat. In the case of the obelisk the depth was about ^ of an inch.''''' A soap and alum solution also has been used with moderate suc- cess for rendering stone waterproof. Ransome's Process. — This consists in applying a solution of sili- cate of soda or potash, water-glass, to the surface of the stone, after it has been cleaned, with a whitewash brush until its surface has become saturated. After it has become dry a solution of chloride of calcium is freely applied so as to be absorbed with the silicate into the structure of the stone.. The two solutions produce by double decomposition an insoluble silicate of lime, which fills the pores of the stone and binds its particles together, thus increasing both its strength and weathering qualities. This process has been used to a considerable extent in England, and is perhaps the most successful of all applications. The process of applying the solutions is more fully described in "Notes on Building Construction," Part III, p. 78. ^ 12. ARTIFICIAL AND MANUFACTURED STONES. 266. GENERAL DESCRIPTION.— A brief mention is made here of the so-called "artificial stones" and "manufactured stones,'' although it may be claimed that they belong more properly, in any strict classification, to' such products as hydraulic cement products, sand-lime products, etc. Artificial cement stones are usually carefully made blocks of cement mortar rendered compact by ramming or compressing such mortar in the moulds, and given any desired .shape by using suitable moulds. To this class belongs the "P>eton Coignet," used in France. An artificial stone, made by a diflferent process, is called *'Ran- some Stone." The mortar is made of sand, silicate of soda and water, arid is compressed into m.oulds in the usual way. A hot solu- tion of calcium chloride is then provided, into which the stone is * "Stones for Building and Decoration." George P. Merrill, BUILDING STONES— ARTIFICIAL— MANUFACTURED 261 immersed under pressure, causing a calcium silicate to form, and resulting in an insoluble cement, and also in a sodium chloride, which latter is removed by washings. Several kinds of artificial stone are manufactured under patented processes, and many are combinations of hydraulic cement, sand, pebbles, stone-dust, etc., with or without the addition of some in- durating material, as baryte, letharge, etc. They are manufactured either in place or in the form of blocks at the factories. To several of the sand-lime products the name "manufactured stone" has been given by the manufacturers. A product, consisting essentially of silica and lime, is in England called "silicate stone." The proportion of lime used is from 5 to 10 per cent, the purity of the silica regulating the quantity. A sand-lime product is manufactured at Wilmington, Delaware, by the Diamond Stone-Brick Company, and called ''Wawaset Lime- stone." The manufacturers claim that the principle underlying its production has been successful for about twenty years, but that its application has not been made commercial until recently. The process is a secret, but it is admitted that it contains no cement whatever, and that it is along the lines of those employed in the manufacture of sand-lime bricks. If the sand-lime -brick theory is a correct one, and there seems to be strong evidence that it is, then this material, supplied on a large scale, should be good, providing the process can be so well carried out that large stones are thor- oughly permeated the same as are small bricks. Quite elaborate tests have been made on these products, and very satisfactory results shown, not only when considered in relation to the manufactured stones themselves, but also when com^pared with the results of comparative tests made with natural limestones, sand- stones, etc. The Wawaset manufactured limestone has been used in several buildings for both exterior and interior purposes and lends itself well to carved, moulded and decorative work of all kinds. It was used in the Spring Garden Street Branch Library building in Phil- adelphia, and in other buildings in the same city and in Wilmington, Delaware. In regard to the products including hydraulic cement mortar and concrete constructive and decorative stones there are a number of companies making them in different parts of the United States. At New Haven, Conn., the Economy Manufacturing Company makes 262 BUILDING CONSTRUCTION. (Ch.V) a concrete building stone, the process involved in which is without secrets or patents, and consists in the pouring of crushed trap rock and cement into a form, letting it stay there about two days, and then rubbing it down in various ways. It is entirely similar to the concrete used in footings and foundations, except that it has about three times the amount of cement usually put into the latter con- structions, and is mixed with much greater care. The artificial concrete stone products of this company have been used in several important buildings, such as the new Cadet Bar- racks at West Point, N. Y. ; Christ Church, West Haven, Conn. ; Trinity Church, New Haven, Conn. ; St. Philip's Church, Durham, N. C. ; St. James' Church, Woodstock, Vt., etc^ Chapter VI. Cut-stonework. 267. INTRODUCTORY.— In order to properly lay out, detail and specify the stonework of a building-, it is necessary to have a thorough knowledge of the different tools and processes employed in cutting and dressing the stone and of the different ways in which stone is used for walls, ashlar and trimmings. The description in this chapter of different classes of work, sup- plemented by critical observation in the stone-yard and at the build- ing, should give one a good idea of the ordinary methods and practices employed in this country. The subject of cut-stonework may be conveniently discussed under seven subdivisions, as follows : 1. Classes of Cut-stonework. 2. Stone-cutting and Finishing. 3. Miscellaneous Trimmings. 4. Treatment of Cut-stonework in- the Wall. 5. Strength of Cut-stonework. 6. Measurements and Cost of Cut-stonework. 7. Superintendence of Cut-stonework. I. CLASSES OF CUT-STONEWORK. - Stonework, such as is used in the superstructure of buildings, may be divided into three classes : Rubble-work, Ashlar and Trim- mings. 268. RUBBLE-WORK. — This is used only for exterior walls in places where suitable stone for cutting cannot be obtained at a relatively low price. There are localities which furnish cheap, dur- able stone which cannot be easily cut, such as the conglomerates and slate stones. They generally split so as to give one good face, and may be used with good effect for walls, with cut-stone or brick trimmings. Fig. 93 shows the usual method of building a rubble wall above ground. After the wall is up the joints are generally filled flush with mortar of the same color as the stone, and a raised false joint 263 264 B UILDING CONSTRUCTION. (Ch. VI); of red or white mortar stuck on, to imitate ashlar. Such work should be specified to be laid with beds and joints undressed, pro- jections knocked off and laid at random and interstices filled with spalls and mortar. If a better class of work is desired, the joints and beds should be specified to be hammer-dressed. Fig. 94 shows a kind of rubble-work sometimes used for build- ings, which is quite effective for suburban architecture. It should be specified to have hammer-dressed joints, not exceeding or 94 of an inch, with no spalls. on the face. This is generally expensive work. Fig. 95 shows a rubble wall with brick quoins and jambs. Occasionally small boulders or field-stone are used for the walls of rustic buildings. In such cases the walls should be quite thick, Fig. 93. — Rubble Stonework, Undressed, Laid at Random. with backings of split stone, to hold the boulders ; and the exact manner in which the walls are to be built should be specified. There are several kinds of rubble used in engineering work, but the above are about the only styles used in buildings. 269. ASHLAR. — The outside facing of a wall, when of cut- stone, is called ashlar, without regard to the way in which the stone is finished. Ashlar is generally laid either in continuous courses, as in Figs. 96 and 97, or in broken courses, as in Fig. loi ; or with- out any continuous horizontal joints, as in Figs. 98 and 99, which represent broken-ashlar. 270. COURSED-WORK. — Coursed-work is always the cheap- est when stones of a given size can be readily quarried, as is usually the case with sandstones and limestones. The cheapest ashlar for CUT-STONEWORK, 265 most stones is that which is cut into 12-inch courses, with the length of the stones varyincr from 18 to 24 inches. When they are cut from 30 inches to 3 feet in length, and with the end joints plumb over each other, as in Fig. 96, the cost is considerably increased, and if this kind of work is desired it should be particularly specified. Fig. 96 is regular-coursed-ashlar, each course being the same height with plumb bond. When the courses of stone are of differ- ent heights it is called irregular-coursed-ashlar. A form of ashlar now much used is that shown in Fig. 97, in which wide and narrow courses alternate with each other. Six inches and 14 inches make good heights for the courses. Fig. 102 shows regular-coursed-ashlar, with rustic quoins and plinth, which is much used in Europe. Fig. 94. — Random-Rubble Stonework with Hammer- Fig. 95. — Dressed Rubble Stone- dressed Joints and No Si)alls on Face, and work with Brick Quoins with Quoins. and Brick Jambs. 271. BROKEN-ASHLAR. — When stones of uniform size can- not be cheaply quarried the stone may be used to better advantage in broken-ashlar, but it takes longer to lay it, and, as a rule, broken- ashlar costs considerably more than coursed-ashlar. This style of work is generally considered the most pleasing, and, when done w^ith care, makes a very handsome wall, as shown by the half-tone illustration. Fig. lOO. It is generally used for rock-face work only. To present the best appearance no horizontal joint should be more than 4 feet long, and several sizes of stones should be used. Broken-ashlar can be more quickly laid, and at le^s expense, if the stones are cut to certain heights in the yard, necessitating the cut- ting of one end joint only at the building. The wall shown in Fig. 98 is made up of stones cut 4, 6, 8, 10, 12 and 14 inches in height, wliile in Fig. 99 only three sizes of stones BUILDING CONSTRUCTION. (Ch.VI) 266 are shown. Fig. 98 shows the combination generally considered the more pleasing. In specifying broken-ashlar the height of the stones to be used should be specified. Broken-ashlar is sometimes 96. — Coursed-aslilar Istonework. Regular Pitimu Bond. arranged in courses from 18 to 24 inches high, as in Fig. loi, when it is called random-coursed-ashlar. It looks very well in piers. 272. QUOINS AND JAMBS.— The stones at the corners of buildings are called the quoins, and these are often emphasized, as Fig. 97. — Coursed-ashlar Stonework. irregular Plumb Bond. Regular- shown in Figs. 94 and 102. They should always be equal in size to the largest of the stones used in the wall. The stones at the sides of a door or window opening are called jambs. Fig. 103 represents CUT-STONEWORK. 26j cut-stone window jambs in a rubble wall. A portion of the jamb- stones should extend through the wall to give a good bond. In rubble walls the quoins and "jambs are often built of brick, as shown in Fig. 95. io Fig. -Broken-ashlar Stonework (Six Sizes). All ashlar work should have the bed-joints perfectly straight and horizontal, and the vertical joints perfectly plumb, or the appearance will be greatly marred. 273. TRIMMINGS. — This term is generally used to denote all — I \ ^ Fig. 99. — Broken-ashlar Stonework (Three Sizes). moldings, caps, sills and other stonework, except ashlar. The trim- mings may be pitched off on the face, but all washes, soffits and jambs should be cut or rubbed. 268 BUILDING CONSTRUCTION. (Ch.VI) Fig. 100. — Broken-ashlar Stonework, Rock-face. Fig. loi. — Random-coursed-ashlar Stonework. Fig. 102. — Regular-coursed-ashlar Stonework, Rustic Fig. 103. — Cut-stone Win- Ouoins and Plinth. dow Jamb, Rubble Wall. SrOXE-CUTTING AND FINISHING. 269 2. STONE-CUTTING AND FINISHING. 274. STONE-CUTTING TOOLS.— In order that the architect may specify correctly how he wishes the stone in his buildings fin- ished, it is necessary for him to be familiar with the tools used in Fig. 104. — Axe or Pean- Fig. 105. — Tootli-axe. hammer. cutting and with the technical names given to different kinds of finish. There are several kinds of hammers used by masons in dressing Fig. 106. — Bush-hammer. rubble, and also a variety of tools used in quarrying, but as they are not used in working the finished stone they will not be described. The Axe or Pean-hammer, Fig. 104, has two cutting-edges. It 2/0 BUILD IXG CONSTRUCTIOhL (Ch. VI) is used for making drafts or margin-lines around the edges of the stones and for reducing the faces to a level. It is used after the point on granite and other hard stones. Fig. 107. — Crandall. Fig. 108. — Patent-hammer. The Tooth-axc, Fig. 105, has its cutting-edges divided into teeth, the number of which varies with the kind of work required. It is used for reducing the face of sandstones to a level, ready for the crandall or tool. It is not used on granites and hard stones. The Biish-hainmer, Fig. 106, is a square hammer, with its ends (from 2 to 4 inches square) cut into a number of pyramidal points. It is used for finishing the surface of the hardest sandstones anel limestones, after the face of the stone has been brought nearly to the plane required. I S 3 4 5 6 7 8 Fig. 109. — Chisels. The Crandall, Fig. 107, is a malleable iron bar about 2 feet long, slightly flattened at one end, in which is a slot y% of an inch wide and 3 inches long. Through this slot are passed ten double-headed points of ^-inch square steel, about 9 inches long, which are held in place by a key. Only one end of the crandall is used, and as the points become dull they can be taken out and sharpened, or the STONE-CUTTING AND FINISHING. 271 ends can be reversed. It is used for finishing sandstones after the* surfaces have been prepared by the tooth-axe or chisel. The Patcnt-hainuicr, Fig. 108, sometimes called the bush-ham- mer, is made of four, six, eight or ten thin blades of steel, ground to an edge and bolted together so as to form a single piece. It is used for finishing granite and hard limestones, the fineness of the finish being regulated by the number of blades used. The Point, Fig. 109, No. 4, has a sharp point, and is used in breaking off the rough surfaces of the stones and reducing them to planes, ready for the axe, hammer or tool. It is also used to give a rough finish to stones for broached worl* and also for picked work. No. I, Fig. 109, represents the tooth-chisel, used only on soft stones ; No. 2 a drove, about 2 or 3 inches wide ; Nos. 3, 7 and 8 different forms of chisels used on soft stones. No. 5 is a tool, usually from 33^ to 4^ inches wide, used for finishing sandstones, and No. 6 is a pitching chisel, used as in Fig. no. 275. DIFFERENT KINDS OF VmiSH.— Rock-faced or pitch-faced work is shown in Fig. no, the face of the stone being left rough as it comes from the. quarry, with the joints or edges ''pitched off'' to a line as shown. The greatest projection of the face of the stone beyond the plane of the joints should be specified. The ashlar shown in Fig. 100 is ''rock-faced." Rock-faced zvork with margin or draft-lines is shown in Fig. III. The margin (often called draft-line) is cut with a tool-chisel on soft stones and with an axe on granites. Sometimes only the angle of the quoins has a draft-line, as in Fig. 112, when it is called an "angle-draft." Rock-faced ashlar is naturally cheaper than any kind of dressed ashlar, particularly in granite. Fig. 1 10. — Rock-faced or Pitch-faced Stone-pitching Chisel. Fig. g. III. — Rock-faced Stone with Draft-line or Margin. 272 BUILDING CONSTRUCTION. (Ch. VI) * Broached Work. — The surface of tlie stone is dressed ofif to a level surface, with continuous grooves made in it by the point. Fig. 113 shows a stone with margin or draft-lines and broached center. Pointed Work (Figs. 114 and 115). — When it is desired to dress the face of a stone so that it will not project more than from ^ to y2 an inch, and when a smooth finish is not required, as in base- ment piers, etc., the rock-face is taken ofif with a point and the sur- face is rough-pointed or fine- pointed, according as the point is used over every inch or half -inch of the stone. The point is used oftener for dressing hard stones than soft stones. Tooth-chiselled Work. — The cheapest method of dressing soft stones is the one in which the tooth-chisel only is used. . This gives a surface very much like pointed work, but usually it is not so regular. (See Fig. 109, i.) Tooled work is done with a flat chisel from 3^ to 43^ inches wide (see Fig. 109, 5), and the lines are continued clear across the width Fig. 113. — Broached Stone with Fig. 114. — Rough-pointed Tooled Margin or Draft-line. Stone with Margin. of the piece, as shown m Fig. ii6. Wh-en well done it makes a very pretty finish for sandstones and limestones, and especially for molded work. Drove work is much like tooled work, but is done with a chisel about inches wide and in rows lengthwise of the stone face, as. shown in Fig. 117. Drove work does not take quite as much time as tooled work, and hence is cheaper; but it does not look so well. (See Fig. 109, 2.) Fig. 112. — Rock-faced Stonework with Angle-draft. STONE-CUTTING AND FINISHING, 273 Bush-hamincrcd Work. — This finish is made by pounding the surface of the stone with a bush-hammer, leaving it full of points, as in Fig. 120. It makes a very attractive finish for the harder kinds of sandstones and limestones, but ought not to be used on soft stones. CrandaUcd Work (Fig. 118). — The face of the stone is dressed all over with the crandall, which gives it a fine pebbly appearance Fig. 115. — -Fine-pointed Stone with Margin. Fig. 116. — Tooled Stone. when thoroughly done. It makes a sparkling surface for red sand- stones, and in Massachusetts is used more than any other finish for sandstones. The crandall is not used on granites and other hard stones. Rubbed Work. — One of the handsomest finishes for sandstones and limestones is obtained by rubbing their surfaces until they are perfectly smooth, either by hand, using a smooth piece of soft Fig. -nrove Work on Stone. Fig. 118. — Crandalled Stone with Margin. Stone with water and sand •for rubbing, or by laying the stones on a revolving bed called a rubbing-bed. When the stone is first sawed into slabs the rubbing is very easily and cheaply done, so that rubbed sandstone ashlar is often as cheap as rock- faced work in yards where steam saws are used. The saws leave the stone com- paratively smooth and "suitable for the top of copings and places which are not in view. Granite marbles and many limestones, when rubbed long enough, take a high polish. 274 BUILDING CONSTRUCTION. (Ch.VI) Picked Work. — In this work the face of the stone is first levelled off with the point and then picked all over. Broken-ashlar finished in this way has a very pretty effect, but is quite expensive. Patent-hanimcrcd or Biish-hammcrcd Work (Fig. 119). — When it is desired to give a finished surface to granites and hard limestones they are first dressed to a rough surface with the point and then to a medium surface with the same tool, and finally finished with the patent-hammer. The fineness of the finish is determined by the Fig. 119. — Patent-hammered Fig. 120. — Bush-hammered Stone with Margin. Stone -with Margin. number of blades in the hammer, and the work is said to be "six- cut," ''eight-cut" or "ten-cut," as six, eight or ten blades are used. Gcvernment work is generally ten-cut. Eight-cut is generally used for average work, and for steps and doorsills six-cut is suffi- ciently fine. The architect should always specify the number of blades to be used when the work is to be finished with a patent- hammer. The same finish may be obtained with the axe or pean- hammer, but it requires much more time. Fig. 121. — Vermiculpted Work Fig. 122. — Fish-scale ^^'ork with with Chiselled Margin. Chiselled Margin. Vermiculated Work (Fig. 121). — Stones dressed so as to have the appearance of having been worked by worms. This work is generally confined to quoins and base-courses. Rusticated Work. — This term is now generally used to denote .sunk or bevelled joints, as in Figs. 102 and 123, although it originally CUT -STONE TRIMMINGS. 275 referred to work honeycombed all over on the face to give a rough effect, as shown in Fig. 102. Fish Scale or Hammered Brass Work (Fig. 122). — Work made to imitate hammered brass, and done with a tool with rounded corners. Vermiculated and fish-scale work are seldom seen in this country. 276. LAYING OUT WORK.~If the cost of the stonework must be considered, the architect should ascertain from some reliable local stone-dealer the most economical size for the kind of stone he intends to use, and lay out his work accordingly. 3. MISCELLANEOUS CUT-STONE TRIMMINGS. 277. ' CUT-STONE TRIMMINGS IN BRICK BUILDINGS.— If the stonework consists merely of trimmings for a brick building, the architect or his draughtsman must first ascertain the exact meas- urement of the bricks as laid in the wall, and the stones must be figured so as to exactlv fit in with the brickwork ; otherwise the Fig. 123. — Rusticated Joints in Ashlar Stonework. bricks will have to be split where they come against the stones, thereby greatly marring tlie looks of the building. Bond-stones and belt-courses built into a pier must conform exactly to the size of the pier. As it is seldom that the bricks from any two yards are of exactly the same size, the exact size of the bricks that are to be used must be taken, as even a variation of j/^ of an inch often makes bad work. 278. DRIPS. — Projecting cornices, belt-courses and other trim- mings should have depth enough to balance on the wall, and all pro- 276 BUILDING CONSTRUCTION. (Ch. VI) jecting stones should have a drip as near the top of the stone as possible, to prevent the water from dripping over the rest of the moldings and down on the wall. Thus in a cornice such as shown in Fig. 124 the stone should be cut at a sharp angle at A, so that some of the water will drop ofif, and there should be a regular drip at B, so that the water will not run down on the wall. It is a good idea to cut a drip in all window sills, as shown in Fig. 125. In the Fig. 124. — Stone Cornice witli Drip and Wash. Fig. 125. — Stone W indow Sill with Drip and Wash. summer dust always lodges on sills and projecting ledges, and when it rains the water washes the dust, which often contains cin- ders, over the face of the stonework and down on the wall, causing both to become streaked and unsightly. The architect will find that if he is careful to provide drips on all moldings and sills his buildings will remain bright and clean for a Fig. 126. — Top of Stone Belt-course Around Pilaster. much longer time than would otherwise be the case. Some think it is even better to slightly change the profile of the molding if necessary, in order to provide a drip, as the most beautiful mold- ing looks unsightly when streaked and stained with dirty water. 279. WASHES. — The top surfaces of all cornices, belt-courses, capitals, etc., should be cut so as to pitch outward from the wall line, as shown in Fig. 124. If the top is left level, the rain water falling upon it will, in time, disintegrate the mortar in the joint above and CUT-STONE TRIMMINGS. 277 finally penetrate into the wall. Surfaces bevelled in this way are called washes. When the face of the wall is broken with pilasters, or the windows r J Fig. 127. — Stone Ashlar Cut to Relieve Lintel or Cap. are recessed, the wash on the belt-courses should be cut to fit the plan of the wall above, as shown in Fig. 126. 280. STONE RELIEVING AND SUPPORTING LINTELS. — A stone lintel is a stone which covers a door opening or window opening, and which, therefore, acts as a beam. It is often called by stonecutters a "cap." VVhen it is necessary to use a rather long lintel in a stone wall the ashlar above the lintel may be arranged so as to relieve the lintel of some of the weight, as shown in Fig. 127. If the wall above the lintel is of brick a relieving- arch may be turned ; but this generally detracts from the appearance of the building,- and the best way to strengthen the lintel, when the length does not exceed 6 feet, is to let it rest on a steel angle-bar the full length of the cap, as shown in Fig. 128. When the width of the opening is more than 6 feet the lintel should be supported by steel beams, as shown in Figs. 129 and 130. A single beam, as in Fig. 129, may be used where only the weight of the lintel and its load is to be supported, and two or more beams where the whole thickness of the wall and also the floor joists must be supported. When the ^intel is the full thickness of the wall, and steel sup- Fig. 128. — Steel Angle- bar, Full Length of Stone Cap. Cap Less Than Six Feet Long. 278 BUILDING CONSTRUCTION. (Ch. VI) ports are undesirable, the strength of the lintel may be increased, when it is a stratified stone, by cutting it so that the layers are on edge, like a number of planks placed side by .side. The Greeks and Romans often cut their lintels in this way, and apparently for this reason. The resistance to weathering, however, is decreased by this method of cutting and setting. In locating windows in a brick or stone wall the designer should be careful to arrange them so that they will not come under a pier. This is not apt to happen in the front of a building, but it sometimes happens in the side or rear walls, where the windows are placed to suit the interior arrangement and without regard to the external effect. If a door or window must be placed under a pier, steel beams should be used to support the wall above and also the lintel. Many Fig. 129. — One 1-Ream Supporting Stone Lintel and Its Load. ■■EM Fig. 130. — Two LBeams Supporting Stone Lintel, Wall and Joists; Three-eighths-inch Steel Plate Rivetted to Beams. broken lintels are evidences of a too frequent neglect of this pre- caution. Another detail that should be carefully considered in laying out the stonework is the building of the ends of caps and sills into the piers. If a pier extends through several stories all the joints will be slightly compressed and the masonry will settle slightly ; and if the ends of the caps and sills of the adjoining windows are built solidly into the piers they are very apt to be broken as the piers setde. It is better to keep the caps and sills back from the face of a pier, and either to build pilasters against it to receive the caps and sills, as shown at A, Fig. 131, or to build the ends of the stones into CUT-STOXE TRIMMIXGS. 279 it ill such a way that they can give a Httlc. When these stones are back from the face of a pier this can easily be done. Lintels should have a bearing at each end of from 4 to 6 inches, • according to the width of the opening. It is better not to build tlie ends into the wall further than necessary to give a sufficient bearing. 281. CO:\IPOSITE STONE LINTELS —Designs sometimes require a stone lintel over a store window 10 to 12 feet wide. To procure such a lintel in one piece is, in many places, impracticable, 1 r 11 1 -A 1 J 1 ' 1 ' 1 ' 1 ' 1 ' 1 1 ' 1 1 ' 1 ' 1 ' 1 ' 1 ' i ' 1 ' i ' 1 ' 1 ' r:\ - ' 1 l-i'i'i' 1 1 1 1 1 ' t '".^ ' ; 1 1 - ' 1 ' ' ' 1 1 1 1 1 1 ; 1 ; 1 1 1 ; 1 1 1 1 ' , 1 , ' — 1 — 1 1 ■ I , 1 , ,1, 1 ■ ' 1 ' 1 ' 1 1 1 ' 1 1 Fig. 131. — Pilasters Against Pier to Receive Stone Caps and Sills. and it is therefore necessary to build up the lintel in pieces. V/hen such is the case three stones at least should be used, and the end joints should be cut as shown in Fig. 132. Stones cut in this way are bound together better, and also appear to be self-supporting. A greater- number of stones, usually five or seven, may be used if preferred, but the joints should be cut in the same way. Such lintels should always be supported by steel beams, as shown in Figs. 129 and 130. 