4 Me : | ( FOREWORD HIS publication is the result of the active co-operation of architects, slate producers and | Ree roofing contractors, governmental departments, manufacturers of accessories and many individual authorities. To all of these The National Slate Association ex- presses ils sincere appreciation of their support and interest. The essence of all this information supplied to the Association and to the Structural Service Bureau and its consulting architect, has been incorporated in the book to the fullest extent possible. In offering this handbook on slate roofs the National Slate Association has been actuated by the desire to supply reliable and definite information on slate and its proper application. It is hoped that this publication will make for the more extensive and appropriate use of slate as a practical, economical and attractive roofing medium besides supplying information on formation and quarrying to users of this invaluable and most unique stone. For the further benefit of the industry and of all specifiers and users of roofing slate, recom- mendations concerning the arrangement and contents, which may make later editions of this publication of even more practical use or widen its scope, will be received with appreciation by NATIONAL SLATE ASSOCIATION 791 Drexel Building Philadelphia, Pa. Each illustration in this book has been carefully selected from the large number of photographs available for the sole purpose of making clear some particular point in the teat. Vor this reason the names of the Architect, Slate Producer and Contractor have been omitted, but can be furnished by the Association if desired. First Edition This is the Second of a Series of Informative Literature on Slate and Its Uses. ““ Slate Roofs” J 1996 The First—‘‘Charm of Slate Floors and Walks’’— Published January, 1925. P Z anuary, ae Copyrighted and Printed in U.S. A. rice, $1.50 H. T. Lindeberg, Architect A Picturesque Slate Roof DIGEST OF CONTENTS (For Complete Index See Page 83) COMPLETE AUTHORITATIVE AND PRACTICAL DATA, DRAWINGS AND SPECIFICATIONS ON ROOFING WITH SLATE Characteristics Color—Basic list, etc. American Roofing Slates Description, where quarried, etc. Grading Commercial Standard Quantity per square Sizes Thickness Weight Nail holes SAS TEN OMe ALC Mey che acts We Ys ip soa, f wgin crs se eon ee 14 Standard Details, Drawings and Descriptions Lap and Exposure Ridges Hips Valleys Eaves and Gables Less expensive methods of slating Roofing Felt: Recommended weights Laying Elastic Cement: Where to use Nails: Recommended grades, sizes, etc. Tables of lengths and gauges Tel ae latin sme rc ie che secre we a Valsiaue s wis 8 Din Materials described and essential data and tables Sizes, gauges Complete detail drawings Rule for estimating, etc. RooteConstrictlonest eee eae ee 34 Handy Rafter Tables for determining size of rafter for given spans and spacings Gonstenction: Detallaye ise oe eee ce en eee ee ae 40 Sheathing or Roof Boards Round Valley Foundation Fireproof Construction Geénetall Datacenter eee Pees tart 42 Roof Slope, diagram and text Eaves Troughs, Gutters and Conductor Pipes Simplified Sizes and Weights Snow Guards Roofs and their Parts Piling Slate Estimating Slate Quantities and Costs SLandardespecliicationemmmm te sere. My ei een de. 48 Complete and Short Forms M—Metal Work S—Standard Slate Roof T—Textural Slate Roof G—Graduated Slate Roof Flat Slate Roofs Specificational data on successful installations Reroofing with Slate Recommended Practice and Suggestions Generals Datavomolate seis ete cs ee oss 71 History and Origin Geological and Chemical Formation Tables Mineral Constituents various slates Quarrying Possibilities in the Use of Slate By Albert Kelsey, F.A.LA. Pencil Sketches and Descriptions Index HE practical purpose of any roof is to protect the interior, the contents and the occu- pants of a building from rain, snow, heat and cold. In addition to these practical con- siderations, the roof should add to the appearance and character of the building, and the passing of time should only enhance its beauty and add to its intrinsic value. The period of usefulness of the roof will depend upon the resistance of the roofing material itself and the materials with which it.is laid to the action of the elements. To be permanent, the roofing material must be unaffected by the action of water, climatic changes and gaseous fumes in the air, and must also be fireproof. For economy, it should require no other material to preserve it. How- ever, even though the material possesses these characteristics, a permanent roof will not be secured unless it ts properly laid and its fastenings are selected for the same enduring qualities. The permanent and fireproof qualities of slate make it eminently suitable for either sloping or flat roofs. In no other roofing material will be found so many characteristics combining to offer such an alluring and indefinable variety in color, texture and line. This is easily understood when it is recalled that slate is a stone, formed by nature to serve the diver- sified uses of man. It requires no admixture of materials, domestic or foreign; it needs no heat to form it and no process to manufacture it other than the handiwork of extracting it from the ground in blocks, splitting and trimming them to the desired size and thickness. Moreover, the first cost of slate is not as great as that of many fabricated products, and with its practically negligible maintenance, it becomes the least expensive roof covering available when service and appearance are taken into ac- count. Besides annual savings in insurance rates most slates when removed from old roofs with care are as good as new. NATIONAL SLATE ASSOCIATION. SLATE ROOFS A Handbook of Data on the Constructing and Laying of All Types of Slate Roofs Slate roofs, the natural stone coverings, may be con- veniently classified as: Standard Slate Roofs. Textural Slate Roofs. Graduated Slate Roofs. Flat Slate Roofs. The following briefly describes each type of roof. More detailed information and a specification for each will be found on pages 48 to 65. Standard Roofs Standard slate roofs are those composed of slate ap- proximately 3/16” thick (Commercial Standard Slate), of one uniform standard length and width, having square tails or butts laid to a line. Slate of this type is commonly obtainable in the basic slate colors. Stand- ard roofs are suitable for any building where a perma- nent roofing material is desired at a minimum cost. It differs from other slate roofs only in characteristics af- fecting the texture or appearance of the roof, through the shape and thickness of the individual units. If desired, the butts or corners may be trimmed to give a hexagonal, diamond or “Gothic” pattern for all or part of the roof, Figure 1. Standard Roof Figure 2. Textural Roof as, for instance, on a church spire. Standard Roofs are sometimes varied by laying two or more sizes (lengths and widths) of Commercial Standard Slate on the same area. For specification see page 52. Textural Roofs The term “Textural” is used to designate those slates | usually of rougher texture than the Standard, with un- even tails or butts and with variations of thickness or size. In general, this term is not applied to slate over 38” in thickness. Varying shades are frequently used to enhance the color effect, which, with the characteristics just mentioned, add interest in line and texture to the roof design. In addition to the basic colors of the com- mercial grades, accidental colorings of bronze, orange, etc., may also be used in limited quantities. For speci- fication see page 55. Graduated Roofs The graduated roof combines the artistic features of the Textural Slate roof with additional variations in thickness, size and exposure. The slates are so arranged Silk Lee eR eOsOur es ey eee ee eka as on the roof that the thickest and longest occur at the eaves and gradually diminish in size and thickness until the ridges are reached. Slates for roofs of this type can be obtained in any combination of thicknesses from 3/16” to 114” and heavier when especially desired. The graduated slate roof presents many opportunities for variation and offers excellent possibilities for inter- esting treatment. The fact that it is especially designed to harmonize with the general character of the building of which it becomes a part or to meet exacting require- ments of construction causes it to be frequently termed the custom-made roof of the industry. Many producers and distributors maintain special design staffs to assist architects in securing the most suitable and satisfactory graduated slate roofs. These services are freely offered Figure 3. Graduated Roof to designers in the interest of better and more harmonious slate roofs. For specification see page 58. Flat Roofs Flat roofs offer a wide field for roofing slate, and are so designated whether or not they are used for “prom- enade” purposes. Slates of any thickness may be used in place of the slag or gravel as a surfacing material for the usual built-up type of roof. The body, weight and enduring qualities of slate make it highly desirable as a protection to the waterproofing beneath the surface, whether or not it is subject to traffic. Only the thicker slates are used on promenades. [or specificational data see page 62. Figure 4. Flat Roof SLATE Characteristics The principal difference between slate and other stones is the natural slaty cleavage of the former, which per- mits it to be more easily split in one direction than in others. A second direction of fracture or “scallop,” usually at right angles to the slaty cleavage, is called the “srain.” Roofing slates are commonly split so that the length of the slate runs with the grain. Slate quarried for roofing stock is of dense, sound rock, exceedingly tough and durable. Slate, like any other stone, becomes harder and tougher upon exposure than when first quarried. It is practically non-absorp- tive, tests on Pennsylvania slate showing a porosity of 0.15 to 0.4 percent. The nature of the surface after splitting is dependent upon the character of the rock from which it is quarried. Many slates split to a smooth, practically even and uni- form surface, while others are somewhat rough and un- even. As a result, a wide range of surface effects is available for the finished roof. Slate from certain localities contains comparatively narrow bands of rock differing to various degrees in chemical composition and color from the main body of the stone. These bands are called “ribbons.” Ribbons containing no injurious constituents and not of unde- sirable color are not objectionable. Slates of this type, when trimmed so that the ribbons are eliminated, are known as “clear slate.” Slates which contain sound rib- bons are sold as “ribbon stock.” NAS ele On NE Ag See AD elie wore: OL Cal Ame TOON Color The color of slate is determined by its chemical and mineralogical composition. Since these factors differ in various localities, it is possible to obtain roofing slates in a variety of colors and shades. It is truly remarkable to find a natural product pos- sessing, in addition to the other qualities before men- tioned, such unlimited possibilities in color effect. The use of slate for roofing makes it possible to obtain a surface of uniform or contrasting colors in cold or warm values. Moreover, if the design of the building requires a roof of one general color, it may be graded up or down the slope from dark to light as desired. Figure 5. Skulping Large Slate Slab To relieve the monotony of a flat uniform body color, various shades of the same color may be used to pro- vide an interesting variation up and down or across the roof or interspersed throughout. A low-eaved, promi- nent roof surface may require a quiet or contrasted blend- ing of the autumnal colors of nature to cause the structure to take its place in its intimate surroundings. Slate not only permits a roof of permanent color, but by the selec- tion of “weathering” slate, one may take advantage of the mellowing effect of age and weather. These and all the steps between these extremes are ever ready at the designer’s bidding in the field of slate. Upon exposure to the weather, all slate is changed slightly in color. The extent of this color change varies with different slate beds, being barely perceptible in certain slates. Those slates in which the color changes but slightly are classed as “permanent” or “unfading.” Those in which the final result is more marked and varied are known as “weathering” slates. Weathering is the natural result of exposure to the weather of the coloring minerals in the slate. Where color is an essential consideration, architects and owners should take this characteristic into account. The quarry operators know from experience the probable nature and extent of the changes in the original color, although dif- ferent quarries in the same state, and often in the same locality, may produce a wide range of colors in both “permanent” and “weathering” slates. To take the fullest advantage of the various effects obtainable, the source of the slate, as well as its ultimate color effect, should be known. Color Nomenclature For the purpose of utilizing the basic natural colors of roofing slate available in large quantities for general usage, The Division of Simplified Practice of the De- partment of Commerce has recommended the following color nomenclature: Basic Slate Colors Black Grey Purple Green Blue Black Blue Grey Mottled Purple Red and Green These color designations should be preceded by the word “unfading” or “weathering,” according to the ultimate color effect that may be desired. For special treatment roofs certain quarries supply other colors and combinations of colors. Many requests were received for inclusion in this book of plates reproducing slate colors. After giving full con- sideration to the various phases and possible misconcep- tion which surround color reproduction, however, it was decided not to include such plates. Some individual pro- ducers have prepared plates but much confusion has been caused by purchasers believing and insisting that each slate on their roof should be an exact match in tone and marking with the one shown in the plate. This, of course, is impracticable when dealing with the eye-resting tones nature has bestowed upon slate with such pleasing vari- ations and gradations even in the same slate and between slates. Samples of slates or color plates furnished by producers can only be taken as indicative of the color tones of certain slates. All slates would be grey, the commercially known slate color were it not for the coloring minerals present, for example, chlorite in the greens, hematite in the purples and hematite and iron oxide in the red. (See page. 75 for table of Mineral Constituents of Slate.) Dalen cl Eee hOB eS AMERICAN ROOFING SLATES Available in Commercial Quantities in All Thicknesses Unless Otherwise Noted COLOR DESIGNATION Blue-Grey Blue-Grey Unfading Grey Grey Grey-Black Blue Black—Hard Vein Unfading Black WHERE QUARRIED BRIEF DESCRIPTION Lehigh-Northampton Counties Penn- Probably the best known, most widely used and most accessible sylvania. Veins extend through entire of the basic slate colors. Sales records substantiate this fact as slate zone. Near Esmont, Virginia and the Arvonia Belt of Buckingham and Fluvanna Counties, Virginia. Northampton County, Pennsylvania. Western part Vermont, Washington County, New York. Veins extend through entire slate zone. Western part Vermont, Washington County, New York. Veins extend through entire slate zone. Chapman Quarries, Pa., and adjacent part of Northampton County, Pa. Peach Bottom, York County, Pa., and adjacent part of Maryland. Piscatsquis County, Maine. the largest shipments of commercial standard slates are made from this district. Production capacity of quarries now in opera- tion assure architects and the public of unlimited supply of this popular color. Just as it is the more generally recognized slate color so is it also the base in cost or price tables of distributors and roofing contractors and nearly all of the latter carry it in stock. Because its blue grey tones harmonize so well with nature’s other handiwork “The Blue Sky”’ may explain why it is so frequently selected for the “roof over his head”’ of every man and by architects in carrying out their effects desired. Acres of these slates have been specified and shelter vast numbers of the state, federal and other public and private institutional buildings. : To more nearly portray the true color characteristics of these Pennsylvania slates they have been designated ‘‘Blue-Grey.” Some architects and older roofers may still continue to refer to them as Pennsylvania black, but to avoid confusion and chance of receiving ‘‘Black-Bed”’ slates (Note 2) architects, builders, roofers and others are cautioned to use this classification “Blue-Grey”’ as the color designation. Some splendid color combinations have been evolved by working together the different shades of these slates, or blending them with the weathering greens of Vermont or with the clear purples where a dark under- lying tone is desired. A tough durable Slate and one which makes an especially beauti- ful roof. This slate is notable for a peculiar luster giving very attractive lights and shadows on the roof. Very popular with architects because of their soft grey tones which harmonize so well with almost any type of wall surface. Unusual transverse strength. Characterized by extremely large quartz crystals and sericite flakes. Considerably lighter in tone than Blue-Grey slates of Pennsyl- vania. In combination with clear purples provides an excellent mixture where dark value underlying tone is preferable to a singleness of color. Some weather and some are unfading. Available in light and dark shades in either plain or mottled effect. Some are unfading and some weather. Most of the grey slates are mottled by streaks of darker grey and for this reason are often used to advantage with other slates. Exceptionally hard durable slate, having one or more hard veins running across the slate. These veins produce a texture and color effect very much desired. The color tone grows darker with exposure to elements. Peach Bottom Slate generally is heavier than many other slates and has a rougher appearance, and it is of the unfading color group. Markedly graphitic. First American roofing slates quarried. Monson roofing slate, quarried in the town of Monson, Maine has long been known as one of the strongest and best roofing slates produced in this country. It is an unfading black slate having a slight lustre, available only in standard thickness of 335". Nothing over this thickness is produced except on occasional and special orders. INGA Os NGAR ee og laAG FRY avArSsS.0> Ci beAvI I OON Unfading Green Weathering Green Unfading Purple Unfading Mottled Purple and Green Variegated Purple Unfading Red Freaks Western part Vermont, Washington Available in light or dark shades. Whatever fading or weathering County, New York. Veins extend takes place is so uniform that a permanently green roof color through entire slate zone. is assured. Western part Vermont, Washington Not quarried in commercial quantities in northern part of pro- County, New York. Veins extend ducing zone. Available in light and dark shades. Exceedingly through entire slate zone. strong and tough, of excellent texture. Upon exposure to the elements some of these ‘‘weather”’ and are transformed into soft tones of brown, buff and gray while others retain their original shade. This weathering action of the elements serves to beautify a roof of this material and in no way affects the durability of the slate. They harmonize with almost any style of architecture and are used on buildings of every description. Quarries now in operation assure architects and the public an unlimited supply of this popular and most widely known and used of Vermont basic slate colors. Carried in stock by many roofing contractors. Western part Vermont, Washington Because of tremendous demand for purples in graduated roofs of County, New York. Veins extend assorted colors, it is now difficult to furnish clear purples in large through entire slate zone. quantities. Western part Vermont, Washington No two slates have exactly the same marking or colors. They con- County, New York. Veins extend sist of slightly varying shades of purples, available in light and through entire slate zone. dark tones, sometimes almost clear, frequently clouded with spots or traces of green, others with light and dark clouds of purple, while occasionally there are some having only a purplish tint that might other wise pass for Green Slate. Western part Vermont, Washington These slates are of a predominating purple tone, some having County, New York. Veins extend spots or streaks of green of varying size. In a small percentage, through entire slate zone. too, green may predominate with only tints of purple. As in the case of other weathering Vermont slates, a percentage change upon exposure to harmonious shades of brown, while others present an unchanged appearance. Washington County, New York only. The only place in the U.S. so far where red roofing slate has been found in deposits of sufficient size to insure profitable operations. Excellent in color, cleavage and strength. The color becomes more pleasing with age. A study of the price lists of slate dis- tributors shows this color as the most expensive. There are delightful combinations or variations in these colors available only for roofs of special treatment. Because of their color they have been termed freak slates. They are just what the name implies—freak slates from rock formations centuries old, of a character that will not permit splitting under 14” in thickness and from this up to 2” for architectural roof purposes. A great array of colors are available, comprising Opals, Bronzes, Buffs and Browns, and others so varied and unique that when displayed en masse one is reminded of a beautiful tapestry. They add charming contrasts and character to a roof. Some of them may not be true slate in every quality that has won for this stone its centuries of sheltering utility, but even should they have no salvage value, they have so enhanced the beauty of the building they have adorned as to fully repay the investment. Notes: (1) (3) Slates from Pennsylvania, especially in a graduated roof, are being widely used to give a wonderfully pleasing color effect by calling for a mixture of blue-black, blue-grey and grey. If so stipulated, the surface or texture may also be had rough and knarled as well as the smooth or standard finish. One other grade known as “Black Bed” is quarried occasionally in Pennsylvania. Due to an excess content of carbonaceous impurities experience has shown that after many years exposure these slates weather out and some slight discoloration and surface deterioration takes place. The members of this Association warn against the use of such slates except on temporary buildings or isolated rural dis- tricts. Through research and the strenuous efforts of the members of the Association only small quantities of such roofing slates are now available as this rock is being diverted into school slates, bulletin black- boards and other uses for which it is ideal. Considering its centuries of sheltering utilization, roofing slate presents a protection record difficult to equal and few failures of slate roofs recorded even after many years of service have chiefly been traced back to this ‘‘Black Bed” slate or other slates of high im- purity content. The demand for more careful selection of color tones in furnishing of architectural roofs has led to a more thorough analysis and inventory of the supply. Special characteristics of certain beds or veins in different or even the same quarries produce graduations of weathering tones which require utmost knowl- edge by roofer of intimate color effect desired on a roof of special treatment so that slates of this class, when used, may be obtained from a quarry which will meet the requirements as nearly as it is humanly possible to be predetermined. Inventive genius some time may eliminate the uncertainty of forecasting or knowing exactly the ultimate color to which slates may weather. The U. S. Bureaus of Standards and Mines and the research engineers of the National Slate Association are working on the problem. 