Wet VAlls and 
 
 Efflorescence 
 
 What Efflorescence is 
 and How to Avoid It 
 
 H. D. Stewart Co. 
 
 505 HILLS BUILDING 
 SYRACUSE, N. Y. 
 
AVERY U:V.SV 
 
 Digitized by.thednteffiet Archive 
 in 2020 with funding from 
 Columbia University Libraries 
 
 https://archive.org/details/wetwallseffloresOOpalm 
 
Wet Walls and 
 Efflorescence 
 
 What efflorescence is and how 
 to avoid it, with examples 
 showing the results of neglect 
 
 By L. A. Palmer, Research Associate 
 
 Results of two investigations conducted at the 
 National Bureau of Standards, U. S. Department 
 of Commerce, Washington, D. C., George K. 
 Burgess, Director 
 
 AMERICAN FACE BRICK ASSOCIATION 
 130 North Wells Street, Chicago 
 
 NINETEEN TWENTWEIGHT 
 
TABLE OF CONTENTS 
 
 Summary of Results ------ 
 
 Gives in brief the most important features of 
 the two investigations. 
 
 Wet Walls and Efflorescence 
 
 Part I. Certain Fundamental Principles - 
 
 Includes an analysis of the conditions under 
 which efflorescence occurs, and shows two 
 drawings illustrating the right and wrong pro- 
 files for a coping. 
 
 Part II. Field Work - - - - - 
 
 Includes 53 photographic illustrations, with a 
 detailed analysis of the causes of efflorescence 
 and possible means of preventing it, in the 
 case of each building shown. 
 
 Efflorescence on Face Brick Walls - 
 
 Reports the results of a study regarding the 
 occurrence of efflorescence-producing mate¬ 
 rials in brick and mortar, and explains how 
 mortar may be made water-repellent. 
 
SUMMARY OF RESULTS 
 
 E fflorescence may 
 
 occur upon the surface 
 of any masonry wall as a 
 whitish deposit. Whenever 
 such efflorescence appears, it 
 means that the wall contained 
 both soluble salts-—usually 
 calcium and magnesium sub 
 fates—and moisture. 
 
 These soluble salts may 
 have been in any or all of the 
 masonry materials used in 
 the wall, in facing, backup or 
 mortar. The moisture may 
 have entered the wall during 
 construction, through expo¬ 
 sure to rain or snow. It may 
 have penetrated from the 
 earth at the base or from im¬ 
 properly flashed parapet 
 walls at the roof. It may have 
 come from leaky gutters and 
 downspouts, or from the lack 
 of drips on cornices and sills. 
 
 It may have entered through 
 poorly filled or cracked 
 mortar joints in the wall. 
 
 Once in the wall, the moisture dissolves some of the salts 
 present, and later passes to the surface when conditions 
 become favorable for evaporation. Then, when evapora¬ 
 tion takes place, the salts are left behind on the wall as 
 efflorescence. No masonry material is always exempt from 
 contributing to the development of noticeable efflorescence, 
 but some materials contain much larger quantities of soluble 
 salts than others, and consequently are much more im¬ 
 portant sources of trouble. 
 
 Prevention of efflorescence must begin with the design 
 of the building, follow through the selection of materials 
 and the methods of work during the construction period, 
 and continue with maintenance of the structure after its 
 completion. However, the methods recommended and the 
 precautions necessary are merely those of good practice and 
 do not involve radical departures from recognized standards 
 except possibly in the case of adding a water-repellent to 
 the mortar. But the neglect of certain simple precautions 
 may bring very unsatisfactory results. 
 
 Wet walls serious fault 
 
 The great importance of excluding moisture from the 
 wall is brought out in Part I of the report on “Wet Walls 
 and Efflorescence,” as follows (page 8): 
 
 “Aside from being the direct cause of efflorescence, an 
 excessive amount of moisture in the materials of a wall 
 accelerates disintegration of such materials through alter¬ 
 
 nate freezing and thawing 
 of this moisture in the wall. 
 Damp interiors are often 
 another undesirable condi¬ 
 tion attending the disinte¬ 
 gration and occurrence of 
 efflorescence. It is therefore 
 seen that a study of efflores¬ 
 cence from the standpoint of 
 proper design, construction 
 and maintenance must of 
 necessity involve also certain 
 phases of the study of both 
 disintegration of materials in 
 walls and damp interiors. 
 This is the most important 
 reason for making a concen¬ 
 trated effort in all future 
 construction to make and 
 preserve dry walls.” 
 
 Note that disintegration 
 and damp interiors are only 
 attendant circumstances. 
 They are not consequences 
 of efflorescence. The alter¬ 
 nate freezing and thawing of 
 moisture disrupts masonry 
 and this happens whether or not there are any salts present 
 in such masonry. The report continues: 
 
 “In view of such facts the manufacturers of face brick 
 are at present outlining a future study of a great many 
 of the factors involved in creating and maintaining the 
 best possible conditions for their material in the walls 
 where they are to be used. Obviously, since face brick 
 must be used with many other materials in such walls, 
 such a study involves not only the building units, brick, 
 but also assemblages of units of brick together with units 
 of various other materials. 
 
 “In the investigation of causes of and remedies for 
 efflorescence on face brick walls (page 24), it developed 
 that the soluble salts that would otherwise be present in 
 clay products used in construction can be practically 
 eliminated by the manufacturer of such materials by certain 
 procedures in the drying and burning of his ware, together 
 with the judicious use of barium compounds in his clay. 
 These procedures are at present being generally used by 
 the face brick industry and in part justify the difference in 
 cost between face brick and the cheaper clay products, 
 hollow tile and common brick used generally as backing up 
 materials. From an economic standpoint, it is not always 
 practicable for the manufacturers of common brick and 
 hollow tile to adopt the procedures used by the face brick 
 industry in eliminating soluble salts. From the standpoint 
 of efflorescence it is therefore very essential that these back- 
 
 This summary has been prepared by the 
 American Face Bricfi Association to present as 
 briefly as possible the outstanding facts about 
 the occurrence of efflorescence on masonry walls 
 and how to avoid it, as determined by two 
 investigations conducted for the Association at 
 the Rational Bureau of Standards, U. S. 
 Department of Commerce, Washington, D. C. 
 It is of course impossible to treat this subject 
 adequately in a summary, and there is no 
 doubt that the short time needed to read the 
 complete reports which follow will be most 
 profitably spent. The 55 illustrations, occur' 
 ring chiefly in Part II of the first report, will be 
 found especially interesting. The investiga' 
 tions described were carried on by L. A. 
 Palmer, Research Associate, under George K. 
 Burgess, Director of the Bureau of Standards, 
 and the Research Committee of the American 
 Face Bric\ Association, composed of F. W. 
 Butterworth, Chairman, Wm. C. Koch and 
 L. B. Rainey. For additional copies of this 
 boofi, write the American Face Bric\ Associa' 
 tion, 130 Tforth Wells Street, Chicago. 
 
6 
 
 WET WALLS AND 
 
 ing up materials be protected from excessive water pene- 
 tration. These efforts on the part of face brick manufac- 
 turers to reduce the amount of salts in their own product 
 will not alone suffice in eliminating efflorescence.” 
 
 Occurrence of soluble salts 
 
 In the investigations at the Bureau of Standards, 55 types 
 of face brick from as many different manufacturers in vari¬ 
 ous parts of the United States were examined for soluble 
 salts. Six types of common brick and four each of widely 
 used limes, portland cements and bricklayers’ cements were 
 also studied. The majority of the face brick contained less 
 than 0.05 per cent of soluble sulfuric anhydride (taken as 
 the chemist’s guide to the soluble salts present). This 
 amount is ordinarily insufficient to cause efflorescence even 
 under conditions favorable for its development. 
 
 Each sample of common brick exceeded this amount and 
 the average of all six types was 0.16 per cent. The lowest 
 figure for the limes was 0.5 per cent. The portland cements 
 and bricklayers’ cements also contained varying quantities 
 of these salts, and in the tests reported under “Efflorescence 
 on Face Brick Walls,” page 24, each was found to develop 
 efflorescence when used in certain panels with face brick 
 which alone—that is, tested without mortar—did not 
 develop efflorescence. Other investigations of limes and 
 building limestones have established the presence in these 
 materials of the same soluble salts found in brick. 
 
 In testing brick for soluble salts, the sample for analysis 
 need not include any material taken from more than one- 
 eighth of an inch below the exposed surface of the brick, as 
 the amount of such salts is usually greatest there. (Bureau 
 of Standards Technologic Paper No. 370, page 617.) 
 