28o BUILDING CONSTRUCTION. (Ch.VI) 282. STONE SILLS. — A stone ''sill" is a piece of stone placed at the bottom of a window opening in a stone or brick wall. Door- steps or thresholds also are often called "sills." A slip sill is a sill that is just the width of the opening, and is not built into the walls at the jambs. A lug sill is a sill that has flat ends, built into the walls, as shown in Fig. 133. All sills should be cut with a wash of at least from j/^ an inch to 5 V 132. — Composite Stone Lintel. Openings to or 12 Feet Wide. Always with Steel Supports. inches in depth, and if the ends are to be built into the wall they should be cut as shown in Fig. 133. In some parts of the country each sill is cut with a straight bevelled surface the full length of the stone, and when it is built into the wall the bricks are cut to fit it. This is not a good method, as the water running down the jamb and striking the sill is apt to enter the joint between the bricks and stone, and the slant- ing surface offers an insecure bearing for the bricks. Slip sills are cheaper than lug sills, but they do not look so well ; and there is also danger of the mortar in the end joints being washed out in time. Slip sills, however, are not likely to be broken by any settlement in the brickwork, and for this reason many architects prefer to use them for the lower openings in heavy buildings and also for very wide openings. Lug sills should be built not more than 4 inches into the jambs, and should be bedded only at the ends when setting. 283. CUT-STONE ARCHES. NAMES OF VARIOUS PARTS. — Figure 134, ''Cut-stone Arch and Vault with Names of the Various Parts of the Arch," illustrates the different construc- tional divisions of this kind of masonry. Fig. 133. — Stone Sill Showing Ends, Wash and . Drip. Lug Flat CUT -ST ONE TRIMMINGS. In stone-cutting" the following terms also are often used for the different parts of arches and vaults : The SoMt. — The concave surface of the arch. The Back. — The convex surface of the arch. The Spandrel fiUing. — The filling, in the triangular spaces above the voussoirs and between the springers and the crown. A Ring-course. — A course of stones parallel to the voussoirs. The Arch-ring. — The voussoirs, taken together. 284. STONE ARCHES. GENERAL DETAILS.— Stone arches are very frequently used in both stone and brick buildings. CrouJrv. Keystone^ Fig. 134. — Cut-stone Arch and Vault with Names of Various Parts of the Arch. They may be built in a great variety of styles, and with either circu- lar, elliptical or pointed soffits. The method of calculating the sta- bility of a stone arch is the same as for a brick arch ; but since a stone arch is constructed of larger pieces, the mortar in the joints adds very little, if anything, to its stability, and a stone arch of the same size as a brick arch is rather more liable to settle or crack than the latter, and should be constructed with greater care. The method of calculating the stability of arches is given in Chapter VIII of the ''Architect's and Builder's Pocket-Book." In block stone arches each block, or 'Voussoir," should always be cut wedge-shape and exactly fitted to the place it is to occupy in the arch. The joints between the voussoirs should be of equal width the entire depth 282 BUILDING CONSTRUCTION. (Ch. VI) and thickness of the arch, in order that the bearing may be uni- form over the entire surface. The thickness of the joints will de- pend somewhat upon the character of the stonework. In finely dressed work j\ of an inch is the usual thickness, while in rock- faced work they are seldom made less than }i of an inch. One- Fig. 135. — Common Semi-circular Stilted Stone Arch. fourth of an inch, however, is all that should be allowed in first-class work. The joints should also radiate from the center from which the intrados is struck, or, in the case of an elliptical arch, they should be at right-angles to a tangent drawn to the intrados at that point. (See Fig. 140, Article 290.) The back of the arch may be either concentric with the intrados, or the ring may be deeper in the center than at the sides. Fig. 136.^ — Semi-circular Stone Arch. Vous- Fig. 137. — Stone soirs Cut to Bond witli Coursed-ashlar. Voussoirs Bonding with Coursed-ash- lar. The most common stone arch is that shown in Fig. 135, the arch .ring being of equal depth and the voussoirs all of the same size, and rock-faced with pitched joints. Occasionally the voussoirs are cut with a narrow margin draft, as shown at B. When the spring- CUT-STONE TRIMMINGS. 283 ing line of an arch is below the center, as shown in Fig. 135, the arch is said to be ''stilted," the distance 6" being called the "stilt." Stilted arches are very common in Romanesque architecture. A semi-circular arch is one of the best shapes for supporting a wall. It must, however, have sufficient abutments, and the depth of the arch-ring, or the normal distance in feet from the intrados to the extrados should be equal to at least 0.2 -f- V radius -f- half span Arches used in connection with coursed-ashlar, especially in Renaissance buildings, often have the voussoirs cut to the shapes shown in Figs. 136 and 137. Such arches are of course more expensive than arches with the Fig. 138. — Built-up Stone Arch. intrados and extrados concentric, as there is more waste to the stone, and more patterns are required. They have a more pleasing appear- ance, however, and are also stronger. Voussoirs of the shape shown in Fig. 137 must be cut with extreme accuracy. In dividing an arch into voussoirs it should be remembered that, as a rule, narrow voussoirs are more economical of material, but more expensive in point of labor. In most arches the width of the voussoirs at the bottom is about three-eighths of the width of the ring, although it may vary from one-fourth to one-half. Two voussoirs are cut very often from one stone, with a false joint cut in the center. This is done generally for economy, although 284 BUILDING CONSTRUCTION. (Ch. VI) in some cases it may add to the stability of the arch. The arch is generally divided into an uneven number of voussoirs, so as to have a keystone, the voussoirs being- laid from each side and the keystone exactly fitted after the other stones are set. There appears to be no necessity of having a keystone, and the author has been informed that Sir Gilbert Scott always used an even number of voussoirs, believing that thereby there is less danger of the voussoirs cracking. 285. LABEL-MOLDINGS ON STONE ARCHES.— In nearly all styles of architecture the better class of buildings have the arch-ring molded. In Gothic and Romanesque work a projecting molding called a "label-mold" is generally placed at the back of the arch. When not very large it may be cut on the voussoirs, but usually it is made a separate course of stone, as shown in Fig. 138. --..^—^ Fig. 139. ~ " ' Spandrel Supports. I ^ A. One .Springing Stone for Two B. Lower \'oussoir of Stone Arch Cut Arches. Full Width of Pier. When this is the case the depth of the arch-ring without the label- mold should be sufficient for stability. The label-mold may be cut into pieces of the same length as the voussoirs, or the joints may be made independent of those in the arch. 286. BUILT-UP STONE ARCHES.— Large arches, especially those which show on both sides of the wall, are often, for the sake of economy, built of several courses of stone, jointed so as to have the appearance of solid voussoirs. Fig. 138 shows the manner in which many of the large arches designed by the late H. H. Richard- son were constructed. Every alternate pair of voussoirs should be tied together by galvanized-iron clamps. 287. BACKING OF STONE ARCHES.— The arches generally seen in the fronts of buildings are usually only about 6 inches thick, and are backed with brick arches. The brick arches should be of the same shape as the stone arches, and the bricks should be laid CUT-STONE TRIMMINGS. 2Ss in cement mortar, so that there may be no settlement in the joints. The backing should be well tied to the stonework by galvanized-iron clamps, 288. RELIEVING-BEAAIS OVER STONE ARCHES.— Very often arches are used for effect in places where sufficient abutments cannot be provided to resist the thrust. In such cases one or more steel beams should be placed in the wall just above the arches, with the ends resting over the vertical supports and an empty joint left under the middle part of the beams. The wall above can then be built on these beams, leaving the arches with nothing but their own weight to support. The additional weight which the beams carry to the abutments also greatly increases the latter's resistance to a horizontal thrust. The beams should be provided with anchors at their ends, with long vertical rods passing through them, to tie the different parts of the wall together. Wherever segmental arches are used it is always a safe precaution to place steel rods back of them to take up the thrust, especially while the mortar in the abutments is green. ♦ 289. SUPPORT FOR SPANDRELS OF STONE ARCHES.— Wherever arches are used in groups care must be exercised in lay- ing out the springing stones to give a level support for the spandrels. Thus where two arches come together, as at A, Fig. 139, if the first voussoir is cut in the shape of the arch on the back a small wedge- shaped piece of stone will be required to fill the space between the first pair of voussoirs. The weight of the wall above coming on this wedge might be sufficient to force the voussoirs in, seriously mar the appearance of the arch and cause cracks in the ashlar above. This danger may be overcome by cutting the lower stone, a, a, in one piece for both arches and extending the voussoir, B, to a vertical joint over the middle of the pier. This gives a level bearing for the lower stone in the spandrel and effectually prevents any pushing in of the voussoirs. Another case very similar to this often occurs where the back of an arch comes almost to the corner of the wall or projection, as shown at B. If the distance between the back of the arch and the angle of the wall is less than 8 inches the lower voussoir should be cut the full width of the pier, as shown in the illustration. 290. ELLIPTICAL STONE ARCHES.— Arches built either in the form of an ellipse or oval, or pointed at the crown and elliptical 286 BUILDING CONSTRUCTION. (Ch. VI) at the springing, are often used for architectural effect in buildings, although very seldom in engineering works. Such arches are very liable either to open at the crown and "kick up" at the haunches, or to fail by the middle voussoirs being forced down. An elliptical arch, especially if very flat, is undesirable for spans of over 8 feet, and should never be used without ample abutments unless beams are placed above the arch as described in Article 288. The joints of an elliptical arch should be exactly normal (at right angles) to the curve of the soffit. If the line of the soffit is not a true ellipse, but is made up of circular arcs of different radii, the joints in each portion of the arch should radiate from the corresponding center. Fig. 140 shows an easy method for laying out the joints where the curve of the soffit is a true ellipse. Let M^, il/o, M.^, etc., Fig. 140. — ]\Iethod of Laying Out Joints of Elliptical Stone Arch. be points on the ellipse from which it is desired to draw the joints. Draw tangents to the ellipse at the points A and B intersecting at C. Draw lines AB and OC Draw lines from il/^, M,, M3, etc., perpendicular to OA and intersecting OC at L^, L^, L3, etc. From these points draw lines perpendicular to AB, intersecting OA at A'-,, N.,, N.„ etc. Lines drawn through N^M^, A',.M.>, etc., will then be normal to the curve and give the joints desired. 291. GENERAL CONSTRUCTION OF A THREE-CEN- TERED ARCH. — When the rise is to be not less than one-third the span, a three-centered arch is usually considered to give a curve more pleasing to the eye than one of a greater number of centers. Fig. 141, "Cut-stone Elliptical Three-centered Arch," indicates the general method of drawing a three-centered curve for an arch, when the two centers of the shorter radii are on the springing line AB. CUT-STONE TRIMMINGS. 287 On tlie span AB and on the rise HF are set off AD and FR respec- tively, these distances being equal to each other, and less than the rise HF. DE is drawn, and is bisecte(1 by the perpendicular CG which is produced to intersect FH at C. Then will C and D be two of the required centers, the third center being found on HB at a distance to the right of H equal to HD. An infinite number of curves may thus be constructed for the same span and rise. 292. CUT-STONE FOUR-CENTERED TUDOR ARCH.— The curve for this arch is shown in Fig 142, and may be con- structed as follows : Divide the span AD into four equal parts, AB, BO, OC and CD. From B and C as centers, and with radii Fig. 142. — Cut-stone Four-centered Tudor Arch. equal to BC, describe arcs intersecting at F. Draw BF and pro- duce it to meet a perpendicular to AD drawn through C ; and draw CF and produce it to meet a perpendicular to AD drawn through B. With 5 as a center and with a radius AB describe the arc AK, and with C as a center and with a radius DC describe the arc DL. Then with // as a center and with a radius HK describe the arc KE, and with G as a center and with a radius GL describe the arc LE. 293. CUT-STONE GOTHIC OR POINTED ARCH.— Fig. 143 illustrates the general form of one of these arches. In this par- ticular example the lines of the intrados and extrados are concentric, and the arch is, as it were, circumscribed or built around an equi- lateral triangle, each side of which is equal in length to the span. 288 BUILDING CONSTRUCTION. (Cii. VI) In this illustration BE is the springing line, and A is in each case the center from which the curve of the intrados of the arch-ring- is drawn, AC being the radius and ecjual to the span. Pointed arches are constructed of many different proportions, bv taking different positions for these centers, and different lengths for the radii. 294. CUT-STONE SEGAIENTAL ARCH.— Fig. 144 illus- trates the general form of a segmental arch, w^hich frequently re- places the full-centered or semi-circular arch because of limited space for rise. It is often used to span openings over doors and win- dows. Its construction is simple and is shown in the figure with c Fig. 143. — Cut-stone Gothic or Pointed Fig. 144. — Cut-stone Segmental Arch. Arch. its intrados curve described with C as a center and with CA equal to CB equal to AB the span, as a radius. 295. FLAT STONE ARCHES.— Shallow flat arches of stone, although somewhat pleasing to the eye, are very objectionable con- structionally. If a flat arch must be used, to be self-supporting it should be of such height that a segmental arch of proper size can be drawn on its face, as indicated by the dotted lines in Fig. 145. Even then it is desirable to drop the keystone about i inch below the soffit line, so as to wedge the voussoirs tightly together. An arch such as is shown in Fig. 145 might be safely used for a span of 5 feet, but with greater caution for larger spans. The strength of such an arch may be increased by making joggled" joints, that is, by notching one stone into the other, as shown by the dotted lines at a. Such joints, however, are quite expensive. A very shallow flat arch, such as is shown in Fig. 146, should be •cut out of one piece of stone, so as to be in reality a lintel with false CUT-STONE TRIMMINGS. 289 joints cut on its face. The ends of the hntel should have a bearing on the wall of 6 inches, as shown by the dotted lines, the face being cut away for about 2 inches in depth and veneered with brick. If this method is too expensive the lintel might be cut in three pieces and supported by a heavy angle-bar, as shown in Fig. 128. Very long lintels are often made in the form of a flat arch (see Article 281), but are, or should be, always supported by steel beams or bars. 296. FLAT ARCH VOUS- SOIRS WITH VERTICAL FACE JOINTS.— Built-up lin- tels and flat arches of stone are sometimes constructed with voussoirs which are cut as shown in Fig. 147. Here the face joints are vertical on both faces of the arch, but the arch principle is carried out by forming the joint vertically on only about 4 inches of the voussoirs back from each face of the arch-ring, and by cutting the joints sloping in the interior as shown. In case only one face of the arch ring is seen, the sloping joints may extend back through the voussoirs to the back face. 297. RUBBLE-STONE ARCHES.— Arches are sometimes built of rubble stones. The stones should be long and narrow and roughly dressed to a wedge shape. They should be built with cement -Flat Stone Arch, Joggled Joints. Fig. 146. — Shallow Flat Stone Arch in One Piece. A Lintel. False Joints. mortar, as they depend largely upon the strength of the mortar for their stability. 298. CENTERS FOR ARCHES.— Every arch, whether of stone or brick, should be built on a wooden center made to exactly fit the curve of the arch and carefully set in place. The center should have ample strength to support the weight of the arch and much of the wall above, as it is undesirable to put any weight on the arch until 290 BUILDING CONSTRUCTION. (Ch. VI) the mortar in the joints has become hard. A center is usually made with two ribs cut out of plank and securely spiked together, and the bearing surface formed of cross pieces about i by 2 inches in size nailed to the top of the ribs, as shown in Fig. 148. The ribs forming the supports for the cross pieces should be placed under each edge of the arch, and if the depth of the arch exceeds 12 inches three Fig. 147. — Stone Voussoirs for Flat Arch. Vertical Face Joints. Sloping Interior Joints. ribs should be used. The center should be supported on wooden posts resting on blocks set on the sill or some sufficient support below. It should not be removed until the mortar in the arch joints has had ample time to set. Fig. 148. — Wooden Center for Stone Arch. Usual Construction. Centers for spans of considerable width are framed together with heavier timbers and in a variety of ways. The general method is shown in Fig. 149, which represents a center for a lo-feet span. CUT-STONE TRIMMINGS. 291 outline of the arch. The cross pieces are then nailed to the top edge of the planks, as in Fig. 148. Such a center should have a support under the middle as well as at the sides. As the centers are only required for temporary use, architects generally allow the carpenter to construct them as he deems best, but the superintendent should satisfy himself that they are of ample strength and well supported before the masons commence building the arch. 299. COLUMNS. — Stone columns not exceeding 8 feet in height usually have the shaft cut in one piece and the caps and bases in separate pieces. For columns of great height it is generally necessary to build the shaft of several pieces. The joints between the cap and base and the shaft, and between the dif- ferent stones of the shaft, should be dressed exactly normal to the axis of the column and to a true plane, so that the pressure will be evenly distributed over the whole area of the joint. Nothing but cement mortar should be used in these joints, and their outer parts for ^ of an inch back from the face should be left empty to prevent the outer edges of the stones from chipping off. :.:\rr- Fig 50. Common Method ( Building Up Parts of Stone Entablature. 292 BUILDING CONSTRUCTION. (Ch. VI) If a column is built against a wall, the pieces from which the cap and base are cut should either extend into the wall or be secured to it by galvanized-iron clamps. 300. ENTABLx\TURES. — Stone entablatures spanning porch openings, etc., may be cut from one piece of stone, or, if of con- siderable height, may be built up with several horizontal courses. Fig. 150 shows a common method of building up the lower parts of an entablature, the corona and facia being in still another course above those shown. When jointed as in the figure the bottom joint should not be filled with mortar except at the ends, near the bearings. The various stones composing the cornice, frieze and architrave should be well tied together with iron clamps, especially at all ex- ternal corners. It is a good idea also to tie the cornices of porches to the building by long rods built inside the mason work to prevent the porches from "pulling away" from the walls. 301. STONE COPINGS.— All walls not covered by the roof should be capped with wdde stones called the copings. Horizontal copings should be weathered on top and should have drips at the bottom edges, as shown in drawing Fig. 151. The width of the coping should be about 3 inches greater than that of the wall. Gahlc copings do not require weathering, but they should pro- ject about inches from the face of the. wall, and should have sharp outer edges, so that the water will not run in against the wall. As the weight of a sloping coping tends to cause it to slide on the wall, the coping should be well anchored, either by bonding Fig. 131. — Stone Copings. K. Ciable Coping Kneeler. L. Gable Coping Bond Stone. C. Horizontal Coping with Drip and Weathering. CUT-STONE TRIMMINGS. 293 some of the stones into the wall, or by nsing- long" iron anchors. The bottom stone, sometimes called the "kneeler," should always be well bonded into the wall and cut with a horizontal bed-joint, as shown at K, Fig. 151. About once in every 6 feet in height a short piece of coping should be cut so as to bond into the wall, as at L. Gable copings sometimes have the part which rests on the wall cut in steps, so that each stone has a horizontal bearing. This method, however, is very expensive, unless the coping is cut in very short pieces ; and this is objectionable on account of the number of joints required. As a rule, copings should be designed with as long stones as possible to decrease the number . of joints and the admission of 302. STONE STEPS AND STAIRS.— These should always be built of spme hard stone, preferably granite, and should have solid bearings. Outside steps generally rest on a wall at each end, and if more than 6 feet long should have a support in the middle. Each step should have a bearing of at least inches on the back part of the one below. Steps to outside entrances should pitch outward about of an inch Steps are much easier to use when cut with nosings ; but owing to the increased expense they are used only in costly buildings. Stone stairs may be built with one end only supported. In Euro- pean buildings, and in many of our Government buildings, the stairs are constructed as shown in Fig. 152, either with or without nosings. One end of each step is built solidly into the wall, and each step is supported by the one below, owing to the way in which they are cut. The bearing of one step on another should be not less than that shown in the figure. The bottom step, obviously, must be well sup- ported its full length, as it has to sustain nearly the full weight of the Fig. 152. — Stone Stairs and Landing. moisture. Horizontal coping stones are often clamped together at their ends to prevent their getting out of place sideways. 294 BUILDING CONSTRUCTION. (Ch. VI) stairs. The steps are usually cut with a triangular cross-section as shown, as this shape is less expensive and reduces the weight, besides giving a pleasing appearance from below. The railing, posts and balusters are generally of iron, and the latter are dowelled into the ends of the steps. The laying out and detailing of other stone trimmings are gov- erned by the principles above noted. 303. CIRCULAR STAIRS IN STONE.— Circular stairs in stone may be constructed in either one of two ways. The steps may be ''hanging steps" which converge toward a well-hole, the outer ends of the steps being built into the outside walls, or they may be S£:cT/ON THRouoH a, b. 3Ecr/oNAL Plan Fig. 153. — Circular Stone Stairs. supported at both ends, by the outside walls and by a central newel. A variation of the latter, and a very common construction, espe- cially for circular staircases of small diameter, is shown in Fig. 153- Each step is cut out in the form indicated, with a circular portion on the inner end having a diameter equal to that of the intended newel. 304. BOND-STONES AND STONE TEMPLATES.— The building regulations of certain cities require that bond-stones shall be used in brick piers of less than a certain size. When such stones are used they should be of some strong variety, and should be cut the full size of the pier. It is also very important that the outside and inside bricks be brought exactly to the same level to receive the stones; for if the latter bear on the outside bricks only, the weight TREATMENT— CUT-STONE IN WALL. 295 will cause these bricks to buckle and separate from the pier, whil^ if the weight is borne by the middle part, the pier is liable to crack through at that point. Bond-stones should not be used in a wall in the manner shown in Fig. 154, as they prevent any spreading of the pressure, and keep concentrating it back to that part of the wall which is immediately under the bond-stones, as shown by the short vertical lines. Bearing-stones used under the ends of beams or girders, to dis- tribute the weight along the walls, are called templates. They should always be very hard, strong stones, laminated if possible; and the thickness of each stone should be one-third of its narrowest dimension, unless the stone is large, but in no case less than 4 inches. It is always better to have templates too large than too small. The bearing surface of the templates should be such that the pressure which it transmits to the wall below shall not exceed 120 pounds per square inch, or about 8^^ tons per square foot for common brick- work; or 150 pounds, or about 10^ tons per square foot for common rubble with flat beds. It is also a good idea to place a flat stone above the end of a wooden girder, so that the wall will not rest on the wood, which is quite sure to shrink and possibly affect the wall. 4. TREATMENT OF CUT-STONEWORK IN THE WALL. Fig. 154. — Bond-stones and Template in I'rick Wall. Incorrect Method of Construction. 305. LAYING OUT ASHLAR.— After the kind and size of ashlar to be used has been determined upon, the draughtsman should show each piece of ashlar on the elevation drawings if coursed- ashlar with plumb bond is to be used, and stones of particular lengths desired. If there are piers on the outside of the building a section drawing should be made showing how the stones in the piers are to be bonded with the rest of the wall. In all public buildings and most office and business blocks it is generally better to show every stone on the plans unless broken-ashlar is to be used, in which case the labor would be wasted. As a rule. 296 BUILDING CONSTRUCTION. (Ch. VI) ii» ordinary stone dwellings, and in fact in most stone buildings, either broken-ashlar or coursed-ashlar of irregular lengths is used, and in either case it is not necessary to indicate the ashlar on the elevation drawings, except to show the heights of the courses, if coursed-ashlar is used. When broken-ashlar is used only the quoins and jambs and a small piece of ashlar indicating the kind of work desired need be shown, as it is almost impossible for masons to careiully follow a drawing showing broken-ashlar. 306. THICKNESS OF ASHLAR.— Broken-ashlar and coursed- ashlar not exceeding 12 inches in height generally varies from 4 to 8 inches in thickness, and averages 6 inches. The dif- ferent courses should vary in Ml ^ thickness, as shown in Fig. In,. i55.-Usual Form of Anchor for Thin 159^ ^ud it is better tO have Ashlar facing. ^^^^ coursc 4 iuchcs and the next 8 inches than to have all 6 inches thick. No ashlar, however, even if of marble, should be less than 4 inches in thickness. Ashlar laid in alternating high and low courses, such as 6 inches and 14 or 20 inches, should be cut so that the low courses will be at least 8 inches thick and the high courses 4 inches thick ; and each stone in the high thin courses, when 18 inches or more in height, should have at least one iron anchor extending through the wall. Fig. 155 shows the form of anchor generally used. The high courses, when of sandstone or limestone, are generally sawed to a uniform thickness. 