9 SEL AS Ey eeneO SORE 7S American Roofing Slate Deposits Now Being Quarried Active roofing slate quarrying in the United States is confined to the states of Maine, Maryland, New York, Pennsylvania, Vermont and Virginia, the chief produc- tion of Pennsylvania is from the Lehigh district, in- cluding parts of Northampton and Lehigh Counties. The Peach Bottom district extends from York and Lancaster Counties, Pennsylvania, across the line into Harford County, Maryland. (See Map, page 84.) The active Vermont district lies in Bennington and Rutland Counties, and extends into Washington County, New York. The Maine slate deposits occur in Pisca- taquis County, about the center of the state. Virginia operations are now conducted only on the Arvonia belt of Buckingham and Fluvanna Counties and near Esmont. A number of other deposits have been worked in the past and may be worked again, but are now idle; others have not yet been developed. A few others are being worked now exclusively for crushed and ground slate. In Canada slate has been quarried chiefly in Richmond County, Quebec, though some slate has been produced in Nova Scotia and in British Columbia. Slates have been obtained from the shores of the Bay of Islands and Trinity Bay, Newfoundland. No Canadian quarries were in operation at time of publication of this book. Grading Practically all producers have their own trade names and “grades” for slate for “Textural” and “Graduated” roofs and the distinguishing features of each should be familiar to the architect or owner before specifying. The National Slate Association has on file a complete list of registered trade names of the various slates. With respect to the characteristics of slate, which have their effect upon grading, Dr. Oliver Bowles, Mineral Technologist of the U. S. Bureau of Mines says, in “The Characteristics of Slate” paper delivered before the American Society for Testing Materials, June, 1923: “Slate is of medium hardness, very fine grained of low porosity, great strength and consists essentially of insoluble and stable minerals that will withstand weathering for hundreds of years. Some slate in Pennsylvania contains ribbons which consist of narrow original beds usually con- taining carbon, and darker in color than the body. There is tendency for some ribbons to contain an excessive amount of the less resistant minerals and they should not appear on exposed surfaces.” Some Pennsylvania slate contains ribbons and the output of some quarries in this district is divided into two classi- fications known as “Clear” and “Ribbon.” The characteristics which are commonly accepted as affecting the appearance of the slate on the roof namely the surface, straightness, condition of the corners and 10 Figure 6. Smooth and Rough Slates thickness are used to determine the “Classification” or so-called “Grade” into which the quarries divide their product. Commercial Standard Means Properly Graded The classification below applies only to slate less than YY," in thickness for “Standard” roofs. When specifying “commercial standard roofing slate” it is unnecessary to further cover the essential character- istics or grading points to be considered by slate in- spectors in selecting and piling the slate in the storage yards at the quarries. The term “commercial standard” embodies certain grading standards which govern the selection of slates for shipment and are as much a part of the process of preparing the slate slabs for roofing purposes as the splitting or any other operation. It is to be regretted that it is impracticable to have one standard for all parts of the country. It will be realized, however, that this is impossible due to some slates con- taining ribbons while others are clear, some having a rough surface, others a smooth surface, and certain other distinguishing features which must be given consideration. In the past many architects have thought it necessary to specify roofing slate by the name of a town or by designated directions from certain towns. That this is too restrictive and unnecessary is apparent when it is realized that any particular color or kind of slate veins may extend through an entire region. A Number Two Slate comes from the same bed as the Number One and is only so classified because of surface characteristics. A knot or knurl or rougher texture on surface of one slate of a pile split from the same slab does not change its mineral constituents. It is not a manufactured or artificial product which can be varied by formula or human avarice to cut down on any ex- pensive ingredient. NGS le ON TAR Delt Lege oa OGIeA Tel OcN Architects and others may rest assured that their speci- fication of “Commercial Standard roofing slates in ac- cordance with the grading standards of National Slate Association” will obtain all the essential characteristics and quality as though they were to prescribe all the fol- lowing details of grading standards used at the quarries. Lehigh-Northampton District, Pennsylvania There are two grades of Commercial Standard Roofing Slates produced in Lehigh-Northampton District, Penn- sylvania, viz: Number 1—Clear Dark blue, blue-grey, or grey in color, uniform throughout. Similar in all respects to No. 1 Clear except for the presence of one or more bands or “‘ribbons”’ which are not ex- posed when on roof. Number 1—Ribbon The following grading rules apply to each of the above grades: Surface Reasonably smooth straight cleavage full length of slate both front and back. The maximum bend shall not exceed Yj” in lengths up to 16”, nor exceed 34” in lengths from 16” to 24”. Shall be free from knots or knurls that in any way interfere with the safe conveyance or the laying of the slate on the roof. Reasonably full corners on exposed ends. No broken corners on covered ends that would sacrifice nailing strength, or the laying of a water tight slate roof. 625 to 750 pounds per square depending on quarry and color. Approximately 7”. Texture Corners Weight Thickness In a few Pennsylvania quarries they are also producing two other grades: Medium Same as No. 1 Clear except that texture is somewhat rougher—less uniform in thickness. Weight 700 to 725 pounds to square. Same as No. | Ribbon except texture is somewhat rougher and ribbons may appear on exposed surface of slate after it is laid on the roof. Nore—Large quantities of No. 2 Ribbon roofing slates are used for damp courses or dampproofing of masonry construction. Number 2—Ribbon Chapman and Hard Vein Quarries, Pennsylvania There are two grades of Commercial Standard slate from Pennsylvania Chapman and Hard Vein quarries, viz., No. 1 and No. 2, both having one or more hard veins running across the slate. Number 1 Surface Reasonably smooth straight cleavage full length of slate both front and back. The maximum bend shall not exceed 1%" in lengths up to 16”, nor exceed 34” in lengths from 16” to 24”. it Shall be free from knots or knurls that in any way interfere with the safe conveyance or the laying of the slate on the roof. Texture Corners Reasonably full corners on exposed ends. No broken corners on covered ends that would sacrifice nailing strength, or the laying of a water tight slate roof. a Thickness Approximately 35”. Weight 650 Ibs. to 700 lbs. per square. Number 2 Surface Same quality as No. 1 but a rougher surface. The veins showing more prominent. Not quite as uniform in thickness as No. 1. Texture Corners Reasonably full corners on exposed ends with no broken corners on covered ends that would sacrifice nailing strength or the laying of a water tight slate roof. Weight 670 lbs. to 725 lbs. per square. Vermont and New York There is only one grade of Commercial Standard Roof- ing Slates from Vermont and New York. Surface Reasonably smooth straight cleavage full length of slate both front and back. The maximum bend shall not exceed 4" in lengths up to 16”, nor exceed 34" in lengths from 16” to 24”. Shall be free from knots or knurls that in any way interfere with the safe conveyance or the laying of the slate on the roof. Texture Corners Reasonably full corners on exposed ends. No broken corner on covered ends allowed that would sacrifice nail- ing strength, or the laying of a water tight slate roof. Weight 650 lbs. to 800 lbs. depending on quarry and color. Thickness NotrEe—‘‘Smooth”’ does not mean an absolutely even face and back, because the natural characteristics of the rock render this impossible. The word “smooth” is therefore used rela- tively only. The rougher slates are selected for use on other than the standard type of roof. Approximately ;”. Monson District, Maine There is only one grade of Roofing Slate from the Monson Maine district. Surface A smooth slate with grain running the length of slate. Corners Reasonably full corners on exposed ends. Weight Approximately 725 pounds per square. Thickness 35" standard thickness. Peach Bottom District There is only one grade of Commercial Standard Roof- ing slate from the Peach Bottom district. Surface Reasonably smooth, straight cleavage out of wind. SL Aa ER OOF Corners Reasonably full corners on exposed ends. Some corners are allowed off on ends under cover, but not enough to damage its service. Weight About 700 lbs. to 750 Ibs. per square. Thickness Approximately 35”. Virginia There is only one grade of Commercial Standard Roof- ing Slate from Esmont district and other Virginia quarries. Surface Exceptionally smooth straight cleavage full length of slate both front and back. Corners Reasonably full on exposed ends. No broken corners on covered ends that would sacrifice nailing strength or the laying of a water tight slate roof. Weight Practically uniform about 700 lbs. per square. Thickness Approximately 7”. Nore—The rougher slates are selected for use on other than the standard type of slate roof. Quantity In the United States slates are sold by the “square.” A “square” of roofing slate is defined by the U. S. De- partment of Commerce, Bureau of Standards, in Simpli- fied Practice Recommendation No. 14, as follows: “A Square of Roofing Slate—A square of roofing slate means a sufficient number of slate shingles of any size to cover 100 square feet of plain roofing surface, when laid with approved or customary standard lap of 3 inches. Slates for surfacing flat roofs are usually laid tile fashion, without lap, in which case a square of slate would cover an area greater than 100 square feet.” The quantity per square varies from 686 pieces for the 10” x 6” size to 98 for the 24” x 14” size, which includes the allowance for a 3” head lap. It should be noted that for roofs of comparatively little slope where a 4” lap is required, an additional quantity must be provided. For steep roofs or siding, where a lap of 2” is sufficient fewer slates will be necessary. Slate, however, is always sold on the basis of quantity required for a lap of 3” even for flat roofs. The data under the next three headings is quoted from Simplified Practice Recommendation No. 14. ROOFING SLATE In accordance with the unanimous action on January 23, 1924, in New York, N. Y., of the joint conference of representatives of manufacturers, distributors and users of slate for roofing purposes, the United States Depart- ment of Commerce, through the Bureau of Standards, 12 recommends that recognized sizes and nomenclature be reduced to those shown below. TABLE 1.—Dimensions of Slate Shingles for Sloping Roofs; Minimum to a Square [Each size split! to thickness of 3, 14, 3%, %, 34, 1, 14%, 1%, 184 and 2 inches.?] Minimum Minimum Face Face dimensions* aes dimensions* ee in inches (3” lap) in inches (3” lap) 10 by 6 686 16 by 10 22) 10 by 7 588 16 by 12 185 10 by 8 515 18 by 9 213 12 by 6 533 18 by 10 192 12 by 7 457 18 by 11 175 I2 by 8 400 18 by 12 160 12 by 9 355 20 by 10 169 12 by 10 320 20 by 11 154 l4by 7 374 20 by 12 141 14 by 8 ByAT 20 by 14 121 14 by 9 290 22 by 11 138 14 by 10 261 22 by 12 126 14 by 12 218 22 by 14 109 l6 by 8 Ql 24 by 12 115 l6 by 9 246 24 by 14 98 1The art of splitting slate blocks consists in progressively reducing resultant halves, until the desired roofing slate thickness has been reached or approximated. This hand-wrought characteristic appeals to architects and owners. It is not a simple matter to precisely control the splitting of this natural rock, nor can a uniformity of thickness throughout be assured. The recommended range of thicknesses to be aimed at by operative splitters will meet all normal requirements, and will insure the maximum of economy in the utilization of the many sizes of quarried blocks. “It is customary to regard a thickness falling between two standard thicknesses as a ‘‘special,’’ and it is the practice to base the price of the ‘‘special’’ upon the greater of the two standard thicknesses. °For thicknesses one-half inch and more, it is not generally con- sidered practicable to use lengths that are less than 16 inches, although for roofs of special treatment it may be done in small quan- tities. (But on large projects it will be found more economical to allow 16-, 18- and even 20 inch lengths than to specify only the 16-inch mini- mum.) In carrying out a desired design on special roofs, it is some- times necessary to make shingles longer than 24 inches, in which case the thicker slates are used. TABLE 2.—Dimensions of Slate Shingles for Flat Roofs [Each size split to following thicknesses: For ordinary service, 75 inch; for promenade and extraordinary service, 4 inch and 3¢ inch] Face Dimensions, In INCHES 6 by 6 10 by 6 12 by 6 6 by 8 10 by 7 12 by 7 6 by 9 10 by 8 12 by 8 SIZES OF SLATE FOR MISCELLANEOUS PURPOSES It is recommended that smaller slate, such as 12 or 14 inch lengths, be used in covering pents, porch and dormer roofs and sides, and garage or other low-roofed buildings. This practice is also recommended even in situations where the main roof is of larger slate. Owing to the fact that certain sizes of slate may be more available than the size called for in the specification or order, it is recommended that architects, builders, engineers, and contractors provide for alternate selection on usual slate roofing installations. In this connection, particular attention is also called to the increasing use of random widths of the desired lengths, and to the fact Nee GOR N aA Sele Ae eee Aor ou) Cano be OFIN that architects are adopting this practice. While slate is plentiful, such practices will bring about the elimination of waste of an important natural resource, and will obvi- ate the necessity of waiting for specified sizes while an accumulated finished stock of other usable sizes is avail- able and accessible. DIMENSION NOMENCLATURE COMMERCIAL STANDARD THICKNESS (that is, average or basic.—The terms “3/16-inch slate,” “full 3/16-inch slate,” or “not less than 3/16-inch slate” indicate a desire for a hand-picked selection, regardless of the added labor and cost. “Commercial standard” is the quarry run of production, and shows tolerable variations above or be- low 3/16 inch. For the thicker slates, however, reason- able plus tolerances only are permissible; thus a 14-inch slate must be a full 14 inch or thicker. W eight A square of slate on the roof, i.e., enough slate to cover 100 square feet of roof surface with a standard 3” lap, will vary from 650 to 8,000 pounds for thicknesses from the commercial standard 3/16” to 2”. The commercial standard thickness (approximately 3/16”) will weigh from 650 to 750 pounds per square. For estimating the dead load on the roof construction, it may be taken at a maximum of 800 pounds per square or 8 pounds per square foot to include slate, felt and nails. Slate used on flat roofs are laid without lap, the ends and sides being butted fairly close together. The ex- posure on a flat roof is thus the size of the slate used and the weight of slate required to cover a “square” of roof surface is correspondingly less. The weight of slate varies with the size of the slate, color and quarry and even sometimes in the same quarry. This variation may be from 10% above to 15% below the weights given in the following table of average weights of slate of different thicknesses for both sloping and flat roofs. Slate Average Weight of Slate per Square (100 sq. ft.) Thickness in Inches Sloping Roof Flat Roof Allowing for 3” Lap Without Lap Standard iis 700 240 Selected full 35 750 250 yy 1,000 335 3% 1,500 500 Vy 2,000 675 34 3,000 1,000 1 4,000 1,330 14 5,000 1,670 1% 6,000 2,000 134 7,000 2 8,000 , 13 ie .oieen eter IIBCHINE: PUSYCHED — HAND PUNCHED Figure 7 Nail Holes No slate should have less than two nail holes. The standard practice is to machine punch two holes in all architectural roofing slate 14” and thicker at the quarry and also in commercial standard slate when so ordered. Four holes should be used for slates 34” or more in thick- ness when more than 20” in length. Holes are punched from one-quarter to one-third the length of the slate from the upper end, and 114” to 2” from the edge. Where four holes are used, it is customary to locate the two additional holes about 2” above the regular holes. Some architects in the past specified that all nail holes should be drilled and countersunk. On normal thickness slates, no method of drilling has been developed which will produce the same clean hole as by machine punch- ing, because the small thickness of stone at the cutting point is insufficient to absorb or dissipate the drilling force. Hence the industry, through the Association, in 1923 adopted the machine punching of nail holes as standard practice. That the results are excellent is demonstrated by the fact that, when given two slates with holes punched by either method, architects have usually selected the ma- chine punched as the better and have even called them drilled and countersunk. Machine punching is preferable to hand punching. The term hand punching usually refers to the use of the double head slaters hammer having one head in the form of a long prong. Machine punching may be done either at the quarry or on the job. Hand punching of holes in fitting hips, etc., is, of course, necessary. LG 470 4th > oO ° = LENGTH MORE THAN 20° 4 ° ° 20 OR LESS: acy Figure 8. Location of Neil Holes N the laying of any roofing material workmanship is Ve. essential as the proper selection of the material. The more enduring the material the more important this factor becomes. Slate, the most lasting