 Maying rnortar water-repellent 
 
 Since water ordinarily penetrates into a wall through the 
 mortar joints rather than through the brick or stone, care¬ 
 ful study was given to methods of making the mortar 
 water-repellent. The plan recommended is the addition of 
 two per cent by weight of calcium or ammonium stearate 
 to the cement, lime or mixture of the two used in the 
 mortar. Mortars so treated were found to be very effective 
 in preventing the passage of moisture in all cases wherein 
 only ordinary capillary forces obtain. While best practice 
 would call for the use of stearate in mortar for backing as 
 well as facing materials, it is especially important that it be 
 employed in laying up the facing where the joints will be 
 subjected to unusual exposure to driving rains or to water 
 running down the surface of the wall. Joints of copings, 
 window sills and parapet walls are all in need of especial 
 care. In repointing joints that have cracked, water-repel¬ 
 lent mortar is called for, as such joints are usually in highly 
 exposed locations. 
 
 Calcium stearate is a powder which is mixed dry with 
 the cement before adding sand and water, while ammonium 
 stearate is a paste which is usually added to the mixing 
 water. On the ordinary building job, the powder has 
 proved the more practical and accurate to use with the 
 equipment commonly available. These stearates can be 
 
 EFFLORESCENCE 
 
 obtained from chemical manufacturers, or integral water¬ 
 proofing compounds containing them can be had through 
 dealers in building supplies and branch offices of companies 
 making such products. Every care should be taken to 
 insure getting reliable material, and unless the particular 
 product being considered is known to be satisfactory, it 
 should be given suitable laboratory tests. 
 
 For addresses of manufacturers of stearates and integral 
 waterproofing compounds containing them, write the 
 American Face Brick Association, 130 N. Wells St., Chicago. 
 
 Other precautions for peeping walls dry 
 
 Specific recommendations that will help in preventing 
 water from entering the wall are as follows: Use imper¬ 
 vious copings, and point joints carefully with water-repellent 
 mortar. Flash parapet walls, carrying the flashing com¬ 
 pletely through the wall one or two courses above the 
 roof level, and waterproof the entire inner side of the wall. 
 Likewise flash the washes of pediments and dormers. 
 
 Always provide adequate drips on all copings, cornices 
 and window sills, making the grooves at least jbs inch wide 
 and inch deep, and provide projections of two inches 
 or more so as to keep the drip away from the wall. 
 
 Use lug sills at windows, with slopes from the sides of 
 the window to the opening and at right angles to the wall, 
 and where practical avoid all joints in the sills. If brick 
 sills are desired, flash under them with suitable metal 
 flashing provided with drips. Employ projecting rows of 
 brick very cautiously, and use water-repellent mortar for 
 the joints beneath them. Avoid vertical joints in any sort 
 of masonry wherever possible, and be sure water-repellent 
 mortar is employed in such joints. 
 
 Protect walls under construction to prevent rain or 
 melting snow from entering. Pile brick, tile, stone and 
 similar materials on boards as delivered to the job to avoid 
 contact with moist ground, and keep them covered. Keep 
 gutters and downspouts in good repair, and make sure they 
 are adequate to carry the water. Point up cracked joints 
 very promptly. Coat the backs of retaining walls with an 
 impervious layer, and keep brick building walls away from 
 contact with the earth. 
 
 Classification of various types of efflorescence 
 
 While efflorescence is most common in the early spring, 
 when walls saturated by melting snow or late winter rains 
 are drying out, it may occur at any time of the year. It 
 may appear quite generally over a wall, or be confined to 
 certain small areas. Analysis shows there are these four 
 conceivable conditions under which efflorescence may occur: 
 
 Condition A. Excessive water with only a normal 
 amount of salts in the wall. 
 
 Condition B. Excessive water and an excessive amount 
 of salts in the wall. 
 
 Condition C. Normal water and normal salts. 
 
 Condition D. Normal water but excessive salts. 
 
 Obviously the first two conditions, A and B, are the 
 worst because disintegration may go hand in hand with 
 
WET WALLS AND 
 
 EFFLORESCENCE 
 
 7 
 
 efflorescence, owing to the disruptive action of freezing 
 and thawing. Condition B is of course worse than A. 
 
 Efflorescence occurring under Condition C is usually 
 very mild, indeed. Condition D may cause some trouble, 
 but like C, is usually only temporary and tends to disappear 
 entirely as time goes on. 
 
 General efflorescence is apt to mean either condition B 
 or D, where the wall contains excessive salts. Special 
 efflorescence usually indicates Condition A, characterized 
 by excessive water which is being allowed to penetrate the 
 wall by some fault in design, construction or maintenance. 
 Every instance of a leaking downspout, dripless sill or urn 
 flashed parapet wall may cause excessive water penetration. 
 
 Field study shows efflorescence preventable 
 
 As part of the field investigation of efflorescence, William 
 C. Koch, of the Research Committee of the American Face 
 Brick Association made an extensive study for the purpose 
 of correlating the fundamental facts about the development 
 of efflorescence with design, construction and maintenance 
 of buildings. Finally, a detailed study was made of 250 cases 
 of efflorescence and the usual accompaniment, wall disinte- 
 gration. The Bureau of Standards report comments as follows: 
 
 “With but one or two definite exceptions, the 250 cases 
 of discoloration and disintegration could have been pre- 
 vented by either proper design, construction or mainte- 
 nance. In some cases only one of these three factors was 
 the direct cause, but usually there were two and in a 
 number of cases all three were at fault. 
 
 “Efflorescence was observed on almost every type of 
 building material...” 
 
 In emphasizing the necessity of promptly pointing up 
 cracked mortar joints which are allowing penetration of 
 water, the report says: 
 
 “Where prompt pointing up was not done and where the 
 condition had lasted over a period of years, disintegration 
 of the mortar joints almost invariably had occurred. In 
 any case where underburned brick had been used, these 
 also had become disintegrated.” 
 
 The action of sulfur dioxide in accelerating the disinte- 
 gration of certain masonry materials is well known, and 
 must be considered in cities burning bituminous coal. 
 Snow water may be sufficiently acid to attack the lime of 
 mortar or certain limestones, but tests made at the Bureau 
 of Standards have shown face brick highly resistant to 
 solutions of sulfur dioxide in water and even to fairly com 
 centrated acid solutions, such as ten per cent hydrochloric, 
 sulfuric and nitric acid. However, the need of prompt 
 pointing up of mortar joints is apparent. 
 
 Recapitulation of results of investigation 
 
 As summing up the results of the entire study of 
 efflorescence on masonry walls, the following recapitula- 
 tion of his report by L. A. Palmer is worthy of careful 
 attention (page 24): 
 
 “The purpose of the foregoing is to point out the 
 
 fact that in the main, the immediate cause of efflorescence 
 and often too of wall disintegration is excessive penetration 
 of moisture into the wall. The field work supplemented 
 the fundamental work that had already been done and 
 that had established the fact that hardly any masonry 
 material is exempt from the possibility of containing 
 soluble salts in quantity such that it may under favorable 
 conditions contribute to the development of noticeable 
 efflorescence. The favorable conditions are wet walls. 
 
 “With but one or two definite exceptions, all of the 
 large number of instances of efflorescence and in some 
 cases wall disintegration that were studied could have 
 been prevented had due consideration and care been given 
 to the proper design, construction and maintenance of 
 these buildings. 
 
 “A few examples of such preventable instances of 
 efflorescence have been shown. Some details in way of 
 design, construction and maintenance which, had they 
 been observed and remedied, would have prevented the 
 occurrences of efflorescence as illustrated by photographs, 
 have been mentioned. There are many more of such 
 details and it is assumed that the architect and builder 
 are more familiar with them than is any one else. 
 
 “Efflorescence can become very noticeable on the wall 
 of a building composed of brick or other masonry ma' 
 terials that are exceptionally low in soluble salt content 
 if an excessive amount of water enters that wall. 
 
 “Any efflorescence appearing on the wall of a building 
 that is suitably designed, constructed and kept in repair 
 in order to avoid excessive water penetration, will be 
 due to rare and abnormal conditions. It will in time 
 gradually diminish and finally disappear. It will never 
 recur under normal conditions even though the soluble 
 salt content of the entire wall be higher than is normally 
 the case. Prolonged and heavy wind-driven rains will 
 bring out efflorescence on almost any wall, but this 
 efflorescence is of the temporary nature described, is 
 usually of short duration, and is generally unaccompanied 
 by disintegration of joints. 
 
 “The effort on the part of manufacturers of face brick 
 to develop products as free as possible from soluble salts 
 (even if the goal, complete elimination, could be attained) 
 will not in itself insure against the development of 
 efflorescence on walls. Their work must be supple¬ 
 mented by a concentrated effort on the part of archi¬ 
 tects, builders and owners to keep the walls as dry as 
 possible. It is also very necessary that manufacturers of 
 the other building materials used in walls with the face 
 brick be equally concerned with the question of soluble 
 salts in their materials. 
 