307. JOINTS IN CUT-STONEWORK. -It is important that Fig. 56. — Bed-joint in .Stonework Worked Hollow. Fig. 157. — Back of Bed-joint in Stonework Slack or Hollow. the exposed surfaces of each stone should be ''out of winde" ; that is, true planes and square to the bed- joints and end joints. The bed-joints should be full and square to the face and n6t worked hollow, as in Fig. 156, as with hollow joints the least settle- TREATMENT— CUT-STONE IN WALL. 297 » 298 BUILDING CONSTRUCTION, (Ch. VI) ment in the mortar will throw the whole pressure onto the edge of the stone as shown at C, and cause "spalls" or small pieces to splinter off, ruining the appearance of the building, and suggesting unsafe construction. Stone-cutters are very apt to work the joints hollow and the back of the joints slack, as in Fig. 157, as such joints require much less labor than evenly dressed joints; and, unless care- fully looked after, they will cut the stones slack in nine cases out of ten. If the back of a joint is left slack and underpinned, as in Fig. 157, the stone is then supported at the front and back only, and is liable to break in the middle, as shown. Of course, in a wall not exceeding 20 feet in height, the danger arising from imperfect joints is not as great as in a wall of six or more stories. The higher the wall the more carefully should the joints be cut. It is also desirable that the joints should not be convex. For very heavy masonry, as in the basement or first story of tall buildings, it is desirable to use rusticated joints (see Fig. 123), as with such joints the face is less apt to spall. The thickness of ashlar joints varies from to ^ of an inch. A j4-inch joint, when pointed, makes very good-looking work. A J^-inch joint is too wide for anything but rock-faced ashlar, and nothing over a i^-i^^ch joint should be used for heavy work. 308. JOINTS. GENERAL PRINCIPLES. JOINTS IN TRACERY. — The following general principles should be observed in arranging the joints of masonry and cut-stonework: (1) All bed- joints should be arranged at right-angles to the pres- sure coming upon them. (2) All joints should be arranged in such manner that all members, such as sills, shall be free from any cross or flexural stress. (3) All joints should be arranged in such manner that there are no acute angles on either one of the pieces of stone coming together. Principle (i) applies to all kinds of masonry, and takes account of the tendency of one stone to slide upon the other. Principle (2) applies chiefly to stone window and door sills. In stonework, where the sills must be set as the work proceeds, their cracking or breaking may be prevented by making a vertical joinl in the line of the face of the reveal, as shown in the elevation of the Gothic window in Fig. 158. When heavy stone mullions trans- mit considerable Weight to the sills, the same precautions must be taken with the latter; while if the mullions are light, and cause no TREATMENT— CUT-STONE IN WALL. 299 \ material pressure, continuous sills may be employed, and no joint is necessary under the mullions. It is better, in all cases, to build the stone tracery work in position, especially if very light, after the building is erected and all settlement has taken place. This prevents any weights being transmitted down through mullions and other portions of the light tracery. Principle (3) applies especially to the tracery joints, and in gen- eral to exposed joints in any other work. Acute angles in cut-stone weather badly, and in stone tracery in which several members inter- sect, the stones must be cut so as to contain the entire intersection and also a short length of each intersecting member, as shown in Fig. 158. The joints in the dif- ferent members abutting should always be cut at right-angles to their direc- tions. By this means acute angles are prevented, as they would not be in case the joints were made along the line of either section of the moldings, and a much bet- ter finish is insured. Joints should never be made in cut-stonework, in tracery^ in other miter line. moldings cannot be cut or carved when mortar joints are made along these lines of intersection. 309. BACKING OF CUT-STONEWORK.— Both stone and brick are used for the backing of ashlar. Brick is used more largely than stone for this purpose, because in most cases it is the cheaper, and because in dry climates plaster can be applied to it directly, whereas, stone backing generally has to be plugged and stripped for lathing. If brick is used for backing, the joints should be made as thin as possible, and it is desirable to use some cement in the mortar to prevent shrinkage in them. The backing, if of brick, should never I— Fig. 159.^ — Bonding and Backing of Stonework. A. Brick Backing. B. Stone -Backing. Neat and lasting intersections of moldings at anv 300 BUILDING CONSTRUCTION. (Ch. VI) be less than 8 inches in thickness. If a hard laminated stone, with perfectly flat and parallel beds can be obtained for backing, a stronger construction will result than if bricjc is used; but irregular rubble blocks are not suitable for any walls but dwelling-house walls, unless such walls are made one-fourth thicker than they would be with brick backing. The backing, whether of brick or stone, should be carried up at the same time the ashlar is laid, and, if of stone, it should be built in courses of the same height as the ashlar courses, as shown in B, Fig. 159. 31a BONDING OF CUT-STONEWORK.— Ashlar not ex- ceeding 12 inches in height is usually sufficiently bonded to the backing by making the stones of different thickness, as in Fig. 159, and by using one through stone to every 10 square feet of wall. Where the ashlar is only from 2 to 4 inches thick, as is generally the case with marble, and often the case with sandstones, each piece should be tied to the backing by an iron clamp, about % of an inch thick and i or 1^4 inches wide, with the ends turned at right- angles, as shown in Fig. 155. The anchors should be made of just the right length for the longer end to turn up close against the inside of the wall. Every stone should have one clamp, and if a stone is over 3 feet long two clamps should be used for it. There should be belt-courses, also, about every 6 feet, extending 8 inches or more into the walls, to add support to the ashlar. The effective thickness of a wall faced with thin ashlar is the thickness of the backing only. When iron clamps are used for tying the ashlar they should be either galvanized or dipped into hot tar to prevent their destruction by rust. 311. SETTING CUT-STONEWORK.— All stones should be set in a full bed of mortar, and any stone too large to be easily lifted by one man should be set with a derrick. In some localities slips of wood of the thickness desired for the joints are prepared and laid on the top of the stone below ; so that when a stone of a course above is set the mortar squeezes out until the stone rests on these slips. After the mortar has set or hardened the slips are withdrawn. The bed of mortar should always be kept back an inch or more from the edge of the stone. This will prevent the stone from bearing on its outer edge, and save raking out the mortar preparatory to pointing. In damp places stonework should be set in cement, or in lime-and-cement mortar; in dry places it may be set in lime mortar. TREATMENT— CUT-STONE IN WALL. Most granular limestones and marbles, and some sandstones, are stained by either Portland or natural cement, and when using any of these stones for the first time the architect should ascertain their liability to be stained. The mortar for bedding the stone can always be kept from its face by exercising a little care, and the joints can be afterward pointed w^ith some material that does not stain. Stone- masons are often very careless in setting stonework, and do not bed the stones evenly, so that when a considerable weight comes upon them they crack. Marble and limestone are sometimes set in a cement made of lime, plaster of Paris and marble dust, and called Lafarge cement. When such cement is used for setting the cut-stonework, and other cements for the backing, the back of the cut-stone should be plastered with the former cement. Window and door sills should be bedded at 1 Fig. 160. — Jointer for Stonework Joint. "V -.v ' r' : ■ ^^^^ their ends only with no mortar under the middle part, as otherwise any set- tlement of the walls will break them. 312. PROTECTING CUT- STONEWORK.— The carpenter's specifications should contain a clause providing for the boxing of all mold- ings, sills and ornamental work with rough pine to prevent the stone from being damaged during the construction of the building. Hemlock stains the stonework, and should therefore never be" used for this purpose. 313. POINTING CUT-STONEWORK.— As the mortar in the exposed edges of the joints is very apt to be dislodged by the expansion and contraction of the masonry and the effects of the weather, it is customary, after the masonry is laid, to refill the 161. — Pointed Joints Stonework. 302 BUILDIXG COXSTRUCTIOK (Ch. VI) joints to a depth of half an inch or more with mortar prepared espe- cially for this pnrpose. This operation is called ''pointing/' Pointing is generally done as soon as the outside of the building is completed, unless it should be too late in the season, when it should be delayed until spring. Under no circumstances should it be done in freezing weather, and it is better to postpone it in extremely hot weather, as the mortar dries too quickly. Portland cement mixed with not more than an equal volume of fine sand and such coloring matter as may be required, with just enough water to give the compound a mealy consistency, makes the most durable mortar for pointing. If the stone employed is stained by a cement, either Lafarge cement should be used, or else a putty made of lime, plaster of Paris and white lead. Before doing the pointing the joints should be raked out to a depth of about an inch, brushed clean and well moistened. The mortar is applied with a small trowel made for this purpose and is then squeezed in and rubbed smooth with a t6ol called a "jointer" (Fig. i6o). Jointers are made with both hollow and con- cave edges, so as to give a raised or concave joint, as shown in Fig. i6i. The concave joint is the most durable, although the raised joint makes perhaps the handsomest work. 314. CLEANING DOWN CUT-STONEWORK.— This con- sists in washing and scrubbing the stonework with muriatic acid and water. Wire brushes are generally used for marble work and sometimes for sandstone, but stiff bristle brushes usually answer the purpose just as well. The stones should be scrubbed until all mortar stains and dirt are entirely removed. The cleaning down is done in connection with the pointing. For cleaning an old front, the sand-blast, using either steam or compressed air, does the work most effectively, as it removes from 1-64 to 1-32 of an inch from the surface of the stone, making it look like new. Even carving can be successfully treated in this way. 315. SLIP' JOINTS IN WALLS.— Where two walls differing considerably in height come together, as, for instance, where the front or side wall of a church joins its tower, these two walls should not be bonded together, but the low wall should be ''housed" into the other, so as to form a continuous vertical joint from bottom to top, as shown in Fig. 162. STRENGTH OF CUT-STOXEWORK. 303 Such a joint is called a "slip joint." All masonwork built with lime mortar will settle somewhat, owing to the slight compression in the joints, and this settlement is sometimes sufficient to cause a crack where a high and low wall are bonded together. In such cases there is a chance also for uneven settlement in the foundations, even when carefully proportioned. With a slip joint a moderate settlement may take place without showing on the outside. 5. STRENGTH OF CUT-STONEWORK. 316. STRENGTH OF STONE PIERS, COLUMNS AND LINTELS. — Practically the only cases in which the strength of stonework need be considered by the architect, other than those having to do with the proper type of construction, are those involving: a, the strength of columns ; There is a great Fig. 162. Slip Joint in Stone Walls. Strength of piers ; h, the c, the strength of lintels. a. Strength of Stone Piers variation in the strength of stone, even when taken from the same quarry. The strength of walls and piers is also affected by the kind and quality of the mortar used, by the way the work is built and bonded, and it also depends upon whether the stone is laid dry or wet. The values which are usually given, therefore, for strength are values which will be safe for the different kinds of masonry built in the usual manner. The larger cities have building laws which specify the greatest loads allowed per square foot on stone piers and other kinds of masonry. A factor of safety of at least 10 should be allowed for stone piers, when the safe resistance to crushing is estimated from tests on the ultimate strength of work of the same character. Some building ordinances fix the maximum stress for dimension- stone piers at one-thirtieth of the ultimate strength of the stone when the beds are dressed to a uniform bearing over their entire surface, and at one-fiftieth of the ultimate strength when the beds are not dressed. They also require all stones to be bedded in Port- land cement mortar when the compressive stress exceeds one- seventieth of the ultimate strength. 304 BUILDING CONSTRUCTION. (Ch. VI) The following table gives the safe working loads for stone walls or piers : TABLE XXIV. Safe Working Loads for Stone Walls or Piers. Rubble walls, irregular stones 3 tons per square foot. Rubble walls, coursed, soft stone 2]/2 tons per square foot. Rubble walls, coursed, hard stone. 5 to 16 tons per square foot. Dimension stone, squared, in cement : Sandstone and limestone '..lo to 20 tons per square foot. Granite 20 to 40 tons per square foot. Dressed stone, with ^-inch dressed joints in cement: Granite 60 tons per square foot. Marble or limestone, best 40 tons per square foot. Sandstone 30 tons per square foot. The height of these piers should not exceed eight times the least di- mension in plan. Ashlar should be at least as thick as it is high and it should be well bonded. When piers are constrttcted of strong stone in courses, one stone to each course, and all bedded even and true, they will support very heavy loads. When the height of such pier is greater than eight times the least dimension, there should be a reduction of the safe load, and in any case the height should not exceed ten times the least dimension. The stones should be laid in i to 2 Portland cement mortar, wdiich should be kept back i inch from the faces of the pier, and the thickness of the joints should not exceed ^ of an inch.* b. Strength of Stone Columns. — A stone column, free from defects, carefully bedded and not exceeding ten diameters in height, should safel\ carry a load equal to one-fifteenth of the breaking load of stone of the same kind and quality. Any column loaded with over fifteen tons to the square foot should be bedded in Port- land cement mortar, of not more than i to i proportions, and the mortar should be kept back i inch from the face of the column until after the work is completed, when the joints may be pointed as in ashlar. As it is difficult to make a mortar joint which will stand more than forty tons to the square foot, that pressure should be the limit of load for a stone column, no matter how strong the stone is, imless extra precautions are taken with such joints. The following values may be used for the safe loads of columns built * For additional data, records of tests, etc., on "The Working Strength of Masonry," "Stone Piers," "Crushins^ Resistances of \'^arious Building Stones," etc., see Chapter V of the "Architect's and Builder's Pocket-Book," by F. E. Kidder. STRENGTH OF CUT-STONEWORK. 305 of the different stones specified, the shaft of each cokimn being in one piece : Columns. One Piece. Longmeadow (Mass.) red sandstone, best. ... 35 tons per square foot. 40 'i Manitou (Colo.) red sandstone, best. . . .25 to 30 " 25 i < 35 " << . .25 to 35 <( ...... 40 (( 40 " 4 inches as the standard size for common bricks, 8^ I J I '-'16 i I I I I n i 2:9 1 A 1 ■ r.3r 1 I I I ni -^-^^ H ; I 1-11 II ^'-^r^ I I i[^ lu ![r:zzDU i^^^w^ i. Fig. 164. — Diagram for gj^ by 4 by i^-Inch Bricks, 3/16-Inch Joints. by 4 by 2^ for face-bricks, 8>^ by 4 by 2^^ inches for paving bricks and 12 by 4 by i>4 inches for Roman bricks. Figs. 163 and 164 are diagrams, reproduced through the courtesy of Gladding, McBean & Co., San Francisco. Fig. 163 shows the average coursing and length of pressed bricks of dimensions 8^4 by 4 by 2^ inches, when laid with j^'V-inch bed and head mortar joints. Fig. 164 shows the same for a ''Roman" shape of dimensions 834 by 4 by inches, laid with joints of the same thickness. As all bricks shrink more or less in burning, it is generally neces- sary to assort even pressed bricks into piles of different thicknesses in order to get first-class work. The weight of bricks varies considerably with the quality of the clay from which they are made, and also of course with their size. 328 BUILDING CONSTRUCTION. (Ch. VII) Common bricks average about 4^ pounds each, and pressed bricks vary from 5 to 5I/2 pounds each. 336 REQUISITES OF GOOD BRICKS.— i. Good building bricks shoukl be sound, free from cracks and flaws and from stones and lumps of any kind, especially lumps of lime. 2. To insure neat work, the bricks must be uniform if! size and the surfaces true and square to each other, with sharp edges and angles. 3. Good bricks should be quite hard and burned so thoroughly that there is incipient vitrification all through the bricks. A sound,' well-burned brick will give out a ringing sound when struck with another brick or with a trowel. A dull sound indicates soft or shaky bricks. This is a simple and generally a sufficient test for common bricks, as bricks with a good ring are generally sufficiently strong and durable for any ordinarv work. 4. A good brick should not absorb more than one-teiith of its weight of water. The durability of brickwork that is e:^posed to the action of water and frost depends more ■ upon the absorptive power of the bricks than upon any other condition ; hence, other conditions being the same, those bricks which absorb the least amount of water will be the most durable in outside walls and foun- dations. As a rule the harder a brick is burned the less water it will absorb. "Very soft, underburned bricks will absorb from 25 to 35 per cent of their weight of water. Weak, light red ones, such as are frequently used in filling in the interior of walls, will absorb from 20 to 25 per cent, while the best bricks will absorb only 4 or 5 per cent. A brick may be called ''good" which will absorb not more than 10 per cent."* 337. STRENGTH OF BRICKS.— Good common bricks, suit- able for piers and heavy work, should not break under a crushing load of less than 4,000 pounds per square inch ; any additional strength is not of great importance, provided the bricks meet the preceding requirements. In a wall the transverse strength is usually of more importance than the crushing strength. For an unusually good common brick the modulus of rupture should be not less than 720 pounds per square inch, or, in other words, a brick 8 inches long, 4 inches wide and 2]/^ inches thick should not break under a center load of less than 1,620 pounds, the brick lying flatwise and having a bearing at each end of i inch and a clear span of 6 inches. A * Ira O. Raker, in "Masonry Construction." BRICKS— MA N UFA CTURE. 329 brick which is considered very hard and first-class in every respect should carry 2,250 pounds in the middle without breaking, and bricks have been tested which carried 9,700 pounds before breaking. 338. SAND-LIME BRICKS.— General Description.— Ssiud- lime bricks were originally made of lime mortar, molded in brick form and hardened by exposure to the air. Such bricks are said to have been largely used in ancient times, and it is claimed that remains of such material are now in evidence and in a good state of preservation. It is know^n that thev were formerly used in Europe in localities where other materials were not readily avail- able, and that they have been used in some localities in this country during the last thirty years. The writer knows of several houses in Haddonfield, N. J., built of such bricks, generally with exterior surfaces plastered. One of them, however, said to be about twenty years old, has not been plastered, and an inspection showed the bricks to be in an excellent state of preservation. Lime-mortar bricks harden by the absorption of carbonic acid gas from the air, which enters into combination with the lime, form- ing carbonate of lime. The hardening process requires several weeks' exposure under cover and the product has not virtues sufficient to commend it where other materials are available. It was discovered in Germany about forty years ago that lime- mortar bricks could be hardened in a few hours under heat and pressure, and it was found later that the chemical reaction under the new process differs essentially from that just described, and that the percentage of lime can be greatly reduced. The fundamental principles of sand-lime brick manufacture are now common property and only the details of manufacture are patentable. The commercial development of the industry dates back about twenty years in Europe, to about 1888, and only seven years in this country, to 1901. There are now, in 1908, over 300 factories in Germany, one of them with a capacity of 200,000 bricks per day. There are said to be now over 200 factories in operation in this country. The economic features of the manufacture are such that the industry will doubtless be rapidly extended and the product come into more general use than in the past. The Process, — Pure silica sand, mixed with from 5 per cent to 10 per cent of high calcium lime and a certain proportion of water, is molded under very high pressure into the form of bricks. These 330 BUILDING CONSTRUCTION. (Ch. VII) are piled loosely on cars holding about i,ooo bricks each and placed in a steel cylinder large enough to hold from lo to 20 cars. The cylinder is then closed, and steam is turned in and maintained at a pressure of from" 120 to 135 pounds to the square inch for from 8 to 10 hours, when the cylinder is opened and the bricks removed, ready for use. The tremendous pressure, which is said to be 100 tons on each brick, under which the bricks are formed, causes great density and a bringing of the component elements into close contact. The heat in the cylinder dries the bricks and causes a chemical reaction be- tween the lime and a portion of the silica, forming calcium silicate, an insoluble and perfectly durable element, which bonds the remain- ing particles of the sand together. The small residue of uncom- bined lime combines, in the course of time, either with silica or with carbonic acid gas from the air, until no free lime remains. The bricks thus become harder and stronger with age. In regard to the constitution of sand-lime bricks, Mr. Edwin C. Eckel, in the chapter on "The Production of Lime and Sand-lime Brick in 1906," in the Government Report on "The Mineral Re- sources of the United States for the Calendar Year, 1906," dated 1907 and published in 1908, writes as follows : *Tn previous publications on the sand-lime brick industry the writer has stated that conclusive evidence had not yet been pro- duced as to the constitution of the binding medium of sand-lime brick. The advocates of the new product not only claimed that a definite lime silicate was formed during processes of manufacture, but usually made the additional claim, by implication at least, that this silicate was the same as that which exists in Portland cement. The fact was overlooked that purely chemical means could not be relied on to prove these facts, if facts they were. Under these cir- cumstances the writer, admitting his own incompetency to decide the question, believed it advisable to consider the matter unsettled, pending a decisive test by the only means possible — the petrographic microscope, used by one of the very few investigators intimately acquainted with the lime-silicate series. "During the past year evidence has been submitted which seems conclusive. Mr. Frederick E. Wright, at the writer's request, ex- amined several specimens of commercial sand-lime brick in the geophysical laboratory of the Carnegie Institution. Mr. Wright states that the binding material of these specimens is a hydrous lime BRICKS— MANUFACTURE. 331 silicate somewhat akin to the famiHar minerals of the zeolite group. The reactions involved in the formation of such a hydrous silicate from lime and sand in the presence of steam are simple and well known. It is to be noted, however, that these reactions are in no way comparable to those which take place during the processes of Portland cement manufacture and that the binding material of sand-lime brick is very different in composition and relationship from Portland cement clinker. 'Tt may safely be assumed, then, that a sand-lime brick as mar- keted consists of (i) sand grains held together by a network of (2) hydrous lime silicate, with probably (if a magnesian lime were used) some allied magnesian silicate, and (3) lime hydrate or a mixture of lime and magnesia hydrates. These three elements will always be present, and the structural value of the brick will depend in large part on the relative percentages in which the sand and the hydrates occur." Quality. — The quality of the product depends mainly upon the selection and treatment of the sand and the lime. Pure silica sands, containing a large percentage of fine grains passing through screens of from 80 to 150 mesh, are preferable. Clay or kaolin are danger- ous elements and should not be present in. quantities of more than 5 per cent. The lime should be, preferably, high calcium lime, the magnesium silicates formed by impure limes not being as strong as calcium silicates. Some manufacturers use ready-hydrated lime, others hydrate the lime themselves, before mixing it with the sand, and others grind the quicklime, mix it with the sand and slaken it in the sand. The other most important element affecting quality is the press. After pressing and before steaming, the bricks are very fragile and the press should be such that they are subjected to no shaking nor friction after the pressure is removed from the mold. Vertical clay brick-presses have been commonly used, but do not appear to be well adapted to the purpose. The rotary table-presses seem to be most successful. Tests. — If the sand is reasonably clean and pure, and the lime finely divided ; and if the bricks are sound and have a good metallic ring, they will stand weather exposure perfectly. If a brick stands in still water for an hour and the moisture rises more than ^ an inch, it is not a first-class brick ; if the moisture rises 2 inches, its use for facings is questionable ; if the moisture 332 BUILDING CONSTRUCTION. (Ch. VII) rises 3 inches, it should not be used on outside work of any impor- tance. Authentic tests* have been made for crushing, fire, frost and acid-resistance and for absorption, from which it may be concluded that under proper conditions of manufacture sand-lime bricks are produced having the following physical characteristics : Crushing strength, average, between 2,500 and 3,000 pounds per square inch, although some specimens in tests have shown over 5,000 pounds per square inch ; modulus of rupture, average about 450 pounds per square inch; fire-resistance, but little inferior to that of fire-brick; frost-resistance, perfect ; acid-resistance, very superior ; absorption, from 8 per cent to 10 per cent in 48 hours; average for complete saturation, 15 per cent; reduction of compressive strength by satu- ration for absorption test, average 33 per cent. The New York laws require for the absorption test, an average not exceeding 15 per cent, and no result over 20 per cent; for the modulus of rupture test, an average of 450 pounds per square inch, with no result below 350; for the compression test, an average of 3,000 pounds per square inch, with no result less than 2,500 pounds ; and for the reduction of compressive strength after saturation, a loss of not more than one-third. The bricks are square, straight and uniform in size and homo- geneous in composition and density. They cleave accurately under the stroke of the trowel and present a weather surface with the good qualities of stone. They can be cut, carved or sand-blasted, are easily washed clean and show no efflorescence. These claims are well established for properly manufactured sand-lime bricks. It should be further stated that common bricks and facings are made in the same press, the only difference being in the selection of the materials and in the handling of the raw bricks. It is there- fore claimed that a rational and homogeneous exterior wall struc- ture is possible, since backings and facings may be built and bonded in even courses, with Flemish or other ornamental bonds. Many factories, however,' are producing inferior bricks and care should be taken in their selection. Colors in Sand-lime Bricks. — The natural color is pearl gray, varying in warmth with the composition of the sand. Permanent * See also "Tests Upon Sand-lime Bricks," made by Professor Ira H. Woolson, in November, 1905, at the Testing Laboratory, Columbia University, New York, for The National Association of Manufacturers of Sand-lime Products. BRICKS-MANUFACTURE. 