roofing material known, should be laid by roofers of experience and training. It is a mistake to assume that those without such experience are qualified to properly lay slate. For Figure 9. Properly Nailed Figure 10. Nail Driven Too Far Figure 11. Nail Not Driven Far Enough instance the nailing of wooden shingles and slates are entirely different. The heads of slating nails should just touch the slate and should not be driven “home” or draw the slate, but left with the heads just clearing the The opposite is true of wooden shingles and a man used to laying this slate so that the slate hangs on the nail. material will invariably handle slate in the same way. As a consequence the slate, held too rigidly in place, is 14 shattered around the nail hole or the head of the nail crushed and eventually the slate may “ride” up over the nail and be blown off in a heavy wind. The blame is Via, SLATE Figure 12. Starting Slate placed on the material whereas the real reason can be traced to the method of nailing. All nails should pene- trate the sheathing and not the joints between boards. This is especially important near the ridge of the roof. It would seem almost unnecessary to mention the fact that there should be no through joints from the roof sur- face to the felt. The joints in each course should be well broken with those below. Where this simple precaution is neglected it is possible that water may find its way through the joints, eventually cause the felt to disin- NOT LESS THAN 3° AND AS {| ENC NTIL: G. TLEVASTPOSSIELE Figure 13. Proper Jointing Where random widths are used the overlapping slate should be jointed as near the center of the under slate as possible and not less than tegrate and leaks develop. NGA el Or INGA, Eb ee Ne ele ee Once tele OUN 3” from any under joint. Where all slates are of one width, this is automatically taken care of by starting every other course with a half slate or, where available and practicable, a slate one and one-half times the width of the others. With but few exceptions, the standard 3” lap should be insisted upon. The “standard 3” lap” or “3” headlap” means the lap of the slate over the second course below, see Figure 15. The small saving in slate through reduc- ing the lap will not compensate for the risk entailed of leakage due to the lessened amount of material over which water might be blown. A practice prevalent among many roofers is that of driving the slater’s stake into the roof boards. To avoid damaging the roofing felt, a plank should be used for this purpose or the stake driven into the scaffold only. Slaters occasionally use a metal strap as a support for the scaffold brackets. This practice should be discour- aged when these are cut off and a part left on the roof. They will rust in time and stain the slate in a most un- sightly manner. Figure 14. A Satisfactory Scaffold Bracket The foregoing applies to slating in general. The forming of slate hips, ridges, valleys, eaves and gables require a description peculiar to themselves. Exposure The “exposure” of a slate is the portion not covered by the next course of slate above and is thus the length of the unit exposed to the weather. The standard lap of the alternate courses used on sloping roofs is 3” and is the basis upon which all roofing slate is sold and the quan- tity computed. The proper exposure to use is then ob- tained by deducting 3” from the length of the slate used and dividing by two. For instance, the exposure for a 24” slate is 24” minus 3” = 21” ~ 2 = 1014” exposure. The following table will be found of use in readily obtaining the proper exposure. 15 Exposure in Inches for Sloping Roofs a " an" Length of Slate Slope : A ) in Inches PSY jee ‘ ap Ag RET EO PRAT eet te SARE on plete ve 10% PUPAR, i BOE EEE gb nA es aL PCRS bes ae Ie RE Page 9% IAD sn ies brerdp hs BAe DA eC OL eee 8% LORE ars ers Alcs freon A eee ee en 7% i Gree ee pe ete rd waa eis Lote 6% Aa Ne wr Seen Ses Ain eke c(t eee 5% des dn once Sic AGS CaENOT Gee Ges PARE Rn Tea LS Een 4s VU ssc tch SOE nc Se ote RRS ae neta ak a meine 3% Sloping roofs having a rise of 8” to 20” per foot of horizontal run should be laid with the 3” lap. Buildings located in the southernmost parts of the country or on the Pacific slope may however be safely roofed with a lap of 2” providing a high standard of workmanship is otherwise maintained. For steeper roofs, such as the Mansard and others nearly vertical in plane a 2” lap will usually be found sufficient. In some sections of the country it is customary to increase the lap to 4” when the slope is from 4” to 8” per foot, while in other parts Flat roof construction should be used for slopes less than 4” per the 3” lap is considered entirely adequate. foot. For vertical walls or siding use 2” lap. Ridges There are two common methods of finishing the ridge of the roof. These are usually known as the “Saddle Ridge” and “Comb Ridge” but each may have other names and certain variations in laying according to local practice. In Figure 16 are illustrated two types of saddle ridge which are known respectively as the “Saddle Ridge” and the “Strip Saddle Ridge.” In the first of these, the “Saddle Ridge,” the regular roofing slates are extended to the ridge so that pieces of slate on the opposite sides of the roof butt flush. On top of the last regular course of roofing slate at the ridge is laid another course of slate called the “Combing Slate” and the pieces on the opposite sides of roof butted flush. The combing slate is usually laid with the grain horizontal and should be of such width that the exposure or gauge Figure 15. Lap and Exposure POINT WITH ELASTIC CENENT evs GNX Th Veg), 2 LATH COMBING SLATE SOMETIMES OMITTED GY PLASTER LATH SOMETIMES OMITTED COMBING SLATE ELASTIC CEMENT SECTION ROOFING SLATE OIRI TZ MOAV OEE BRY OGE BUTT JOINTS COMGBING. SLATE LAID WI/TIlt GRAIN VERTICAL COMBING SLATE ELASTIC CEMENT- ROOFING SLATE DETAIL COMBING SLATE LA/D WITH GRAIN HORIZONTAL WHEN THE COMBING SLATE ARE LAID ALTERNATELY IMALLER SLATE (OF VW PROPER, 15/1 Z2E (MAY Sie PROJECTING ON EITHFR SIDE OF THE RIDGE, USED WO GIVE SAME VEXPOSUCRENMASE GE OWE (3) THIS TYPE 1S KNOWN AS A "COXCOMB’ RIDGE. OF ROOF COURSES. FIGURE 16. STANDARD DETAILS SLATE RIDGES—NATIONAL SLATE ASSOCIATION Ne Agee OaNe as |: Sele ee ee ee Oot On GelAm lL TeOgN of the roof is maintained approximately uniform. For example if 20” x 12” slates are used on the roof with an 814” exposure, 12” x 8” slates laid horizontal could be used on the ridge. It will be noted in Figure 16 that the combing slates overlap and break joints with the under- neath slate. In this way all the nails in the combing slate are covered by the succeeding slates except the nails in the last or finishing slate on the ridge and these nails should be covered with elastic cement. In Figure 16 it will be seen that only two nails are used in each slate. For this reason the end of the slate which is not nailed should be held in place by elastic cement. The joints on top of the ridge formed by the butted edges of the combing slates should be filled in with elastic cement when subject to heavy rainfall. Some roofers do not use BLASS Wood BEND DOKN TO SLATE THE COPPER MOLD 45 SECURED IN PLACE BY BRASS WOOD SCREWS ~- CLAMPS AS SHOWN MAY BE UVSED MADE OF $e +/* BRASS AND PLACED ABOUT 30" APART L£/ITHER INSIDE OR OUTSIDE OF THE MOLD JF PLACED INSIDE - THE CLAMPS ARE RIVETED TO THE MOLO BLE FORE ERECTION Z HOS THREE TYPES OF *1/P OR RIDCE FLASHING SOR A SLATE ROOF Figure 17 any elastic cement on either the hips or ridges, but this practice is not recommended except under favorable cli- matic conditions. The nails should be arranged to go In some parts of the country it is customary to clip the between the joints of the slate immediately below. upper edges of the last roof slate as shown in the draw- ing, Figure 16, Plate 1. Many architects prefer to keep the grain of the slate vertical, using the same type of ridge with top or combing slate of the same width as the regular roofing slate and the length the same as their exposure. In such cases the starting slate could be a “slate and a half” in width rather than a “half slate.” Another type of saddle ridge is that known as the “Strip Saddle Ridge.” This ridge is laid in a similar manner to the above except that the combing slates do not overlap but butt flush and each combing slate has LZ, Figure 18. Ridge and Closed Valley four nails. The combing slate may be the same width as the regular roofing slate or narrower as the designer The nails should be covered with elastic cement and the edges of the combing slates set in elastic may wish. cement as shown in Figure 16. The “Combing Ridge” is laid in the same manner as the “Saddle Ridge” except that the combing slate of the north or east side extends beyond the ridge line as shown in the detail, Figure 16. This extension should not be more than 1”. This type of ridge may be laid with the comb- ing slate having a grain vertical or horizontal. In either case, the edge of the slate should be set in elastic cement, as shown, and the nails covered with elastic cement. If the top or combing course is projected 1/16” to 14” above the under top courses, it will make a much better finish and will be more easily filled with elastic cement. A variation of this type of ridge is known as the “Cox- Figure 19. Fantail Hip Se Am Shien eOaQOehas comb Ridge” in which the combing slate alternately pro- ject on either side of the ridge. It will be noted that in Figure 16 the top courses of the regular roofing slate have the edges set in elastic cement. This is done to avoid their lifting under action of the wind and should in no sense be construed as being necessary from the standpoint of weather-proofness. Hips There are several methods of forming hips on slate roofs, some of which are illustrated in Figure 22. These are the ones most common in all sections of the country although they may be known by other names than those given herein. Figure 20. Open Valley The “Saddle Hip” may be formed by placing on the sheathing forming the hip one or two plaster lath or a 31%” cant strip and running the roofing slate up to this strip. On top of the cant strip and the slate are laid the hip slates which are usually the same width as the ex- posure of the slates on the roof, although they may vary in width on different classes of work. It will be noted in the detail Figure 22, Plate 1, that the four nails used to fasten the hip slate to the roof are driven into the cant strip and do not go between the joints of the slate. The heads of these nails are then covered with elastic cement and the lower part of the 18 next slate bedded therein as shown. Elastic cement is also placed on the joint between the roofing slate and the plaster lath and on the peak of the hip before the hip slates are laid. A variation of the “Saddle Hip” is known as the “Strip Saddle Hip” which is used on less expensive work and may be formed of narrower slates laid with butt joints which do not necessarily line up with the course of the slate on the roof. Another type of hip is that known as the “Mitred Hip.” In forming this type of hip the slates forming the roof courses and the hip are all in one plane as is shown in Figure 22, Plate 2. The hip slates should be cut accu- rately to form tight joints and the joint should be filled in with elastic cement. The nail holes should be so placed as to come under the succeeding hip slate. A variation of this type of hip is that known as the “Fantail,” shown on Figure 22, which is laid in the same manner as the “Mitred Hip” but which has the bottom edge of the hip slate cut at an angle to form a fantail. Another very popular type of hip is that known as the Boston Hip. In this type of hip the slates are woven in with the regular courses of the roofing slates, as shown in the detail. The nails are then covered with elastic cement and the lower part of the succeeding slate bedded therein. It is sometimes recommended that metal or slip flash- ings be woven in with each course of “Mitred Hips” but this is usually unnecessary if proper care and workman- ship are exercised in cutting, fitting and bedding the hip slates.. There are some roofers who do not use elastic cement on the hip slates and secure satisfactory results. Valleys Of the two methods of forming the valleys the first, and without doubt the more satisfactory, is the open valley. The second, known as the closed valley, is considered by many to be the more pleasing in appearance and is much used on high-grade work. Variations of the closed val- ley, frequently used in connection with the Graduated or Textural roofs, are the “round” valley and the “canoe” valley. OPEN VALLEY The open valley is formed by laying strips of sheet metal in the valley angle and lapping the slate over it on either side, leaving a space between the slate edges to act as a channel for water running down the valley angle. The width of the valley, or the amount of space between the slate edges should increase uniformly toward the bottom. The amount of this increase, or taper, has been determined as | inch in 8 feet. For example, in a valley 16 feet long, the distance between slates will be 2 inches greater at the bottom than at the top, as the width in- BEVELED STRIP OR ONE OR TWO PLASTER LATH SOMETIMES OMITTED. HIP SLATES ARE SOMETIMES SMALLER SLATES. ON LESS EXPENS/VE WORK S7R/P SADDLE HIPS ARE LAID WITH BUTT JOINTS oy WHICH DO NOT ALWAYS om ( i {| ‘| | 6 ee eee : = SECTION A-A’ AND NY PERSPECTIVE VIEW CUE SIDE qn? OF SADDLE HIP SECTION AA’ AND PERSPECTIVE VIEW OF MITRED HIP JERE UOMO Tad (TEM ANA E7/ P FIGURE 22. STANDARD DETAILS SLATE HIPS--NATIONAL SLATE ASSOCIATION | 2ESTEEELTTTITT RACRRCRATRL'S) WLLL TTA ETT TT PE OS IOS 5 egos FF SSS SSS SET OS TOITATs CLIN LITTT EO CLALIT D SOLE E TERT TL ID O8 Oe LITO Y LE L —t SLATE VOT gn eA LI IA LALLA LAAT LLY BS SSTSS SI SSS TSS SSIS SSS SSS SSS I L777 Xi LITT a Oe NE 0b OOF OPTED | hhh hack hn P77 pn) >< | aa See 7 eG ena ¥ . . . 2 sf TABLE CON LUTE UMW AVENUES — (ROLY MY W/TH EACH COURSE OF SLATE ii FLASIANG [SHEET 1} APPED\ \3" FOO. 1D Ve (5) Vi AiLgalaey ‘UNDER EAVE” OR STARTER SLATE RS SSS RM SECTION 8-8 FLASHING ROOF SHEATHING SWSGIMKOM (GAE, (4) (6) FIGURE 23. STANDARD DETAILS SLATE VALLEYS, EAVES AND GABLES—NATIONAL SLATE ASSOCIATION (We IRE CHOY ING Ae el ORNAS I Selly ete eS OnGuls ARTs IO ON Closed Valley Figure 21. creases at the rate of 14” in 8 feet on each side of the valley. This permits a uniform width of about 2/3 the width of the slate under the slate adjacent to the valley. The difference in width or taper allows the slate to be laid closer to the valley at the upper than the lower end and takes care of the increase in water received. This tapering of the valley also has the very practical effect of allowing any ice which may form to free itself and slide down as it melts. This increase of width in the valley must be allowed for in placing the flashing strips. Valley flashings are generally laid in pieces up to 8 feet long. The best theoretical manner of taking care of the taper would be, of course, by tapering the sheets. As this involves con- siderable additional expense in labor and material it is often more practicable to use sheets shorter than 8 feet and increase the width of each sheet an amount sufficient to take care of the taper. This increase in width amounts to 1/8 of an inch per foot. The increase in the widths of succeeding sheets of various lengths necessary to take care of this taper is shown in table No. 3. Figure 23 shows the method of installing the sheets. The slate should start 2” each side of the valley center at the top and should taper away from the center at the rate of 14” for every eight lineal feet. The metal flashing should be of sufficient width to extend up under the slate not less than 4” (preferably 6” to 8”), and as far as is possible without being punctured by the slating nails. Where the two roofs forming the valley have consid- erable difference in slope or the roofs are much different in size and cause a large variation in the volumes of water to be delivered into the valley, the metal should 21 be crimped or made with a standing seam to break the force of the water from the steeper or longer slope and prevent its being driven up under the slate of the oppo- site side. TABLE 3 Showing increase of widths of untapered sheets in a tapered valley. Length of Increase in Length of Increase in Sheets Width Sheets Width 24 A 60 x 30 15 66 i 36 3% G2, 34 42 ae 84 , 48 Vy 96 if 54 S Exampte: A valley is 19 feet long. The sheet extends 5 inches under the slates and is fastened by cleats. What width of sheets can best be used? As a 4-inch minimum under the slate is necessary two eight- and one three-foot length can be used. Starting at the top the first sheet would be 2+2+5+5+%+ 44=15 inches wide. If the three foot is used at the top, the first eight foot sheet would be 153g or 15% inches wide and the second one 163% or 161% wide. Condensation forming on the underside of valley flash- ings, when not free to run off or evaporate, may attack It is therefore recommended that the felt be omitted under metals if other than copper is used. If felt is used under other metals they should be well painted on the underside. the metal. For inexpensive roofs as provided for in the specifica- tion for a Standard Roof the copper for valleys is laid flat without crimps or cleats. For high-grade work the copper sheets should be secured to the roof boards and over the felt with metal cleats from 8” to 12” apart. COPPER PLASHING LAID IN LONG SHEETS: CONT/NY- OVS OVER ROOF SHEATH- ING -THE UPPER SHEL 7 70 LAP FOUR /MCNES Wee VANE LOWE SHEE]: Y f | N 7 \ y, COPPER FLASHING ROOF GLLATH/NG ‘SECTION O-D: \ nid aN AS ES FLASHING FORA CLOSLD VALLLY USINGLONG SHEETS UNDERNEATH SLATE Figure 24. Another Type of Closed Valley Sel Ay Eos ReOmOnies The edge of the sheet is turned over 14” and the bent end of the cleat hooked under. The cleat is then nailed to the roof boards with two nails and the cleat bent over to cover the nails. A method sometimes used on wide valleys with the best work is to fold the metal 4” or 5” from the valley line and 3” from the cleat fold. This is known as “Fold-over” flashing. CLOSED VALLEY The closed valley is formed with the slate worked tight to the valley line and pieces of metal placed under the slate as shown in Figure 23. The size of the sheet to be used is determined by the length of the slate and the slope of the adjoining roofs. Each sheet should extend 2” above the top of the slate on which it rests so that it may be nailed along the upper edge of the roof sheath- ing without the nails penetrating the slate. Each sheet should be long enough to lap the sheet below at least 3”, and should always be set back of the butt of the slate above so that it will not be visible. These sheets are separated by a course of slate (Section BB). Each sheet must be wide enough so that the vertical distance from the centre of the valley to a line connecting the upper edges of the sheet will be at least 4”. This dimension depends upon the nailing of the slate which should not penetrate the sheets. Some roofers form the sheets with a center crimp (Figure 24), thus stiffening them and forming a straight line to which to set the slates, and preventing water from one slope forcing its way above the sheet on the other slope. Another method of forming a closed valley is shown in Figure 25. Round Valley 22 Figure 26. Eaves and Gables Figure 24, The sheets are laid in long pieces directly on the paper or felt covering the roof sheathing before the slate is laid. They may be of any desired length and should lap in the direction of the flow at least 4”. They should be nailed about every 18” along the outer edge, and care shculd be taken to avoid penetrating the sheet when nailing the slate. ROUND VALLEY The round valley forms a pleasing transition between two intersecting slopes when used in connection with the Graduated or Textural roof. However, if not properly laid out it will produce disaster and mar an otherwise beautiful roof. For this reason its laying should be entrusted only to those fitted by knowledge and experi- ence to do this particular work. It requires the most careful workmanship and experienced knowledge of the problem to secure a job that will be both pleasing in appearance and water-tight. Primarily the round valley requires a suitable founda- tion to establish the general contour. The method of building this foundation is described under sheathing and roof boards on page 40. The valley slates must be at least 4” longer than the slates used in the corresponding courses of the roof. The sides of the slates must be trimmed to the proper radius and the tops shouldered to make the slates lay flat. The round valley slates are sometimes bedded in elas- tic cement. If proper care is used in the trimming and fitting, no flashings should be necessary. Where the workmanship is not dependable, flashings of metal or prepared roofing cut to the proper radius should be used NG OR NP AS oper AG lt AT Sts O Gor ATT 1 OUN as a precautionary measure. F lashings should always be used wherever ice may form. The radius of the round valley starts as a maximum at the eaves and gradually diminishes to practically zero at the ridge. For appearance, as well as to facilitate lay- ing the valley slates, the distance across the