 “Means of preventing efflorescence by keeping the 
 walls dry have been outlined. It is hoped that architects 
 and builders generally will proceed much further with 
 this study and that the face brick industry will have 
 their full co-operation in keeping dry the face brick walls 
 of buildings yet to be constructed.” 
 
WET WALLS AND EFFLORESCENCE 
 
 (Publication Approved by the Director of the Bureau of Standards of the U. S. Department of Commerce) 
 
 I. Certain Fundamental Principles 
 
 T HE fundamental cause of efflorescence on the exterior 
 walls of buildings has been found to be generally due 
 to soluble salts in masonry materials. ( x , 2 , 3 and 4 .) 
 
 No masonry material is always exempt under all condi- 
 tions from contributing to the development of noticeable 
 efflorescence on the exterior surface of the wall of a build' 
 ing. This is true whether such material be used either in 
 the facing or among the backing up materials of the wall. 
 
 In the investigation 2 conducted by the American Face 
 Brick Association at the National Bureau of Standards, 55 
 types of face brick from as many different manufacturers 
 in various parts of the United States were examined for 
 soluble salts. Incidentally, during this investigation six 
 different types of common brick were similarly examined. 
 
 The majority of the face brick contained less than 0.05 per 
 cent of soluble sulfuric anhydride, an amount insufficient to 
 cause efflorescence under conditions favorable for such. 
 The soluble salt content of the common brick exceeded 
 somewhat this amount in all six cases, the average being 
 0.16 per cent. During this same investigation, four each 
 of widely used limes, portland cements and bricklayers’ 
 cements were studied in order to determine their tendencies 
 to develop efflorescence. It was found that these materials 
 used as mortars in panels constructed with the 55 different 
 types of face brick did actually contribute to efflorescence 
 on the panels. The lowest sulfuric anhydride content of 
 the four limes used was 0.5 per cent. This was mainly in 
 the form of calcium sulfate, a soluble salt. The portland 
 cements studied contained varying amounts of calcium 
 sulfate of necessity added by the manufacturer to retard 
 the set of the cement. All of the bricklayers’ cements con' 
 tained appreciable quantities of soluble salts. The be' 
 havior of these mortar materials in the panel tests is dis- 
 cussed 5 in the report to architects and users. 
 
 J. S. Rogers 4 investigated 35 commercial chemical limes 
 which are generally conceded to be at least as free from 
 soluble sulfates as the limes used for building purposes. 
 He found these limes to contain from a trace to 1.50 per 
 cent of sulfuric anhydride and suggests that this was intro' 
 duced by burning limestone with coal containing sulfur. 
 It is reasonable to assume that a considerable portion of 
 this sulfuric anhydride in these chemical limes was in the 
 form of calcium sulfate, a soluble salt very often present 
 in the efflorescence material. 
 
 In Bureau of Standards Technologic Paper 349, pages 
 540 et seq., it is shown that the sulfates of calcium and 
 magnesium sometimes contained in brick and mortar ma¬ 
 
 terials, are also contained in various limestones used in the 
 building industry. It is further shown in this publication 
 (pages 528 et seq.) that soluble organic material, causing a 
 brown discoloration, is often present in such limestones. 
 
 Two facts must be well understood. First, the soluble 
 salts are not confined to any one building material, but are 
 widely distributed among practically all of such materials 
 and, second, the condition, wet walls, is most favorable 
 for the development of efflorescence produced by such salts. 
 
 Thus the wide occurrence of these soluble salts among 
 various building materials becomes apparent. It is essen¬ 
 tial that this fact be borne in mind if there is to be co¬ 
 operation on the part of all manufacturers and producers 
 of masonry materials with architects and builders. They 
 must also use precaution to reduce the amount of moisture 
 penetration into walls containing these salts and thereby 
 overcome this annoyance, efflorescence. 
 
 Wet walls also accelerate disintegration 
 
 Aside from being the direct cause of efflorescence, an 
 excessive amount of moisture in the materials of a wall 
 accelerates disintegration of such materials through alter¬ 
 nate freezing and thawing of this moisture in the wall. 
 Damp interiors are often another undesirable condition 
 attending the disintegration and occurrence of efflores¬ 
 cence. It is therefore seen that a study of efflorescence 
 from the standpoint of proper design, construction and 
 maintenance must of necessity involve also certain phases 
 of the study of both disintegration of materials in walls 
 and damp interiors. This is the most important reason 
 for making a concentrated effort in all future construction 
 to make and preserve dry walls. 
 
 In view of such facts the manufacturers of face brick 
 are at present outlining a future study of a great many of 
 the factors involved in creating and maintaining the best 
 possible conditions for their material in the walls where 
 they are to be used. Obviously, since face brick must be 
 used with many other materials in such walls, such a study 
 involves not only the building units, brick, but also assem¬ 
 blages of units of brick together with units of various 
 other materials. 
 
 In the investigation of causes of and remedies for efflores' 
 cence on face brick walls 5 , it developed that the soluble 
 salts that would otherwise be present in clay products 
 used in construction can be practically eliminated by the 
 manufacturer of such materials by certain procedures in 
 the drying and burning of his ware, together with the 
 
 ■Efflorescence and Capillary Fissures in Cement Mortars, “Rock Products", Vol. 30, Feb. 5, 1927, Page 83. 
 
 2 Cause and Prevention of Kiln and Dry House Scum and of Efflorescence on Face Brick Walls, L. A. Palmer, Bureau cf Standards Technologic Paper No. 370 . 
 
 3 The Physical Properties of the Principal Commercial Limestones Used for Building Construction in the United States, D. W. Kessler and W. H. Sligh, Bureau of Stan¬ 
 dards Technologic Paper No. 349, pages 540 et seq. Also pages 526 et seq. 
 
 *Oom posit ion of Commercial Chemical Limes, J. S. Rogers, “Industrial and Engineering Chemistry," Vol. 19, Oct. 1927. Page 115/. 
 
 Efflorescence on Face Brick Walls, L. A. Palmer, Special Report to Architects and Users of Face Brick. (See page 24 of this book.) 
 
WET WALLS AND EFFLORESCENCE 
 
 9 
 
 judicious use of barium compounds in his clay. These pro¬ 
 cedures are at present being generally used by the face 
 brick industry and in part justify the difference in cost 
 between face brick and the cheaper clay products, hollow 
 tile and common brick used generally as backing up ma¬ 
 terials. From an economic standpoint, it is not always 
 practicable for the manufacturers of common brick and 
 hollow tile to adopt the procedures used by the face brick 
 industry in eliminating soluble salts. From the standpoint 
 of efflorescence it is therefore very essential that these 
 backing up materials be protected from excessive water 
 penetration. These efforts on the part of face brick manu¬ 
 facturers to reduce the amount of salts in their own 
 product will not alone suffice in eliminating efflorescence. 
 
 M ortar made water-repellent by stearates 
 
 It was further developed during the above mentioned 
 investigation ( 2 and 5 ) that the addition of an amount of 
 either calcium or ammonium stearate with mortar ma¬ 
 terials reduced the extent to which they contributed to 
 efflorescence. These two stearates render the mortar 
 more water-repellent and an amount of either stearate 
 equal to two per cent by weight of the cement or of the 
 lime or of the lime plus the cement, if both cement and 
 lime are used, is suggested. This treatment will practi¬ 
 cally prevent water penetration of the mortar due to 
 capillary forces only. 
 
 It must, however, be borne in mind that the original 
 moisture introduced during construction and contained in 
 mortar so treated may be subjected to freezing to an extent 
 sufficient to cause cracking of the mortar joints. Cracking 
 of mortar joints containing the water-repellent materials 
 may also occur as a result of settlement, ffence it is seen 
 that no chemical treatment of materials will alone suffice. 
 Prompt pointing up is required in this case if the mortar 
 so treated is to maintain its original water-repellent 
 property. 
 
 Water brings salts from wall interior 
 
 Water which has penetrated to the interior of a wall 
 subsequently usually finds its way through the pores of 
 the masonry to the face brick and there evaporates, de¬ 
 positing any salts which it has taken into solution from 
 the backing up materials. It may not occur to one who 
 has not studied the subject that any material other than 
 that which he sees has contributed to the unsightly ap¬ 
 pearance of the wall. The salts thus being left on the 
 face brick may lead one to conclude that the face brick 
 are directly responsible, whereas they may have been 
 practically free from soluble salts originally. 
 
 Summing up, it is seen that whereas the fundamental 
 cause of efflorescence is the presence of soluble salts in 
 the materials of the wall, the immediate cause is excessive 
 moisture penetration into the wall. To avoid the latter 
 condition requires the full cooperation of architects and 
 builders as well as manufacturers of all masonry materials. 
 