333 colors are produced by introducing mineral oxides with the raw- materials in quantities varying according to the intensity of color fiesired ; but as the oxides are foreign materials in the bricks, they affect the quality of the latter in proportion to the quantity used- Production of Sand-liuic Bricks. — In the year 1906 the product TABLE XXV. Production of Sand-lime Bricks in the United States in: 1906, BY States. state Alabama, Kentucky. Mississipri and Ten- nessee Arkansas, Kansas, Minnesota,Nebraska, South Dakota and Texas California Colorado and Idaho. . . Delaware, Maryland and Virginia Florida.'. Georgia Illinois and Wisconsin Indiana Iowa Michigan New Jersey New York North Carolina Ohio Pennsylvania Other States 6 Total Average value per M Num- ber of oper- ating firms re- port- ing Common bricks 87 Quan- tity (thou- sands) Value 14,877 4,837 5G9 9,403 11,678 5,139 8,150 17,077 3,921 27,281 6,.52() 21,288 3,147 1,232 6,673 148,669 $51,079 '96,128 " 38,789 6,043 61.719 83,306 37,701 49,150 84,361 28,271 162,879 49,143 169,257 22,225 7,049 50,211 997,311 6.71 Front bricks QuaTi- tity (thou- sands) 1,276 1.897 1,900 2,191 (a) (a) ia) 690 326 (a) 1,796 1,910 (a) (a) 978 2,718 15,682 Value Fancy bricks Quan- tity (thou- sands) $11,94^ 17,982 ((f) 22,400' 22,743 (-0 (n) in) 6,060 2,474 (a) 12,022 22,064 (a) (a) 12,710 32,963 163,345 10.42 Value (a) in) (a) (a) 121 121 (ft) ia) (a) $3,473 3,473 28.70 Block.^ value (^0 Totar valuer (a) 'ia) $5,876 ! $63,02® 114,360> 61,189 31,464 67,U9' 89,306;. 40,701 55,210. 86,880- 38,255:. 174.921 50,14X: 191,321 32,975. 10,184 62,921 5,876 1,170,00* a Included in other States. b Includes all products made by less than three producers in one State, to prevent dis- closing individual operations. c The total of other States is distributed among the States to which it belongs im order that they may be fully represented in the totals. Value of production of sand-lime bricks in the United States, igo^-rgod. Year Number of plants Value of product 1903 16 $155,040* 46:3, 128-. 972,064 1,170,005. 1904 57 1905 84 1906 87 of the sand-lime brick industry was valued at $1,170,005, an increase of 20 per cent over the value, $972,064, in 1905. During 1906 the 334 BUILDING CONSTRUCTION. ' (Ch. VII)' value of the common building bricks made by this process averaged $6.71 per thousand, as against $6.59 in 1905. The front-bricks averaged $10.42 per thousand, as against the 1905 average of $11.02. Almost 90 per cent of the entire sand-lime product is marketed as common bricks, a result which could hardly have been anticipated when these bricks were first introduced into this country. Detailed statistics for 1906 are presented in Table XXV. 339. CEMENT BRICKS. — Cement bricks are on the market in many places, and are used generally for facing purposes. Their characteristics are similar to those of concrete hollow blocks, and observations made of one product are generally true of the other. They are manufactured by machine, by hand or by power presses, and the following general principles should be observed. Other conditions being equal, wet concrete mixtures tend to density, non-absorption and fineness of face. Concrete attains its normal strength with its seasoning. Cement bricks should not be used earlier than two weeks, and should not carry considerable loads earlier than one month after the date of manufacture. Lean mixtures, however, require more time than rich mixtures. Cement, sand and stone mixtures are stronger, denser and less absorbent, and require less cement than cement and sand mix- tures. One part of cement to 4 of sand, or i part of cement to 3 of sand and 3 of aggregates from io lA an inch in size, are given as minimum proportions of cement for cement bricks. Much depends upon the character of the sand. It should contain both fine and coarse grains and should be clean and sharp. By the selection of the color, shape and size of the aggregates and by the subsequent treatment, either by washing with acid or with water and stifif brushes, the faces of the bricks may be given various textures and colors. Various colors, also, are used in the cement. Good cement bricks should stand the following minimum tests Average minimum ultimate compressive strength, at 28 days, 1,000 pounds per square inch. Average modulus of rupture at same age, not less than 150 pounds per square inch. Absorption not over 15 per cent. * "Standard Specifications for Concrete Hollow Blocks," prepared by E. S. Larned, C. E., for National Association of Cement Users BRICKWORK IN GENERAL. 335 Cement bricks for any particular building should be carefully investigated and rigidly inspected for uniformity of quality. For further discussions of concrete mixtures, concrete blocks, etc., see Chapter X. 2. BRICKWORK IN GENERAL. 340. In order to build any kind^of brick structure so as to make a strong and durable piece of work, it is necessary to have a bed of some kind of mortar between the bricks. Brickwork, there- fore, consists of both bricks and mortar, and the strength and dur- ability of any piece of work depend upon the quality of the bricks, the quality of the mortar, the way in which the bricks are laid and bonded and whether or not they are laid wet or dry. The strength and stability of a wall, arch or pier also depend upon its dimensions and the load it supports ; but for the quality of the brickwork, only the above items need be considered. The kinds and qualities of mortars used for laying brickwork are described in Chapter IV. The majority of the brick buildings in this country have been built with common white lime mortar, to which natural ' or Portland cement has been added. For brickwork below ground either hydraulic lime or cement mortar should be used. (See Articles 153, 164 and 200.) The function of the mortar in brickwork is threefold, viz. : 1. To keep out wet and changes in temperature by filling al! crevices. 2. To unite the whole into one mass. 3. To form a cushion to take up any inequalities in the brick?^ and to distribute the pressure evenly. The first object is best attained by grouting, or thoroughlv ''flush- ing" the work ; the second depends largely upon the strength of the mortar, and the third is effected principally by the thickness of the joints. 341. THICKNESS OF MORTAR JOINTS.— Common bricks should be laid in a bed of mortar at least and not more than of an inch thick, and every joint and space in the wall not. occupied by other materials should be filled with mortar. The best method of specifying the thickness of joints is by the height of eight courses of bricks measured in the wall. This height should not exceed by more than 2 inches the height of eight courses of the same bricks laid dry. 33^ BUILDING CONSTRUCTION. (Ch. VII) As common bricks are usually quite rough and uneven, it is not always easy to determine the thickness of a single joint; but the variation from the specification in any eight courses that may be selected should be very slight. It is not uncommon to see joints ^ of an inch thick in common brickwork, especially where the Avork is not superintended. ^ Pressed bricks, being usually quite true and smooth, can be laid with ^-inch joints, and they are often so specified. A yVi^ch thick- ness is probably stronger, however, as it permits a more thorough filling of the joint. It is impossible to completely fill or -f^-inch joints with mortar. Numerous small holes admit driving rains in streams. Efflorescence can in many cases be traced to holes in the facing. \^ery little first-class work is now done with fine joints, the tendency being toward wall surfaces with character and texture. The joints' should be thick enough to bring the facings to an even bed with the backings, and to allow them to be bonded with the headers, and they may be from j4 of an inch to i inch in thickness. They are frequently recessed from j/^ to ^ of an inch. The hori- zontal joints may be recessed with the vertical joints flush ; or the horizontal joints may be thick and the vertical joints thin. 342. LAYING BRICKS.— A. C-ommon Bricks.— Tht best way to build a brick wall is, first, to lay the two outside courses by spreading the mortar with a trowel along the outer edge of the last course of bricks, to form a bed for the bricks to be laid, scraping a dab of mortar against the outer vertical angle of the last brick laid ; and then to press the bricks to be laid into their places with a sliding motion, forcing the mortar to completely fill each joint. • Having continued the two outer courses of bricks to an angle or opening, the space between the courses is filled with a thick bed of soft mortar and the bricks pressed into this mortar with a downward diagonal motion, so as to press the mortar up into the joints. This method of laying is called "shoving." If the mortar is not too stiff, and is thrown into the wall with some force, it will completely fill the upper part of the joints, which are not filled by the shoving process. A brick wall laid up in this way is very strong and difficult to break down. This class of work is BRICKWORK IN GENERAL. 337 commonly called ''shoved work." It is done only under constant supervision and is more expensive than ordinary brickwork. « A very common method of laying the inside bricks in a wall is to spread a bed of mortar and on this lay the dry bricks. If the bricks are laid with open joints and thoroughly slushed up it makes very good work; but unless the men are carefully watched the joints are not filled with mortar and the wall is not as strong as when the bricks are shoved. Grouting. — Another method of laying the inside bricks is to lay them dry on a bed of mortar, as described above, and then to fill all the joints full with a very thin mortar. This is called "grout- ing," and, while it is condemned by many writers, it is contended by persons having large experience in building that masonry care- fully grouted, when the temperature is not lower than 40 degrees Fahr., will give the most efficient result ; and the author knows from Fig. 165. — Struck Joint Fig. i66. — Struck Joint with Drip. without Drip. actual experience that when properly done it makes very strong work. Many of the largest buildings of New York City have grouted walls. The iMersey Docks and Warehouses at Liverpool, England, one of the greatest masonry works in the world, were grouted throughout. No more water than is necessary to make the mortar fill all the joints should be used, and grouting should not be used in cold or freezing weather. Grouting is especially valuable when very porous bricks are used. (See Article 206, "Grout," in Chapter IV.) Striking the Joints. — For inside walls that are to be plastered the mortar projecting from the joints is merely cut off with the trowel flush with the face of the walls. For outside walls and inside walls, where the bricks are left exposed, the joints should be "struck'' as in Fig. 165. This is done with the point of the trowel, by hold- 338 BUILDING CONSTRUCTION. (Ch. VII) ing it obliquely. Fig. i66 is the easiest joint to make, and is the one ^generally made unless that shown in Fig. 165 is insisted on. For inside work it makes no particular difference which joint is used, but for outside work Fig. 165 is much more durable, as the water will not lodge in it and soak into the mortar, as will be the case when it is made as in Fig. 166. When "struck joints" are desired they should always be specified, otherwise the brick-mason may claim that he is not obliged to strike them. B. Face-bricks. — (See also Article 341.) Face-bricks are usually laid in mortar made of lime putty and very fine sand, often colored with a mineral pigment. (See also Articles 150, 216, 217 and 218.) The joints should not exceed Vie of an inch, except in cases where a horizontal effect is desired, when the horizontal joints are made ^ of an inch and the vertical joints as narrow as possible. For very fine work the joints are sometimes kept down to of an inch. The joints should be carefully filled with mortar and either ruled at once with a small jointer or else raked out and left for pointing. In very particular work a straight-edge is held under the joint and the jointer drawn along the top of it, thus making a perfectly straight joint. This is called ''ruled work." In laying the soffits of arches and vaults with face-bricks, the joints cannot be finished until the centers are removed ; the joints should therefore be not quite filled with mortar, and should be raked out and pointed after the centers are removed. Many makes of pressed bricks and some hand-made bricks have one or more depressions in the larger surfaces to give better keys to the mortar. When the depressions are on one side of a brick only, that side should be uppermost. When building with face-bricks, a piece of brickwork at least 2 feet 6 inches long should be built up, as a sample piece, in an out- of-the-way place as soon as the first lot of bricks is delivered ; and all stone or terra-cotta work should be made to conform absolutely to this brickwork. Sorting. — Pressed bricks, even from the same kiln, generally vary in size and shade, the darker bricks being often inch thinner than the lighter bricks and also shorter. If, therefore, a perfectly uniform color is desired the bricks must be sorted into BRICKWORK IN GENERAL. 339 piles, so that each lot will be of the same shade, and each shade laid in the building by itself. The changes between the different shades should occur, where possible, at string-courses or at angles in the building. Many architects, however, consider that handsomer and brighter walls are secured by mixing the different shades, so that hardly two bricks of exactly the. same shade come together. If the mixing is well done the general tone of a wall at a distance will be uniform. With colored bricks this haphazard method undoubtedly gives the most artistic and sparkling effects. Circular Work. — For circular walls, faced with pressed bricks, the latter should be made of the same, or of very nearly the same, curvature as that of the wall. ]\Iany manufacturers of pressed bricks carry circle bricks of different curvatures in stock, and bricks of any curvature can be made to order. When circle bricks cannot be obtained, straight bricks may be used for curvatures with a radius of 12 feet or over, and for shorter radii half bricks or headers should be used. 343. WETTING BRICKS.— Mortar, unless very thin, will not adhere to dry, porous bricks, because they rob the mortar of its moisture, preventing its proper setting. On this account bricks should never be laid dry, except in freezing weather; and in hot, dry weather it is impossible to get the bricks too wet. When using very porous bricks the wetting of them is of more consequence in obtaining a strong wall than any detail of the operation. As wetting the bricks greatly increases their weight and consequently the labor of handling them, besides making it harder on the hands, masons do not like to wet them unless they are obliged to, and it should , always be specified and insisted upon by the superintendent, except in freezing weather. Pressed bricks cannot very well be laid dry, and the masons generally wet them for their own convenience ; but they will often tell all sorts of stories to escape wetting the common bricks. 344. LAYING BRICKS IN FREEZING WEATHER.— Brickwork in lime mortar should not be laid in freezing weather. If the temperature is below 40 degrees Fahr. and liable to fall below 32 degrees at night, salt should be mixed with the mortar, the bricks heated before laying and the top of the wall covered with boards and straw at night. If the mortar in any part becomes frozen, the 340 BUILDING CONSTRUCTION. (Ch. VII) courses in that part should be removed and cleaned before they are used again. Cement mortar is not injured by frost after the first set has taken place. It may be used in freezing weather if precautions are taken by heating the materials, by protecting the walls or by the use of salt, to prevent freezing before this set has taken place; otherwise a sudden thaw is liable to soften the mortar and cause settlement. But it is not considered good practice to attempt to lay bricks in temperatures below from 17 degrees to 23 degrees Fahr. unless the walls are in warmed enclosures. Lime in the mortar retards the setting, and mixing the mortar with hot water hastens the setting and keeps the walls warm longer. Salt in amount from 2 per cent to 8 per cent of the water by weight prevents frost, but is objected to by many on account of a resulting tendency to efflorescence. Higher percentages retard setting and reduce the strength at short periods. In any case the bricks should not be freezing cold nor wet, and they must be clean. For the efifect of freezing on mortar see Articles 213 and 214. 345. PROTECTION FROM STORMS.— Moisture without frost does not injure the strength of brickwork, but if rain strikes the top of a wall it will wash the mortar out of the joints and stain the face of the wall. The excessive wetting of walls is also injurious, as it takes a long time for them to dry out, and they are likely never to dry to a uni- form color. For this reason the tops of the walls should always be protected at night, or, when leaving ofif work, by boards placed so as to shed the water. 346. ORNAMENTAL BRICKWORK.— American practice in the design of ornamental brickwork has been derived chiefly from examples in England and northern Italy, and it is well to note that the long continued cold weather in our northern localities demands a treatment of such work very different from the practice in those countries. The upper surfaces of copings and brick projections are the sources of serious danger to the continued good appearance and to the permanency of the walls in which they occur, unless protected by overhanging coverings with drips. Through the action of the frost the mortar in the exposed joints finally loses its hold upon the bricks and permits moisture to follow the joints to the interior of the walls. Thence the water is likely to percolate to lower levels BRICKWORK IN GENERAL. 341 and to the outside surfaces, depositing the chemicals dissolved in its path upon the faces of the walls in stains or efflorescence, decom- posing the mortar in the joints and ultimately destroying the walls. The ornamental effects to be obtained by the varied uses of bricks are exceedingly numerous. First, there are the constructive fea- tures, such as arches, impost courses, pilasters, belt-courses and string-courses, cornices and panels ; then there is a large field for design in surface ornament, by the use of bricks of different hues, tints or shades, laid so as to form patterns. For the constructive features both plain and molded bricks may be used, although only very plain effects can be produced with plain bricks alone. In nearly all of our large cities, and especially in those near which Fig. 167. — Brick Belt-course Fig. 168. — Brick Belt-courses, with Wash. pressed bricks are manufactured, a great variety of molded bricks can be obtained, by means of which it is possible to construct almost any moldings, belt-courses, etc., that may be desired. Belt-courses and cornices, and in fact any details of molded work built of bricks, are much cheaper than the same moldings cut in stone. In designing brick details the projections should be kept small. The tops of the belt-courses should have washes on the top sur- face, as shown in Fig. 167. The top course, W, should be laid with stretchers* when the pro- jection is not over 3 inches, in order to reduce the number of end joints; and the bricks should also be laid in cement mortar, so that that which is in the end joints will not be washed out. If IV is 2L stretcher course at least every other brick in the course below should be a header'. If bevelled bricks cannot be obtained for the top courses, and if 342 BUILDING CONSTRUCTION. (Ch. VII) plain bricks must be used, the upper surface should be protected by sheet-lead built into the second joint above it, as shown in Fig. i68 A; or the top of the bricks may be plastered with Portland cement, as shown in Fig. i68 5.* Unless some such precautions are taken to protect the tops of the projecting bricks from excessive moisture, the rain-water will after a while soften the mortar in the joints, P, and penetrate the wall. The end joints in the belt- courses are always liable to be washed out. Belt-courses and cornices should always be well tied to the walls by using plenty of headers or iron ties. The tops of the walls should also be well anchored to the rafters or ceiling joists by iron anchors, as the projection of a cornice tends to throw a wall outward. In using molded bricks in string-courses and cornices, it is more economical to use bricks that can be laid at stretchers, as it takes a smaller number of stretchers than of headers to fill given lengths, and the cost is the same. One of the greatest objections to brick moldings is the difficulty in getting them perfectly straight and true. Nearly all molded bricks become more or less distorted in molding and burning, so that when laid the abutting ends do not match evenly, and mold- ings present an appearance like that shown in Fig. 169. Some makes of bricks, however, are quite free from these defects, and before selecting molded bricks to be used in this way the archi- tect should endeavor to ascertain what makes give the truest and most perfect work. By being very careful in laying the bricks so as to average the defects, and by ruling the joints, the effects of the distortion may be largely overcome. Distortion is more apt to show with stretchers than with headers. 347. BRICK CORNICES.— Brick bed-molds for wood or iron Fig. 169. — Molded Brick Course, Showing Distortion. * A temporary expedient, which must be renewed from time to time. BRICKWORK IN GENERAL. 343 ig. 172.— Simple ^ji^c^'j^CoJ-nice with Copper Fig. 173.— Design of Molded Brick Cornice. 344 BUILDING CONSTRUCTION. (Cii. VII) cornices may be designed in wide variety and with excellent effect. Whole cornices may be designed in brick, although only a com- paratively slight projection is practicable, and metal or terra-cotta coverings with efficient overhanging drips are essential. Fig. 175. — Design for Molded Brick Cornice has used Fig. 76. — Design for Molded Brick Cornice. •Design for Molded Brick Cornice. Figs. 170 and 171, taken from The Brickhuilder, are suggestions for molded brick cornices for three and four- story buildings. Fig. 172 shows a section of a simple brick cornice that the author on brick churches having pitched roofs. All brick walls or cornices should be capped by projecting copings of metal, terra-cotta or stone, provided with a hol- low drip to throw off the water. For brick cornices a copper or galva- nized-iron crown-mold, such as is shown in Fig. 170, is very appropriate. The metal should be carried over the top of the wall, if a parapet, and down 5 inches at the back. BRICKWORK IN GENERAL. 345 Figs. 173, 174, 175 and 176 show additional designs for brick cornices, reproduced through the courtesy of the Eastern Hydrau- lic-press Brick Company, Philadelphia, from ''Suggestions in Brick- work." Figs. 173 and 175 show overhanging eaves which may or may not be used. The height of the brick cornice in Fig. 173 is 16 inches and the projection 13 inches; in Fig. 174 the height is 24 inches and the projection 14 inches; in Fig. 175 the height is 42 inches and the projection 14 inches ; and in Fig. 176 the height is 12 inches and the projection 7 inches. Fig- 177- — Brick Cornice Modelled After Cornice of Baptistry of San Stefano, Bologna, Italy. Fig. 177 is a design modelled closely after the cornice of the Bap- tistry of San Stefano, Bologna, Italy. If the walls terminate as shown in Fig. 171 the upper courses should be laid in cement mortar and the tops well plastered with Portland cement at the same time the bricks are laid. This will protect the walls for several years, but is not as lasting as terra- cotta or metal. 348. SURFACE PATTERNS.— Surface patterns, or diaper 346 BUILDING CONSTRUCTION. (Cii. VII) work, are very common in brick buildings in Europe, and they have been introduced to a considerable extent in this country. Their chief object is to give variety to a plain wall space. When used in exterior walls they should not be so marked as to make the Fig. 178. — Simple Brick Diaper Pattern for Frieze. pattern insistent and thus interfere with other features of the building. Sorting the bricks into light and dark shades, or varying the color of the mortar in which the pattern is laid, is usually sufficient for any surface decoration, the best success in this class of decora- tion being obtained by using comparatively simple designs and quiet contrasts of color. If different colors are used the greatest care must be exercised in Fig. 179. — Surface Pattern for Brick Panel. their selection, and even with care and thought it is not granted to all architects to use color successfully. One of the best opportunities for the use of color lies in the direc- tion of pattern work for frieze-courses and band-courses. BRICKWORK IN GENERAL. 347 Fig. 1/8. shows a simple brick diaper for a frieze, and Figs. 179 and 180 an ornamental panel and a chimney, the latter designed by Mr. H. P. Marshall. Fig. 181 shows some diagrams which suggest possibilities of arrangement in band patterns, as indicated in the upper drawings, 5CAL^ : \ - ? FUtLT Fig. 181. — Brick Band and Diaper Patterns. and in diaper work, as indicated in the two lower drawings. These drawings are reproduced through the courtesy of the Eastern Hy- draulic-press Brick Company, Philadelphia, from "Suggestions in Brickwork." All the designs in Fig. 181 are made by the use of stretchers only. Proportions and sizes of designs can be materially changed by the use of headers. The lower pattern suggests three different shades of bricks. The coloring is optional, but strong contrasts should be avoided. Fig. 182 is an interesting example of mediceval Italian brickwork 348 BUILDING CONSTRUCTION. (Ch. VII) from San Stefano, Bologna, Italy. The patterns are partly filled with pieces of stone and terra-cotta. Fig. 183 is an example of English wall pattern in brickwork, the figure being in bricks of a slightly lighter shade than that of the wall itself. The detail is from a residence in North Mymms, Hertford- shire, England. Surface patterns should generally be flush with the walls. When 1 I I I I . ■ I ] r r r . 1 1 1 1 ' 1 ' 1 ' 1 Fig. 182.— Brick Wall Surface from San Stefano, Bologna, Italy. used as in Fig. 180 the pattern may project j4 i^ch from the surface or panels. Diaper work may also be used with good effect on interior brick walls of waiting-rooms, corridors, public baths, etc. 3. CONSTRUCTION OF BRICK WALLS. 349. GENERAL CONSIDERATIONS.— The proper construc- tion of a brick building involves many things besides the mere lay- ing of one brick on top of another with a bed of mortar between. The manner of laying or bedding the bricks and the general methods CONSTRUCTION OF BRICK WALLS. 