eaves should not be less than 26”. If the roof condition will not per- mit this, the “canoe” valley should be used. The canoe valley is a variation of the round valley and is laid in the same manner except that the radius at the eaves and ridge is practically zero. The radius is gradually increased until it becomes a maximum half- way between the eaves and the ridge. Eaves and Gables The under-eave slates should start on a cant strip of suitable thickness, depending upon the thickness of the slate, to enable the second course of slate to be correctly laid. In the case of a cornice, this slate should project about 2” beyond the cant strip, sheathing or finishing member. The length of the under-eave slates is found by adding 3” to the exposure being used on the regular slates. Thus, if 16” slates are used, the exposure is 614” and the size of the under-eave slate required is 914”. Half slate are sometimes used, or roofing slates of the proper width may be laid horizontally. If the first course is 34” in thickness, use 34” slates for the under-eave course or 1,” slates if the starters are 44”, although the under-eave and first course are sometimes made the same thickness. The first course of slate is laid over the under-eave course with the butts of both courses flush, and the joints broken. Figure 27. Laying Slate 23 When changing from a roof of flat slope to one of steeper slope as in the case of a Gambrel roof, the slate of the upper and flatter roof should project 2” to 214” beyond the steeper roof below. A cant strip should also be used upon which to start the slate of the roof of lesser slope the same as at the eaves. At the gables the slate should overhang the finishing Where close-clipped gables are used or the construction is such that the gable slates have ample nailing, this dimension may be increased, but the projection ought not to be too Also there are many inter- member of the verge board not more than 14”. great for good appearance. esting ways to lay “Gable end” or “Barge” slates under regular courses along gable ends where shadow effect is desired. Ways and means of using and securing all gable end slates depends on type of construction. Roofing Felt It should be emphasized that a standard slate roof can be laid water-tight on open lath without felt, as is often done in the South or on buildings where heat is not required. The thickness of the felt has little relation to the water-tight qualities of a slate roof. The opinion has been held by many that the thicker the felt, the tighter will be the roof. When it is realized that every nail used in fastening the slate is driven through the felt it will be seen how erroneous is this idea. Roofing felt, how- ever, does have three other distinct uses in connection with slate roofs. The felt placed as soon as the roof is sheathed will protect the building, when necessary, until the slates are laid. It has considerable insulating value in resisting the heat of the summer sun and the transference of heat from the inside during the winter months. Increasing heating costs in the colder localities makes this a factor worth careful The use of laths over the felt and under the slates to obtain an air space, a method recommended consideration. by English roofers, adds much to the insulating value of the felt. The third value of the felt is to form a cushion for the slate. While not of great moment in the case of commer- cial standard slates, its value in this respect increases as For the commercial standard slate felt weighing 14 pounds per square will be found satisfactory. The same weight is Any of the heavier weight felts, as 20, 30 or 40 pounds per square, may be used where the appropriation allows. For Graduated roofs, the 30 pound weight is commonly used when the slates are 34” or less in thickness and the 50 the thickness and weight of the slate increases. ordinarily used under Textural roofs. pound for slates 1” or more. It is customary in some localities to place two layers of felt under the slate on a Sule ieee ReOsORhES Graduated roof. The first layer is usually 30 pound felt and the second 14 pound. This provides an extra cushion for the heavy slates. The joints and laps should always be staggered. The felt should be laid in horizontal layers with the joints lapped toward the eaves and at the ends. A lap of at least 3” should be used and the edges should be well secured to the surface over which it is laid. A lap of not less than 2” should be used over the metal lining of valleys and gutters. If metal other than copper is used as a lining the felt should be omitted in the valleys. Extend the felt over all hips and ridges at least 12” to form a double thickness. Asphalt saturated rag felt should always be used. The so-called “Slaters’” felt includes many types of materials which cannot be recommended. Elastic Cement In the past the extensive use of Elastic Cement has often been recommended because it was supposed to be necessary in order to make a slate roof water-tight. It is now realized that this is erroneous and that it is not only possible but practical to omit Elastic Cement en- tirely and in some localities experienced roofers have abandoned its use and secured absolutely water-tight roofs. It has even been found that in certain locations on the roof the use of cement may prove to be detrimental rather than helpful. An instance of this is under slates adjacent to open valleys where the cement may dam the water and force it back under the slates instead of per- mitting it to run out into the valley. Elastic Cement does have its value, however, and is used under slates forming hips and ridges to help hold securely in place those slates which are usually smaller than the regular roofing sizes and which cannot be so well nailed. Elastic Cement is also used for pointing the peaks of hips and ridges. The requirements which should govern the selection of Elastic Cement are few but important. It should be water-proof. It should have a high melting point to pre- vent the slates from slipping under the heat of the sun and a low freezing point to prevent its becoming brittle and cracking in cold weather. It is important that the cement should not dry out and pulverize when ex- posed to the air. The best grades of cement are of an oily, sticky nature and, considering the small amount ordinarily required for a slate roof, it is economical to use only the best quality. The Elastic Cement should match as nearly as possible the color of the slate, but it should be noted that cements of certain colors may fade upon exposure, and experi- ence only will show those that are fast and satisfactory. 24 Slater’s Tools The tools commonly used by the slater are the punch, hammer, ripper and stake. If much punching is done at the yard or on the job by the roofer, a punching ma- chine should be used for punching the nail holes and cutting the slates. It is adjustable to any size or shape, cuts and punches at one operation with a countersunk hole. The hand or mawl punch is forged from fine tool steel hardened and ground about 414” long with one end tapered. The butt end is struck with a mawl to punch the nail hole. <— AypiN.— > Figure 28. Slater’s Tools Slater’s tools are all drop forged. An approved ham- mer is forged solid, all in one piece, from crucible cast steel, with an unbreakable leather handle to avoid slip- ping and blistering the hands. One end terminates in a sharp point for punching slate, the other in the hammer head. There is a claw in the center for drawing nails, and on each side of the shank there is a shear edge for cutting slate. The head, point and cutting edges are properly tempered to withstand heavy work. The slater’s stock size hammer has a 12” handle. The ripper is about 24” long and is forged from cru- cible cast steel. It is used for removing broken slate and making repairs. A hook on the end provides a means of cutting and removing the slating nails. The blade is drawn very thin and the hook end correctly tempered for hard wear. The stake is about 18” long and T-shaped. The long edge is used as a rest upon which to cut and punch slate or as a straight edge to mark the slate when cutting and fitting around chimneys, hips, valleys, etc. The short NEG eR OUND Agen oe Am ls ee AY Seo O, IRA TION arm is tapered and pointed for driving into a plank or scaffold. These tools, as well as 24” stakes, shorter rippers, left- hand hammers or special hammers or tools, can be ob- tained from any slate producer distributing roofing slate or from manufacturers of such tools. The slater’s equip- ment is completed with a nail pouch, tinner’s snips, rule and chalk line. Nails Slate, being a permanent material, is worthy of care and thought in the proper selection of the various mate- rials used in connection with it, and especially as to the method of securing the slate to the roof construction. Like any other construction unit, a slate roof can only be as strong and enduring as its weakest part, and the majority of slate roof failures over a period of years may be attributed to the punching of the nail holes, the As has previously been stated, the art of properly laying and nailing slate is not to be discounted and belongs to men trained especially in the work. The punching and nail- nailing of the slates, or the nails themselves. ing of the slate have been described under the heading, “Laying Slate,” on page 13. Before nails came into extensive use, the slate were held in place by means of wooden pegs driven through the slate and hooked over the roof lath. It is the practice in some localities today to hang the slate to the laths or battens by means of heavy wire hooked through the slate and over the laths. This method is in general use where the slate is laid directly on steel construction. Copper nails of sufficient length to be securely hooked and clinched over the structural angles may also be used. These should have large heads and the shafts be of No. 10 or 11 gauge metal. Nailing is more extensively used today than other methods for securing the slate, and careful attention should be given the characteristics of nails selected for this purpose. The important considerations involved are shape, size and material. For all practical purposes, the ordinary diamond point and smooth shaft are sufficient for a slating nail and the needle point is seldom, if ever, necessary or of advantage. The shaft, since it supports a greater weight and must resist a small shearing stress, should be larger than that of the shingle nail. To prevent the slate from being lifted up over the nail after being laid, the diameter of the head should be greater than that of shingle nails. The temptation to use shingle nails instead of slating nails should be discouraged, for the slight saving in cost on the entire roof cannot approach the cost of repairs which may develop as a result of this practice. Archi- 29 tects and owners should insist that the roofer use nails of proper size and kind of non-ferrous metals. The much-mooted question of the material of which the nails should be made must remain a matter of opinion and judgment until an impartial investigation shall throw further light upon the subject. It is hoped that research in this field may be under- taken in the near future and definite results furnished those interested. It is a generally accepted fact that copper is one of the most enduring of metals and that iron and steel, adequately protected from corrosion by a heavy coating of zinc applied by the hot-dipped process, Plain or ordinary galvan- Nails having a copper content, such as “yellow metal,” or will give reasonable service. ized nails should not be used for laying slate. “Muntz Metal” and cut zinc nails are sometimes used. Nails should be carefully selected and be the best grade of a reputable manufacturer. Recently “Cimet,” “Ever- dur” and similar chrome-iron alloy nails and other types particularly suited to resist atmospheric corrosion, have been put on the market. Their cost is higher than copper, yet for certain buildings with excessive or unusual acid fumes under and surrounding the slate roofs, it may prove economical to use such nails. Time and wider use of these newer types will prove whether they are or are not superior to copper. When cost is an item, the “Cop- perweld” nail, being less expensive than solid copper, is often used and may prove to be the satisfactory method of protecting the steel shaft. Under ordinary conditions, it will be found satisfactory to use 3d nails for commercial standard slates up to 18 inches in length. Use 4d nails for the longer slates and 6d on the hips and ridges. Thicker slates require longer and heavier gauge nails. The proper size may be deter- mined by adding 1 inch to twice the thickness of the slate. Where the through penetration of the sheathing LENGTH - INCHES of 1% 12 1% Figure 33. Full Size Nails DEL RAR Ere ReOLO shes will not ordinarily be seen, it provides evidence that nails of sufficient length were used. Thus a 14” slate will require a 4d nail which is 114” in length. Where the under side of the roof boards is exposed to view, as is sometimes the case of overhanging eaves, a nail of such length as will secure sufficient penetration but not be driven through the sheathing must be selected. Figure 29 Figure 30 Figure 31 Figure 32 Copper Wire Large Flat- Regular Cut Large Flat- Nail. (Simi- Head Copper Copper Nails Head Cut lar to Steel Wire Nail. Copper Wire Nails) (Slating Nail) Roofing Nail [Note difference in head of ordinary wire nail (Figure 29) and large flat-head wire nail (Figure 30)]. Nails suitable for roofing purposes are made in four forms, each of which has its advantages. The common wire nail (Figure 29) is used generally for nailing flashings, sheathing, and sometimes for shing- ling. It is not suitable for slate work, for it is of light gauge and small head. The slating nail (Figure 30), as may be seen, is espe- cially adapted for slating, as it is of heavy gauge and has a wide, flat head. These features make it much more desirable than the common wire nail. The roofing nail (Figure 31) is not recommended. While the shaft is of proper thickness, its head is too small. The cut nail (Figure 32) is made from sheets and is of quite different shape than any of those made of wire. The enlargement of the shaft gives it more stiffness than the wire nail has, but there is some danger of splitting the slate if too large a nail is used. The following tables of slating nail sizes will be found useful in estimating or specifying: ‘““Copperweld”’ Slating Nails c Diameter Nails Lb. Size Length Inches fackes (Mppee) 2d 1 .102 386 3d 1% 114 ZaAl\at 4d 1% 128 176 5d 134 ar28 133 6d 2 144 87 Copper Wire Slating Nails Length Gage No. per_lb.* i% 1p 303 il ip 270 1% 10 144 1% 11 196 14% 12 231 1% 10 134 1% 1 210 13; 10 112 2 10 104 2% 8 46 *Add 5% to above for Brass Nails. Cut Copper Slating Nails Length Weight | No. per lb. Length Weight 1 2d 2% 8d 14% 3d 190 234 9d 14% 4d 135 3 10d 134 5d 100 34% 12d 2 6d 244 7d Cut Brass Nails No. per Lb. Length Weight Slating Roofing 1% 172 1% 3d 164 Ly, 144 1% 4d 140 216 134 5d 108 172 2 6d 88 132 24 7d 80 24% 8d 64 IAs 2% 9d 52 3) 10d 48 75 3% 16d 66 Cut Yellow-Metal Slating Nails (60-40 mixture) Length Weight No. per Lb. 14 3d 154 1% Ad 140 An Up-to-date Photo of a Crude Old Slate Date. A more precise design worked out in two colors of slate may provide permanent roof markings for aviators. 26 HE materials commonly used for flashings are cop- per, tin, lead, galvanized iron and zinc. Flashing materials should be selected with the same care as the The used other materials entering into the roof construction. When with a material as permanent as slate, it is, of course, first consideration should be durability. poor economy to use any but the most permanent and non-ferrous metals and the best workmanship. Copper Copper is peculiarly suitable for all flashings (inclu- ding valleys) as it is easily worked and shaped and adjusts itself to temperature stresses. Copper sheet is made in a wide range of weights and thicknesses and in what is known as soft or “Roofing Temper” copper and hard or “Cornice Temper” copper. Soft copper only should be used for flashings. It is generally defined by the ounce weight per square foot; that is, “l6-ounce cop- per” pound per square foot. be rolled from copper conforming to the Standard Speci- fications of the American Society for Testing Materials. Sixteen-ounce copper sheet is the minimum weight that should be used for flashings of any kind. Many architects will specify nothing lighter than 18-ounce material, and with the best work, where heavy sheets are used, 20-ounce metal is recommended as better practice. Flashings lighter than 16-ounce are undesirable. All rain water carries with it off the roof dust and grit which It is well to use means copper sheet weighing 16 ounces or one All copper sheets used should have some erosive effect on the metal. metal thick enough to do the work of carrying away the water for a period of time at least as long as the life of the building. Sixteen-ounce copper will meet such condi- tions; 14-ounce is too light. The following table will be found of value in specify- ing the weight of sheet copper. Copper for flashings should always be specified by weight and never by gauge. Nearest Gauge Weight Thickness arate Oz. Sq. Ft. Inch eee ries B.&S8. | Stubbs | U.S 24 . 0324 20 PA 22\I 20 .0270 Alt ide 23 18 . 0243 Dap 24 24 16 0216 ES 25 25 RCP ORES AISA SESRSENEEEEE 27 %, a Pace i Copper sheets may be obtained in widths from 6” to 108” and in lengths from 6” to 200”. Roll or strip copper is made in widths from 2” to 20” and in rolls of 75’ or strips from 6’ to 10’ long. Sheets from 24” to 42” wide and from 60” to 96” long are in general use in the sheet metal trade and are carried in stock. All specifications and details should be drawn with these sizes in mind. The edges of all copper flashings to’ be soldered must be tinned 114” on both sides and the seams thoroughly sweated with solder. Proper care in making the seams tight is of utmost importance. Use pieces up to 96” in length, and except on steep slopes (15° or over), lock and solder all base flashings. Cap or counter flashings need not be soldered. The joint is made by lapping the sheets in the direction of the flow. When there is any likelihood of deep, wet snow packing in or of wind lift- ing the cap flashings, the joints should be soldered, using either locked or lapped seams. All exposed edges of flashings—such as the bottom edge of cap flashings—should have a 14” fold back under for stiffness against wind action. This is a practice that should be axiomatic with good flashing. Copper requires no painting or other treatment unless it is desired to hasten the development of the natural green patina. In this case it is absolutely necessary that all the grease and oil used in the manufacturing process A strong soda solution A uniform finish will not be obtained unless the copper is be removed from the copper. (4 to 6 ounces per gallon of hot water) will do this. thoroughly cleaned. Copper can be painted provided the surface be thor- oughly cleaned and roughened. This can be done by washing the copper with a solution of 4 ounces of copper sulphate in 4 gallon of lukewarm water in a glass or earthen vessel, to which has been added 14 ounce of nitric acid. Before painting, the surface must be care- fully washed with clean water to remove the last trace of the solution. For additional data regarding coloring copper, refer to Part 3 of “Copper Flashings,” of the Copper and Brass Research Association, or write that association direct at 25 Broadway, New York City. Tin Tin used for flashings is more properly known as “Terne-Plate.” The base is of iron or steel and the coat- Sele Ee REO Oak ts ing a mixture of lead and tin put on the sheet by the hand-dipped process or Patent-roller process. The base metal recommended for flashings is the IX thickness, weighing about 6214 pounds per 100 square feet, or from 250 to 260 pounds per box of 112 sheets size 20” x 28”. The lighter weight, or IC thickness, may be used but is seldom satisfactory. The weight of the base gives body to the metal, but its enduring qualities depend mainly upon the weight and thoroughness of the surface coating. Heavy coated tin will weigh from 290 to 300 pounds, or represent about 40 pounds of coating. While tin is sold in sheets of various sizes from 10” x 14” to 20” x 28”, the two sizes in more common use are 14” x 20” and 20” x 28”. IX tin is approximately 28 gauge (U.S. standard) IC tin is 30 gauge and weighs about 10 ounces per square foot. All joints should be securely locked and joints and seams thoroughly sweated with solder. and averages about 12 ounces per square foot. Tin should always be thoroughly painted one coat on the under side before laying, and all grease and dirt cleaned off, and then painted one coat on the top side after laying. Particular attention should be paid to this under-side coat and a heavy coat applied, as this pro- tects the flashings from the effects of condensation. Metallic brown, Venetian red, red oxide or red lead may be used, mixed with pure linseed oil. No turpentine or dryer should be added. A second coat should be applied to the surface two weeks after the first coat. One or two additional coats may then be applied to obtain the desired surface color. Tin