 Analysis of wall conditions 
 
 For convenience, the conditions obtaining generally in 
 the occurrences of efflorescence may be classified as follows: 
 
 Excessive water, normal salts 
 
 A. The condition: more than the normal or usual 
 amount of water penetration of a wall containing a normal 
 or average amount of soluble salts, the excessive water 
 penetration being due to either faulty design, construction 
 or maintenance or to combinations of these undesirable 
 conditions. 
 
 Excessive water, excessive salts 
 
 B. The condition: more than the normal or usual ex¬ 
 tent of water penetration of a wall containing more than 
 the usual amount of soluble salts, the high degree of water 
 penetration being due to the same causes given under A. 
 
 ?formal water, normal salts 
 
 C. The development of efflorescence attended by the 
 condition: normal amount of water penetration of a wall 
 containing a normal or average quantity of soluble salts. 
 
 formal water, excessive salts 
 
 D. The appearance of efflorescence with the condition: 
 normal water penetration of a wall containing a relatively 
 large amount of soluble salts. 
 
 In the above classifications, “normal water penetration” 
 and “normal or average amount of soluble salts” are only 
 relative and arbitrary terms. No one has defined either 
 condition. However, it is reasonable to hypothesize the 
 existence of such conditions. Most careful observers and 
 practically all architects and builders will recognize an ex¬ 
 treme condition as regards water penetration. Most 
 chemists familiar with building materials will recognize an 
 extreme condition if the average salt content of the ma¬ 
 terials in the wall is greater than two per cent by weight 
 of total mass of materials and another and highly favorable 
 extreme condition if the salt content is below 0.01 per 
 cent of the total weight of masonry. Either condition 
 will seldom be realized. 
 
 Cases involving excessive moisture most frequent 
 and most serious 
 
 Normal or average water penetration is exceeded by 
 every instance of a leaking downspout, dripless sills, de¬ 
 fective flashing of parapet walls, etc. If one were to 
 estimate as to which of conditions, A, B, C and D pre¬ 
 dominate in the numerous instances of efflorescence, he 
 would, following an extended field study, most likely con¬ 
 clude that conditions A and B obtain in by far the majority 
 of cases. There are certain other things also that would 
 become evident after such a study. It would be noted 
 that conditions A and B are the ones most usually at¬ 
 tended by disintegration of the wall. It is evident that 
 in all cases of excessive water penetration, alternate freez¬ 
 ing and thawing are especially severe and disrupt the 
 masonry in time. 
 
10 
 
 WET WALLS AND EFFLORESCENCE 
 
 Furthermore, after long and constant observation of 
 buildings which develop efflorescence under the condi- 
 tions, C and D, the observer will note that such occur¬ 
 rences are usually temporary. The efflorescence will in 
 such cases gradually diminish more and more and finally 
 never again appear. In these instances also one 
 seldom notes any wall disintegration. This would indi¬ 
 cate that wall disintegration is not a consequence of 
 efflorescence but rather that it is an attendant cir¬ 
 cumstance, the two, efflorescence 
 and disintegration usually occurring 
 simultaneously under the conditions 
 A and B and from the same im¬ 
 mediate cause, i.e., excessive water 
 penetration of the wall. 
 
 If brick are used which have had 
 no barium treatment or if the drying 
 and burning conditions were not so 
 controlled as to insure their having a 
 low soluble salt content, there will 
 result then either condition, B, the 
 worst of the four conditions, or con¬ 
 dition D, which though better than 
 B is yet very undesirable. 
 
 Condition A is second in undesir¬ 
 ability only to B. It is chiefly within 
 the power of architects and builders 
 to eliminate condition A. To relieve 
 condition B requires effort on the 
 part of producers of masonry ma¬ 
 terials as well as architects and 
 builders. The producers alone are 
 responsible for condition D. 
 
 Condition C is the best of the 
 four. Efflorescence appearing under 
 this condition is at the worst only temporary and 
 usually it is little more than barely noticeable. 
 
 Melting snow may saturate walls 
 
 It often happens that certain structural or maintenance 
 defects on buildings are so located that saturation of the 
 walls at such places can only occur through the melting 
 of snow. On account of large overhangs, such locations 
 are amply protected from moisture in the form of rain. 
 Nevertheless, driven snow can readily accumulate at these 
 places. When melting, this snow will saturate the walls 
 beneath the overhangs and produce efflorescence and dis¬ 
 integration in such locations during early spring. This 
 is one of many reasons for the great prevalence of efflores¬ 
 cence during the early spring season. 
 
 It can be noted in almost any city that along with the 
 usual white efflorescence, on the same building there may 
 be seen unsightly stains on the faces of belts and cornices. 
 In most cases, failure to provide drips at the nibs of the 
 projecting cornices is the direct cause of the streaks and 
 stains on the stone, terra cotta, etc. Solid particles of 
 soot settle on the washes, become softened by rain and 
 run down the face of the moldings. These discolorations 
 are cumulative and in most manufacturing cities become 
 
 jet black. The soot contains more or 
 less of sulfur which gives to water in 
 contact with it acidic properties 
 which may be a factor in disintegra¬ 
 tion of mortar joints, making soluble 
 otherwise insoluble material. 
 
 Drips greatly reduce 
 water penetration 
 
 While it is true that drips at the 
 nibs may in some cases slightly modify 
 the customary proportions of certain 
 members, the advantage gained in re¬ 
 ducing water penetration is sufficient 
 to outweigh any such objection. 
 Quoting from Bureau of Standards 
 Technologic Paper No. 132: “Where 
 rain falls on the top surface of a pro¬ 
 jection, it runs over the outer edge 
 and following the lower surface 
 reaches the wall which becomes soak¬ 
 ed for some distance below. Also 
 snow which is allowed to remain on 
 these projections finally melts and 
 causes the same difficulty. By the 
 simple method of ‘throating’—that 
 is, making a groove in the lower sur¬ 
 face of projecting members —this difficulty is overcome, 
 as the water when it reaches this groove drops to the 
 ground.” Further than this, only a little consideration 
 is necessary to clearly see that a small drip groove is 
 of little value, as the droplets of water can span such. It 
 is good practice to make the grooves at least fP wide and 
 deep. Another necessary precaution is to have the 
 projection at the rear of a coping at least 2" to give room for 
 a drip of this size and to keep the drip away from the wall. 
 FIGURE 1 illustrates the conventional profile. FIGURE 2 
 is no less pleasing to the eye as regards profile and will 
 serve to keep the moldings clean, whereas water and dirt 
 will run down the face of the moldings of FIGURE 1 and 
 disfigure it as well as the face brick or other materials be¬ 
 low it in the wall. 
 
 Dirt from wash 
 wifi run c/owr? { 
 face of mould- // 
 inqs 
 
 Figure 1. Conventional profile 
 
 Drip of- nib ^ 
 wifi keep 
 the mouldings 
 clean 
 
 Figure 2. Improved profile 
 
II. Field Work 
 
 S UPPLEMENTARY to the work of finding necessary- 
 fundamental facts concerning the development of efflor' 
 escence, William C. Koch of the Research Committee 
 of the American Face Brick Association, undertook an 
 extensive study for the purpose of correlating these facts 
 with the subjects of design, construction and maintenance. 
 Certain buildings which were prone to develop efflorescence 
 were observed carefully from season to season and some facts 
 not at all obvious at first were brought out. Finally an 
 intensive field study was made in which 250 cases of 
 efflorescence and the usual accompaniment, wall disim 
 tegration, were studied and an attempt was made to 
 interpret these data. With but one or two definite excep' 
 tions, the 250 instances of discoloration and disintegration 
 could have been prevented by either proper design, com 
 struction or maintenance. In some cases only one of 
 these three factors was the direct cause, but usually there 
 were two and in a number of cases all three were at fault. 
 
 Efflorescence was observed on almost every type of 
 building material. The efflorescence on stone which is more 
 nearly the color of the stone was often not apparent until 
 a close examination was made. This same efflorescence 
 would have been very conspicuous had the stone been as 
 dark in color as brick. 
 
 Prompt pointing up of mortar joints essential 
 In some instances the joints in the wall areas were care' 
 fully pointed up following the first few occurrences of 
 efflorescence. Due to settlement, cracks often appeared 
 and this condition augmented the penetration of water 
 into the interior of the wall. Where prompt pointing 
 up was not done and where the condition had lasted over 
 a period of years, disintegration of the mortar joints almost 
 invariably had occurred. In any case where underburned 
 brick had been used, these also had become disintegrated. 
 