349 of doing the work having been considered, we will next consider the details of construction required to obtain strong and durable walls, and the precautions to be taken to prevent settlements and cracks and to adapt the work to the purposes for which it is intended. Aside from the quality of the materials and the character of the work, the bonding of a wall has the most to do with its strength. 4 — M — 1= — 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 II II II II ^ rV : — W VS^ — ' 1 'l 1 'l ' l' 1 1 ' l' ,0' ^ II II II I! ! , 11 -11 II Fig. 183.— Detail from Residence, North Mymms, Hertfordshire, England. 350. BOND IN BRICKWORK.— Bond in brickwork is the arrangement of the bricks adopted for the purpose o^ tying all parts of a wall together by means of the weight resting on the bricks, and also for the purpose of distributing the effects of a concentrated weight over an ever-increasing area. Common Bond.— A brick laid with its long sides parallel to the face of the wall is called a "stretcher," and with its long sides at right-angles to the face of the wall a "header." Common brick walls in this country are almost universally built by laying all the bricks as 350 BUILDIXG CONSTRUCTION. (Ch. VII) stretchers for from four to six courses, and then by laying a course of headers as shown in Fig. 184. When a wall is more than one brick in thickness, the heading courses should be arranged as at cither A or B, Fig. 185. For first-class work such a wall should be bonded with a heading course every sixth course. Plumb Bond or Diagonal Bond. — This is sometimes called ''Amer- ican bond," and is generally used when the walls are faced with pressed bricks. All the face-bricks are laid as stretchers with the joints plumb above each other from bottom to top of walls, as shown at A, Fig. 186. The bonding of the face-bricks to the common bricks Fig. 184. — Common Bond. Fig. 185. — Cross-section of Common Bond Brick Wall. is accomplished by clipping ofif the back corners of the face-bricks in every sixth or seventh course and by laying diagonal headers behind, as shown at B, Fig. 186. This does not make as strong a tie as the use of regular headers, but if carefully done it appears Fig. 186.— Plumb Bond. to answer for some purposes. Very often where this bond is used only one corner of each face-brick in the outside course is clipped, so that only half as many diagonal bricks, or headers, as are indicated in Fig. 186, are used. This of course does not make as strong a bond as when both of the back corners are clipped. In walls exceed- ing one story in height the architect should see that both corners are clipped. The strongest method of bonding for face-bricks is by the Flemish or cross bonds, described further on. The objec- tion to these bonds, however, .is the increased expense occasioned by using so many face-brick headers, and also the fact that the face- CONSTRUCTION Of BRICK WALLS. 331 bricks and common bricks cannot usually be laid so as to come out to exactly the same heights. In this case it is necessary to clip the common bricks if face-brick headers are used in every course^ or even in every third or fourth course. Face-bricks, when laid as in Fig. 186, are often tied to the back- ing, as shown in Fig. 187, by pieces of galvanized-iron or tin, which have their ends turned over stiflf wires, about 4 inches long. The wires are not absolutely essential, but should always be used in first- class work. Still better ties for bonding face-bricks to the backing- are the Morse wall-ties, shown in Fig. 188, or similar ties. These ties are made from -'/^.^ and ^-inch galvanized-steel wire, 7, 9, 12 and 16 inches in length. The / .^,,-'mch wire is used for ordinary pressed brickwork, and the ^-inch size for very closely Fig. 187. — ]\Ietal Tie for Face-brick Fig. i88. — Morse Wall-tie for Face-brick and Backing. and Backing. laid w^ork. These ties, or similar ties, are now very extensively Ased in the eastern portion of the country. One advantage obtained in using metal ties is that it is not neces- sary to have the joints in the face-work and backing on the same level, as the ties can be bent to conform to the dififerences in level, as shown in Fig. 187. Face-bricks bonded in this way should be tied at least every fourth course with one tie to each face-brick. The common American practice of laying all the facing bricks as stretchers, with ^-inch joints, is peculiar to this country, and is recognized the world over as thoroughly bad, constructively and artistically. Such facings are mere veneers and contribute but little to the strength of walls. The building laws of New York, San Francisco and some other cities require that they be ignored in com- 352 BUILDING CONSTRUCTION, (Ch. VII) pitting the necessary thickness of exterior walls; while the Boston law requires full headers and prohibits ''diagonal bond/' ''This class of work is laid up with joints which are too thin to be of use constructively, and which rob the work of all character, giving to it a hard, dry, sleek appearance, that appeals to no artistic instinct."* The better method is to lay the facings on even beds with the backings and to bond with headers in such an arrangement as will best suit the architectural purposes of the designer. Thick joints and headers give character and texture to the wall surfaces, and •every different arrangement of headers has its own decorative value. Figs. i89,t i9ot and 191 are good examples. "The supposed economy of the common method will be found, upon examinaton, not to be economical, but the reverse.''^ The principal additional expense in bonded work is in the labor. Our bricklayers are generally not accustomed to such work and take more time per square foot of wall. Fig. 189. — Brickwork for Singer Building, New York. Joints Recessed Three-eighths of an Inch. English Bond. — Fig. 192. This is a method of bonding much used in England, and consists of alternate header and stretcher courses. It is probably the strongest method of bonding common bricks, but is not applicable where face-bricks are used in the usual American manner. It does not make very attractive work, and is scarcely ever used in this country. Flemish Bond. — This is shown in Fig. 193, and consists of alter- * Mr. Ernest Flagg, in The Brickbuilder. Vol. 7. No. 12. t These and other drawings are reproduced through the courtesy of The Brick- builder. For Figs. 189 and 190 see \^ol. 7. No. 72, pages 259 and 260. Fig. 189 shows brickwork in the Singer building, New York; Fig. 190 shows brickwork in a house for the Clark estate. t Ernest Flagg, The Brickbuilder, \'ol. 7, No. 12. CONSTRUCTION OF BRICK WALLS. q ii__ zr^ ir:zz]L zz^r — irni-zTZicnczr ^==°Tr~ii II icn V C I]CIIZ ]III|i IE rni 11 ^1 II II II II II ~ii ii ^ II "1 1 1 r — II II iir rni oc_ Fig. 190. — Brickwork of House for Clark Estate. T r r i ll Fig. 191. — Brickwork. Interior in St. Bartholomew's Church, Brighton, England. 354 BUILDING CONSTRUCTION. (Ch. VII) nate headers and stretchers in every course, every header being immediately over the middle of a stretcher in the course below. Closers (a) are inserted in alternate courses next to the corner head- ers to form the necessary lap. This makes a very strong bond. A modification of this bond, which consists in laying every fifth course with alternate headers and stretchers, is sometimes adopted. It Fig. 1 9 J. — English Bond. Fig. 193. — Flemish Bond. makes stronger work than the diagonal bond and looks about as well. English Cross Bond. — This is a variety of English bond and is said to be much used in Holland, its name being suggested by the appear- ance of the surface, on which the bricks seem to arrange themselves into St. Andrew's crosses. It differs from ordinary English bond only in having the stretchers of the successive stretcher courses break joint with each other, as well as with the headers in the adjoining courses on the face of the wall, as shown in Fig. 194. This makes a iijuch better-looking wall than results from the ordinary English bond. 351. HOOP-IRON BOND IN BRICKWORK.— Pieces of hoop-iron are often laid flat in the bed-joints of brickwork to increase its longitudinal tenacity and to prevent cracks due to unequal set- tlement. The ends of the iron should be turned down about 2 inches and inserted in the vertical joints. Noth- ing less than No. 18 iron should be used, and the holding power of the ties may be greatly improved by dipping them in hot tar and then covering them with sand. Hoop-iron bond is strongly to be recom- mended for strengthening brick arches and the walls above them, the walls of towers, the joining of interior with exterior walls, etc. Twisted iron bars are still better for this purpose. 352. ANCHORING BRICK WALLS.— Although this belongs 94. — Cross Bond. CONSTRUCTION OF BRICK WALLS, 355 more espe^ally to the carpenter's work, it is mentioned here as a very important detail in securing the stabiHty of walls and in pre- venting any from inclining outward. Brick walls should be -tied to every floor at least once in every 6 lineal feet, either by the use of iron anchors, built solidly into the walls and spiked to the floor joists, or by means of box-anchors or joist-hangers. The forms of iron anchors commonly used for this purpose are Fig. 195. — Iron Anchors for Floor Fig. 197. — Destructive Effect of Joists. Anchor at Top of Joist. those shown in Fig. 195, the one shown at a being the most common, and about as good as any. The anchor shown at b answers the pur- pose just as well, but costs a little more. |^nchors like a and b are spiked to the sides of the floor joists and built into the walls, as shown in Fig. 196. In the case of side or rear walls, where appearances are not oi much consequence, it is better to have the anchors pass clear through them, with plates on the outside, as such anchors take much bet- ter hold on walls than is possible when they are built into the middle parts only. The form of the cheapest anchor for this purpose 356 BUILDING CONSTRUCTION, (Ch. VII) is that shown at c. The anchor has a thin plate of ii^n dowelled and upset on the outer end. Anchors of this style may be used also for building- into the middle of the walls. Where the ends of girders are to be anchored, or where particu- larly strong anchors are desired, the form shown at d is undoubtedly the best. These anchors are made from ^-inch bolts, flattened out for spiking to the joists and provided with cast-iron star washers. An anchor of this kind possesses the advantage of having a nut on the outer end, which can be tightened up if desired after the walls are built. All of these anchors should be spiked to the sides of the joists or girders, near the bottom, as shown in Fig. 196. The nearer an anchor is placed to the top of a joist the greater will be the destruc- Fig. 198. — Duplex Wall-hangef. Fig. 199. — Goetz Box-anchors. tive effect on the wall by the falling of the joist, as shown in Fig. 197. For anchoring walls that are parallel to the joists, the anchors must be spiked to the tops of the joists ; and either they should be long enough to reach ovei* two joists, or pieces of i^-inch boards should be let into the tops of three or four joists and the anchors spiked to them. The objection to all of these anchors is that in case the beams fall during a severe fire or from any other cause, they are apt to pull the walls over with tffem. To overcome this objection, as well as to secure other advantages, the Duplex wall-hangers, shown in Fig. 198, and the Goetz box-anchors, shown in Fig. 199, have been invented. These devices hold the timbers by means of ribs or lugs gained into their lower surfaces. The anchoring is perhaps not as efficient as is secured by the anchors shown in Fig. 195, but it is ample for all ordinary conditions, as every joist is anchored when these devices are used. CONSTRUCTION OF BRICK WALLS. 357 These devices ofifer also the additional advantages of not weaken- ing the walls, while they increase the bearings of the timbers and reduce the possibility of dry rot to a minimum. They also permit of easily replacing the joists after a fire. A stronger form of the Duplex is the wall-hanger shown in Fig. Fig. 200. — Stronger Form of Duplex Wall-hanger. 201. — Goetz Wall-hc 200. The Goetz Box-anchor Company also make wall-hangers of a. form shown in Fig. 201, which have the advantage of great simplicity and strength. The ''Truss-coN" wall-hangers, Fig. 202, are well- designed single-plate pressed-steel hangers which have satisfied very high tests for strength. Wall-hangers of the general types illustrated in Figs. 198, 200, Fig. 202. — The "Truss-coN" Wall-hanger. Fig. 203.— Beam Anchored to Party-wall Wall-hangers. 201 and 202 are especially desirable for party-walls and partition walls, as they obviate the necessity of building the beams into the walls and permit the walls to be as solid at the floor levels as in other portions. (See Fig. 203.) 358 BUILDING CONSTRUCTION. (Ch. VII) The importance of anchoring the joists to the walls, and thus pre- venting the latter from being thrown outward either from settle- ment in the foundation or from pressure exerted against the insides of the walls, is very great, and should not be overlooked by the archi- tect. Many walls, which might have been saved by proper anchor- ing, have either fallen, or have had to be rebuilt. 353. CORBELLING BRICK WALLS FOR FLOOR JOISTS. — In some localities it is the custom to form ledges to support the floor joists by building continuous corbels of three or more courses. This is done to prevent the ends of the floor timbers from weakening the walls; for, of course, wherever wooden timbers are built into them, they make the section or bearing area of the walls smaller by just the amount of space taken up by the timbers ; and in partition walls this is very con- siderable. The Chicago Building Ordi- nance provides that all walls, 16 inches or less in thickness, shall have ledges of the thickness of the furring, lath and plaster to support the floor joists; and in all cases where ledges are built they are to be carried to the tops of the joists, as shown in Fig. 204. When walls are corbelled" in this way it requires plaster or wooden cornices, as shown by the dotted lines, to give a proper finish for the angles of the rooms ; and for this reason corbelling is not usually done when not required by law. Corbelling for floor joists should not be attempted with soft or poor bricks. 354. CARRYING UP BRICK WALLS EVENLY.— The walls of a building should be carried up evenly, no part being allowed to be carried up more than 3 feet above any other part, except where it is stopped by an opening. The building up of one part of a wall ahead of the adjacent parts tends to cause unequal settlements; and the joints in the higher parts setting before the rest is added, the brickwork which is laid last is apt to settle away from the other and to weaken the walls, besides marring their appearance. Whenever it Fig. 204. — Brick Corbel for Floor Joists. CONSTRUCTIOX OF BRICK IV ALLS. 359 is necessary to carry one part of a wall higher than the rest of it the end of the higher part should be stepped or racked back, and not run up vertically, with only toothings left for connecting the re- mainder of the work. 355. BONDING OF BRICK WALLS AT ANGLES.— An important detail in the construction of brick buildings is the secure bonding of the front and rear walls to the side or partition walls. When practicable, both walls should be carried up together, so that each course of bricks in both walls may be well bonded together. If, in order to avoid delay, the side walls must be built up ahead of the front wall, the ends of the side walls should be built with toothings, as shown in Fig. 205, eight or nine courses high, into o d 1 ' ' 1 .1 r rr — S I a b r r- c Fig. 205. — Toothing and Anchoring of Side Brick Walls. Fig. 206. — Cracks in Brick Walls Caused by Piers and Openings. which the backing of the front wall should be bonded. In addition to the brick bonding, anchors made of ^ by 2-inch wrought-iron, with one end turned up 2 inches and the other welded around a ^-inch round bar, should be built into the side walls about every 5 feet in height, as shown in the figure. The anchors should be of such lengths that the rods will be at least 8 inches in from the back of the front wall and extend at least 17 inches into the side walls.^ The building regulations of most of the larger cities require that all intersecting brick walls shall be tied together in this way. 356. OPENINGS IN BRICK WALLS.— The locations of all door and window openings in brick walls should be carefully con- 360 BUILDING CONSTRUCTION. (Ch. VII) sidered, not only as regards convenience, but also as to their effect on the strength of the walls. The combined widths of the openings in any bearing wall should not much exceed one-fourth of the length of that wall ; and as far as possible the openings in the different stories should be over each other. The placing of a window either under a pier or directly over a narrow mullion, as at a or b, Fig. 206, should be especially avoided. If windows must be used in these positions, steel beams should be placed over the windows a and c, as a stone lintel or a brick arch would be quite sure to crack from the combined effects of the load and the set- tlement of the joints in the brickwork on either side of the windows. All openings in exterior walls should have either relieving-arches or cast-iron or steel beams behind the stone caps or face-arches. Ordinary relieving-arches (see Article 372) are commonly used where the widths of the openings are less Joining New to Old Br ick than 6 feet, and steel beams where the Walls widths are greater. In bearing walls, where the tops of the openings come within 12 inches of the bot- toms of the floor joists, it is hardly safe to use relieving-arches, unless the floor loads are very light. For door openings in unplastered brick partitions, cast-iron lintels may be used to good advantage, as they give smooth, level soffits to the openings and show only narrow strips of metal on the faces of the walls. 357. JOINING NEW TO OLD BRICK WALLS.— When a new wall is to be joined to an old one, at right-angles, a groove should be cut in the old wall similar to that shown in Fig. 159 for ^ the new wall to fit into and for the purpose of allowing it to settle independently. A cheaper method, and one more commonly used in light work, is to nail a scantling, a 2-inch by 4-inch piece of timber, to the wall of the old building, so that it will come in the middle of the new wall, as shown in Fig. 207. A similar method can be used for joining the ends of old and new walls. New work should never be toothed to old work unless the former is laid in cement. 358. THICKNESSES OF BRICK WALLS.— There is no prac^ tical rule by which it is possible to calculate the necessary thickness CONSTRUCTION OF BRICK WALLS. 361 of a brick wall, as the resistance to crushing, which is the only direct stress, is usually only a minor consideration. We must therefore rely principally upon experience in determin- ing the thicknesses of walls for any given building, unless the con- struction of the building is controlled by municipal or State regula- tions. In nearly all of the larger cities of the country the minimum thick- nesses of the walls are prescribed by law or ordinance ; and as these requirements are generally ample they are usually adhered to by architects when designing brick buildings. TABLE XXVL='^ Thicknesses of Walls of Mercantile Buildings in Various Cities, Shown Graphically. Cities JBoston Sam ri-arioSsco .Den.ver Minneapolis Chicago Philadelphia Memphis Kevy Yoi'k jBoston San Erancisco .Denver .Minneapolis Chicago -■Philadelphia Memphis J^lew York San Francisco Denver Minneapolis Chicago Philadelphia Memphis .New York San Trancisco Denver ^Minneapolis Chicago Philadelphia Memphis s § ^ ^ ^ Cities San Francisco Denver Minneapolis Chicago Philadelphia .Memphis New York P.uston Denver Munieapolis Chicago Philadelphia, Memphis Denver Minneapolis Chicago Philadelphia Memphis New York- Denver Minneapolis Chicago Philadelphia 3Iemphis Boston Minneapolis' Chicago Philadelphia Memphis SeAv YorJi Table XXVI and other matter of this chapter was prepared by Mr. Julian Millard. See also Tables X and Y in Appendix. 362 BUILDING CONSTRUCTION. (Ch. VII) TABLE XXVII. Maximum Story-heights for Thicknesses in Table XXVI. Cities Maximum story-heighis in feet Limits of lengths in feet 1st 2d Inter- mediate Top More than Less than 40 105 is* 15* 14* 75 125 100 4of 14 12 16 40 125 18* 15^- 14* 100 * In the clear. t Applies to walls over 60 feet high. Table XXVI shows graphically the thicknesses of walls of ware- houses and mercantile buildings in eight representative American cities. In this table each vertical subdivision represents ten feet of wall height and each horizontal line represents a half-brick (4 or inches) of wall thickness. Thus, three lines represent a 12 or 13-inch wall. The short cross lines show story-heights. If the law limits heights of stories, such limits are indicated by the small circles. Table XXVII shows the maximum story-heights in feet for which the thicknesses in Table XXVI apply ; and the minimum and maxi- mum lengths (not heights) in feet within which the thicknesses of Table XXVI apply. The columns marked "limits of lengths" refer to lengths unsupported by buttresses or cross-walls. Many ordinances require that in computing the thickness of exterior walls, facings in ''running bond" shall not be included. Although there is some difiference in the thicknesses of walls given it|i the tables, a general rule might be deduced from the table, for mercantile buildings over four stories in height, which would be somewhat as follows : For bricks equal to those used in Boston or Chicago, make the thickness of the zvalls of the three upper stories 16 inches; of the next three below, 20 inches ; of the next three, 24 inches ; and the next three, 28 inches. For a poorer quality of material, make the walls of the two upper stories only, 16 inches thick; those of the next three, 20 inches ; and so on down. CONSTRUCTION OF BRICK WALLS. 363 In buildings less than five stories in height the top story may be 12 inches in thickness. For the walls of dwellings, 13 inches and 9 inches may be used for two-story buildings ; for three-story buildings the walls should be 13 inches thick the entire height above the basement; and for four- story buildmgs 17 inches in the first story and 13 inches for the entire height above. In determining the thickness of walls the following five general principles should be recognized : First. Walls of warehouses and mercantile buildings should be heavier than those used for living or office purposes. Second. Clear spans exceeding 25 feet and unusually high ^ stories require thicker walls. Third. Great length is a source of weakness in a wall, and its thickness should be increased 4 inches for every 25 feet over about ICQ feet in length. Fourth. Walls containing over 33 per cent of openings should be increased in thickness. Fifth. Partition walls, if not over 60 feet long, may be 4 inches less in thickness than the outside walls, but no partition should be less than 8 inches thick. 359. BRICK PARTY-WALLS.— There is much diversity in building regulations regarding the thickness of party-walls, al- though they all agree that such walls should never be less than 12 inches thick. About one-half of the laws require the party-walls to be of the same thickness as exterior walls ; the remainder are about equally divided between making the party-walls 4 inches thicker or 4 inches thinner than if they were independent side walls. When the walls are proportioned by the rule previously given, the author believes that the thickness of the party-walls should be increased 4 inches in each story. The floor load on a party-wall is obviously Iwice that on the side walls, and the necessity for thorough fire-protection is greater in the case of party-walls than in that of other walls. 360. BRICK CURTAIN-WALLS.— In buildings of the skele- ton type the outer masonry walls are usually supported either in every story or every other story by the steel framework, a*nd carry nothing but their own weight. Such walls may, therefore, be con- sidered as only one or two stories high, and are often made only 3^4 BUILDING CONSTRUCTION. (Ch. VII) 12 inches thick for the whole height of a twelve or fifteen-story building unless building laws require a greater thickness. 361. WOOD IN BRICK WALLS.— As a rule, no more wood- work should be placed in brick walls than is absolutely necessary. Wooden lintels for supporting brick walls are objectionable not only on account of their non-resistance to fire, but also on account of their tendency to shrink. It is generally impossible to obtain fram- ing lumber that is thoroughly dry, and when a brick wall is partially supported by a wooden lintel a crack is quite sure to develop sooner or later in the manner shown in Fig. 208. The crack is obviously caused by the shrmkage of the lintel, which permits the portion .of the wall supported on it to settle by an amount equal to the shrinkage of the wood. The portion of the wall a, being supported on the brick pier, does not settle. Bond-timbers, or pieces of studding laid under the ends of the floor joists, are also objection- able, because they are quite sure to shrink, leav- ing the walls above them unsupported. Bond- timbers are very convenient for the carpenters. Fig. 2o8.-Cracks in ^s they givc a level bearing for the floor joists. ^bTsJ^inkag''e"'of^ ^^^^ distribute the weight over the brickwork; Wood Lintel. ^^^^ ^YiQy should ucvcr be used in buildings which are over two stories in height, nor in walls which are less than 12 inches thick. If used at all, they should be selected from the driest lumber that can be obtained. For the proper use of wooden lintels under relieving-arches see Article 372. Strips of wood are sometimes built into walls to. form a nailing for the wood finish or for the furring strips. Such strips should not be used in buildings over two stories in height, and should not be over ^ of an inch thick, so that they may take the place of the mortar joints. Wooden bricks also, or blocks of wood of the size of bricks, are sometimes built into brick walls to provide nailings for furring strips, door frames, etc. These not only tend to weaken the walls, but the}^ also generally shrink enough to become loose, thereby losing their holding power. Plugs. — It is a common practice to drill holes in the brickwork and to drive in wood plugs for the nailings. While these plugs are CONSTRUCTION OF . BRICK WALLS. 365 generally efficient, they cannot be depended upon, as they are often loosened by the shrinkage or split by the nails. In first-class work nailings should be provided as the walls are built by porous terra-cotta blocks or by the Rutty metal wall- plugs, shown in Fig. 209. The porous terra-cotta will hold nails almost as well as timber will, but greater dependence can be placed upon the metal plugs than upon either of the others. These wall- plugs are made of steel, thoroughly japanned, and may be* obtained in either of two forms. One type is intended to be set in the joints with the edges flush with the masonry, as in Fig. 210. The others, called "non-furring plugs.," Fig. 211, are set with their faces J4 of an inch out from the masonry, as in Fig. 212. Wood furring- strips or metal-lath may be nailed directly to these, and thus be entirely insulated from the walls. 362. CRACKS IN BRICK WALLS.