flashings should be gone over, re- Where dirt or leaves lodge and are retained on the flashings, it paired and repainted about every three years. is advisable to remove any such accumulations and re- paint at yearly intervals. Proper maintenance will add immeasurably to their life. Lead The use of lead for building purposes is not new, and it is frequently very desirable for flashings. It is un- affected by ordinary atmospheric conditions and its soft- ness, pliability and malleability make it especially. valu- able in places where other materials cannot be easily introduced. Until the introduction of hardlead, the only lead available was soft lead, which, while possessing many excellent qualities, was impractical for flashing because of its low physical strength. Hardlead has a much greater tensile strength which permits its use in comparatively thin sheets. Lead is protected by nature through oxidation of the surface upon exposure, and requires no further treatment. Hardlead is rolled in sheets 24”, 30” and 36” wide and 96” long, weighing 214, 3, 4, 6 and 8 pounds per square 28 foot. With respect to the proper weight of hardlead sheets to be used, one manufacturer states that this de- pends upon the purpose, and adds: “For gutter linings, cornice coverings, base flashings and roofing purposes generally, the 3-pound sheet is rec- ommended, and for cap flashings and batten roofs where the battens are spaced 18” or less on centers, the 214- pound sheet may be used.” The lead should be so installed that it can expand and contract, and nailing directly through the sheet should never be permitted. The sheets should be fastened by means of cleats. These cleats should be made of 16- ounce soft rolled copper or 3-pound hardlead, fastened to woodwork with two hard copper wire nails and to masonry with brass screws and lead shields. The cleats should be spaced about 8” on centers, but on steep roofs continuous cleats for the horizontal joints are recom- mended. Where the edge of the metal is fastened by means of a reglet, there should be a continuous cleat of 3-pound hardlead caulked into the reglet and the sheet should be locked to the reglet. Never caulk the sheet into the reclet. Where the edge of the metal is unfastened, such as cap flashings and similar conditions where a lapped joint is provided, the free edge of the metal should be hemmed about 14”. All nails should be hard copper wire flat-head nails not less than 34” long. All screws should be of brass and all shields of lead; iron or steel nails and screws, coated or uncoated, should not be used. The sheets should be joined together by means of locked seams. Lapped and soldered seams are not recommended. Wooden tools should always be used in working and beating the material into place. Zinc Zinc for roofing and general sheet metal work has been used in Europe for more than a century, where its perma- nence and freedom from repairs have been thoroughly proven. Its use in this country, while of more recent years, has shown similar results. Zinc is a metal, not an alloy of other metals, which is extremely resistant to the corrosive action of the ele- ments. It rapidly acquires a protective coating (a basic carbonate of zinc), which will continue to form as long as there is any raw zinc exposed. This protective coat- ing gives the metal a light battleship grey color which will deepen with age and approach the color of grey slate. Zinc does not need paint as a protection, but paint can be readily used if other than the natural color of FLASHINGS TO BE WOWEN INTO SLATE COURSES-EACH FLASHING SHEET TOLAP ff, THE NEXT LOWER ATLEAST TWOUMTIES ; \ COURSES AND E: VE UNDER CAP FLA SH- ING ATLEAST FOUR ly a Sy i ~ / g Yes YY 3_/ <> \ YA « Z BUILT IN BASE FLASHING OR DORMER LULA BASE TEAS IINGS OR CHTINEY W/NDOW ON SLATE ROOF | Oi DROPS On SaA/, LAO, COPPER COVERED CRICKET- COPPER EXTENOS VP VNDER SLATE ATLEAST SIX INCHES COPPER TURNED VP AGAINST CHIMNEY AND COUNTER FLASHED CAP FLASHING S ATLEAST 2 INCHES 1 SLATE TOLAP ie ie | OPPER AT LEAST Me ; f E CAP PLASHING FLASIING [OR CINMNEY ON SLOPE, FLASHING [OP CIVMINE Y ON RIDG O@rOLATE. ROOF Caan eA OOF FIGURE 34. STANDARD DETAILS FLASHINGS—NATIONAL SLATE ASSOCIATION Tl Ss form to t Stand search Association nese and all flashing details conform to the Standards of the Copper and Brass Re Sela Ee aheOTORE zinc is desired. The Association will be glad to furnish specifications for the painting of zinc upon request. Rolled zinc for flashings should be not less than No. 11 zine gauge (0.024” thick) and should be laid in the usual manner, not nailed, but held in place by means of zinc clips or cleats. Zine flashing against masonry, concrete and stucco should be laid on a good grade of water-proof sheathing paper. If the cap flashing is set in a reglet, it should be pointed with elastic cement. Solder The agent used to join pieces of metal into one length or sheet is known as “solder.” The best grade, composed of equal parts of new tin and new lead, should be used and should conform to the “Standard Specifications for Solder Metal,” Serial Designation B-32-21, American Society for Testing Materials. To hasten its melting and conserve the heat in the solder iron, a flux is used. bL/INDS WOOD SILL COPPER FLASHING 7O EXTENO UNDER SILL AND LAP SLATE AT LEAST FOUR INCHES SLATE SLATE JS/D/ING—p> A COPPER FLASHING HELD |) 4Y COPPER NAILS FLASHING FOR DORMER WINDOW S/LL ai FLASHING FOR WOOD WINDOW HEAD Figure 35 On copper, rosin is the best agent for this purpose, and the use of acid as a substitute should be avoided when- Acid flux of an improper kind may do irreparable damage to the finest workmanship. Rosin is harmless to the metal and makes good seams. There are some objections to its use, such as sloping roofs and windy days. Under these conditions it is much easier to use killed acid for it will not blow away although it may run down a slope and spatter on windy days. Rosin can be kept in place by “burning” it on with a small soldering copper just hot enough to melt the rosin. The proper preparation of acid for use as a flux is of great- est importance. The acid is hydrochloric or muriatic. Pieces of zinc are put in the quantity to be used until it stops working; then it is properly killed. If the kill- ing is done hastily or by any one not familiar with the procedure, the acid may be used in a still active state and attack the copper. The acid to be used for the entire job should be prepared several days before the work starts and allowed to stand. On zinc and galvanized metal, acid should be used. Where the joints of the metal are not thoroughly sweated or soaked with solder, they may be loosened by expansion or contraction of the metal ever possible. 30 or leave small holes in the joint through which moisture readily finds its way. A new product known as soldering salts may also be used as a flux. It is claimed that these salts do not require so hot a soldering iron and that they also have other advantages. LLL GLEE OHLPY LSE ATLL , £2 4 / ; j Le OEE Aap) ~ SS aa pe STRIP. Si oeip —/ f COOP AGAINST SL OTE FLASHING [OR WOOD WATE? TABLE OR CLAPBOARD WALL Figure 36 Galvanic Action Dissimilar metals, when in contact in the presence of an electrolyte, set up galvanic action which results in the deterioration of the most electropositive metal. Any possibility of galvanic action between copper and iron or steel should be carefully avoided by proper insu- lation. This insulation is effected in various ways, three of which are: (1) covering the steel member with asbes- tos, as is frequently done in skylight construction; (2) placing strips of sheet lead between the two metals, as when new copper gutters are placed in old iron hang- ers; and (3) heavily tinning the iron, as is often done with iron or steel gutter and leader supports. Flashings—General Flashing should be used at all intersections of vertical or projecting surfaces through the roof or against which the roof abutts, such as walls, parapets, dormers, sides of chimneys, etc. Flashings used over or under the roof covering and turned up on the vertical surface are known as “base flashings.” Metal built into the vertical surface and bent down over the base flashing is termed a “cap flashing” or “counter flashing.” Base Flashings The base flashings should be extended under the upper- most row the full depth of the slate or at least 4” over the slate immediately below the metal. The vertical leg must be turned up not less than 4” and preferably 8” on the abutting surface. Where a vertical surface butts against the roof slope, it is necessary to build in the base INGA Lele OsNir As See bee onoe O2Cr Loan ON CL EAT- SOLOERED LAP SEA/Y | LOCK SLAM SECURED TO ROOF WITH CLEATS i | COPPER NAILS JO SECURE FLASHING BUILT-UP ROOFING SLASHING TOR EDGE OF COMPOSITION DECK KOOF ABOVE A SLOPING SLATE ROOF TWO-/LY ROOFING WER FLASHING a — COPPER FLASHING AND GRAVEL STOP- STONE, CONCRETE, OR TERRA COTTA COPING COPPER CAPFLASHING- tae eer JO EXTEND THROUGH BRICK WORK AND LA, ROOK SHLATH ING STONE ONE /NCH weal u Y FLASHING [OR A BRICK PARAPLT WALL [ACED WITH STONE Figure 37 31 Sf a When a parapet wall is flashed on the top and back with metal, the flashing should be carried over and down to within one inch of bottom of cap flash- ing formed as _ here shown, so that most of the water is deflected out onto the slate. StLeAsT rE RIOCOsETS COPPER FLASHING TO LAP COPPER VENTILATOR SLATE FROM 670 8/NCHES AND BE FORMED OVLR (8 PA 1H 2 Xa O) xa) 24. SEXO 336 © Dx Hx G Rox O exe 0) Dexa) Be & Se 6 2x 6 13 nO ae GO Re O ase @ 38 {8 Boe (6) Exe XE BSE xe Hee 16 LOMpae rrr ete. 16 se | Bar GO |) Bax G |) See G I Boe G | Bae He Ase Gi se i |) Pree Gy I] Wee 6 24 2x 10 xanli() 24 xe 10) 2x 10 Pao, ts) Dox © BS Boe © 3xe nO Bixee (6) 12 De OR Rox G Bx Boxe Boxe Boe Doe Re (6 Bx DES (5) (eR Re es on Aten 16 Xe MY exau 2 MG Xa © Boxe C Box Dax EC Be 6) a6 2X 9S 24, eXane xan ey Po xe AN) exe) 6 ANG xe LO 2x10 2x LO Dexwi() EXaG 19? 7 SE AKY) BEM) 2x0 2x0 ExaenG DI Boe 1G 3x 6 Roe LO Ve Ree eA 3 3 o-ac Gee 16 Dexa xe te 2 xa 0 2x10 2x U0 Pee AKY) 2x 10 Pee 8 Pare fa 3x. 6 24 aac IKW) Sexe) exe be 74, 3 1 exalt, P2356 1174 BMD Zea) PS AUD) Dexa LO) 12 xa, Dexa 2 xoO Pees Kl) Bae ID) 2256 NG) Dexa PES 83 PIO £85 Dixe xa Me 3x 10 3x 10 24, Pap an 2 Bye 1127 38 UY ayo 1174 ia 12 3x 12 2x12 3x 10 3x 10 A Np. wh apathy Pk Ae SUN 3 Wn LR Eg eee SRae pec 16 Sax 112) 3) xe 1B B5e 11D) De 24, 3x 14 Sexe lA: 35¢ 17 Boxe WP? 2x14 By sxe IPs Seall2 Boe MNP DO MA a Rene Soar rte Rca 16 3x 14 3x 14 3x12 3x12 24 3x 14 Soe {ah 3x 14 12 3x 14 3x14 35 xe 17 ay xe 11 CON MAS ie ia aR er a, Bae SS GUTTERS OVER 18 IMHES MIDE LOCALITY ag NN FACE OF SAW TOOTH ROOF / Saini SHADOW y= 7——FLAT OR STANOING SEAM COPPER ROOPING = LOCKED SEW SOLDERED — va 4 SOLDERED LOCKED ) SCAM FORMED IN THEGNTRE Ys OPAL GUTTERS OVER 12 fii WCHES WIDE—> AN INCORRECT METHOD OF LEGO) ANOTHER CORRECT METHOD OF [OR/1- GUTTLR SOR SAW TOOTH ROOF ING GUTTER [OR SAW TOOTH ROOF Figure 45 roof to accomplish this, or carry the leader across the porch roof to the gutter. In the latter case the leader should never have a slope of less than 45°; otherwise, ice may form in the leader. When it does become abso- lutely necessary to discharge the water on to a lower roof, metal spreaders should be used. When a mansard roof is of slate and the deck is copper covered, it is sometimes advisable to frame a gutter in the deck because the drippings from the deck may discolor the slate. This gutter should be lined with cold rolled sheet copper and have a water outlet lead to the inside of the building. When a low roof drains into a leader from a high roof, it is sometimes advisable to install a trap in the lower roof leader. If this is not done, the water pouring down from the higher roof may back up on to the low roof. Adequate provision should always be made for carry- ing the water discharged by the leaders away from the walls of the building. This can sometimes be accom- 2 plished by “splash stones” or masonry gutters, or if the leaders do not connect with storm sewers, a cistern for rain water may be dug not closer than 50’ to the building. This may be lined to collect the water for household use or left unlined in order that the water may seep into the soil. The drain from leader to sewer or cistern should be placed below the frost line and slope about 1” in 10’. Simplified Sizes and Weights In accordance with the unanimous action on October 14, 1924, of the general conference of representatives of manufacturers, distributors and users of eaves trough and conductor pipe, the United States Department of Com- merce, through the Bureau of Standards, recommends that simplified rules, practices, sizes and weights of eaves trough and conductor pipe be established as follows: Plain round conductor pipe: 2”, 3”, 4”, 5” and 0”. Round corrugated conductor pipe: 2”, 3”, 4”, 5” and 6”. Square corrugated conductor pipe: 2”, 3”, 4” and 5”, Eaves trough: 314”, 4”, 5’,67, 7” and 8”, Conductor pipe elbows: No. 1, 45°; No. 2, 60°; No. 3, vos No#4.90". 1. Along with the elimination of certain sizes of con- ductor pipe and eaves trough goes also that of the fittings formerly used therewith. 2. No eaves trough or conductor pipe to be made lighter than 28-gauge full weight; 27-gauge is to be elim- inated. 3. All elbows, shoes, mitres and ali accessories, inclu- ding ridge rolls, valleys, gutters and so on, are to be of 28-gauge full weight. 4. All eaves trough, conductor pipe, shoes, mitres and all accessories, including gutters, valleys, ridge rolls and so on, when made of copper, to be not lighter than 16 ounces. The 2” pipe should be used only for small roofs such as porches, etc., where there is a small amount of water to be carried away. The table below gives the nominal and actual sizes of the square corrugated pipe listed above: Nominal Size..... UE ou Altt 5" Actual Sizes 134" x 214 "1234" x 3M "1234" x 416 "1334" x 5" Snow Guards Snow guards are a necessary accessory to most slate roofs in sections of the country where the snowfall is sufficient to accumulate masses of snow and ice which are Figure 46. Snow Guards Ne ee ONE AG eer beer As eC. LAPT OUN liable to slide from the roof. On the slate roofs of the Harriman estate, along the Hudson, 35,000 copper wire snow guards were used. The appearance of many slate roofs in such localities has been marred by streaks of rust stains from such guards, or snow brakes, as they are sometimes called. FLASHING EAVES Figure 47. Parts of a Roof Years ago, according to one manufacturer, they mar- keted 90 black-painted guards to every 10 galvanized. But now, since research shows wisdom of proper installa- tions and better construction is demanded, this manufac- turer says he sells 75 galvanized to every 25 black- painted. While the “hot dip” process of galvanizing is the best, experts have still to be convinced that any galvanizing is perfect or rust proof. Hence, for first-class jobs only non-ferrous metals should be used for snow guards or any slate roof accessories. Snow guards should be placed in manner prescribed by their manufacturers on all slate roof surfaces above 7 SINGLE PITCH SHED ROOF OR LEAN 7O RIDGE DOUBLE ROOF OR GABLE ROOF HIP ROOF GAMBREL ROOF [ne HIP FRENCH OR MANSARD ROOF RiDck \ GAC GABLE ROOF WITH VALLEY AND H/P Figure 48. Types of Roofs doorways, porches, sidewalks, playgrounds or places where people are liable to pass or gather. They are essential to prevent masses of snow and ice from falling and as a protection to lower roof surfaces and gutters from such sliding masses. They are absolutely indis- pensable to retain snow on roofs when water from roof is collected for cistern or household purposes. Snow guards are made in various forms, some of which are illustrated in Figure 46. Each type requires different methods of application and may be obtained from slate distributors or quarriers of roofing slate or from manu- facturers. The Association can furnish a list of the latter concerns if desired. Some types may easily be placed on old roofs. Lightning Rods Where lightning rods are desired or used it is impor- tant at all times that they be properly grounded. All connections must be electrically perfect; that is, they must have very low contact resistance. Tips of rods should be silver, gold or platinum plated and all sharp bends in the conductor cable avoided. All extensive masses of metal such as water or gas pipe systems or cast iron soil pipe should be connected to the ground by soldered connections of not less than No. 10 B. & S. wire, preferably stranded. It is generally assumed that a lightning rod protects the area and any structures included within a 45° angle cone whose apex is the tip of the rod itself. Types of Roofs and Their Parts To the majority of the users of this Manual, the types of roofs and their parts will need no explanation but for the benefit of those not familiar with the names and technical descriptions used herein, reference to the accom- panying illustrations will provide the lay reader with the elementary information essential to a full understanding of the parts and types of roofs mentioned. Piling Slate In piling slate the important factors are the founda- lions, starting the piles, arrangement of piles and indi- vidual slates and the separations of the tiers. seal TE PILED HORIZONTALLY WITH HO THROUGH JOINTS /E NOT SUPPORTED BY | | I WALL AT THIS END VERTICAL SLATE | | OULD PILES OF SLATES i, | } FLIT ASAT OTHEREND Hl, \ Hill HI A® HORIZONTAL SLATE GROUND LATH OR STRAW SSS —— SS VERTICAL SLATE VERTICAL SLATE || ROPER MANE JOD SOR PLING OLA TE. Figure 49 Silene sie he OrOeisS The earth foundation upon which the slate are to be piled should be level, dry and solid. A layer of two-inch plank will keep the slate off the ground, help to dis- tribute the load and assist in maintaining straight even piles. The tiers of slate cannot be kept level if the foundation is not even or free from settlement. The first tier should be started by laying one pile of slates flat to a height equaling the width of slate being piled; i.e., for 20” x 12” slate the flat pile is 12” high. The following slates of the first tier are placed in an upright position on edge lengthwise, and should be kept as straight and vertical as possible. The bottoms of each handful should be tight against the bottom of the preceding slates. In this way the top is maintained straight and level. After the first tier has been laid to the desired or a convenient length, lay a double row of wooden lath lengthwise over the top of the first tier. Place the lath 1” from the outside edges of the slate tiers and interlap each lath one or two inches. A liberal quantity of straw may be used as a substitute for the lath. Rest the flat or starter of the second tier one half on the first tier starter and one half on the upright slates. This will help to prevent the piles from overturning and “slumping” down obliquely. Keeping the following slates as nearly perpendicular as possible is especially important in the first two tiers. Slates up to and including 20” x 11” may be safely piled up to 6 tiers high. Slates of a larger size should never be piled more than 4 tiers high. Closely piled, 100 commercial standard slates average 20” to 24”. When the slates are stored in an open yard, cover the piles with overlapping boards or use tar paper weighted down. Adequate protection prevents the slates from being frozen together. While slates are of ample strength when used in their proper place, reasonable care should be used in the handling of the material. Estimating Slate Quantities and Costs Architects and others interested should confer with local roofing contractors and through them obtain the “per square” or approximate total price for a particular type of roof, or have them estimate the quantities re- quired and furnish a definite price for each individual roof. Producers are always glad to co-operate with roof- ing contractors to furnish architects a layout or recom- mendations for slate suitable for any design or desired effect and to furnish roofing contractors estimates so they can give architects or owners comparative cost data to assist them to arrive at amount to spend for slate roof. A mistake frequently made is that of measuring the roof surface and assuming it as the exact or very close 46 approximate quantity required, then multiplying it by a price quoted in the price-list of one of the slate com- panies and perhaps adding an assumed sum for labor and contractors’ profit. In preparing estimates for a slate roof, every roofing contractor has his own method of making compensating allowances for waste, breakage, projections through roofs, dormers, hips, ridges, valleys and other factors occasionally entering into the question of quantity and labor. These are usually based upon experience with his own regular labor, local conditions or practice, and possibly other items peculiar to a locality. The follow- ing suggestions are therefore offered mainly for archi- tects and others not actively engaged in selling and lay- ing slate roofs, as a guide to many factors which should to be taken into consideration. For rough estimates a good roof costs from 6 to 8 per cent of total cost average building or home. From the time work is first started at the quarry until the material is laid on the building, there are certain costs which must be taken into consideration. These may be listed as follows: 1. Cost of slate (punched) on cars at the quarry. . Freight from quarry to destination. . Loading and hauling to storage yard. . Unloading, piling and waste at storage yard. . Loading and hauling to job. . Unloading and piling at job. . Placing on roof and laying. (a) Roofing felt. (b) Elastic Cement. (c) Nails. (d) Snow guards, or Snow Rails. (e) Sheet Metal. (f) Labor, including compensation insurance.. (g) Waste in handling, cutting and fitting. 