 In the atmosphere of cities consuming annually large 
 quantities of bituminous coal, the sulfur dioxide so lib' 
 erated in conjunction with water in the form of rain or 
 melting snow may accelerate the disintegration of certain 
 masonry materials. Parr 6 in discussing the prevalence 
 of sulfur dioxide in the atmosphere makes the following 
 statement: 
 
 “I recall a certain dwelling far removed from possible 
 contamination by gases from coal fires where the window 
 screens have remained continually in place for twenty 
 years. The iron wire of which they are made is still whole 
 and sound, whereas the iron wire screens of another 
 dwelling in the center of the soft coal belt corroded and 
 fell completely out of their frames after one winter season.” 
 
 Professor Parr states further that the annual combustion 
 of 600 millions of tons of coal, mostly bituminous, in the 
 United States liberates approximately 40 billion pounds 
 or 400 billion cubic feet of sulfur dioxide, most of which is 
 
 concentrated in manufacturing centers. If sulfur dioxide 
 from this source is in concentration sufficient to corrode 
 an iron wire screen in one season, it very likely also would 
 tend to corrode any masonry material containing lime, 
 such as mortar or limestone. ( 3 and 7 ) All brick manu' 
 facturers know what sulfur dioxide will do to a clay 
 containing limestone in a humid drying chamber. 
 
 Face bric\ resistent to acid solutions 
 
 On the other hand, the author has made numerous tests 
 with concentrated solutions of sulfur dioxide in water on 
 face brick. In all cases the solvent action of this reagent 
 was negligible. In by far the majority of cases there was 
 no solvent action whatsoever. In addition, the author 
 immersed face brick in fairly concentrated acid solutions, 
 such as ten per cent solutions of hydrochloric, nitric and 
 sulfuric acids for periods of from ten days to two weeks. 
 While these acids are sufficiently strong to rapidly dis' 
 solve certain limestones, the brick thus treated remained 
 practically unchanged. It is reasonably safe to assume 
 that underburned brick would not have been so resistent 
 generally. 
 
 In the light of the above comments by Professor Parr, 
 it is very likely that sulfur dioxide of the atmosphere can 
 accelerate any decomposition of mortar joints initially 
 begun by frost action or cracking due to settlement. 
 Prompt pointing up of joints is, therefore, very necessary 
 and further than this since pointing up is usually required 
 on those portions of the wall most exposed to excessive 
 moisture penetration, mortar containing the water-repeb 
 lent stearates should be considered for such pointing up. 
 
 Snow water may hasten mortar disintegration 
 
 In connection with the field work, some analyses of 
 snow water were made. In one instance water from 
 melted snow accumulating over a period of three months 
 in a small, open area in the city of St. Paul contained 
 0.005 per cent of sulfuric anhydride. This water was 
 distinctly acid, the “pH” (logarithm of the reciprocal of 
 the hydrogen ion concentration) being 3.5. Water of 
 this acidity could easily attack the lime of mortar or 
 certain limestones (forming soluble calcium sulfate) if 
 left in contact with such building materials for consider' 
 able periods of time. Such water entering cracks due 
 to settlement or frost action would tend to accelerate 
 any disintegration of mortar. Here then is another 
 possible source of efflorescence. 
 
 Careful and prompt pointing up of mortar joints is 
 especially necessary in brick masonry as a safeguard 
 against efflorescence, as observations showed. For ex' 
 ample, consider two walls, one of stone and one of brick. 
 The ratio of amount and number of exits (principally 
 joints) in brick work to those in stone work is such as to 
 
 6 Some Combustion Problems in their Relation to Public Health, Samuel W. Parr, “Industrial and Engineering Chemistry,” Vol. 20, May 5, 1928, Page 454 
 
 7 H. Pemberton, Journal Franklin Inst. Vol. 106, Page 62 
 
12 
 
 WET WALLS AND EFFLORESCENCE 
 
 promote freer flow of water in the wall of brick, carrying good, cracking became noticeable at the left end of the stone 
 the salts to the surface. Furthermore, joints in stone coping due to settlement. Water leaks through this crack and 
 are generally thinner than those in brickwork and the through similar ones not visible and particularly through 
 area of each joint in the latter case is consequently greater the crack along the entire length of stone and back of same 
 than in the case of stonework. These dimensional fac- whence it easily penetrates to the face of the brick wall at 
 tors result in restricted flow of saltdaden water in the the points where vertical joints in the stone and between 
 
 case of stone. This fact may account 
 in part for the popular notion that 
 limestone and sandstone contain very 
 little of soluble material. 
 
 FIGURE 3 shows efflorescence on red 
 sandstone. Water penetrated the wall, 
 draining in from the small porch over 
 this discoloration. In FIGURE 4 there 
 is seen efflorescence on both the brick' 
 work and stone arches beneath the win' 
 dow jutting through the lower part 
 of the roof. The design in this 
 case is very favorable for carrying 
 water into the wall at the area 
 covered by the white salts. FIGURE 5 
 shows again efflorescence on sandstone. 
 Prompt pointing up of the cracks be' 
 tween mortar joints and stone due to 
 settlement would have prevented this. 
 FIGURE 6 shows efflorescence on 
 porch cheeks of concrete block due to 
 seepage and splashing at the base and 
 in addition to this, water has entered 
 from the porch floor. Moisture also 
 has progressed down the column from 
 the cap of the porch pier. 
 
 Settlement crac\s need immediate 
 attention 
 
 It is reasonable to assume that crack' 
 ing of joints due to settlement is more 
 likely to occur at the bond of stone 
 copings, sills, etc., than it is among the 
 joints between the brick in a wall faced 
 with brick. This assumption is more 
 justifiable when stone or brick walls 
 exposed to a normal amount 
 of water penetration are 
 being considered. Evidence 
 for this assumption was 
 found in many instances and 
 FIGURE 7 is an lllustra' 
 tion of one. The brick 
 being small units, the 
 stresses induced by settle' 
 ment tend consequently to 
 be more evenly distributed 
 than in the case of a wall 
 built entirely of stone. In 
 FIGURE 7 although the 
 construction was originally 
 
 
 Figure 3. Efflorescence on red sandstone, 
 below porch. 
 
 
 Figure 4. 
 
 Efflorescence on both brickwork 
 and stone arches. 
 
 the stone and the brick have disintegra' 
 ted or have cracked open. A little point' 
 ing up should have been done promptly. 
 
 In this connection it is well to con' 
 sider that the number of mortar joints 
 per unit area of a brick wall, being con' 
 siderably greater than the number of 
 such in the same area of a wall built 
 entirely of stone as above mentioned, 
 water can therefore flow more freely 
 into the wall built of brick on account 
 of this larger area of mortar. Referring to 
 FIGURE 7, there is then consequently 
 more water penetration in the brick wall 
 below the stone coping which has 
 cracked loose from the mortar bond due 
 to settlement than would have obtained 
 were the wall built entirely of stone. 
 It is not therefore that in the matter of 
 proper maintenance more pointing up 
 is required in a wall built of brick, but 
 it is the fact that prompt pointing up 
 is of especial importance. It is also 
 apparent that there being more mortar 
 material in the brick wall, any contribu' 
 tion which a given mortar makes to the 
 development of efflorescence is greater 
 in a brick than in a stone wall. 
 
 More consideration should be given 
 to the future use of a building by those 
 who design and construct it. FIGURE 8 
 shows a creamery covered in places 
 by efflorescence. A photograph of this 
 structure taken two years previous to 
 the time of obtaining the one here given 
 
 Figure 6. Efflorescence on 
 concrete block. 
 
 Figure 5. Prompt pointing up of cracks in the mortar joints would 
 have prevented this efflorescence (on sandstone'. 
 
WET WALLS 
 
 AND EFFLORESCENCE 
 
 13 
 
 Figure 7. The stone coping has broken loose from the adjoining 
 masonry, allowing water to enter the brickwork. 
 
 Figure 10. Leaking downspouts are frequent sources of water 
 penetration, leading to efflorescence. 
 
 Figure 8. Water condenses on the inner walls of this creamery except 
 in the office, which is at the right. 
 
 Figure 9. Closer view of wall shown above. Note disintegration of 
 
 mortar joints. 
 
 also shows efflorescence appearing on 
 the same parts of the wall as those 
 covered with such in this case, two 
 years later. Water condenses inside 
 where operations are carried on. The 
 middle portion of the exterior wall 
 to the right is free from efflorescence. 
 This area is the outer wall of the 
 company’s office and consequently 
 there was a dryer interior at 
 this locality. The efflorescence 
 in this instance could possibly have 
 been prevented altogether or 
 at least considerably reduced by 
 waterproofing the entire inner walls 
 of the humid rooms. Waterproofing 
 the exterior surface of these walls 
 would merely result in a progressive 
 accumulation of the efflorescence at 
 those areas where the exterior coat' 
 ing of waterproofing material is de- 
 fective. Such areas are always de- 
 veloped to a greater or lesser extent. 
 