— It is a very common thing to see cracks in brick walls. These cracks may be produced by any one of several causes. Probably the most frequent cause of the cracking of masonry walls is the settlement of the foundations, due either to their im- proper design or to a settlement of the ground caused by excessive moisture. A strict observance of the rules laid down in Articles 25, 32 and 33 will generally prevent cracks due to faulty founda- tions. Fig. 210. — The Rutty Steel Wall-plug. Face Flush with Masonry. Fig. 211. — The Rutty Non-furring Wall-plug. :^hG BUILDIXG construction: (Ch. VII) ' The effect produced on certain soils by a saturation with water is described in Article 9. Next to faulty foundations, probably the commonest cause of cracks in brick walls is the use of wooden lintels, as described in Article 261. Besides the cracks resulting from these causes are those which often appear over openings, and which are due to the settlement of the mortar joints in the piers or to the spreading of arches. Small cracks are commonly seen just above the ends of door sills ■or window sills, as shown in Fig. 213. Such cracks generally appear near the bottom^s of high walls, and are caused by the compression of the mortar in the lower joints of the piers. They may be avoided by using slip-sills, as described in Article 282, but are not likely to occur when cement mortar is used. Another place where cracks produced by the settlement of mortar joints sometimes occur is where a low wall joins a very high one. Fig. 212. — The Rutty Non-furring Wall-plug. Fig. 213. — Cracks Over Sills Caused by Joint Com- pression. To prevent such cracks the walls should be joined by a slip- joint, as described in Articles 315 and 357. Cracks are generally miore likely to occur in walls that are broken by frequent openings than in those that are plain and unbroken. The use of plenty of anchors and thorough bonding does much toward preventing cracks. 363. DAMP-PROOF COURSES.— When buildings are built on ground that is continually moist or wet, the moisture is very apt to soak up into the walls from the foundations, rendering the building unhealthy and often causing the woodwork to rot. To prevent the moisture rising in this way a horizontal damp-proof .course should be inserted in all walls below the level of the first floor CONSTRUCTION OF BRICK WALLS. 367 joists. It should be at least 6 inches above the highest level of the soil touching any part of the outer walls, and should run unbroken all around them and at least 2 feet into all the cross walls ; and on very wet ground, where the water is but a few feet below the sur- face, it should be continuous through all the walls. In buildings fin- ished with parapet walls it is also desirable to insert a damp-proof course just above the flashings of the roofs or gutters to prevent the moisture from soaking down into the woodwork of the roof and into the walls below. Materials. — These damp-proof courses may be formed of any one of several materials : Asphalt. — A layer of rock asphalt ^ of an inch thick makes an excellent damp-proof course. The surface to receive the hot asphalt should be quite dry and should be made smooth to economize mate- rial, and all the joints should be well flushed up with mortar. The best asphalts for this purpose are the natural rock-asphalt from Seyssel, Val de Travers or Ragusa, which are imported into this country in the shape of blocks and cakes.. When used the cakes are melted in large kettles, and mixed with a small proportion of coal- tar and applied hot. One or two layers of tarred felt also, imbedded in the hot asphalt, may be used with good results. "Roofing slates, or even hard vitrified bricks, two courses break-* ing joint, laid in half cement and sand mortar, or such bricks laid without any mortar in the vertical joints, form an inexpensive damp course." Glass also has sometimes been used for this purpose. -Portland Cement. — A 5^ -inch layer of Portland cement mortar, mixed in the proportion of i part of cement and I of sand, will often answer the purpose, but is not as desirable as the materials mentioned above. There are many other special preparations used for this purpose. 364. HOLLOW BRICK WALLS. THEIR OBJECT.— It is well known that solid brick walls readily absorb moisture and trans- mit heat and cold. A driving rainstorm will often penetrate 12-inch brick walls so as to dampen the wall-paper or soil the fresco deco- rations.* It is also known that a house with damp walls is unhealthy and a frequent cause of rheumatism; besides this, the moisture in * So-called solid brick walls are by no means really solid, and facings, apparently tight, have frequent holes through which water will gain admittance. There is. therefore, nothing- mysterious in the above statement. But if the walls are made so solid and dense that they are impervious to water, their conductivity is high, and the warm air o£ the interior rapidly deposits its moisture and dirt upon the walls. Such conditions are even more unsanitary than conditions resulting in moisture from the outside. BUILDING CONSTRUCTION. (Ch. VII> the brickwork prevents the mortar, if made of Hme, from becoming hard, and is also liable to communicate itself to the woodwork, thereby causing- rot. A building with damp walls will also require the consumption of very much more coal to warm it than one with dry walls, as the moisture must be evaporated before the temperature of the walls can be raised. To overcome these objections to solid brick walls, particularly in residences and school-houses, hollow or vaulted walls have been used, and earnestly recommended by various persons. Theoretically, a hollow wall should prevent the passage of moist- ure through it, or insulate the interior from the exterior surfaces, and by providing air-spaces in the walls, make the building much cooler in summer and warmer in winter. In the actual construction of the walls, however, certain difficulties are met with, which, to a considerable extent, offset the advantages ; so that hollow walls are comparatively little used in this country. The author believes, however, that their use might be much extended with beneficial results, especially for isolated buildings. To obtain the full benefit of the air-spaces they should be con- tinuous throughout the walls, and the bonds or connections between the two parts should be of such niaterial and of such shape that the moisture which penetrates the outer portions cannot be conveyed across to the inner portions. To provide continuous air-spaces in walls penetrated by openings is practically impossible, although it may be quite closely approxi- mated. The objections commonly urged against vaulted walls are in- creased cost and increased ground area, the latter being an impor- tant consideration in city buildings. 365. METHODS OF HOLLOW-WALL CONSTRUCTION. — There are several ways of constructing hollow or vaulted walls. They differ principally in the method of bonding and in the thick- ness of the inner and the outer portions of the walls. Generally, at least one portion of the wall must be made 8 inches thick to sustain the weight of the floors, the other portion being only 4 inches thick. The thicker portion is more commonly placed on the outside of the walls ; but this necessitates extending the floor joists across the air-space, thus to a great extent neutralizing the "benefits expected to be derived from it. By this method the thicker CONSTRUCTION OF BRICK WALLS. 369 Fig. 214. — Brick Hollow-wall Construction Two-story Buildings. portion of the wall is still sub- jected to the injurious effects of outside moisture. For two-story buildings the author recommends that the walls be constructed as shown Fig. 214. If the wall-plates come above the attic joists the latter may be supported on two 4-inch walls if well built. If the bricks are not of good qual- ity the inner 8-inch wall should be con- tinued to the upper joists. When the bricks, mortar and work- manship are of the best quality there is no reason why this construction should not answer for even four or five-story buildings, if used only for dwelling or lodging purposes, by making the inner portions 8 inches thick the full height, and by increasing the width of the air-spaces to 6 inches. For warehouses the bearing wall in the lower stories should be increased in thickness. A hollow w^all of a given number of bricks, securely bonded, is much more stable than a solid wall of the same number of bricks, and will also withstand fire better. It requires much better workmanship, however,, than is ' generally be- stowed on solid walls,* * A 4-inch brick wall is more likely than a thicker wall to be solid and to have well-filled joints. 370 BUILDING CONSTRUCTION. (Ch. VII) Fig. 215. — Brick Hollow Walls for Cheap Cottage Constructions and the mortar, particularly in the outer portions, must be of the best quality, and preferably of cement. The outer and inner walls should be built of the same kind of mortar and at the same time', to avoid unequal set- tlement. For country and suburban houses the following, shown in Fig. 215, gives a reasonably good hollow- wall construction at small expense : The foundation walls are made solid to the bottoms of the first-story joists. Upon these are built two 4-inch walls, 2 inches apart, bonded across with wire bonds. The walls are made solid for two or three courses below the second- floor joists, and thence continued as hollow walls to the second course below the ceiling. Frcm this level they are made solid up to plates, reducing to 8 inches in thickness back of the cornice. The corners are made solid, and 4-inch solid withes are built at the jambs of openings. The heads are made solid. A wire bo«nd is used in every square foot of wall surface. A few holes left through the solid parts, giving air cir- culation from cellar to attic, will tend to quickly evaporate any moisture be- fore it passes in any perceptible quan- tity from the outside to the inside. Cement mortar or lime-and-cement mortar should be used, although in dry climates lime mortar is used with suc- cess. This construction is very stable when used in houses not over two stories in height. It requires neither furring nor lath, and usually is no more expensive than solid walls, furred and lathed. It is especially recom- CONSTRUCTION OF BRICK WALLS. 371 mended for houses that are to be plastered on the outside. At prevailing prices (1907) it costs but little more than wood con- struction and less than brick-cased or veneered construction. Facing-brick may be used on the outside if both parts are laid in cement mortar. Nearly all building regulations require that at least the same quan- tity of bricks shall be used in the construction of hollow walls as would be used if the walls were built solid ; and many of them require that both portions of the walls shall be at least 8 inches thick, if they are used as bearing walls. For heavy buildings, with steel floor joists and girders, it is better to build the outer walls the full thickness that vyould be required in the case of single walls, and to' make the inner walls only 4 inches thick, to serve merely as a furring and to receive the plaster. Where fire-proof arches are used for the floors, these inner walls might without injury rest on the floor arches. 366. BONDING OF HOLLOW W^ALLS. — To secure proper strength in these walls it is necessary that the two portions shall be well bonded together, so that neither will buckle nor get out of plumb. Until within a few years this bonding was usually accom- plished by placing brick headers across .the air-spaces with the ends built a short distance into the two portions of the walls, as shown Fig. 216. — Bonds and Ties at a, Fig. 216. for Brick Hollow W alls. Brick bonding, however, neutralizes much of the benefit gained by an air-space, as it permits ^the passage of moisture through walls wherever they are bonded. The moisture not only passes through the bond bricks, but also through the mor- tar droppings that invariably collect upon them. The best method of bonding, and the only one which retains the full benefits of an air-space, is the one using metal ties provided with a drip in the middle. Any one of the metal ties shown in Fig. 216 may be used. That shown at h is the ''Morse" tie, which is made of different sizes of galvanized-steel wire and which varies from 7 3/2 BUILDING CONSTRUCTION. (Ch. VII) to 1 6 inches in length. The other ties are not patented, and may be made by any blacksmith. The one shown at e is probably the best shape where both walls are 8 inches thick, as it takes a firm hold on the walls and is also much stiffer than the wire ties. The iron ties should be either galvanized or dipped in hot asphalt or coal-tar. Wire ties are probably best for 2-inch air-spaces, as they stop no mortar droppings and accommodate themselves to slight settlements without injury to either wall. In wider spacings greater stiffness is advisable and plate-iron ties should be used, although the same result might be attained by using wire ties at more frequent inter- vals. Galvanized wire and sheet-metal ties are manufactured in great variety for use in solid walls, hollow walls and brick-cased or veneered walls. It should be noted that in hollow walls mortar droppings will pile up on any ties which present horizontal flat surfaces. If ties of any of the shapes shown at b, c or d are used they should be spaced every 24 inches in every fourth course. The tie e, being stronger, need be used in every eighth course only. 367. CONSTRUCTION AROUND OPENINGS IN HOL- LOW WALLS. — Wherever door or window openings occur in hollow walls it is necessary to build the walls solid for 8 inches at each side of the openings, and also to carry the relieving-arches entirely through the walls. It is almost impossible to prevent some moisture from passing through the walls at these points ; but much may be done by covering the tops of the relieving-arches with hot tar and laying the connecting brickwork in cement mortar. The tops of the relieving-arches are obviously the most vulnerable points, and should be protected in some way and kept as free as possible from mortar droppings. 368. VENTILATION OF AIR-SPACES IN HOLLOW WALLS. — There seems to be some difference of opinion as to whether or not the air-spaces should be connected with the outer air. American writers, however, appear to be generally of the opinion that the air-spaces should be ventilated to carry off the moisture that collects on the inside of the outer portion of the walls. I It is recommended that the bottoms of the air-spaces be ven- tilated through openings into the cellar, and that openings be left iin the inner portions of the walls just under the copings of parapet CONSTRUCTION OF BRICK WALLS. 373 walls, or above the attic floor joists if the walls are covered by the roof. If the air-spaces cannot be ventilated into the attic, then ven- tilation flues should be carried up and topped out like chimneys, or built in connection with chimneys. It is also recommended that U-shaped drain tile be laid at the bottoms of the air-spaces to col- lect any moisture that may run down the outer walls. 369. ' HOLLOW BRICK WALLS WITH BRICK WITHES. — Brick walls are sometimes built with 4-inch inner and outer Fig. 217. — Brick Hollow-wall Construction. Congress Hall, Saratoga, N. Y. facings connected with solid brick withes, as shown in Fig. 217, the air-spaces being made 4, 8 or 12 inches, according to the height and character of the buildings. Congress Hall, Saratoga, N. Y., a por- tion of which is seven stories high, was built in the manner shown 'in Fig. 217, and stood successfully. If such walls are built with the best kind of common bricks, and if the workmanship is perfect, they should have ample strength for any ordinary three or four- story building, and would certainly be more stable and conduct less heat and moisture out of and into the building than in the case of solid walls containing one-half more bricks. With such poor bricks and workmanship as are commonly found in maily parts of this country, however, walls built in this way should never be used 374 BUILDING CONSTRUCTION. (Ch. VII) for any building larger than an ordinary two-story dwelling. Theo- retically, the insides of the walls opposite the withes would be subject to dampness, but of course not to so great an extent as in the solid walls. For two-story dwellings these walls, if well constructed, and if the withes are securely bonded to the facings, should make much healthier and more comfortable buildings than those built with solid walls. There are several forms of plaster-blocks and plaster or stucco- boards which may be applied with excellent results to the inside of brick walls, to form air-spaces. As plaster of Paris is very absorbent, care must be taken to prevent any contact with the brickwork. The Rutty metal non-furring plugs may be set where wanted in the joints when the bricks are laid. The faces of these plugs stand ^ of an inch from the brickwork. Plaster blocks may be tied to nails driven into these plugs, and for plaster-board, strips may be nailed to the plugs for a nailing. Either method is a great advance over ordinary wood furrings and laths. 370. FURRIXG-BLOCKS FOR BRICK WALLS.— For office buildings furring-blocks designed for that especial purpose are often used for lining or furring the external walls, and sometimes hollow bricks are used for the inner 4 inches of solid walls ; but the latter have not proved a success in excluding moisture. The objection to . any kind of furring and to hollow bricks is that there must neces- * sarily be some connection between the material of the lining or furring and the walls themselves, and this connection allows the passage of heat and moisture. 371. BRICK-VENEER CONSTRUCTION.— It is quite com. mon in many sections of the country to build dwellings, and even three and four-story buildings, with outer walls of frame con- struction veneered with 4-inch facings of brick. Buildings built in this way have the same appearance, both outside and inside, as if the walls were built entirely of brick. Where lumber is cheap and brickwork comparatively dear, this method of construction possesses some advantages, although it is not generally approved by architects; and it should be used only where hollow brick walls cannot be afforded. The advantages possessed by brick-veneered frame walls over soHd brick walls are the lower cost, and the air-spaces, which latter prevent any pos- COXSTRUCTIOX OF BRICK WALLS. 375 sibility of the passage of moisture, and also make the houses much warmer in winter and cooler in summer. About the only advantage that it possesses over a method result- • ing in well-built frame buildings is that it reduces the insurance rate, as the veneer offers some protection from fires starting in adjoining buildings. Veneered buildings, however, are not nearly as free from danger from fire as brick buildings are, and they would probably be destroyed by fire on the inside about as rapidly as though the frame were covered with siding or shingles. The only differences in the planning of a veneered building from that of a frame building are that in the former the walls are about 5 inches thicker and the foundations project sufficiently beyond the frame to support the veneer. The elevations are drawn the same as for a building with solid brick walls. The wooden frame should be constructed in the best manner, with at least 4 by 6-inch sills, 4 by 8-inch posts, 4 by 6-inch girts and 4 by 4-inch plates, and should be well braced at the angles. After the frame is up it should be sheathed diagonally and then covered with tarred felt. It is also very important that, the framing timber should be as dry as possible, and particularly so for the sills and girts. The frame must also be perfectly plumb and straight. The veneer is usually laid with pressed or face-bricks, with plumb bond, which should be tied to the wooden walls with metal ties. Ties similar to the Morse ties, shown at a, Fig. 218, are probably the best for this purpose, although the author has used ties of the form shown at b with very satisfactory results. The ties should be placed on every other brick in every fifth course. Fig. 218. — Brick-veneer Construction. Metal Ties. 376 BUILDING CONSTRUCTION. (Cii. VII) In laying out the walls on the floor plans 6 inches should be allowed from the outside of the studding to the outside face of the brick walls. This gives an air-space of about i inch between the bricks and sheathing and avoids chipping the bricks where the wooden walls are a little full. It is a good idea to build 2-inch U-shaped drain tiles in the foundation walls under the air-spaces to collect any moisture that may penetrate the veneer. The air- spaces should also be ventilated at the bottom through 2-inch drain tiles, as shown in Fig. 219. The top of the brickwork generally terminates under the eaves or gable finish. If the building has a flat roof, with parapet walls, the latter should be coped with either copper or galvanized-iron and tinned on the back down to the flashing. Fig. 219 shows a partial section through the foundation and a portion of the first-story wall of a veneered dwelling to illustrate the construction described above. Fig. 220 shows a section through a brick-veneered wall, with .f. Fig. 219. — Common Type of Brick-veneered Construction. CONSTRUCTION OF BRICK WALLS. OtCTlOAf t)CAueL Fig. 220. — Sections Through Brick-veneered Wall. some variations in de- tails of construction from those shown in the preceding figures ; and the following is a brief description of the construction shown and a mention of the claims made for it by its advocates in the Middle West districts of the coun- try. Stone veneer as compared with brick veneer is also men- tioned. In the Middle West both brick and stone veneer construction is now (1908) regularly used, especially in the first story. This story, up to the tops of the first-story windows, is veneered with briok- work or with rough field-stones. The sec- ond story is covered with siding or shingles. The cost of such veneered houses, at the present time, is very little higher in these districts than that of houses built with solid brick walls. As shown in this sec- tion, the walls are generally 10^ or 11 378 BUILDING CONSTRUCTION. (Ch. VII) inches thick, allowing 4^ inches for the brick veneer, i inch fpr the air-space and paper, of an inch for the sheathing, 35/^ inches for the studs and ^ of an inch for the plaster-board, sheathing- lath or lath and plaster. Any water absorbed by the brickwork runs down the inside face to the copper flashing, out through occasional holes cut in the lower bricks, down the face of the water-table and to the ground from the drip. Bricks similarly perforated and placed at the top of the wall act as ventilators for the air-space. The veneer is tied to the sheathing by metal ties tacked to the latter and imbedded in the mortar joints. Fig. 221. — Detail of Bay-window in Brick-veneered Wall. In order to imitate special brick bonds, half bricks are sometimes used to represent headers. When the stone veneer' is used there is a variation of the con- struction to effect the bonding of the stonework. When rough field-stones are employed long bond-stones are run in between the studs occasionally, and plaster-board or sheathing-lath substituted MISCELLANEOUS DETAILS. 379 for the sheathing, and put on the inside of the studs. Metal ties are used in this construction also. Fig. 221 shows the details of a bay-window in a brick-veneered wall. The mullions are of brick, and the window frames made for double-hung sash. The bricks for the mullion angles are ground rather than clipped. In this construction there is ample room for the weight-boxes. \ Fig. 222 shows the details of a wooden bay in a brick wall, the Fig. 222. — Detail of Wooden Bay in Brick Wall. wall being in this illustration solid. Whether the walls are' solid or veneered, there is often difficulty met with in getting room enough for the weights in the boxes when the bay mullions are of wood ; and either the widths of the mullions have to be increased or special- shaped weights of greater lengths used. With casement window sash or brick mullions these difficulties disappear. 4. MISCELLANEOUS DETAILS IN BRICKWORK. 372. BRICK ARCHES.^^— Brick arches are generally used for * For a discussion of the stability of arches, reference may be made to the "Archi- tect's and Builder's Pocket-Book." Frank E. Kidder. 38o BUILDING CONSTRUCTION. (Ch. VII) spanning the openings in brick walls, and where there is sufficient height for an arch it forms the most durable support for a wall above. The arches should be laid with great care and with full joints, and all having a span of over lo feet should be laid in strong cement mortar. It is indeed much safer to lay all brick arches in cement mortar. Gauged Arches. — When arches are built of common bricks the latter are laid close together on the inner edge, with wedge-shaped joints, as shown in Fig. 229 ; but when built of face-br'cks the arch rim. is laid out on a floor and each brick is cut and rubbed to fit exactly the place chosen for it, so that the radial joints are of the same thickness throughout. Such work is called "gauged work." Bond in Brick Arches. — The only detail requiring especial men- tion in connection with brick arches is the bond. When gauged Fig. 223. — Bonded Gauged Brick Arch. Fig. 224. — Rowlock Brick Arch. arches are used the bricks are generally bonded on the face of the arch to correspond with the face of the wall, as shown in Fig. 223. Such an arch is called a ''bonded arch.'' Bonded gauged work makes the neatest and strongest work, but it is too expensive to be used in common brick arches. Arches of common bricks are generally built in concentric rings, either constructed so that they have no connection with each other, except that resulting from the tenacity of the mortar, or else bonded every few feet with bonding courses built in at intervals like vous- soirs, as shown by the heavy lines at A, Fig. 225. When the con- centric rings are all headers, as in Fig. 224, the arch is designated a *'rowlock arch," and the bond ''rowlock bond" ; and when the arch is built with bonding courses, as in Fig. 225, the bond is known as "block-in-course bond." Segmental arches are gften built with con- MISCELLANEOUS DETAILS. 381 centric rings of stretchers (Fig. 226), which niay be bonded at right-angles to the face of the arch by hoop-iron. When the radius is over 15 feet this latter construction should be stronger than the rowlock bond. Common brick arches are sometimes bonded by introducing head- ers so as to unite two half -brick rings wherever the joints of two . — iJrick Arch with Block-in-coiirse J>on(l. Fig. 226.- Arch with Concentric Rings of Stretchci s. such rings happen to coincide. Fig. 227 shows the bonding em- ployed in arching the Vosburg tunnel on the Lehigh Valley Rail- road, the span being 28 feet. The objection to building an arch in concentric rings is that each ring acts nearly or quite independently of the other, and the least settlement in the outer rings throws the entire pressure on the inner ring, which may not be able to resist it. When bond- ing courses are used, however, they serve to tie the rings together and to distribute the pressure between them, so that the above objection is over- come. For arches of wide span, or for those heavily loaded, some form of block-in-course bond should be used. Hoop-iron is often built into arch-rings parallel to the soffit, and is also often worked into the radial joints to unite the different rings. The stability of an arch may be greatly increased by its use. Skewbacks for Brick Arches. — In building brick arches of large span it is important to have solid bearings for the arches to spring Fig. 227. — Brick Arch over \'osburg Tunnel, Lehigh Valley Railroad. 382 BUILDING CONSTRUCTION. (Ch. VII) from. Such bearings may be best obtained by using stone skew- backs, as shown in Figs. 226 and 227. The stones should be cut so as to bond into the brickwork of the piers, and the springing sur- faces should be cut to true planes, radiating from the center from which the arch is struck. The skewbacks should always be bedded in cement mortar. Flat Arches of Brick. — Flat arches are often built over door or w^indow openings in external walls for convenience or architectural effect. Such arches, if built with perfectly level soffits, almost always settle a little, and it is better to give a slight curve to the soffits, as in Fig. 228, or else to support the soffits of the arches on angle-bars, the vertical flanges of the bars being concealed behind the arch. Brick Relicviug-archcs. — The portion of a wall back of a face- brick arch or stone lintel over a door or window opening should be Fig. 228. — Brick Flat Arch with Curved P"ig. 229. — Brick Relieving-arch. Soffit. supported by a rough brick arch, as shown in Fig. 229. A wooden lintel is first put across the opening, and on this a brick core or center is built on which to turn the arch. Sometimes arched wooden lintels are used and the arch turned on them. In the case of plastered walls without furring, the method shown in the figure is the best, as there is less woodwork. The wood lintel should have a bearing on the wall of not more than 4 inches, and the arch should spring from beyond the end of the lintel, as at A, and not as at B, as in the latter method the arch is afifected by the shrinkage of the lintel. 