8. Contractor’s overhead on organization and equip- NAN S& w bv ment. 9. Cost of guarantee or Bond. 10. Contractor’s profit. Items 3 and 4 are omitted when material is hauled direct to the job and unloaded. Freight to any locality from a quarry remains a fixed charge based upon either carload or less than carload lots. Less than carload lots carry a freight charge about double that of carload quan- tities. The question of loading, hauling, unloading and laying depends upon local labor costs, how fast the men work and nature of the contractor’s equipment. Some roofing contractors have slate punching machines and buy their slate unpunched, punching same at the job or in the yard on idle days or during inclement weather. While it may seem a comparatively simple problem to estimate the net quantity, it is not so easy to allow for the additional material required for slate around chim- neys, dormers, hips, valleys, etc. These allowances de- Ne Ace LL OUNe Ad Silane hae ao OG WAST IT OEN pend largely upon the judgment and experience of the estimator and the roof design. Method Suggested for Estimating 1. Obtain the net area of the roof in square feet, adding 6” to rafter length to allow for waste of normal roof. 2. Deduct one-half of the area of chimneys and dormers if over 20 sq. ft. and less than 80 sq. ft. Make no deduction if less than 20 sq. ft., and deduct 20 sq. ft. less than actual area if more than 80 sq. ft. . Include areas of dormer roofs, sides of dormers if slated, slate saddles, or other places where slate is used in addition to the main roof area. Include over- hanging parts of dormers, etc. 4. Add 1 sq. ft. for each lineal foot of hips and valleys, for loss in cutting and fitting. 5. Allow from 2% to 15% additional slate, depending upon the extent to which the roof is intersected by other roofs, dormers, walls, other contingencies, etc. 6. Divide the total of the above by 100, which will give the number of “squares” of roofing required. It should be noted that slate is always sold at the quarry on the basis of the quantity required to cover “100 sq. ft.” or a “square” of roof when slate is laid with a 3” head lap. If the roof is flat or other than 3” lap is used, the quantity must be corrected to the equiva- lent amount required as though the 3” lap was used. The following information should be given local roofing contractor when asking for a price: co 1. Kind and color of slate. 2. Size of slate desired, stating length and “all one width” or random width. 3. Thickness, as “commercial standard,” 14”, 3%”, etc. 4. Type of roof, as standard, textural, graduated or flat. 5. Kind of nails, as zine clad, zinc, “yellow metal,” copper clad or copper. 6. Kind of valleys and flashings. 7. If hip or gable roof. 8. Kind of snow guards, as galvanized, yellow metal or copper. 9. If snow rails, size of pipe and number of rows of pipe. 10. Location of job; if in city or vicinity, or out of city. 11. When job is to be finished. Prices Many requests have been received from architects and builders for the inclusion in this book of a definite list of prices for the various grades and colors of roofing slates. The compilers regret that it is impracticable to do this, for several reasons. The Association recom- mends, therefore, that when an architect or builder de- 47 sires the price of any particular grade and color of slate, he consult his local slate roofing contractor for estimates for the slate in place on the roof. Such estimates will then include the many factors listed in the section on “Estimating,” all of which must be given consideration. This can best be given by responsible contractors who are familiar with local conditions and costs. Advantages of Slate During the preparation of this book many requests to include in it a list of the advantages of slate in direct comparison with other roofing materials were received from architects, contractors, and especially from pros- pective home builders. The policy of the National Slate Association is, and always has been, never to point out the faults or weak- nesses of a competitive or a substitute material for any of the uses of slate. Such procedure conforms with sound business ethics, and, in line with this policy, the editors merely list in convenient form the outstanding characteristics which make slate such a valuable roofing material. Each of these qualities will be found discussed elsewhere in this book. Natural Stone Non-combustible—F ireproof Waterproof Permanent Wide range of effects possible Appearance Color Thickness Surface Texture Roof Texture Little or no maintenance costs Resists climatic changes Requires no other material to preserve it Reduces insurance premiums High salvage value Increases property values Investigation has shown that the cost of the roof of any structure ought to bear a certain definite relation to the cost of the entire building, not only from the stand- point of protection, but also from appearance. Every permanent building should be roofed with a material which will give it lasting protection, and at the same time be in character with the house itself and its surroundings. Because it does possess these qualities, for centuries slate has been the criterion by which other roof coverings have been judged. A slate roof has that indefinable “some- thing” which distinguishes any object of real value and completes the picture of a well constructed building or home. as SPECIFICATIONS, | GENERAL NOTES—ALL SPECIFICATIONS (a) The following specifications for “Standard,” “Textural” and “Graduated” slate roofs give in detail the pro- cedure to be followed in the laying of each type of roof on any type of structure from the smallest bungalow to the largest mansion. (b) A “Short Form” of each of these specifications is given just ahead of the “Basic Form” and is intended to be written into the architect’s specification. The “Short Form” refers to the “Basic Form” of the National Slate Association as printed herein and carries with it all the provisions contained in the “Basic Form.” In each “Short Form” the architect should fill in the color and size of the slate desired; otherwise it is complete as printed. (c) It will be noted that the “Sheet Metal Work” is a separate specification. The architect or owner can use it as a separate specification if this work is the subject of a separate contract or add it to the slate roofing specification if it is to be part of the slate roofing contractor’s work as is the custom in certain localities. (d) In each specification it is assumed that sheathing boards, crickets, cant strips or other under-roof surface will be specified elsewhere under the proper trade. (e) The marginal notes are informative and indicate optional changes which may be made in the specifications. (f) These specifications do not in any case include General Conditions or items relative to administrative mat- ters such as usually form the first part of an architect’s specification. Such items include fire, compensation, liability or other insurance and the use of hoists, water, telephone, watchman, temporary heat and light, and storage. (¢) The attention of the architect and owner is called to this fact in order that they may be fully acquainted with all conditions and advise the roofing and sheet metal contractor to arrange for the proper disposition of such items with the owner when the contract is direct or with the general contractor when his status is that of a sub-con- tractor. (h) The National Slate Association recommends the use of the Standard Documents of the American Institute of Architects and especially the “Standard Form of Sub-contract” which is a form of agreement between the General Contractor and the Sub-contractor. It calls attention, however, to paragraphs f and g above as these subjects are only covered in a general way in the “Standard Form.” STANDARD SPECIFICATIONS FOR SHEET METAL WORK IN CONNECTION WITH A SLATE ROOF NOTES 1. This specification used as here given will provide for sheet metal work in connection with a slate roof as follows: Paper—Rosin sized or asbestos felt, 6 lbs per sq. (unless already covered for slate) Nails—Copper. Flashings—16 oz. copper. Valleys—Open. 2. The following must be written into the specification, if required: Decks, Cornices, ete. Gutters and Downspouts. 3. See also General Notes—All Specifications, page 48. 48 ING Agel OpeNg Agee oe oe ep sek eh A On oe Orl As ly OUN SHORT FORM SPECIFICATION 1. Sheet Metal Work All materials and labor in connection with all sheet metal work shall be furnished and performed in strict com- pliance with the recommended practice and Standard Specification “M” for Sheet Metal Work, 1925, of the National Slate Association, 791 Drexel Building, Philadelphia, Penna. 2. Decks, Cornices, Etc. If required specijy materials and methods. 3. Gutters and Conductor Pipes If required specify materials and methods. STANDARD SPECIFICATION “M” (Covering in detail Flashings, etc., in connection with a Slate Roof) 1. General and Guarantee . (a) The General conditions of the contract are hereby made a part of the contract and this contractor shall examine these General Conditions and thoroughly acquaint himself with all the require- ments therein contained. (b) This contractor shall furnish all materials and labor in ac- cordance with the drawings and these specifications. (c) This contractor shall carefully examine all surfaces prepared for flashings, etc., by other trades, shall point out all defects to the proper authority, and shall see that the necessary corrections are made before proceeding with his work. This contractor shall arrange his work so as to co-operate at all times with other trades and prevent delay or damage to other work. (d) During construction care shall be taken to prevent damage to flashings in place by walking or placing heavy materials on them. As soon as soldering is done and flashings are completed, the work shall be thoroughly cleaned. Toward completion, all damaged work shall be repaired, all stains and débris shall be removed, and sheet metal work shall be left in perfect condition. (e) The contractor shall furnish his own scaffold or rigging, or arrange with the general contractor for the use of scaffolds furnished by others. (f) A written guarantee shall be furnished that the materials used are in strict accordance with these specifications, and that any and all repairs required on the roof due to defective materials or work- manship furnished under this contract shall be made without cost to the owner, for a period of one year. 2. Preparation of Surfaces All surfaces to receive flashings shall be made smooth and even, and all nail heads shall be set. 3. Building Paper All surfaces to be covered with copper shall be covered first with rosin-sized or asbestos-felt paper weighing not less than 6 pounds per 100 square feet. Paper shall lap 2” and be nailed with flat-head copper nails. If surfaces have already been covered with paper or felt by the roofing contractor this paper may be omitted. 4. Nails and Fastenings All nails, rivets and similar fastenings, if any, used throughout the work shall be of best grade hard copper or brass. Nails shall be wire nails not less than No. 12 gauge and not less than 7%” long. 5. Copper All flashings shall be 16 ounce soft copper, rolled from copper If other than copper is to be used, specify materiat, conforming to the standard specification of the American Society for gauge, weight, painting and method of laying. Testing Materials. The edges of all sheets to be soldered shall be tinned 114” on both sides. 49 SULBARL FER nO sOghaS eee 6. Solder and Rosin All solder shall be of the best grade, equal to Specification B-32-21 of the American Society for Testing Materials, and shall be composed of one-half pig lead and one-half block tin (new metals). Rosin shall be used as a flux. 7. Exposed Edges The exposed edge of all flashings shall be folded under 14”, in in such manner as to conceal them from view. 8. Flashings—Where Required All intersections of roofs with vertical surfaces of every kind and all openings in roof surfaces, shall be flashed with copper. The method of flashing, except as otherwise shown or specified, shall be base and counter, or cap, flashing. 9. Base Flashings (a) Unless otherwise specified or shown on the drawings, base flashings shall be, in general, at least 4” high. They shall project at least 4” out on to the roof. Flashings shall be full 96” in length. On sloping roofs they shall lap longitudinally at least 3”. On flat roofs the joints shall be flat-locked and soldered. (b) Against stucco-coated walls, metal lath shall lap outside the flashing so that the stucco shall finish over the flashing. 10. Cap Flashings or Counterflashings Cap flashings shall turn down over base flashings not less than 4”. They shall be secured to vertical surfaces, as follows: Wood Work: They shall extend up under exterior coverings not less than 4” above the roof, and shall be nailed along the top edge about every 8”. Mason Work: They shall extend into joints of masonry walls 4” and have the inner edge turned back on itself 14”. The sheets shall be bent to the required shapes, and built in with the mason work. No cutting out of joints for setting flashings will be allowed. Reglets: Where indicated on the drawings or where specified, flashings shall finish in reglets in the masonry cut by others where located by this contractor. The flashing shall be turned into the reglet the full depth and shall be turned back to form a hook. After the flashing is in place the reglet shall be filled and caulked, using molten lead on flat surfaces, and lead wool on vertical surfaces. After caulking the reglet shall be made smooth by filling with elastic cement. Stucco on Wood: When used with stucco-covered wood-frame walls, cap flashings shall be formed over a 7%” base board and extend up the wall at least 2” above the base board, and be nailed at the top edge with nails about 12” apart. Metal lath shall be placed over the flashing and the stucco should be finished against the base board. Stucco on Masonry: They shall be built into the masonry as the work progresses and shall project out from the wall as required and turn down over the base flashing. The stucco shall finish against the cap flashing. Concrete Walls: They shall be set in the forms before the con- crete is poured. They shall extend into the wall at least 2” and shall have the inner edges turned back 14”. 50 Specification writer should include here only those paragraphs which apply to the work and make suit- able provision in mason and carpenter specification for preliminary work. Make provision in proper specification for base- board, metal lath, etc. Ng oe ee OnE Ag Sele be eer. LOA alZOnN 11. Step Flashings Step flashings shall be used where vertical surfaces occur in con- nection with slopes. They shall be formed of separate pieces built into the masonry as specified for cap flashings in masonry. Steps shall lap generally 3”, but in no case less than 2”, and shall not be soldered. Lap joints shall be vertical. 12. Vent Flashings All pipes passing through roofs shall be flashed and counter- flashed. Base flashings shall extend out on the roof not less than 6”. They shall be of sufficient length to cover the slate course next below the pipe and to extend up under the slate course above as far as possible without puncture by nails. Patented vent-flashing devices may be used, subject to the approval of the architect. They shall be made of 16 ounce copper, shall be the product of a recognized manufacturer, and shall be installed according to manufacturer’s directions. 13. Open Valley Flashings (a) Open valleys shall be not less than 4” wide. The proper width shall be determined by the following rule: Starting at the top with a width of 4”, increase the width one inch for every 8 feet of length of the valley. Flashing pieces shall be full length sheets and of sufficient width to cover the open por- tion of the valley and extend up under the slate not less than 4” on each side. (b) Where two valleys of unequal size come together, or where the areas drained by the valley are unequal, there shall be placed in the valley a “crimp” angle or tee not less than 1” high. This “crimp” may be formed in the valley sheet before placing, or it may be made of a separate piece soldered to the valley sheet. 14. Crickets or Saddle Flashing Crickets or saddles formed back of all vertical surfaces, such as chimneys, etc., breaking through sloping roofs, shall be covered with copper. The flashing of these crickets shall be made of part of the flashing along the sides of the chimney, etc. 15. Other Work This contractor shall furnish all flashing pieces to other trades such as the Mason, Carpenter and Roofing Contractor for building in with that particular work and shall co-operate with these con- tractors in doing their work. 16. Decks, Cornices, Ete. 17. Gutters and Down Spouts If closed valleys are desired, specify as follows: Flashing pieces, for closed valley shall be of suj- ficient length to extend 2 inches above the top of slate roofing piece and lap the flashing piece below 3 inches, and of width sufficient to extend up the sides of the valley far enough to make the valley 8 inches deep. They shall be placed with the slate so that all pieces are separated by a course of slate. Pieces shall be set so as to lap at least 3 inches and to be entirely concealed by the slates. They shall be fastened by nails at the top edge only. A small inequality in the areas drained would not require this. Specify framing and blocking for crickets under carpentry. Make provision in mason specifications for building in these flashings, and the cutting of any necessary reglets. If required specify materials and methods. If required specify materials and methods. Standard Specification “M”—Sheet Metal Work, 1925 ol ed bate) BS yea O(a bd Beas STANDARD SLATE ROOFS The “Standard” slate roof has been developed to provide a serviceable, permanent roof at a minimum cost. Any changes which have been made in the usual specification do not in any way affect those valuable features which are to be found only in a slate roof but merely eliminate so far as possible every factor which might increase the cost of slating. As has previously been explained, the nature of slate stone is such that every piece cannot be split to an exact thickness and in order to eliminate a selection of the material with its resultant rehandling and calipering of each piece, a slight variation in the thickness of the slates is permitted. “Commercial Standard” slates are the quarry run of production and may show tolerable variations above or below 3/16”. A second change is found in the note opposite paragraph 3, page 53, of the Specification. The Architect or Owner will find it to his advantage to confer with the roofing contractors in his locality regarding the size (length and width) or sizes of the slate economically available. The number of sizes shown on page 12 is due to the nature of the material which makes it necessary to cut the blocks into a large number of different sized pieces to secure the fullest utilization of the slabs as they are taken from the quarry. It will therefore be readily appreciated that certain sizes may be more easily obtained than others and that to insist on slates of a definite dimension may not only add to the cost of the roof but may delay the work owing to difficulty in locating a quarry having that particular size in stock. On roofs of large area sufficient economy can often be effected by a proper selection of sizes to make a preliminary investigation of value. The smaller sizes ranging from 10” x 6” to 14” x 10” are usually more plentiful than the larger sizes and when laid with a narrow exposure will be found to produce a most interesting and artistic effect similar to that secured in the same way on the wonderful chateaux of France. STANDARD SPECIFICATION FOR A STANDARD SLATE ROOF NOTES 1. This specification used as here given will provide for a complete slate roof as follows: Felt—Saturated Asphalt, 14 lbs. per sq. Ridges—Saddle Flashings—16 oz. copper Nails—Copper Valleys—Open Slate—Commercial Hips—Saddle standard (approx. 3/16”) Cement—Elastic waterproof 2. The following must be written into the specification under paragraph: 3-b. Slate—size 3-c. Slate—color 3. It should be noted that metal work is not covered by this specification, as separate Standard Specifications for Sheet Metal Work are given on page 48. The specifications for Slate Roofing and sheet metal work are so arranged, however, that they may be handled separately or together to conform to variation in custom in different sections of the country. 4. See also General Notes—AlIl Specifications, Page 48. SHORT FORM SPECIFICATION Note: In using the Short Form if any optional paragraphs are desired so state. 