 Among the various types of 
 faulty maintenance, leaking rain 
 
 Figure 11. Efflorescence closely follows the 
 downspout on this limestone wall, showing 
 penetration of moisture. 
 
 leaders and gutters are very numer¬ 
 ous. FIGURES 9 and 10, photo¬ 
 graphs of the same wall, amply illus¬ 
 trate the disintegration induced first 
 by cracks due to settlement and 
 later accelerated by the excessive 
 penetration of water due to a leak¬ 
 ing downspout. In this instance, 
 the mortar joints have disintegrated. 
 The courses of brick projecting out¬ 
 ward from the wall add to the ex¬ 
 cessive accumulation of moisture. 
 This point relative to design will 
 be further illustrated in this report. 
 Again, note the efflorescence near 
 the downspout in FIGURE 11. 
 This wall is of limestone and its 
 color is nearly the same as that of 
 the salts of efflorescence. 
 
 Gutter drains should be higher 
 toward the building. A few in¬ 
 stances were noted where the re¬ 
 verse was the case and in many in¬ 
 stances, the level toward the wall 
 was the same as that farthest from 
 
14 
 
 WET WALLS AND 
 
 EFFLORESCENCE 
 
 Figure 12. Excessive moisture has here caused the disintegration of 
 paint, as in numberless instances. 
 
 Figure 13a. Seepage and splashing have brought about extensive 
 stucco disintegration at the base of this building. 
 
 Figure 13b. In addition to causing efflorescence, excessive water 
 penetration has here resulted in disintegration of the stucco, which 
 has fallen off, exposing the brickwork beneath. 
 
 Figure 14a. The unusually severe exposure of this wall has resulted 
 in marked efflorescence. 
 
 Figure 14b. In this view of the same wall, note the peeling of paint 
 and the failure of mortar joints. 
 
 Figure 14c. Here is the final collapse of part of the wall shown in 
 the above illustrations. 
 
 Figure 14d. In this addition to the same wall, both the stucco cover 
 and the mortar joints are disintegrating. 
 
WET WALLS AND EFFLORESCENCE 
 
 15 
 
 the wall. It is also necessary that gutters and drains be and construction, it is seen that in the newer part, 14d, 
 of ample capacity for carrying away water from heavy the brick are not covered by earth. There is a concrete 
 rains. Also, at the returns of porch roofs where overflow base in this case. However, the design of the sills is 
 will result in discoloration and cracking of masonry wrong, they having no drips, and there are no eaves; 
 material, special attention should be given to the design of hence, covering the brick with stucco brought no material 
 gutters and downspouts. The end joints should be benefit. It is seen that the stucco cover is beginning to 
 thoroughly protected with sheet lead, copper or other disintegrate, showing the brick underneath. The mortar 
 
 suitable flashings. 
 
 In order to illustrate the 
 damaging effect generally of 
 exposure of all building ma' 
 terials to an excessive amount 
 of moisture, the accompany' 
 ing photograph, FIGURE 12, 
 is shown as a typical example 
 of numerous instances ob' 
 served of paint disintegration 
 from this cause. FIGURE 
 13a shows disintegration of 
 stucco at the base of a build' 
 ing brought about by seepage 
 and splashing. The eaves are 
 wide enough to protect most 
 of the walls, but there is no protection 
 at the base. The stucco was at the 
 soil level originally. FIGURE 13b is 
 another example of disintegration of 
 stucco resulting from excessive water 
 penetration. 
 
 FIGURES 14a, 14b and 14c show in 
 increasing order of magnitude the effect 
 of needless exposure of a wall. Efflo' 
 rescence is shown in (a), in (b) is seen 
 efflorescence and disintegration of the 
 mortar joints, and (c) shows the final 
 collapse of the wall. FIGURE 14d 
 shows an addition to the building made 
 after that part illustrated by FIGURES 
 14a, 14b and 14c had shown signs 
 of deterioration. By profiting partially 
 by past mistakes in the way of design 
 
 Figure 15. Maintenance alone is at fault in this instanc 
 the gutters are defective. 
 
 Figure 16. The downspout leaks, and set¬ 
 tlement cracks above the stone set in the 
 brickwork have not been pointed up, re¬ 
 sulting in much efflorescence. 
 
 joints are also beginning to 
 rapidly disintegrate. Note 
 also the disintegration of 
 paint in the illustrations, 
 14a and 14b. This is also 
 likely due to the unusually 
 severe exposure of the wall. 
 
 FIGURE 15, unlike the 
 cases 14a, 14b, 14c and 
 14d, is a case of faulty main' 
 tenance only. Due to defec' 
 tive gutters, there has been 
 more than normal penetration 
 of water into the wall. If 
 the bales are fixed, the next 
 good rain will have washed 
 off the efflorescence and it may not 
 recur. FIGURE 16 is another example 
 of improper maintenance. The design 
 and construction were all right in this 
 case. The downspout is leaking and, 
 what is worse, there has been no 
 pointing up of cracks (due to settle- 
 ment) at the top stone courses. 
 
 Excessive water penetration 
 from lac\ of drips 
 
 A typical example of wrong design 
 is shown in FIGURE 17, a and b. 
 Both are pictures of the same build- 
 ing. There are no drips on the flat 
 inclined stone caps at the top of the 
 buttress piers and the inevitable result 
 is in evidence. 
 
 Figure 17a. Efflorescence caused by failure to provide drips on the 
 stone caps over the buttress piers. 
 
 Figure 17b. Another view of the same building illustrating the 
 necessity for adequate drips. 
 
16 
 
 WET WALLS AND EFFLORESCENCE 
 
 Figure. 18. This general efflorescence, chiefly on the mortar 
 joints, probably came from excessive salts in the wall. 
 
 Figure 19. Water has penetrated these walls of underburned brick, 
 because of poor design and poorly constructed coping. 
 
 Figure 20. Flashing should be carried completely through the 
 parapet wall to keep water from penetrating downward. 
 
 Figure 21. Efflorescence has appeared in this case below the 
 water exit in the parapet wall. 
 
 Figure 22a. Defective flashing, absence of suitable drips and Figure 22b. Faulty maintenance is also responsible in part for 
 
 projections at the buttress tops caused this trouble. the efflorescence shown on this church. 
 
 
WET WALLS AND EFFLORESCENCE 
 
 17 
 
 It is very probable that condition D, namely normal 
 water penetration of a wall containing more than the usual 
 amount of salts, obtained in the case of the building, 
 FIGURE 18. The efflorescence was in this case generally 
 distributed over the wall. This building is new and the 
 design and construction were good. It may be noted that 
 the efflorescence was in this instance mainly on the mortar 
 joints. It is likely that these salts were carried outward 
 to the surface by evaporation of the moisture absorbed 
 and entrapped during construction. 
 
 Bric\ walls need protection during construction 
 Mention should be made here of the need of protection 
 of brick walls during the process of construction from 
 avoidable exposure to moisture. The tops of unfinished 
 walls should be well covered with canvas or tar paper at 
 the end of each day’s work. 
 
 Proper flashing essential 
 Defective flashing is one 
 of the most numerous of 
 the immediate causes of 
 efflorescence and wall dis¬ 
 integration and often also 
 there are in addition poorly 
 designed and constructed 
 copings. Wall copings, 
 
 cornices, rails, chimney 
 caps, etc., should be built 
 of concrete, stone, terra 
 cotta or metal with ample 
 overhanging drip groove or 
 lip, and watertight joints. 
 
 FIGURE 19 shows a building constructed of underburned 
 brick, which have been subjected to freezing and thawing 
 of water penetrating into the interior of the wall through 
 poor design and poorly constructed coping. This building 
 is old and it is likely that the underburned brick that have 
 in this case disintegrated to some extent, were burned 
 in scove kilns which in early days were fired with 
 wood. FIGURE 20 is a typical example of defective 
 flashing on a parapet wall. Note the efflorescence below 
 the water exit in the parapet wall illustrated in FIGURE 21. 
 Considering the favorable conditions for excessive water 
 penetration, there is remarkably little efflorescence on 
 the exterior walls of the church, FIGURES 22a and 22b. 
 Defective flashing, together with the absence of suitable 
 drips and projections at the stone caps at the tops of 
 the buttress piers, is directly accountable for the white 
 efflorescence. Faulty maintenance has added to the deplor¬ 
 able condition. 
 