373. BRICK VAULTS. — Brick vaults are usually constructed in the same way as common brick arches, except that the bricks should be bonded lengthwise of the vault. Cross vaults, or groined vaults, are generally supported at the intersections by diagonal arches of the proper curvature, built so as to drop from 8 or 12 inches below the soffits of the vaults. MISCELLANEOUS DETAILS. 383 Vaults may be economically constructed by a combination of brickwork and concrete, or even entirely of concrete. When built entirely of concrete, however, very strong centers are required. Fig. 230* shows a method of constructing vaults much used by the ancient Romans. A light temporary center of wood was first put in place, and on this light brick arches were built to form a framework for supporting the weight of the vault until set. These brick arches were called ''armatures," and as they became the real support of the vault only very light wooden centers were required. After the armatures wxre built the spaces between them were filled with rough masonry or concrete, as shown in Fig. 231.'^' 374. BRICK CHIMNEYS. t — In planning a brick chimney the principal constructive details to be considered are the number, arrangement and size of the flues and the height of the chimney. Every fireplace should have a separate flue extending to the top of the chimney. Two or three stoves, however, may be connected with one flue if it is of suflicieht size, and the kitchen range may be connected with the furnace-flue without bad results, and often the draught of the furnace will be benefited thereby. For ordinary stoves and for a small furnace an 8 by 8 inch or a 9 by 9 inch flue, depending upon the way the bricks are laid and bonded, is sufli- * Figs. 230 and 231 are taken from The Brichhnilder by permission, t Suitable sizes for flues for house heaters are given in tables in the "Architect's and Builder's Pocket-Book." Frank E. Kidder. 334 BUILDING CONSTRUCTION. (Ch. VII) (ciently large if built so that it is smooth on the inside; but it is generally better to make furnace-flues 8 by 12 inches or 9 by 13 inches and the fireplace-flues, also, the same size, except those for very small grates. . ^ The best smoke-flue is one built of bricks and lined with fire- clay tiles, or else one made of a galvanized-iron pipe supported in the middle of a large brick flue. When the latter arrangement is used the space surrounding the smoke-pipe may be used for ventilating the adjoining rooms by simply putting registers in the walls of the flue. When galvanized-iron smoke-pipes are used the metal should be Fig. 231. — Roman Method of Brick-and-concrete \'ault Construction. at least No. 20 gauge, and No. 16 gauge for boiler-flues. Even then the pipes are liable to be eaten away by rust or acids within ten or twelve years. Fire-clay flue lining, on the other hand, is imperishable. Smoke-flues are sometimes made only 4 inches wide. Such flues may work satisfactorily at first, but they soon get clogged with soot and fail to draw well, and should never be used unless it is impracticable to make the width greater. Flues smoke or draw poorly oftener on account of the insufli- cient height of the chimney than from any other cause. A chimney should always extend a little above the highest point of a building or of buildings adjacent to it, as otherwise eddies formed by the wind may cause downward draughts in the flues, making them MISCELLANEOUS DETAILS. 385 smoke. If it is impracticable to carry a chimney above the highest point of a roof, it should be topped out with a hood, open on two sides, the sides parallel to the roof being closed. The walls and the zvithcs, or partitions, of a chimney should be built with great care, the joints carefully filled with mortar and when there is no lining the joints should be struck and the I ft ■ I inside surfaces made as smooth as J I I L^g''^'^f possible. I I Specifications sometimes call^ for H| I I |H . flues plastered smoothly on the inside I I with Portland cement, both to prevent mm J & sparks from passing through the walls ^ ^ and to increase the draught ; and in England chimneys were formerly plastered with a mixture of cowdung and lime mortar, which was called "pargetting." Portland cement is not affected by heat and is the best ' material for this purpose. Many building laws, Uowever, for- bid the plastering of the fliie surfaces on account of the tendency of the plaster to fall ofif in places, carryings with it pieces of mortar from the joints of the brickwork and increasing the chances of sparks passing through. In building a chimney more or less mortar and also pieces of brick are sure to drop into the flues, and a hole should be left at the bottom of each one, with a board stuck in on a slant, to catch the falling mortar. After the chimney is topped out the board and mortar should be removed and the hole bricked up. If there are bends in a flue openings should be left in the walls at those points for cleaning out any bricks and mortar that may lodge there. The outer walls of chimneys should be 8 inches thick, unless flue linings are used, in order to prevent the smoke from being chilled too rapidly. Fig. 232. — Brick Chimney Flues for jL iirnace and Fireplaces. MISCELLANEOUS DETAILS. 387 During the construction of a building the architect or superin- tendent should be careful to see that no woodwork is placed within I inch of the walls of any smoke-flue, and that all flues are smooth through their entire length. The arrangement of chimney Hues is ordinarily very simple. Fig. 232 shows the ordinary arrangement of flues in a chimney con- , taining a furnace-flue, fireplaces in the first and second stories, and an ash-flue for the second-story fireplace. Fig. 233, from Part 11. of ''Notes on Building Construction,"* shows the arrangement of the flues in a double chimney, with fire- places in five stories. Radial Block Chimneys. — There are several systems of con- structing high factory chimneys by special forms of blocks, radial or otherwise. Among those who make a specialty of such work are the Alphonse Custodis Chimney Construction Company, New York; H. R. Heinicke, Inc.. New York; George H. Thirsk, Philadelphia. 375. BRICK FIREPLACES.— r/z^- Rough Opening.— In build- ing a fireplace, no matter how it is to be finished, it is cus- tomary first to build a rough opening in the chimney from 6 to 8 jnches wider than the intended width of the finished opening, and I or 2 inches higher, drawing in the bricks above to form the flue, as shown in Figs. 232 and 233. The front wall of the chimney, over the opening, may be supported by a segmental arch when there are sufficient abutments ; but when the side walls are only 4 or 8 inches thick heavy iron bars should be used to support the brick- work. The depth of the rough opening should be at least 12 inches, to permit of an 8-inch flue. When there are fireplaces the bottom of the chimney is usually built hollow so as to form a receptacle for the ashes f tom the grate, as shown in Fig. 234. If the fireplace is to be used fre- quently an ash-pit is almost a necessity, especially in residences, and it should always be provided when practicable. When the fire- place is above the ground floor a flue can generally be built to connect the bottom of it with the ash-pit. In the chimney shown in Figs. 232 and 234 the ash-flue is built back of the lower fireplace. When there is no furnace-flue the ash-flue can be carried dovv^n on one side of the lower fireplace, thereby saving 4 inches in the thick- * Rivington's South Kensington Series. 388 BUILDING CONSTRUCTION. (Ch. VII) ness of the chimney. One ash-flue will answer for several fire- places. A cast-iron door and frame, usually about lo by 12 inches, should be built in the bottom of the ash-pit so that the ashes can be removed. The ash-pit, rough opening and flues form the chimney, and are all built at the same time by the brick- mason, who builds the trimmer arch also. The Trimmer Arch. — In buildings with wooden floor construction each fireplace hearth is usually supported by a "trim- mer arch," commonly 2- feet wide by the width of the chimney in length, turned on a wooden center from the chimney to the joist header, as shown in Fig. 234. The wood center is put up by the car- penter, one side being supported by the header and the other by a projecting or by flat the brick course on the chimney pieces of iron driven into Although not needed for support after the arch has set, the center is generally left in place to afford a nail- ing for the laths or furring strips on the ceiling below. Sometimes a flagstone is -Section Through Brick Fireplace, Chim- ney Flues and Ash-pit. hung from the joists to sup- port a hearth, but a stone generally costs more than an arch, and in the opinion of the author is not as good, as the arch will adjust itself to slight settlements in the chimney, and is not affected by any shrinkage of the floor joists. The Finished Fireplace. — After a building is plastered the finished fireplace is built, usually by the parties furnishing the material, unless it is brick, when the work may be done by any- skilled brick-mason. At the present time the larger number of fireplaces are probably built with fire-brick linings and tile facings and hearths, with wooden mantels, after the manner shown in Figs. 234 and 235. In building such a fireplace the hearth is first levelled up with brick or MISCELLANEOUS DETAILS. 389 concrete, after which the hearth and the ''imder-fire" are laid, the metal frame at the edge of the opening set up and the lining and the backing for the tile facing built. After this work is completed the tile facing is set, and when the mortar has dried out, the mantel, if of wood, is set against it. Glazed tiles are usually employed for the hearth and facings, and they should always be set in rich Port- land cement mortar. The sides of the linings forming the fire-box should be bevelled about 3 inches to the foot, and the back should be brought inward at the top, as shown, so that the opening into the flue will be only about 3 inches wide. The opening is called the Chimney Plastered. Chimnei) Furred Fig. 235. — Sections Through Fireplace, Linings, Furrings, Mantel, etc. ''throat," and its proportions determine in a great measure whether the draught will be good or bad. A damper should always be provided for closing the throat. The simplest arrangement is a piece of heavy sheet-iron with a ring on the edge, as shown at A, Fig. 234. It may be operated by the poker. A much better device, and one now quite frequently used, consists of a cast-iron frame with a door which may be pushed back to give the full opening. The door has a sliding damper also suffi- cient to let ofif the gases after the fire is well started. This device can be obtained of most mantel dealers, and generally insures a good draught. A small cast-iron ash-dump, also, should be placed in the bottom of the fireplace when there is an ash-pit. The Grates. — There are a great many styles of grates that may be used in fireplaces. In one such as has been just described the ''club-house" grate is probably most frequently used in localities where soft coal is burned. It consists of a cast-iron grate supported by four legs, and with an ornamental front about 6 inches high. It has no back or sides, and should fit close to the fire-brick lining. There is also a movable front to close the opening beneath the grate. These grates are well adapted to soft coal or coke. 390 BUILDING CONSTRUCTION. (Ch. VII) For fireplaces that are to be frequently or steadily used a narrow opening, about 21 inches, is most desirable, as wider openings are very wasteful of coal. Fireplaces in which wood is to be burned may have openings up to 4 feet wide, 3-feet openings being quite common. Wood is gen- erally burned on andirons. Fig. 236. — Details of a Large Brick-and stone Fireplace. stcTion For burning hard coal, especially in ornamental fireplaces, basket- grates, having open fronts and solid backs and ends, are often used. They are made of various sizes and may be used in any fireplace. One of the most practical devices is the "portable fireplace," which is a complete cast-iron fireplace with fire-box, dampers, shaking grate and separate front piece for summer. It can be set in any opening of suitable size, and is sure to draw well if the flue is reasonably large and high. These fireplaces are finished with MISCELLANEOUS DETAILS. ornamental frames about 3 inches wide, in different finishes, and can be used with tile, marble or brick facings. They are made with 20 and 24-inch openings. Brick-and-stonc Fireplaces. — Fig. 236 shows the details of a large brick fireplace in which stone is used for the hearth, base, keystone, shelf and brackets. In the Middle West and Northwest fireplaces of this kind are very common, and are used in large living- rooms or halls. They are designed to burn large wood logs and have openings of sufficient width and depth to receive several at one time, and to receive them back of the line of the throat to prevent smoke from coming out into the room. The throat is made narrow and long, with a shelf above, made flat as shown, and forming the top of the throat corbelling. This shelf extends back to the inside face of the outer wall so as to assist in preventing down draughts. The walls of the chimney flues are made not less than 8 inches thick, unless they have tile flue-linings, in which case they are fre- quently reduced to 4^ inches if the height permits. The ash-flue leads to the ash-pit in the cellar, and in case there is a fireplace above on the second floor connected with the same chimney, the ash-flue from this fireplace also is carried down as shown along- side the first-story fireplace and into the same ash-pit. A large fireplace is sufficient to amply ventilate a very large room, and even all the rooms of an entire story of a moderate- sized house in which the communicating doors are left open. A fireplace may be built also with pressed-brick facings, with either a square or an arched opening, and with a wood mantel set against it, the same as with tile facings. If wood is to be burned, pressed bricks may be used for the linings also, but they will not stand the intense heat of a coal fire. For the latter fire-bricks should be used for the linings. Brick and Terra-cotta Mantels. — Although brick facings in con- nection with wooden mantels have been much used, the practice does not seem to be one to be recommended, either from a practical or decorative standpoint. If brick is to be used at all, it would seem better to make the entire mantel of brick or of brick and terra- cotta. In fact there are no materials which can be used with better efifect for the finish about a fireplace than brick or terra-cotta, although they require artistic skill in the selection of the color and in their arrangement. 392 BUILDING CONSTRUCTION. (Ch. VII) The great drawback in the past in building brick mantels has been the difficulty of obtaining bricks of suitable color and accuracy of form which could be adapted to a satisfactory decorative treatment. This difficulty, however, no longer exists, as there are now several companies that make a specialty of producing brick mantels of artistic design. These arc skilfully designed with good architectural Fig. 237. — Brick and Terra-cotta Fireplace Mantel. Manufactured by Fiskc & Co. J. II. Ritchie, Designer. effects, and all the parts are accurately fitted, so that they can be easily put together by any skilled brick-mason. They are in a variety of designs and colors, and can be varied within certain limits of size to fit any particular space. The mantels of several manu- facturers are extensively used, and with very satisfactory results. In many of them the ornamentation is largely of terra-cotta MISCELLANEOUS DETAILS/ 393 Instead of molded bricks, and a special feature of this terra-cotta ornamentation is that the pieces are made in standard sizes which are interchangeable. This feature has often been utilized by archi- tects, as it affords them an opportunity of making designs to suit their own individual tastes as regards the choice and arrangements of ornamentation, by bringing together in any desired comxbination the standard interchangeable pieces, thus gaining practically all the desirable features of special designs, with the additional advantages of moderate cost and certainty of delivery. Figs. 237, 238, 239 and 240 illustrate various designs of brick Fig. 238. — Brick and Terra-cotta Mantel. Philadelphia and Boston Face-brick Co., Boston. and terra-cotta mantels. Fig. 237 is by Fiske & Co., Boston ; Fig. 238 by the Philadelphia and Bo.ston Face-brick Co., Boston; Fig. 239 by the Eastern Hydraulic-press Brick Co., Philadelphia, and Fig. 240 by Gladding, McBean & Co., San Francisco. Fig. 241 shows, on a large scale, the construction details of the molded bricks used in the arch of the mantel shown in Fig. 240. In the mantel of Fig. 237 8 by ii/2-inch bricks are used. The mantel shown in Fig. 239 is a suggestion for a chimney-piece suit- 394 BUILDING CONSTRUCTION, (Ch. VII) able for a club, hotel, railroad station or other semi-public building. The design, even to the hearth, is entirely of brickwork. This chimney-piece is about lo feet wide and lo feet 6 inches high. The fire-opening is about 4 feet wide and 3 feet 5 inches high. In the mantel shown in Fig. 240 ''Roman"-shape bricks, 8^ by Fig. 239. — Brick Chimney-piece. Eastern Hydraulic-press Brick Co., - Philadelphia. 4 by inches, are used, with ^-inch mortar joints. The following are the dififerent dimensions for this mantel : Feet. Inches. Width of breast 7 8 Height of mantel 4 10/^ Width of opening 4 4/i Length of hearth 7 8 Returns at sides : i 0% Depth of fire-box i 9 Height of opening 2 9 Width of hearth 2 i ■ Width of opening between hobs 2 9K MISCELLANEOUS DETAILS. 395 376. BRICK STAIRS. — For building- fire-proof stairs there is probably no better material than brick, unless it be Portland cement concrete in combination with metal tension bars. Brick stairs may easily be built between two brick walls by springing a segmental Fig. 240. — Design for Brick Mantel. Gladding, McBean & Co., San Francisco. arch from wall to wall to form the sofht and by building the steps on top of this arch ; or, if one side of the stairs must be open, that side may be supported by a steel I-beam, which should be protected by fire-proof tiling. This is shown in Fig. 242. The stairs in the L Fig. 241. — Detail Section and Elevation of Arch of Mantel Shown in Fig. 240. Pension Building at Washington were constructed in this way. The treads of the steps may be of hard-pressed bricks, or slate treads may be laid on top of the bricks. Iron treads are not. desirable, as they become slippery. 396 BUILDING CONSTRUCTION. (Ch. VII) Brick Spiral Stairs.— Fig. 243 shows a brick spiral staircase, of former days, in the House of Tristan, the Hermit, Tours, France. Fig. 244 shows a method of constructing spiral stairs of brick- — Details of Brick Stairs, Pension Building, Washington, D. C. work commonly employed in Madras, India. These stairs are built without any centering, and cost in Madras less than one-third as much as iron stairs. It would seem as though this construction might be advantageously employed in this country where spiral stairs MISCELLANEOUS DETAILS. 397 are to be built in fire-proof buildings. The dimensions of a typical Madras spiral staircase are about as follows : ^ Diameter of stairs, wall to wall, inside 6 feet. Diameter of newel in center i foot. Headway, from top of step to arching overhead, 7 feet inches. Risers, each 6 inches. Tread at wall i foot 2]/^ inches. Tread at newel 2)^ inches. Fig. 243. — Staircase, House of Tristan, the Hermit, Tours, France. SECTION ONAB. PLAH. Fig. 244. — Brick Spiral Stairs. Construction Used in Madras, India. Having determined the rise and number of steps in the usual way, work is commenced by building up solid two or three steps, when the arch is then started by ordinary terrace bricks, 5 by 3 by i inch, in lime mortar (i>2 parts slaked lime to i of clean river sand). The bricks are put edgewise flat against one another, with their lengths in radii from the center of the stairs, and are simply stuck to one another by the aid of the mortar without any centering. These arch bricks are arranged as shown at S , the soffit being a continuous incline, as shown in the section CD. A slight rise, about inches, is given to the arch as shown in the section. For forming the steps over this arching ordinary bricks are used, usually 398 BUILDING CONSTRUCTION. (Ch. VII) 9 by 41/2 by 3 inches, trimmed to position and placed on edge as at T in the plan. After a reasonable time for the mortar to harden, the work shaald bear a load of 300 pounds placed on a step and show no sign of giving. With gocrd materials the steps will bear much heavier loads.— J. M., in Indian Engi-, neering. BRICK NOGGING.— "Noggiiig" is a term that is applied to brickwork filled in between the studding of wooden partitions. Brick nogging is often employed in wooden partitions of dwellings and tenement-houses to obstruct the passage of fire, sound and vermin. As no particular weight comes upon the bricks, and as they are not exposed to moisture, the cheapest kind of bricks may be used for this purpose. The bricks should .be laid in mortar, as in 4- inch walls. If a partition is to be lathed W'ith wooden laths it is necessary that the width of the bricks shall be not quite equal to that of the studding, in order to allow for the clinch of the plaster. When 3^-inch studding is used it will be necessary either to clip the bricks or to lay them on edge. ' When the studding of a partition rests on the cap of the partition below, it is an excellent idea to fill in the space between the floor and the ceiling below with nogging to prevent the passage of fire and mice ; and two courses of bricks laid on horizontal bridging is also a good method of preventing fire or vermin from ascending in a par- tition. 378. CLEANING DOWN BRICKWORK.— Soon after the walls are completed all pressed or face-brick should be washed and scrubbed with muriatic acid and water, using either scrubbing- brushes or corn brooms. The scrubbing should be continued until all stains are removed. At the same time all open joints under window sills and in the stone and terra-cotta work should be pointed, so that when the cleaning down is completed the entire walls will be in perfect condition. 379. EFFLORESCENCE ON BRICKWORK.— A white efflorescence often appears on walls after they have been soaked with water. There are at least three different substances that may cause this efflorescence. Of these carbonate of soda appears most frequently on new walls, and is due to the action of the lime in the mortar upon the silicate of soda in the bricks. Silicate of soda sel- dom occurs in bricks unless a salt clay is used. The only other white efflorescence of importance is composed chiefly of sulphate of magnesia, due to pyrites in the clay ; and this, MISCELLANEOUS DETAILS. 399 when burned, gives rise to sulphuric acid, which unites with the magnesia in the mortar. The above are the resuhs of investigations made by Mr. Samuel Cabot, chemist. The conclusions he arrived at are these : (1) The efflorescence is never due to the bricks alone, and sel- dom due to the mortar alone. (2) To avoid efflorescence, the bricks should be rendered imper- vious with some preservative having the property of keeping salts from exuding. Linseed-oil cannot fill the requirements, as it is injured by the mortar. In order to make brick walls impervious, howxver, it is necessary^ before coating them, to minutely examine all joints and fill all holes. It is the opinion of the writer that if reasonably hard bricks are used for facings, the joints closely examined and filled and all brick projections and exposed tops waterproofed and provided with drips, but little efflorescence will appear. 380. DAMP-PROOFING BRICK WALLS.— All brick and stone walls absorb more or less moisture, and a wall 12 inches thick .may sometimes be soaked through in a driving rainstorm. In the dry climates of Colorado, Arizona and New Mexico such storms rarely occur, and it is customary in those localities to plaster directly on the inside of the walls. In nearly all other parts of the country, however, it is desirable, for the sake of health and for economy in heating, even if not absolutely necessary, either to fur or strip the inside of solid walls with i by 2 inch strips, or to render the w^alls damp-proof, either by a coating of some kind applied to the outside of the walls, or by building the walls hollow. Furring the walls with wooden strips and then lathing on them prevents the moisture from coming through the plastering, but it does not prevent the walls themselves from becoming soaked, thereby necessitating more heat to warm a building and tending to gradually destroy the walls. A hollow wall, when properly built, is probably the best device for preventing the passage of moisture and also of heat ; but in most cases it is also the most expensive method. Brickwork may be rendered impervious to moisture either by painting the outside of the walls with white lead and oil or by coat- ing the walls with preparations of paraffine, or by some of the patented waterproofing processes. The preparations containing paraffine are usually applied hot, and the walls also are heated by a portable heater previous to the application. They give fairly good 400 BUILDING COXSTRUCTION. (Ch. VII) results, but are quite expensive, owing to the time and labor required for their application. Sylvester's process, which consists in covering the surfaces of the walls with two washes or solutions, one composed of Castile soap and water and one of alum and water, has been used w^ith much success for this purpose. A full description of the successful appli- cation of this process to the walls of the gate-houses of the Croton Reservoir in Central Park, New York, is given by Ira O. Baker in his "Treatise on Masonry Construction." All of these preparations change somewhat the color and grain of the bricks, and are generally looked upon as detracting from the appearance of the building. Boiled linseed-oil is often applied to brick walls, and two coats will prevent the absorption of moisture for from one to three years. The oil does not greatly change the color of the bricks, and generally improves the appearance of a wall which has become stained or dis- colored in any way. Common white-lead-and-oil paint is probably the best material for damp-proofing external walls above ground, but it changes entirely the appearance of the building. Painting of new work should be deferred until the walls have been finished at least three months, and three coats should be given at first ; after this one coat applied every four or five years will answer. A preparation known as "Duresco" has been used for damp-proofing with very satisfactory results. It has been used in some cases for coating the inside of the walls before the plastering is applied, to prevent the moisture penetrating the plastering, which purpose it seems to have successfully accom- plished. Diiresco, when applied to common or soft bricks, not only renders them weather-proof, but its color gives the permanent appearance for which pressed bricks are valued. It dries with a hard, uniform, impervious surface free from gloss, and does not flake off or change color.. It is put up in 56-pound kegs, that quantity being sufficient for covering 1,000 square feet with two coats. Cabot's Brick Preservative is claimed by the manufacturer to form a thorough waterproofing for brickwork and sandstone, thus preventing white efflorescence, disintegration of chimneys by frost, and growth of fungus. It does not change the natural texture of the material to which it is applied and it leaves no gloss. It has been found by actual experi- MISCELLANEOUS DETAILS. ment that one coat of this preservative makes as good a waterproof- inof as three coats of boiled hnseed-oil. The preservative is manufactured in two forms : One kind is colorless, for use on any kind of bricks, to render them waterproof and to prevent efflorescence ; and the other has red color added, to bring the bricks to an even shade without destroying the texture. This material is applied with a brush in the same way that oil is applied, no heat being necessary. To obtain the best results, the brickwork should first be washed down with acid, preferably nitric acid, to remove any efflorescence already formed. One gallon will cover about 200 square feet on average rough bricks and a little more on pressed bricks. One coat is generally sufficient unless the bricks are extremely soft and porous. To prevent moisture from penetrating the tops of brick vaults built underground, a coating of asphalt, from ^ to % of an inch thick and applied at a temperature of from 360° to 518° Fahr., seems to give the best results. Common coal-tar pitch is often used for this purpose, but is not as good as asphalt. If a vault is to be covered with soil for vegetation, the top course of bricks should be laid in hot asphalt in addition to the coating. 