1. Slate Roofing For standards and optional materials and methods, ; : : : see the following paragraphs in the complete form. (a) Furnish all materials and labor and cover with commercial = oe s rt f the building sh arked or indi- Paragraph 1—Guarantee standard slate all portions of the building shown, marked or indi Pe ee ein cated for Slate, and form all slate hips and ridges in accordance Patasraphs = Slave with Specification S for a Standard Slate Roof, 1925, of the National Paragraph 4—Hips Slate Association, 791 Drexel Building, Philadelphia, Pa. Paragraph 5—Ridges Paragraph 6—V alleys Paragraph 7—Elastic Cement Paragraph 8—Nails (Continued on Page 53) Paragraph 9—Slating a2 Nee ele ORN Ag Sole ie te ARS nO CU lAsL LO aN (b) The size of the slate shall be (c) The color of the slate shall be 2. Sheet Metal Work Paragraph 3-b—Size of Slate Paragraph 3-c—Color of Slate If part of the slate roofing contractor's work, quote here the Short Form for Sheet Metal Work on page 49. STANDARD SPECIFICATION ‘S” (Covering in detail all materials and labor in connection with a Standard Slate Roof) 1. General and Guarantee (a) The General Conditions of the contract are hereby made a part of the contract and this contractor shall examine these General Conditions and thoroughly acquaint himself with all the require- ments therein contained. (b) This contractor shall furnish all materials and labor in ac- cordance with the drawings and these specifications. (c) This contractor shall inspect all surfaces prepared for slating by other trades, point out to the proper authority all defects, and shall not proceed with the laying of felt, flashings or slate until the necessary corrections have been made. (d) Roofing shall be applied by workmen experienced in the applying of slate. (e) The roofing contractor shall furnish his own scaffold or rig- ging, or arrange with the general contractor for the use of scaffolds furnished by others. (f) A written guarantee shall be furnished that the eat used are in strict accordance with these specifications, and that any and all repairs required on the roof due to defective materials or workmanship furnished under this contract shall be made without cost to the owner, for a period of one year. 2. Roofing Felt (a) On all boarding to be covered with slate, furnish and lay asphalt saturated rag felt, not less in weight than that commercially known as “14 pound” felt. In this weight, per 100 square feet, a tolerance of one pound plus or minus will be allowed. (b) Felt shall be laid in horizontal layers with joints lapped toward eaves and at ends at least 2” and well secured along laps and at ends as necessary to properly hold the felt in place and protect the structure until covered by the slate. All felt shall be preserved unbroken, tight and whole. (c) The felt shall lap over all hips and ridges. (d) Felt shall be lapped 2” over the metal of any valleys or built-in gutters. 3. Slate (a) Slate shall be of commercial standard quality and thickness. (b) Size of slate shall be of length(s). , or random widths (c) Color of slate shall be (Continued on Page 54) 53 For additional data regarding roofing felt, see page 23. Commercial standard slate is approximately 3/16” in thickness. If any other thickness is desired, so state and omit “Commercial.” For table of standard sizes, see page 12. A definite size must be stated to place all estimates on an equal basis. To obtain a roof at a minimum cost, confer with local roofers as to the size or sizes economically available. Standard roofs are usually laid with slate of one size on any one area. If random widths are desired, so state. For list of slate colors see page 7. Ij weathering slate are desired, so state, otherwise unfading colors will be furnished. If @ particular quarry product is desired, so state. Se beg Ee SReOeOsikes (d) All slate shall be hard, dense, sound rock, machine punched for two nails each. All exposed corners shall be practically full. No broken corners on covered ends which sacrifice nailing strength or the laying of a watertight roof will be allowed. No broken or cracked slates shall be used. 4. Hips (a) All hips shall be laid to form “Saddle” Hips without metal underneath. 5. Ridges (a) All ridges shall be laid to form “Saddle” Ridges. The nails of the combing slate shall pass through the joints of the slates below. 6. Valleys (a) All valleys shall be laid to form “Open” Valleys. 7. Elastic Cement (a) Cement shall be an approved brand of waterproof elastic slaters’ cement colored to match as nearly as possible the general color of the slate. 8. Nails (a) All slate shall be fastened with two large-head slaters’ solid copper nails. Use 3d (114”) nails for slates 18” or less in length, 4d (144") for 20” or longer, and 6d (2”) for slates on hips and ridges. 9. Slating (a) The entire surface of all main and porch roofs, the roofs and sides of any dormer windows, if shown, and all other surfaces so indicated on the drawings, shall be covered with slate in a proper and watertight manner. (b) The slate shall project 2” at the eaves and 1” at all gable ends, and shall be laid in horizontal courses with the standard 3” headlap, and each course shall break joints with the preceding one. Slates at the eaves or cornice line shall be doubled and canted 14,” by a wooden cant strip. (c) Slates overlapping sheet metal work shall have the nails so placed as to avoid puncturing the sheet metal. Exposed nails shall be permissible only in top courses where unavoidable. (d) Neatly fit slate around any pipes, ventilators, etc. (e) Nails shall not be driven in so far as to produce a strain on the slate. (f) Cover all exposed nail heads with elastic cement. Hip slates and ridge slates shall be laid in elastic cement spread thickly over unexposed surface of under courses of slate, nailed securely in place and pointed with elastic cement. (¢) Build in and place all flashing pieces furnished by the sheet metal contractor and co-operate with him in doing the work of flashing. (h) On completion all slate must be sound, whole and clean, and the roof shall be left in every respect tight and a neat example of workmanship. “Machine punched” does not exclude hand punch- ing by means of the punch and mawl or hand punch- ing with the hammer, as the slate is laid, to properly locate holes for fitting hips, etc., or obtaining suitable nailing to the roof boards. Ij any other type of hip is desired, so state. Ij combed ridges, ridge rolls or cresting are desired, so state. If “Closed” Valleys are desired, so state. Vertical surfaces may be laid with 1” headlap. Specify cant strips of proper thickness under Carpentry. Where cant strips occur above gutters, they should be placed before the metal. Standard Specification “‘S’”—Standard Slate Roof, 1925 National Slate Association o4 Neel Om Ne Ag ogee eta encore On. AN TOL OFN TEXTURAL SLATE ROOFS The term “Textural” is applied to slate roofs in this publication for the first time, so far as is known. It has been here coined to designate those charming roofs of slate which cannot be classified as strictly Standard or Graduated but which range between the two and produce a distinctive and altogether individual result. The Textural roof presents most fascinating possibilities to the designer, for it may be varied in almost hundreds of ways to conform and harmonize with the structure of which it is to become a part. It may be made nearly as chaste as the Standard or it may be almost as elaborate as the Graduated. For example, the slates may be uniform in length but vary in thickness, or the thickness may be kept uniform and the length (and exposure) varied. The width may vary or be uniform. Very rough surfaced slates may be introduced into an otherwise almost smooth roof. The slate may be laid with varying exposure or the butts may be chipped and broken at irregular angles. When the thick- ness is varied the usual range is from 3/16” to 3%” but if a heavier and more irregular effect is desired, this may be accomplished by incorporating certain percentages of thicker slates. These present only a few of the opportunities for interesting treatment. In addition, the color of the slates may be used with splendid effect by mixing slates of different tones, but the tone value or predominating color effect desired should always be specified. When color is used, accidental or “freak” slates may be introduced throughout the roof, adding greatly to the picturesque effect of the ensemble. The cost of a Textural roof will depend entirely upon the effects desired, and although usually slightly greater than the Standard roof, will not equal in either material or labor the cost of a Graduated roof. The various details of construction, sheathing, ridges, hips, valleys, flashings, etc., shown in connection with the Standard slate roof apply also to the Textural roof. The construction may require additional collar beams, supports or slightly heavier rafters than for a Standard roof, depending upon local conditions and construction as well as the weight of the slate selected. STANDARD SPECIFICATIONS FOR A TEXTURAL SLATE ROOF NOTES 1. This specification used as here given will provide for a complete slate roof as follows: Felt—Saturated Asphalt commercially known as 30 lbs. per sq. Flashings—16 oz. copper. Slate—3/16” to 34”, random width, approved lengths. Valleys—Closed. Hips—Saddle. Cement—Elastic Waterproof. Ridges—-Saddle. Nails—Copper. 2. The following must be written into the specification under paragraph: 3-c Slate—Predominating color. 3. It should be noted that metal work is not covered by this specification, as separate Standard Specifications for Sheet Metal Work are given on page 48. The specifications for Slate Roofing and sheet metal work are so arranged, however, that they may be handled separately or together to conform to variation in custom in different sections of the country. 4. See also General Notes—All Specifications, Page 48. SHORT FORM SPECIFICATION Note: In using the Short Form if any optional paragraphs are desired so state. ]. Slate Roofing For standards and optional materials and methods. (a) Furnish all materials and labor and cover with slate all por- See the following parcgraphs.th the complete jor: tions of the building shown, marked or indicated for slate, and Sep pause form all slate hips and ridges in accordance with the Specification ye Del adlad le tel ees 5 2 Paragraph 3—Slate T” for a Textural Slate Roof, 1925, of the National Slate Asso- Paragraph 4—Hips ciation, 791 Drexel Building, Philadelphia, Pa. Paragraph 5—Ridges Paragraph 6—Valleys Paragraph 7—Elastic Cement Paragraph 8—Nails (Continued on Page 56) Paragraph 9—Slating Sys) Sale he ROL OsKesS (b) The predominating color of the slate shall be 2. Sheet Metal Work Paragraph 3-b—Sizes of Slate Paragraph 3-c—Color of Slate If part of the slate roofing contractor’s work, quote here the Short Form for Sheet Metal Work on page 49. STANDARD SPECIFICATION “T” (Covering in detail all materials and labor in connection with a Textural Slate Roof.) 1. General and Guarantee (a) The General Conditions of the contract are hereby made a part of the contract and this contractor shall examine these General Conditions and thoroughly acquaint himself with all the require- ments therein contained. (b) This contractor shall furnish all material and labor in accordance with the drawings and these specifications. (c) The roofing contractor shall furnish samples of the slate he proposes to use. If required, a layout shall be prepared by the producer and submitted to the Architect for approval. (d) This contractor shall inspect all surfaces prepared for slating by other trades, point out to the proper authority all defects, and shall not proceed with the laying of felt, flashings or slate until the necessary corrections have been made. (e) Roofing shall be applied by workmen experienced in the applying of slate. (f) The roofing contractor shall furnish his own scaffold or rig- ging, or arrange with the general contractor for the use of scaffolds furnished by others) (g) A written guarantee shall be furnished that the materials used are in strict accordance with these specifications and the samples submitted, and that any and all repairs required on the roof due to defective materials or workmanship furnished under this contract shall be made without cost to the owner, for a period of one year. 2. Roofing Felt (a) On all boarding to be covered with slate, furnish and lay asphalt saturated rag felt, not less in weight than that commercially known as “30 pound” felt. (b) Felt shall be laid in horizontal layers with joints lapped toward eaves and at ends at least 2” and well secured along laps and at ends as necessary to properly hold the felt in place and protect the structure until covered by the slate. All felt shall be preserved unbroken, tight and whole. (c) The felt shall lap over all hips and ridges. (d) Felt shall be lapped 2” over the metal of any valleys or built-in gutters. 3. Slate (a) Slate shall be in combinations of thicknesses from 84” to 3/16” thick. (b) Slates shall be of random widths and of such lengths as approved by the Architect. (c) The predominating color of the slates shall be (d) All slate shall be hard, dense, sound rock, machine punched for two nails each. No cracked slate shall be used. All exposed corners shall be practically full. No broken corners on covered ends which sacrifice nailing strength or the laying of a watertight roof will be allowed. No broken or cracked slates shall be used. 36 For additional data regarding roofing felt, see page 23. If a percentage of thicker slates are desired, state the thickness and percentage of each. If a layout is required, state—‘in accordance with approved layout.” If definite sizes must be furnished, so state. To obtain a roof at minimum cost, confer with local roofers as to sizes economically available. For list of slate colors see page 7. Colors will be of the “weathering” class unless otherwise noted. “Machine punched” does not exclude hand punch- ing by means of the punch and mawl, or hand punching with the hammer to properly locate holes for fitting hips, etc., or obtaining suitable nailing surface. NGA lRORNT Agi ee elem ha Asst on OsCalele 1 iON 4. Hips (a) All hips shall be laid to form “Saddle” Hips without metal underneath. 5. Ridges (a) All ridges shall be laid to form “Saddle” Ridges. The nails of the combing slate shall pass through the joints of the slates below. 6. Valleys (a) All valleys shall be laid to form “Closed” Valleys. 7. Elastic Cement (a) Cement shali be an approved brand of waterproof elastic slaters’ cement colored to match as nearly as possible the general color of the slate. 8. Nails (a) All slate shall be fastened with large-head slaters’ copper nails of sufficient lengths to adequately penetrate roof boarding. Care shall be taken to avoid exposing the nails on cornice, soffits, overhanging eaves, etc. 9. Slating (a) The entire surface of all main and porch roofs, the roofs and sides of any dormer windows, if shown, and all other surfaces so indicated on the drawings, shall be covered with slate in a proper and watertight manner. (b) The slate shall project 2” at the eaves and 1” at all gable ends, and shall be laid in horizontal courses with the standard 3” headlap and each course shall break joints with the preceding one. Slates at the eaves or cornice line shall be doubled and canted by a wooden cant strip. (c) Slates overlapping sheet metal work shall have the nails so placed as to avoid puncturing the sheet metal. Exposed nails shal be permissible only in top courses where unavoidable. (d) Neatly fit slate around any pipes, ventilators, etc. (e) Nails shall not be driven in so far as to produce a strain on the slate. (f) Cover all exposed nail heads with elastic cement. Hip slates and ridge slates shall be laid in elastic cement spread thickly over unexposed surface of under courses of slate, nailed securely in place and pointed with elastic cement. (g) Build in and place all flashing pieces furnished by the sheet metal contractor and co-operate with him in doing the work of flashing. (h) On completion all slate must be sound, whole and clean, and the roof shall be left in every respect tight and a neat example of workmanship. If any other type of hip is desired, so state. If combed ridges, ridge rolls or cresting are de- sired, so state. If open valleys are desired, so state. “Round” or “Canoe” valleys may be used if desired but will add to the cost of the roof and are more frequently used with Graduated Roofs. For data see page 22; for Specifications see Standard Specification for a Graduated Slate Roof, page 59. Vertical surfaces may be iaid with 1” headlap. Specify cant strips of proper thickness under Car- pentry. Where cant strips occur above gutters, they should be placed before the metal. Standard Specification “T’’—Textural Slate Roof, 1925. a SEL eA CE ane ORs GRADUATED SLATE ROOFS The origin of the graduated roof forms an interesting bit of history. Their use in Europe dates back several cen- turies before the days of standardization, to the time when sufficient slate to cover the roof was extracted from the quarry by primitive methods without regard to definite size or established thicknesses. Doubtless the sizes made were those most convenient. Sent to the building, the slates were evidently sorted to some extent and hooked to roof lath by means of oak pegs. If an accident occurred to the roof, a messenger and cart would be dispatched to the nearest quarry for a “load of slate,” no attention probably being paid to size or thickness, and the roof was patched and repaired as well as the material might allow. As a result, a careful study of the roofs of former years discloses the fact that the charm of such roofs may be traced to mass, slope, the mellowing effect of age and weather, and the irregular texture, as a result of roughness of the surface and variations in length, width and size, all being more or less random. The graduated slate roof is the custom-made roof of the industry, and is therefore subject to individual characteris- tics and many variations to meet contingencies of design and conditions. In designing a roof of this type, the method of graduating will depend upon the size of the roof and its span, the “scale” of the building upon which it is used, and the general effect desired. A properly designed graduated roof should show no decided or noticeable break between the various thicknesses, sizes, etc. An agreeable and harmonious result can only be obtained by care in design and laying and the selection of the correct colors, sizes and texture. The interpretation of the design of such roofs is so much a matter of experience and good judgment that certain producers who have made a specialty of this work should be consulted and their suggestions obtained as to how to obtain the architectural effects desired. For most cases a maximum thickness of 1” will be found entirely satisfactory and pleasing in effect. The approxi- mate thicknesses always obtainable are 3/16", 14”, 39”, 1%”, 34”, 1", 144” and 1144”. The maximum practical thickness which can be used is 2”, but this is rarely used except for unusual conditions. Once the architectural effect desired has been determined upon, the length of the roof slope and the resulting number of courses will determine the rate of decrease in thickness or the number of courses of any one thickness which can be used. The occasional introduction of slates of varying thicknesses in the same course in some roofs is regarded as a desirable feature and affords another method of influencing the irregular character of the surface. In general, the large, thick slates used near the eaves will occur in fewer courses than the thinner slates toward the ridge. In addition to the usual standard sizes, slates above 14” thick are produced in lengths up to 30”. The graduations in lengths generally range from 24” to 12”. The longest slates are used at the eaves and the length usually diminished with the thickness. Here, again, good design dictates the range of graduations in length for any particular roof. The variations in length will at once provide a graduation in exposure by using the standard 3” lap. To illustrate, a suitable range of lengths might be: Under Eave Course %%” thick 14” long No exposure First Course yi PE ae 101,” iL 14 3,” (74 ae ce 101,” (74 2 Courses LU oie KTS ONE Y “se 1," (74 20” 66 81,” (14 2 (14 30" oe 204 (74 81," (<4 A (14 3” (<4 13” (14 TY” (14 Py 74 yy,” (74 We” 74 614” 74 a (14 1,” (14 4? (44 olf” (14 3 (74 BAO (74 a (a4 olf,” (+4 8 74 3/16” 66 De (74 Alf” 66 Random widths should be used and so laid that the vertical joints of each course are broken and covered by the slate of the course above. The variation in widths also tends to add interest to the texture and prevents a mechanical effect. The effect can be further enhanced by mixing percentages of heavier or lighter slates in each course of a given thickness. In splitting the thick slate, a slightly roughened surface is obtained and the edges are more or less broken. The usual tendency is for the thinner slates to split cleaner and with greater evenness of surface. As a result, the slate toward the ridge are smoother in surface texture and should be selected for their roughness or at least sufficient used to avoid a flat, mechanical appearance in contrast with the heavier slates near the eaves. This is especially important 98 Nee el OSNG AS eee ee alia oo eOCC Ar I OuN since the ridge slate, being farther from the eye, will naturally tend to appear smoother and more even than those lower down the roof. In addition to the variations described above, the color possibilities should not be forgotten. With proper selection the roof can be gradually blended from light to dark. In general, a dark roof appears to better advantage than a light color. Great care should be used in blending light to dark so there will be no pronounced line of demarcation of different shades. Slates for graduated roofs may be had in all the natural slate colors, and many interesting effects may be obtained by the use of harmonious and contrasting colors laid at random. If not too “spotty,” the weathering and ageing will tie the colors together, blending into a unit of unrivaled character. Heavy slates require the best of nailing. Any slates over 34” in thickness and 20” in length should be machine punched for four nails each. The smaller and thinner slates may be punched for two holes. Use only the best grade of non-ferrous slaters’ nails with large heads and heavy gauge shafts of sufficient length to secure ample penetration into the supporting roof surface. A heavy grade of felt will provide a cushion for the slates and provide additional insulation value. It is recom- mended that felt weighing from 30 to 50 pounds per square be used. (See Roofing Felt, page 23.) It is decidedly unwise to use any but the best of flashing materials and workmanship on so fine a roof. The construction of slate hips, valleys and ridges has been fully covered under the laying of slate, pages 14 to 23, and a repetition of this description is unnecessary here. Rafters and their supporting members should be carefully proportioned to the load which they must sustain. Sheathing boards of 7” material are ordinarily sufficient. When unusually thick slates are used, 114” sheathing boards should be specified. STANDARD SPECIFICATION FOR A GRADUATED SLATE ROOF NOTES 1. This specification used as here given will provide for a complete slate roof as follows: Felt—Saturated Asphalt, 30 lbs. per sq. Cement—Elastic Waterproof. Flashings—16 oz. copper. Ridges—Saddle. Hips—Saddle. Nails—Copper. Slate—34” to 14” thick, 24” to 12” long. 2. The following must be written into the specification under paragraph: 3-c Slate—Color. 