 In the case of parapet walls as illustrated by FIGURE 20, 
 the flashing should be carried completely through the 
 wall, one or two courses above the roof level. The 
 parapet wall is then completely separated by an impervious 
 membrane from the other portion of the wall and conse¬ 
 quently water can not penetrate downward into the wall. 
 Architects should also waterproof the entire inner side of 
 
 the wall and should use impervious coping with carefully 
 pointed joints. It is out of the province of this report to 
 discuss the various details of design. These are subjects 
 with which the architect is familiar. However, the 
 accompanying illustrations show that these necessary 
 precautions are often overlooked and neglected. 
 
 In an article entitled, “Keeping Buildings Dry,’’ and 
 in regard to discoloration on the underside of balconies, 
 Cecil Fidler, Engineer of Standards, Atlantic Terra Cotta 
 Company has stated as follows: 
 
 It is almost impossible to make the deck of a balcony 
 watertight by means of a cement or tile finish. A cover¬ 
 ing of sheet metal should be used in all cases. In flashing 
 the tops of balcony slabs with sheet metal, it is necessary 
 to run the flashing out to the nib if the best results are 
 
 to be obtained. Quite fre¬ 
 quently the floor of a 
 balcony is properly flashed, 
 but the flashing terminates 
 in reglets in the base of 
 the balustrade. This prac¬ 
 tice almost invariably re¬ 
 sults in the saturation of 
 the balcony slab by water 
 which finds its way in at 
 the joints in the balustrade 
 and runs down behind and 
 underneath the flashing. By 
 carrying the flashing under¬ 
 neath the base course, any 
 water that enters at the 
 joints of the balustrade can not penetrate to the balcony 
 slab, and the soffit of the balcony is kept dry and unstained.’’ 
 
 In the case illustrated in FIGURE 23, there is no flashing 
 at all on the balcony below which the efflorescence ap¬ 
 pears. The stonework is covered by large copings which 
 communicate directly in a vertical direction with that part 
 of the stonework showing the efflorescence. A number 
 of the vertical joints in this coping have partially dis¬ 
 integrated. 
 
 Mr. Fidler further recommends the complete flashing 
 of the washes of pediments and dormers to avoid the evils 
 of saturation and makes the statement: 
 
 “While the use of sheet metal for the protection of 
 mortar joints may entail some slight additional expense 
 at the time of the erection of the building, it will be found 
 more economical in the end because the cost of mainte¬ 
 nance will be avoided.” 
 
 Mortar joints often not water-tight 
 
 It became apparent during the field study that architects 
 and builders were placing too much reliance on the mortar 
 joints. Close inspection of many cases of wet walls 
 showed that water was entering the mortar joints in the 
 wash of the cornice and parapet coping. For some reason 
 water-tight joints are not being produced by caulking and 
 
 Figure 23. The stonework below the balcony is not protected 
 by flashing and shows marked efflorescence. 
 
18 
 
 WET WALLS AND EFFLORESCENCE 
 
 Figure 24. A projecting metal flashing with drips should be 
 placed below brick sills like those shown here. 
 
 Figure 25. Joints in the window sills have cracked, allowing 
 excessive moisture to enter the brickwork below. 
 
 grouting. A number of things may be accountable for 
 this condition of the joints, such as poor workmanship, 
 inferior mortar or mortar that is too lean, disintegration 
 through alternate freezing and thawing of the original 
 moisture introduced during construction in late fall or 
 winter, or cracking due to uneven settlement and thermal 
 expansion. 
 
 Avoid vertical joints exposed to excessive moisture 
 
 Vertical joints exposed to an excessive amount of 
 moisture as are those in window sills should be avoided as 
 much as possible. FIGURE 24 is typical of what will 
 follow if this precaution is not observed. This wall is of 
 sanddime brick and efflorescence is noticeable beneath 
 the rowlock brick sills with many intervening mortar 
 joints in each sill. Of course, there are no drips on such 
 sills. If such sills must be used, there should be placed 
 beneath such a sill a suitable metal flashing, projecting 
 and with drips. FIGURE 25 shows a church whereon crack' 
 ing and initial disintegration of joints, especially of the 
 vertical ones, has occurred. As a consequence of the 
 failure to observe these precautions, the brick above the 
 stone belt line and beneath the sills are here being exposed 
 to an excessive amount of moisture. It would have been 
 better had the sills been in each case one solid piece of stone 
 with a slope to the wall on each side. Furthermore such 
 sills (lug sills) should project at least two inches and be 
 provided with suitable drips. This also applies to the 
 cornice. 
 
 FIGURE 26 illustrates protection against excessive water 
 penetration at the sills. Note that each sill is a single 
 unit and not two or three units with intervening vertical 
 mortar joints. This illustration typifies the ideal drainage 
 for sills. There are good drips underneath and an up' 
 ward slope in each case from the window area toward the 
 wall to left and right. The sills also project more than 
 two inches. Good cornice and well pointed joints are 
 
 also characteristic features of this building. Another 
 model of good design is illustrated by FIGURE 27. Here 
 there are good drips on sills which are single units with 
 no vertical joints. Other desirable features are the wide 
 eaves, the cornice reentering, protection against seepage 
 at the base by having the brick on stone some distance 
 from the soil and the rain water leaders extending to the 
 ground thus avoiding splashing. 
 
 Projecting courses may cause ejflorescence 
 Projecting courses of brick such as the rowlock or soldier 
 courses apparently intended to enhance artistic beauty in 
 a wall, in reality are most conducive to discoloration as 
 well as to disintegration. Where such courses of brick are 
 laid in a wall, there should be ample protection against 
 excessive water penetration. The vertical courses of 
 brick illustrated in FIGURE 28 are being exposed to exces' 
 sive moisture. Efflorescence will inevitably result on such 
 exposed areas and what is far more undesirable, disintegra' 
 tion will always be accelerated when mortar joints are so 
 exposed. Note in this instance the marked efflorescence on 
 
 Figure 26. Thi9 illustrates good drainage for sills, with adequate 
 drips and the proper slopes at the ends. 
 
WET WALLS AND 
 
 EFFLORESCENCE 
 
 19 
 
 the mortar joints. Lime putty mortar was used. The 
 combination, poor materials together with poor design 
 from the standpoint of excessive moisture penetration, 
 brings about condition B, the most undesirable of the 
 four mentioned. In this particular instance, the brick 
 are remarkably free from efflorescence, considering 
 the extent of exposure to which they have been 
 subjected. In time, however, the soluble salts on the 
 joints as illustrated may be carried by moisture over 
 the face brick, and one who observes the wall then 
 for the first time may think that the brick are directly 
 responsible for the efflorescence. FIGURE 29 shows 
 a corbelled area on a new building that is dark with 
 moisture. This may be expected eventually to result 
 in disintegration of joints and efflorescence similar to 
 conditions illustrated in FIGURE 33. The small 
 recess below the window sill collects a maximum of 
 water for the vertical joints below. 
 
 Figure 27. This building illustrates good design as regards sills, wide 
 eaves, cornice and protection at the base. 
 
 Figure 28. The projecting courses of brick shown here receive 
 excessive moisture. 
 
 Figure 29. The corbelled area is dark with moisture, and as the build¬ 
 ing ages, will doubtless show efflorescence and disintegration of joints. 
 
 In the design of all walls built of brick some consider' 
 ation should be given to protection against water 
 penetration rather than to but one thing, namely artistic 
 appearance. To corbel out with one or more courses of 
 brick or any other masonry material, is always a dangerous 
 
 procedure unless such projecting brick courses are to be 
 so situated as to be amply protected from undue exposure 
 to moisture penetration. 
 
 Protect masonry through attention to design 
 It is believed that a realization of what can happen 
 through improper design will go farther toward cor' 
 recting this evil than will a recital of a large number of 
 details necessarily involved in construction planned 
 to protect the wall. The builder is familiar with 
 these various details and due probably to the fact 
 that he relies too much upon the weather resistance 
 properties of all masonry materials he too frequently 
 does not consider the possibility of modifying the 
 design so as to protect them more. Such an example 
 as the accompanying illustration, FIGURE 30, 
 typifies such a tendency on his part. Here again 
 are the maximum number of exposed vertical 
 joints. 
 
 Figure 30. By modification of design, greater protection can be given 
 masonry materials in cases like this. 
 
20 
 
 WET WALLS AND EFFLORESCENCE 
 
 Figure 31b. In retaining walls, the exposure is especially severe. Even well-burned brick, 
 such as were used here, must have adequate drainage to resist frost action. 
 
 Figure 31c. The mortar joints in this wall have been pointed up twice and need attention again. 
 Direct contact with moist ground at the back of the wall, without insulation 
 or proper drainage, is responsible for this trouble. 
 