381. THE CRUSHING STRENGTH OF BRICKWORK.*— In the majority of brick and stone buildings the crushing strength of brickwork need be considered only in connection with piers and arches and under bearing-plates or templates. The strength of brickwork varies with the strength of the individual bricks, the quality and composition of the mortar, the workmanship and bond and the age of the brickwork. It is not the purpose here to dis- cuss the subject of the strength of materials, but it may be stated that for general practice the following safe loads may be allowed for the compressive strength of brickwork in the cases above men- tioned ; For New England or similar hard-burned bricks, in lime mortar, from 8 to 10 tons per square foot (112 to 138 pounds per square inch). For the same bricks laid in mortar composed of natural cement I part, and sand 2 parts, 12 tons per square foot (166 pounds per square inch). For the same bricks laid in cement-and-lime mortar, i to 3, 14 tons per square foot (194 pounds per square inch). * Further details on this subject may be found in the "Architect's and Builder's Pocket-Book," by Frank E. Kidder. 402 BUILDIXG COXSTRUCTION. (Ch. VII) For the same bricks laid in Portland cement and sand mortar, i to 2, 15 tons per square foot (280 pounds per square inch). Average hard-burned Western bricks, in Louisville cement mor- tar, I to 2, 10 tons per square foot. For the same bricks laid in Portland cement mortar, i to 2, 12^ tons per square foot (175 pounds per square inch). In computing the safe resistance of brickwork from actual tests of the ultimate strength of work of the same kind, a factor of safety of at least 10 should be allowed for piers and 20 for arches. Piers higher than 6 times their least sectional dimension should be increased 4 inches in size — that is, in their lateral dimensions — for each additional 6 feet in height. In most cities the maximum permissible loads for dif¥erent kinds of masonry are fixed by the building laws. It should always be remembered that the strength of brick piers depends largely upon the thoroughness with which they are bonded, and the building of all piers should be carefully watched by the superintendent. 382. MEASUREMENT OF BRICKWORK.— Brickwork is generally measured by the one thousand bricks laid in the wall. The usual custom of brick-masons is to take the outside superficial area of the wall, the corners being measured twice, and multiply it by 15 for an 8 or 9-inch wall, by 22^ for a 12 or 13-inch wall and by 30 for a 16 or 18-inch wall, the results giving the number of bricks. These figures give about the actual number of bricks required to build the walls in the Eastern States, but in the Western States, where the bricks are larger, they give about one-third more than the actual number of bricks contained in the walls, and the price is regu- lated accordingly. During the author's experience, in both the Eastern and Western States, he has never known any deviation made from these figures by brick-masons. In the West two kinds of measurements are known, kiln count being used to designate the actual number of bricks purchased and used, and wall measure, the number of bricks there would be on the basis of 22^ bricks to every superficial foot of a 12-inch wall. No deduction is made for openings of less than 80 superficial feet, and when deductions are made for larger openings the width is measured two feet less than the actual width. Hollow walls are measured as if solid. Footings are generally measured in with a wall by adding the * SUPERINTENDENCE OF BRICKWORK. 403 width of the projections to the height of the wall. Thus — if the footings project 6 inches on each side of a wall, i foot is added to the actual height of the w^all. A chimney-breast or pilaster is measured by multiplying the girth of the breast or pilaster from the intersections with the wall, by the height, and the product thus obtained by the number of bricks corre- sponding to the thickness of the projection. Flues in chimneys are always measured solid. A detached chimney or chimney-top is measured the same as a wall having a length equal to the sum of one long side and the two ends of the chimney, and having a thickness equal to that of the chimney. The rule for independent piers is to multiply the height of each pier by the distance around it in feet aud to consider the product as the superficial area of a wall whose thickness is equal to the width of the pier. In practice many masons measure only one side and one end of a pier or chimney. Arches of common bricks over openings of less than 80 super- ficial feet are usually disregarded in estimating. If an arch is over a larger opening the height of the wall is measured from the spring of the arch. No deduction is made in wall measurement for stone sills, caps or belt-courses, nor for stone ashlar, if the same is set by the brick-mason. If the ashlar is set by the stone-mason the thick- ness of the ashlar is deducted from the thickness of the wall. Custom varies somewhat in the measurement of brickwork, and when work is done "by the thousand in the wall," the contract should state distinctly how the work is to be measured, and if deductions are to be made for the openings and stonework. Some builders reduce all the brickwork to cubic feet and estimate the cost in that way for common brickwork. 5. SUPERINTENDENCE OF BRICKWORK. 383. DETAILS REQUIRING SPECIAL ATTENTION.— The various portions of the work that require special superintend- ence have been mentioned in describing the manner of doing the work. In general the particular details in which brickwork is com- monly slighted are the wetting and the laying of the bricks. The importance of wetting the bricks is fully set forth in Article 343. In laying the bricks it is often difficult to get the masons to use sufificient mortar to thoroughly fill all the joints and to get them to 404 BUILDING CONSTRUCTION. (Ch. VII)* ''shove" the bricks. The quaHty of the mortar should also be fre- quently examined, as brick-masons in some localities like to mix a little loam with the sand to make the mortar ''work well." The bonding of the walls should be watched to see that the bond courses are used as often as specified. The bonding of piers should be particularly looked after. The laying of the face-bricks and ornamental details requires more skill, but is not so apt to be slighted as are the backs of the walls. The superintendent should also see that the dimensions of the building are properly followed, that openings are left in their proper places, and that the courses are kept level and the walls built plumb. In very high stories, and particularly in those of halls and churches, the walls should be stayed with temporary braces until the permanent timbers can be built in. It is also important to see that all bearing-plates are well bedded, all floor-anchors securely built in, all recesses for pipes, etc., which are marked on the plans, left in the proper places and all smoke-flues and vent-flues smoothly plastered. Chapter VIII. Architectural Terra-cotta. 384. COMPOSITION AND MANUFACTURE.— Terra-cotta is composed of practically the same material asjDricks, and its char- acteristics, as far as the material is concerned, are the same. Terra- cotta, however, requires for its successful production a much better quality of clay than is generally used for bricks, while the process of manufacture is entirely different. The first consideration in the manufacture of terra-cotta is the selection of the material. No one locality gives all the clay required for first-class material, and each shade and tint of terra-cotta requires the mingling of certain clays from different localities to regulate the color. A great variety of excellent clays are mined in Northern and Cen- tral New Jersey, large quantities being marketed annually for mak- ing terra-cotta, as well as for fire-bricks, pottery, tiles, etc. The color varies from light cream to dark red. A partial vitrification of the body is desirable, but a clay that is too fusible causes warping in the kiln. To overcome this tendency to twist, one at least of the component clays should be highly refrac- tory, and to further insure straightness, from 20 to 25 per cent of ground burned clay called ''grog" or ''chamotte" should be added. The clay after being mined is sometimes seasoned before being delivered to the factory. After being received, any one of several methods is employed to thoroughly grind and mix the clay with grog and water, and usually it is finally tempered in a pug-mill before being sent to the pressing room. If several pieces of terra-cotta of the same size and shape are required, a full-sized model of plaster and clay is first made, and from this a plaster mold is taken. In the making of these models and molds the highest grade of skilled labor is required. When the molds are dry they are sent to the pressing department ; here the plastic clay is pressed into the molds by hand, and when partially dry the work is turned out on the floor. The ware is then ready for 405 4o6 BUILDING CONSTRUCTION. (Ch.VIII) the carver or modeller, if it is decorative work that requires the use of their tools ; or for the clay finisher if it only requires undercutting or some special work to make it fit in with other construction. The work is carefully dried on the drying floor or in the dryers and is then ready to receive the surface treatment. This is done by spraying on the surface of the terra-cotta, by means of com- pressed air and an atomizer, a thin "slip" or liquid mixture which, when burned, give^ the terra-cotta a surface which is vitrified, full-glazed, etc., as the case may be. This operation also gives the terra-cotta greater evenness in tone and its exact shade of color, the body colors used being comparatively few, while the surface colors are almost without limit. It is then put into the kilns, where it remains from seven to fifteen days, according to the size of the kiln, before it is ready for use. The kilns used are the down-draught, beehive-shaped kilns, and an inside lining or "muffle" is used to prevent the flames from coming in direct contact with the terra-cotta. In this drying and burning process all the water in the clay is expelled, and in conse- quence, a shrinkage in the size of the pieces takes place. This shrinkage is about one inch to the foot, for which allowance is made by the draughtsman, who makes the drawings for the mold-maker. The pieces are then carefully inspected, fitted and numbered, in accordance with setting drawings prepared for that purpose. The fitting operation consists in placing the various pieces in the relative positions which they would have in the building, and then by the use of the chisel, in trimming joints where necessary, so that the pieces will all fit accurately together. By the use of the rubbing- bed, the joints are rubbed to an absolutely straight line in the same manner that stonework is rubbed. The rubbing of the joints is of great advantage in ashlar-work, as it insures absolute alignment of the joints. The numbering operation consists in marking each piece with a number for identification. A corresponding number is placed on the setting drawings. The work is then finally shipped to the building. If only one or two pieces of terra-cotta are to be made, or if no repetition is intended, no molds are used, the clay being modelled by hand, with the use of templates, into the required shape. Single pieces of modelling are worked up on ashlar and plain blocks. The finished product thus bears directly the impress of the modelling ARCHITECTURAL TERRA-COTTA. 407 ^artist. It can be studied, improved or modified, and, when entirely satisfactory, burned. On this account terra-cotta possesses, for highly decorative work, an advantage over all other building materials. Terra-cotta has this advantage even where repetition is intended and molds are made, because the ornamental portions of the models are made of clay, which under all circumstances is the best material that can be used for modelling purposes ; they can therefore be studied and improved before the molds are made. The architect sometimes examines the models in person, and the alterations are then made directly under his eye. Sometimes photographs are made and sent for his inspection and approval. If the ornament is of sufficient importance to make it desirable to bear the direct touch of the modelling artist, he can retouch each piece after it is turned out of the mold. • Terra-cotta is usually made in blocks from 24 to 30 inches long, from 6 to' 12 inches deep and of a height determined by the char- acter of the w^ork. To save material and prevent warping, the blocks are formed of an outer shell, connected and braced by partitions about inches thick. The partitions should be arranged so that the spaces do not exceed 6 inches, and should have numerous holes in them to form clinches for the mortar and brickwork used for filling. 385. THE SURFACE OF TERRA-COTTA.— The body of all good terra-cotta is very much the same, but there are several ways of treating the surface, resulting in products which may be classified as follows : Standard Terra-cotta, Vitreous Surface Terra-cotta, Mat-glazed Terra-cotta, Full-glazed Terra-cotta and Polychrome Terra-cotta. Standard Terra-cotta has no surface given it, which affects its porosity, a drop of water placed upon it being soon absorbed. It will absorb, also, a great amount of dirt from the atmosphere and will become very much darker from continued exposure. On some buildings this "weathering down" is not objectionable; in fact it sometimes lends a charm, producing an antique appearance which is often very desirable from an artistic point of view. Someone has said that "time is the greatest artist," and therefore, when it is desired to produce an aged effect, Standard Terra-cotta should be used. It is, consequently, a good material to use for "rustic work," in connection with country houses, college buildings, gateways, cer- 4o8 BUILDING CONSTRUCTION. (Ch. VIII) tain styles of churches, etc. This class of material is made in any color desired. Vitreous Surface Terra-cotta has a very thin spray on the surface which vitrifies in the burning process, forming a thin glaze which sheds water. This terra-cotta will not absorb much dirt from the atmosphere, as the rain of each storm washes it off ; it therefore practically retains its original color. This class of material is made in any color desired and is used more than any other kind at the present time, as it seems to satisfy the greatest number of require- ments. The 'Tlatiron" Building, New York, D. H. Burnham & Company, architects, was of this material. Mat-glazed Terra-cotta. — In Western cities where soft coal is used, and where, consequently, most buildings are cleanecf about once every year, any material of a non-porous nature is very desir- abre ; and it has been found that glazed terra-cotta ranks with the most superior materials in this respect. On this account white glazed terra-cotta is used to a great extent in these cities. The luster of the glaze is deadened for artistic reasons, the glare of the sunlight on full-glazed terra-cotta being very severe. This is now done in the process of burning, as it has been found that sand- blasting the material neutralizes the purpose of the glaze ; and this method has long been abandoned by the leading manufacturers. There are m_any examples of buildings constructed of this material in the West, and the most notable example in the East is the Plaza Hotel, Fifty-ninth Street, New York, H. J. Hardenburg, architect. Full-glazed Terra-cotta. — For light-courts, loggias to office- buildings, theatres, interiors of railroad stations, ferry-houses, train-sheds, natatoriums,* power-houses, etc., the full-glazed terra- cotta is preferable, as it helps illumination and gives a more brilliant effect. Polychrome Terra-cotta. — The full-glazed terra-cotta and mat- glazed terra-cotta are made in any color required, and when various colors are used on the same building the material is termed ''poly- chrome." The various colors may be applied to the same piece if desired, or each separate color may be kept on a separate piece, if the design will permit. The next article, 386, ''Color of Terra- cotta," explains the uses to which this class of material may be put. 386. COLOR OF TERRA-COTTA.— Within the past twenty ARCHITECTURAL TERRA-COTTA. 409 years a great impetus has been given to the production of special colors in architectural clay products. In 1885 fully four-fifths of the terra-cotta produced in the United States was red; now (in I9q3) there is less of red used than of almost any other color. Buffs and grays of several shades, white and cream-white and the richer and warmer colors of old-gold and brown are now the prevailing colors. By the use of ceramic colors almost any required tone may be produced and the effect obtained by using glazed terra-cotta of various colors in combination, such as blue, yellow, white, purple, brown, old-gold, green, red, etc., is often very beautiful. If any particular shade of color not included in the manufacturer's standard samples is desired, the architect should consult with the manufacturer, who will then experiment until the required color is not only produced, but guaranteed to be permanent and free from all tendency to crack cr craze. It is quite generally agreed that there is a great field for this polychrome terra-cotta, especially for theatres, restaurants and buildings of a similar nature ; for interiors, loggias, fountains, etc. ; for department-stores, when a striking design is required for advertising purposes ; and for certain styles of church work. Although the art of using colored terra-cotta is very ancient, having been in practice before the Christian Era, it is, to some extent, an undeveloped field in this country and offers alluring possibilities in architectural design and construction. It can be used in a very modest and sparing manner, as well as very profusely; and either in soft tints or in brilliant colors, as the taste of the architect may dictate. Where a rich decorative treatment is required, as in the interiors of large public buildings like our great union-stations, hotels, theatres, etc., polychrome terra-cotta can be employed most effectively and economically. In variety and beauty of tones, polychrome terra-cotta has now reached a very high standard of excellence, and may be used by the architect to express the highest type of his art. The almost un- limited possibilities presented by the judicious application of colored glazes for exteriors, as well as for interiors, has awakened an unusual interest in the use of polychrome terra-cotta, a building material with superior qualities of resistance against the deterio- rating effects of time and of the action of fire and frost. Under the direction of some of our most noted architects a large 410 BUILDING CONSTRUCTION. (Cii.VIII) amount of this polychrome terra-cotta has been produced during the last few years, and the following are some notable examples Academy of Music, Brooklyn, Herts & Tallant, architects ; Madison Square Presbyterian Church, Madison Square, New York. McKim, Mead & White, architects; Statler Hotel, Buffalo, N. V. ; Essenwein & Johnson,, architects ; Munsey Building, Washington, D. C, McKim, Mead & White, architects; St. Ambrose Church, Brooklyn, N. Y., Geo. H. Streeter, architect ; Seminary for the Society of Redemptorist Fathers, Esopus, N. Y., F. Joseph Untersce, architect; the New York Subway Stations, Heins & La Farge, architects; the Hudson Terminal Concourse, New York, Clinton & Russell, architects ; a number of railroad stations, New York, New Haven & Hartford Railroad, Cass Gilbert, archi- tect ; and the Automobile Club of America, New York, Ernest Flagg, architect. In the West, abo, colored terra-cotta is being used to a great extent. Polychromatic .ornamient like that of the Madison Square Presbyterian Church, New York, and the Brook- lyn Academy of Music, would seem to demonstrate that our climate and atmosphere are well adapted to the use of polychrome exterior construction, especially when produced in glazed tile or terra-cotta. 387. USE OF TERRA-COTTA.— Terra-cotta is not imitation stone and should not be used as such. It is a material having peculiar qualities which give a distinctive character, and therefore, to be successfully used, it should be em- ployed in such a way that its individual characteristics will be expressed, and not in such a way that it will appear as an imitation of, or as a cheap substitute for, some more expensive material. This may be brought about in several w^ays. There may be used certain architectural forms and certain styles of ornament more character- istic of terra-cotta than of any other material. One architecty has evolved a certain style that he has applied to many buildings, and which is not suitable to any material other than terra-cotta. This may be said of both the form and ornamentation of his buildings. The architects $ of the 'Tlatiron" Building and of the Wanamaker Building in New York have successfully used this material for its own sake and not as an imitation. Another firm of architects§ have * The polychrome terra-cotta for the buildings mentioned was made by the Atlantic Terra-cotta Company, J\ew York. This company rendered most valuable assistance in the rewriting of this chapter. t Mr. L. H. Sullivan, Chicago. t I). H. Burnham & Co., Chicago. § McKim, Mead & White, New York. ARCHITECTURAL TERRA-COTTA. 411 used profusely modelled terra-cotta to produce highly ornamental effects not' so easily obtainable in other materials, and their recent use of colored terra-cotta is typical of this material alone. In the West Street Building, New York, the architect* has made a design distinctly expressive of the material used, viz. : terra-cotta. This is noticeable in the ornamentation, in the form of cornices and molding, in the coloring and even in the plain shaft of the building. In the Brooklyn Academy of Music the architectsf have accomplished this result by the use of color. In regard to the use of colored terra-cotta, it has been said that ''it is by the use of polychrome terra-cotta that the material has its best opportunity for expressing its individual character. It was so in antiquity, in the Middle Ages, and is so at the present time, because polychrome terra-cotta is a material complete in itself, and used for its own sake ; and it cannot by any means be considered in imitation of, nor a substitute for, something better." 388. DURABILITY. — The principal value of terra-cotta lies in its durability. When made of the right materials and properly burned it is impervious to water, or nearly so; and when glazed it is absolutely impervious, and hence not subject to the disintegrating action of frost, which is a powerful agent in the destruction of stone. It does not "vegetate," as is the case with many stones. The ordinary acid gases contained in the atmosphere of cities have- no effect upon it, and the dust which gathers on the moldings is washed away by every rainfall. Underburned terra-cotta does not possess these qualities to so high a degree, as it is more or less absorbent. Another great advantage possessed by terra-cotta is its resistance to heat, which makes it a most desirable material for the trimmings and ornamental work in the walls of fire-proof buildings. Although terra-cotta has been used in this country for but a com- paratively short time, it has thus far proved very satisfactory, and the characteristics above indicated would point to its ranking, in common with the better qualities of bricks, with the most desirable of building materials if, indeed, it is not the most durable of all building materials. In Europe there are numerous examples of architectural terra- cotta which have been exposed to the weather for three or four * Mr. Cass Gilbert, New York, t Herts & Tallant, New York. 412 BUILDING CONSTRUCTION. (Ch.VIII) centuries and which are still in good condition, while examples of stonework, subjected to the same conditions, are more or less worn and decayed. "There is at the Louvre in Paris, to-day, some glazed terra-cotta said to have been made by the Assyrians in the sixth century before Christ, and in other museums there are some vases and other ancient terra-cottas from Egypt and Greece, as well as the famous Lucca Delia Robbia work made in the Middle Ages, many of these pieces being as perfect as if recently made. All these ancient terra- cottas tell the story of durability and proclaim terra-cotta to be a material worthy of the genius of those artists of antiquity who wrought so beautifully in this sympathetic medium. "Specimens made two thousand years ago have been found in the ruins of ancient buildings in an almost perfect state of preservation, v^hile the stones among which they have been found have long since crumbled away from their original size and shape." 389. INSPECTION.— A sharp metallic, bell-like ring and a clean, close fracture are good proofs of homogeneity, compactness and strength. Perfection of form is in the highest degree essential, and can result only from a homogeneous material and a thorough and experienced knowledge of firing. No spalled, chipped or warped pieces of terra-cotta should be accepted, and the pieces should be so hard that they will resist scratching with the point of a knife. The blocks should be of uni- form color also, and all moldings should come together perfectly at the points. Terra-cotta with a vitreous surface and mat-glazed terra-cotta should be so non-absorbent that water will lie in drops on its sur- face without being quickly absorbed. Full-glazed terra-cotta should be so non-absorbent that ink will not penetrate the surface and may be entirely washed away with water. 390. LAYING OUT TERRA-COTTA.— On account of the manner in which terra-cotta shrinks in the drying and burning process, it always has a tendency to warp and to vary in size. By careful methods in manufacture these tendencies are kept under control to a great extent, but it is always best in jointing terra-cotta to arrange the joints so as to provide for the adjust- ment of any such inaccuracies. Figure 245*, showing a terra-cotta * Courtesy of the Atlantic Terra-cotta Company, New York. ARCHITECTURAL TER^RA-COTTA. 413 doorway with hidden joints, illustrates a system of back joints to provide for such adjustment. If any piece of the jambs or ashlar shrinks too much, or too little, there is an edge on that piece that - EL£ VAT 1^/1 ~ -y^CrUOM' ' PLAN A A - ' D£TAJ L^J/7I/^T fo concccd rr^^iy of fbe Joujti • jiOiJifcl* - Thit rodlyod of joiijifvnj • cooeefcU njifcnjf joiofi u