8-a Valleys—Type. 3. It should be noted that metal work is not covered by this specification, as separate Standard Specifications for Sheet Metal Work are given on page 49. The specifications for Slate Roofing and sheet metal work are so arranged, however, that they may be handled separately or together to conform to variation in custom in different sections of the country. 4. See also General Notes—All Specifications, Page 48. SHORT FORM SPECIFICATION Norte: In using the Short Form if optional paragraphs are desired, so state. 1. Slate Roofing For standard and optional materials and methods, (a) Furnish all materials and labor and cover with slate all por- see the| following paragraphs tn the complete form. tions of the building shown, marked or indicated for slate; form all Paragraph 1—Guarantee slate hips, ridges and valleys, in accordance with Specification “G” Paragraph I—Samples and Layout for a Graduated Slate Roof, 1925, of the National Slate Association, pa esioes awe 791 Drexel Building, Philadelphia, Pa. (Note: if hee sizes and thicknesses than those in specification “G” are desired, specify exception at end of this paragraph.) Paragraph 4—Hips Paragraph 5—Ridges Paragraph 7—Elastic Cement Paragraph 8—Nails (Continued on Page 60) Paragraph 9—Slating 39 Saleen eOrOei aS (b) The slate shall be ; Paragraph 3-c—Color of Slate (c) The valleys shall be 2 Paragraph 6—Valleys 2. Sheet Metal Work If part of slate roofing contractor's work, quote here the Short Form for Sheet Metal Work on page 49. STANDARD SPECIFICATION “G” (Covering in detail all materials and labor in connection with a Graduated Slate Roof.) l. General and Guarantee (a) The General Conditions of the contract are hereby made a part of the contract and this contractor shall examine these General Conditions and thoroughly acquaint himself with all the require- ments therein contained. (b) The roofing contractor shall furnish samples of the slate he proposes to use. A layout showing graduations, courses and color distribution shall be prepared by the producer and submitted to the Architect for approval. (c) This contractor shall furnish all materials and labor in ac- cordance with the drawings and these specifications. (d) This contractor shall inspect all surfaces prepared for slating by other trades, point out to the proper authority all defects, and shall not proceed with the laying of felt, flashings or slate until the necessary corrections have been made. (e) Roofing shall be applied by workmen experienced in the applying of slate. (f) The roofing contractor shall furnish his own scaffold or rig- ging, or arrange with the general contractor for the use of scaffolds furnished by others. (g) A written guarantee shall be furnished that the materials are in strict accordance with these specifications, and that any and all repairs required on the roof due to defective materials or workman- ship furnished under this contract shall be made without cost to the owner, for a period of one year. 2. Roofing Felt (a) On all boarding to be covered with slate, furnish and lay For additional data regarding roofing felt, see asphalt saturated rag felt, not less in weight than that commercially peer known as “30 pound” felt. (b) Felt shall be laid in horizontal layers with joints lapped toward eaves and at ends at least 2” and well secured along laps and at ends as necessary to properly hold the felt in place and protect the structure until covered by the slate. All felt shall be preserved unbroken, tight and whole. (c) The felt shall lap over all hips and ridges. (d) Felt shall be lapped 2” over the metal of any valleys or built-in gutters. 3. Slate (a) Slate shall be in combination of thicknesses from 34” to 14”. Any desired range may be used, inserting the de- (b) Slates shall be random widths from 24” to 12” in length. sired thicknesses and lengths. (c) Color of slate shall be ——————————— State color or color mixture, permanent or weather- ing, and percentages of each desired. (d) All slate shall be hard, dense, sound rock, machine punched _ “Machine punched” does not a ae pee for two holes. Slates 34” and thicker, when 20” or more in length, oa ae ae Ha ls Dung Pie a ne eres. shall have four holes. All exposed corners shall be practically full property locatedheles dors pte bine) Ce ormolrare and no broken corners on covered ends which sacrifice nailing ing suitable nailing to the roof boards. strength or the laying of a watertight roof will be allowed. No broken or cracked slates shall be used. 60 Nese le OoNt As eet eA teh FACS SO C1 A Tole O N 4. Hips (a) All hips shall be laid to form “Saddle” Hips without metal underneath. 5. Ridges (a) All ridges shall be laid to form “Saddle” Ridges. The nails of the combing slate shall pass through the joints of the slates below. 6. Valleys (a) All valleys shall be 7. Elastic Cement (a) Cement shall be an approved brand of waterproof elastic slaters’ cement colored to match as nearly as possible the general color of the slate. 8. Nails (a) All slate shall be fastened with large flat-head slaters’ copper nails of sufficient length to adequately penetrate nailing surface. Use four nails for slates 34” and thicker when 20” or more in length. Care should be taken to avoid exposing the nails on cornice, soffits, overhanging eaves, etc. (b) Nails securing slate must in no instance be driven through flashing. 9. Slating (a) The entire surface of all main and porch roofs, the roofs and sides of any dormer windows, if shown, and all other surfaces so indicated on the drawings, shall be covered with slate in combina- tions of colors, sizes and thicknesses shown on approved layout drawing furnished by Slate Producer. (b) The slate shall project at the eaves and at all gable ends as directed, and shall be laid in horizontal courses with the standard 3” headlap, and each course shall break joints with the preceding one. Slates at the eaves or cornice line shall be doubled and canted so that the succeeding course will have flat contact. (c) Slates overlapping sheet metal work shall have the nails so placed as to avoid puncturing the sheet metal. Exposed nails shall be permissible only in top courses where unavoidable. (d) Neatly fit slate around any pipes, ventilators, etc. (e) Nails shall not be driven in so far as to produce a strain on the slate. (f) Cover all exposed nail heads with elastic cement. Hip slates and ridge slates shall be laid in elastic cement spread thickly over unexposed surface of under course of slate. (¢) Build in and place all flashing pieces furnished by the sheet metal contractor and co-operate with him in doing the work of flashing. (h) On completion all slate must be sound, whole and clean, and the roof shall be left in every respect tight and a neat example of workmanship. If any other type of hips is desired, so state. If combed ridges, ridge rolls or cresting are de- sired, so state. Insert necessary following paragraphs: 1—Laid to form “Open” Valleys. 2—Laid to form “Closed” Valleys. 3—Of slate laid to radius. The slate shall be tapered, shouldered, securely nailed and shall be 4” longer than the slates used in the corresponding courses on the roof and laid to allow the tail coursings to line up. Proper copper flashing under each course. Vertical surfaces may be laid with a head lap ayy I Specify cant strips of proper thickness under Carpentry. Where cant strips occur above gutters, they should be placed before the metal. If other construction at eaves and gables is de- sired, this should be noted here. Standard Specification “G’’—Graduated Slate Roof, 1925 6l Sele shee ReOLOsr ss FLAT SLATE ROOFS Serviceable and permanent flat roofs are readily obtained by the use of roofing slate. The durable and wearing qualities of slate for promenade roofs are familiar to all who have seen and used slate for walks or floors. Slate possesses an apparent roughness due to slight irregularities of the “quarry cleft” surface and variation of color which give the appearance of a rough texture without actually being rough or hard to walk upon. As a result, where the design demands a promenade having qualities of this nature in addition to long life, slate will be found admirable. Its flexibility of arrangement adds to its other desirable features and allows unlimited possibilities in design. Where the roof does not serve as a promenade, slate can be used also to advantage in place of the usual slag, gravel, slate chips or plastic slate covering of any built-up roof. The nature of the material is such that it affords maximum protection against injury to the waterproofing mem- brane proper. The shape and weight of the units assure their being retained in place as first laid. The waterproof and non-absorbent characteristics of slate make it highly desirable as a surfacing material. Slate While any size slates may be used, the following have been recommended by the Division of Simplified Practice, United States Department of Commerce, as being readily available, economical and satisfactory: Approximate thickness of slate pieces; in inches................ Commercial Standard, average or basic; 35". For promenade or extraordinary service: 14 and 3%. Dimensions of Slate Pieces; in Inches. 6x 6 10 x 6 1DExa6 6x 8 10x7 Dexa 6x9 10x 8 11 Se 3 For promenades the above or any size or shape required by the design may be employed. While the commercial standard slates may be used for ordinary flat roofs, it is recommended that the 14” thickness be used. For promenades it is advisable to use the 14” or thicker. The 3/16” slates afford ample wearing surface, but the 3%” will permit better bedding and remain more securely in place under traffic. Thicker slates may occasionally be required by unusual conditions or other than ordinary use. A leading manufacturer of built-up roofings recom- mends slates at least 34,” to 1” thick, with sawed edges. The slate should be ordered without punching or drilling. Slates less than 3/16” thick are dressed or trimmed square with usual chamfered roofing slate rough edges. Slates 14” and more may be either dressed or sawed edges if desired, although the latter is more expensive. When using Pennsylvania blue-grey slates for flat roofs clear stock should be specified. Imbedding the Slate There are several methods of imbedding the slate. Some roofers mop over the felt waterproofing with an elastic bedding compound of 60% pitch and 40% asphaltum. In Newport, R. I., a manufacturer and roofer specializing in built-up roofs recently found it necessary to vary this mixture or top mopping coat to give satisfactory service to 50% Coal Tar Roofing Pitch and 50% Trinidad Roofing Asphalt. Another roofer has used Trinidad Steep Roofing Asphalt successfully. A San Francisco roofer has found that all mastics made for other work would not answer for slate. The com- pound must cement the slate fast to the felt and yet not run in hot weather, nor crack in cold. It is poured on hot with a ladle and the slate pressed down into it firm so it fills joints solid. This concern then runs a cutter over joints to cut down surplus compound which extends above level and does not stick to surface of slates because they first apply a preparation thereon, so it is readily peeled off leaving the surface clean. In several localities no special methods are employed. The three, four or five plies of felt are laid as recom- mended by their manufacturers, or in accordance with method of waterproofing employed, and standard thickness roofing slate are placed with butt joints in the top mopping coat instead of slag, gravel or slate chips, or other usual surfacing material. Many such roofs have been in service for several years. One case is known where standard thick- ness slate flat roof on a recreation pier has been walked on, danced on, and given very hard usage. For such installa- tions of standard thickness slate, the metal legs of benches or chairs should be nailed to a wood strip in order to avoid damaging the joints or crushing through the slate edges and puncturing the waterproofing below. Many successful installations have been obtained through use of cold plastic material for bedding slate. As a 62 Nee ale OM Neg ee ele AD be Anoo or Or Gel Ayr 170. N rule, about 10% of Portland Cement mortar or hydrated lime is added to the plastic to give it the proper stiffness and rigidity. Another group recommending and using roofing slate for surfacing flat roofs claim only a plastic compound troweled on hot gives satisfactory bedding of slate if a plastic material is to be used. A concrete setting bed is also recommended for promenades. Concrete composed of one part Portland Cement and three parts of sand or medium-size gravel is laid over the waterproofing felt. The concrete 34” in thickness forms a setting bed to receive the slate. After imbedding the slates and leveling them, grout the joints full or fill them with mineral wax. Expansion joints at intervals of 15 feet in each direction with suitable filler should be provided over the roof area. W ater proofing The supporting roof surface should be waterproofed by the method found by the designer to be most satisfac- tory in accordance with locality. Where nailings may be necessary to hold felt in place, this should be done in such a way that the nails are cov- ered with at least two layers of felt. Metal flashings should be covered with one or two pieces of felt before the imbedding material is applied and the slate laid. Roof Foundation The supporting surface of the roof may be of wood or concrete. If of wood, the usual sheathing boards as de- scribed under sloping roofs may be used. For mill construction, use plank sheathing of proper thickness for the span or rafter spacing. Whether wood, concrete or other material is used for this purpose, it is important that the surface be fairly smooth and free from nails or other projections which might puncture the felt or wear through under traffic. The sheathing slab or filling under the waterproofing should be sloped to the roof drainage points so that any possible water getting under the waterproofing from seepage of coping wall joints, etc., may be readily carried off. Roof Slope. The slope for roofs of this type should not exceed 4” rise in 12” of run. Slopes of less than this amount are recommended. For most conditions, 44” or 34” per foot will be found ample and as little as 14” will be satisfactory. When the slope is less than 14” per foot, it is important to see that the surface is evenly maintained and hollow spots avoided. Weight of Roofing The weight of the roofing material above the roof slab or boards is given in the following tables: WEIGHT OF FLAT SLATE ROOF WITHOUT CONCRETE BEDDING SLAB Weight of Materials Total Weight Total Weight Materials per sq. (100 sq. ft.) per sq. (100 sq. ft.) pounds per sq. ft. Waterproofing (Weight varies, assumed here to be 150 lbs.).... 150 Nail cspala bLesmo fies, ote sess cect are org ccsvedouss stoke. ons Glslotehal cisco. creect tens 26 V O Wialleyisgirrscvcstccepaethe ete Sra roe cereale aicie the ciosiersreoteete opevlore 18 Oo CUPOLA EOP dD NY Re ene ies: eS Foe 70 Malleys) Ganoer occ se oom ociiemicte Sine elec a sisal siere-osiniciors slat ereis 23 Le sata Pp Walleye Closed ixas ows chats cseide ss sates Selese idee actions otters 22 WValleyss Open tress ocies oe are aoe nice eretaie vege ising eechere nec uteyesreieks 18 Pit” QUIS” Gago eiomolmocins Gc DOS ree Hrere Oey nas cee Innes 45 alleys) Round Sioa cic coe coalesce tis scene siseus et echt sets 22 Possibilities in Use of Roofing Slate ...................05. 17 Valley; Round) Foundation: 20... 2.0 6s so ae oes ec cess eee 40 83 NATIONAL SLATE ASSOCIATION MEMBERS ARE RELIABLE SOURCES OF SUPPLY This publication, together with recent brochure on “Charm of Slate Floors and Walks” and other informative literature on slate, have been made possible only through the complete co-operation of the members of the Association. < Soweeen eves gO The officers of this Association desire to thank the active or quarry and mill members, a substantial majority of the slate industry, who have so gener- “\@\RaRAairigs ously contributed of their time and money to make these works available to the — public. These members have been imbued at all times with the idea that the Active Members public should benefit from a wider knowledge and use of slate and that slate Associate Members Leswnte for its many uses may be properly installed to give the service warranted by Insignia the inherent qualities of this natural stone. In the past, when roofing slates were produced by haphazard and rule of thumb methods, some slates may have found their way on to roofs which present-day operators influenced by results of scientific knowledge and technical investigations would not tolerate. This is the trend of times in all industries for better products and better service from products. The National Slate Association is striving to secure for all users of roofing slate the centuries of sheltering service and high salvage value that this stone will give. Membership in this organization is an evidence of desire and willingness on the part of any quarry to furnish only high-grade, properly selected slate. Users of roofing slate will do well to specify and insist that their requirements come from quar- ries of members. This is not said with any idea of restrict- ing competition for any new Me SERMONT/ | MAINE capital or active concerns, for ' the development of quarries eee in the worthwhile deposits F . will be gladly welcomed and encouraged by the Association. Portland en To protect the public the 10) Cees x ONTAR! Association stands ready at ae Z GlensF merle all times to identify and ees Syracuse e HAMPSHSY) classify any slate. Recently Le eet degta, 2 “MASS it has developed that some \\ stag Cs slates formerly quarried do not come up to present stand- f ee: a ards of members so _ that ie PEVANi Aes nee architects and owners will do & well to obtain a report from the Association on any slates 5 dew new sd) ¢ io submitted for aroof from other >: JERSEY 4 than quarries of members or Albany | Sete AS Easton (Ay ya FIVE ACTIVE ROOFING deposits not located in the five ‘ : On SLATE QUARRYING AREAS distinct and active quarrying Py ae () maine areas of the United States. North Blanchard 2 ° p Monson Architects, builders and WER MOT one ay oR owners may be assured that Granville- NY. 5 ° . Middle Granville - 1 they will be dealing with h ©. . : . Pouliney, Vt responsible parties if they Washingto ee aes obtain estimates and informa- ~~ ttle, . . . . VIRGINIA © PENNSYLVANIA tion on their slate require- Bangor ments in their localities from po RL al associate members of the Na- Charlottesville : Wind Cay : tional Slate Association. Such Chapman Quarries : : PEACH BOTTOM slate distributors, roofing and . coach eben setting contractors are readily elta,Pa 5 A C5 Lynchburg Cardiff, Md. identified by their member- ship insignia displayed on letterheads, bidding sheets, in- voices, advertising, etc., or at their offices.