 Walls severely exposed 
 
 The subject, retaining walls, 
 is interesting. It is here that 
 masonry materials are given the 
 most severe exposure if not pro- 
 perly protected. FIGURE 31b 
 shows a coping of well burned 
 brick on a retaining wall. Even 
 well-burned brick or other good 
 materials must have sufficient 
 drainage if they are to resist frost 
 action. The result here is due to 
 lack of proper drainage. FIG¬ 
 URE 3 1 c is another retaining 
 wall that has been pointed up 
 twice and a third operation of the 
 kind is in need of being done. 
 
 FIGURE 3 Id is especially inter¬ 
 esting. Below each disintegrated 
 vertical joint in the cap of this 
 wall, there is a crack in the solid 
 concrete below. Perhaps no 
 comments on FIGURE 31e are 
 required. FIGURE 3If shows 
 how mortar has disintegrated 
 under a cap with no drip. This 
 is also part of a retaining wall. 
 
 This same principle applies in the construction of chim¬ 
 neys. Chimneys are peculiarly vulnerable to severe 
 weathering conditions. The accompanying photograph, 
 FIGURE 32 is but one of a large number of instances of 
 the sort. Here again too much dependence was placed upon 
 the vertical mortar joints in the brick at the cap. Such a 
 chimney should have had a stone cap with good projection 
 and furnished with drips of wide and deep grooves. The 
 thin covering of stucco in this case has not endured the test. 
 
 As final illustrations of a combination of faulty design, 
 
 construction and maintenance, FIGURES 33 and 34 should 
 be self-explanatory. FIGURE 33 is a small portion of the 
 building of which FIGURE 34 is a more complete view, 
 not however showing the portion shown in FIGURE 33. 
 This closeup indicates what may be expected in years to 
 come in wall areas like that shown in FIGURE 29, which 
 is on a new building. Corbelling such as illustrated in these 
 two pictures usually leads to excessive moisture penetra¬ 
 tion. 
 
 In FIGURE 33 it may be noted that both mortar joints 
 
 From this illustration to the 
 next, FIGURE 31a, there is 
 added the further undesirable 
 condition, soil in immediate 
 contact with the brick in the 
 retaining wall. To have put tar 
 or tar paper back of this wall or 
 still better to have dug a trench 
 back of this wall, lining the 
 trench with impervious concrete 
 and then to have filled the trench 
 with gravel would have been an 
 additional expense well worth 
 while. Within a short time it 
 will be necessary to rebuild this 
 wall and this procedure will cost 
 considerably more than would 
 the initial precautions. 
 
 Figure 31a. Moisture has entered this wall from the soil, which is in contact with the brickwork. 
 
WET WALLS AND EFFLORESCENCE 
 
 21 
 
 and a window sill are disintegrating. Repair and pointing up 
 are badly needed. Leaking downspouts, defective flashing 
 both at the chimney base and in the parapet walls, project' 
 ing courses of brick with vertical joints exposed, poorly 
 designed drips on sills (such being too shallow and so close 
 
 Figure 3 Id. The vertical joints in the coping have disintegrated, 
 and below each a crack has formed in the concrete. 
 
 to the wall as to be ineffective), the sills themselves being 
 of soft porous sandstone and not weather resistant and the 
 truncated water exit (FIGURE 21, same building), were 
 the immediate causes in this instance of the efflorescence 
 attended by disintegration. 
 
 Figure 31e. An endless number of retaining walls in varying stages 
 of failure might be shown. 
 
 Figure 3If. Under this cap, which has no drip, the mortar has 
 disintegrated badly. This is also 
 part of a retaining wall. 
 
 Figure 32. Chimneys receive particularly severe exposure. The 
 vertical mortar joints here have allowed water to enter 
 between the stucco and the brick. 
 
 Figure 33. Corbelling of the brick is the chief reason for the 
 failure at the right, whereas the trouble directly under 
 the left window is due in large measure to 
 the sill. 
 
 Figure 34. This efflorescence has resulted from a number 
 of clearly recognizable faults of design, construction 
 and maintenance. Figure 33 shows a closeup 
 view of another part of this building. 
 
22 
 
 WET WALLS AND EFFLORESCENCE 
 
 Again, to further illustrate combined faulty 
 design, construction and maintenance, com 
 sider FIGURES 35a, 35b, 35c and 35d, all 
 pictures of the same building although parts of 
 an adjacent building are seen in FIGURES 35a 
 and 35c. This was originally Condition B, 
 without doubt. Kiln run common brick, a 
 portion of which are underburned, compose 
 the wall. FIGURE 35d shows the extent to 
 which these brick as well as the intervening 
 mortar joints near the soil have disintegrated. 
 Efflorescence, very noticeable in the past, is 
 becoming less noticeable at present while 
 disintegration progresses. The walls have 
 received quantities of water to wash out the 
 salts for the most part. Galvanised iron which 
 corrodes comparatively readily was used for 
 flashing of the parapet wall which is about 
 eight feet above the roof. There is both 
 seepage and splashing, causing saturation of 
 the lower wall. The coping is poorly designed. 
 There are downspouts but these are inside 
 the building and have undoubtedly become 
 clogged. As a result, the overflow spouts 
 have been called on to do the work with the 
 results herein illustrated. As the joints pn> 
 gressively disintegrate the degree of satura' 
 tion during a wet season increases. Below 
 the wide recesses in the wall are projecting 
 header courses of brick. It would be difficult 
 to devise a more favorable condition for 
 entrapping the maximum amount of moisture. 
 Horizontal exposures are here unprotected 
 by either sloping or by drips. 
 
 Figure 35a. This and the next three illustrations all show parts of the 
 
 same building. 
 
 Figure 35b. The walls of this structure are composed of kiln run brick, some 
 of which are underburned. 
 
 Some consideration might also be given 
 finally to the analogous weathering of rock 
 in nature. In connection with the following 
 illustrations, one might make the appropriate 
 statement: “Nature destroys her own.” In 
 FIGURE 36a can be seen in the distance 
 across the river, the result of frost action, sup' 
 plemented by erosion by water and wind. 
 
 FIGURES 36b, 36c, and 36d give one some 
 notion as to the tremendous forces brought 
 to bear in repeated freezing and thawing. 
 
 Dynamite could hardly do more. These 
 stones, of course, had no drips. The sand' 
 stone base illustrated in FIGURE 37 is 
 almost as much at the mercy of the elements. 
 
 FIGURE 38 shows a bridge railing with' 
 out drip or enough slope. One might go on 
 indefinitely, but it is hoped that the preceding 
 illustrations show that there is required today more con' salts or whether such salts are in very small quantity in 
 
 sideration of the subject, water penetration, in the building the masonry. Best of all, there will also result far less' ten' 
 
 industry. Reduce water penetration and efflorescence will dency toward disintegration and this after all is a far more 
 diminish in any case, whether there is a great deal of soluble serious incident than is efflorescence. 
 
 
 Figure 35c. 
 
 Disintegration progresses while efflorescence becomes less marked 
 as the soluble salts are washed out. 
 
WET WALLS AND 
 
 EFFLORESCENCE 
 
 23 
 
 Figure 35d. This closeup reveals the extent to which the mortar 
 joints and even the brick have disintegrated. 
 
 Figure 36b. Viewed close at hand, the destruction wrought by 
 repeated freezing and thawing is seen to rival the 
 power of dynamite. 
 
 Figure 36a. Talus slopes such as this are common sights below 
 cliffs of solid rock, along shore lines everywhere, for frost ac¬ 
 tion is a relentless force, initiating the process of disintegra¬ 
 tion and opening the way for erosion by water and wind. 
 
 Figure 36c. Another type of rock broken up by frost action. 
 
 Figure 37. Moisture penetrating this sandstone base has begun 
 its powerful disintegrating action. 
 
 Figure 36d. Still another variety disintegrated by frost. 
 
 Figure 38. This bridge railing has no drips and too little slope 
 to dispose of the water. 
 
24 
 
 WET WALLS AND EFFLORESCENCE 
 
 Summary 
 
 The purpose of the foregoing is to point out the fact 
 that in the main, the immediate cause of efflorescence and 
 often too of wall disintegration is excessive penetration 
 of moisture into the wall. The field work supplemented 
 the fundamental work that had already been done and 
 that had established the fact that hardly any masonry 
 material is exempt from the possibility of containing solu- 
 ble salts in quantity such that it may under favorable 
 conditions contribute to the development of noticeable 
 efflorescence. The favorable conditions are wet walls. 
 
 With but one or two definite exceptions, all of the large 
 number of instances of efflorescence and in some cases wall 
 disintegration that were studied could have been prevented 
 had due consideration and care been given to the proper 
 design, construction and maintenance of these buildings. 
 
 A few examples of such preventable instances of efflores- 
 cence have been shown. Some details in way of design, 
 construction and maintenance which, had they been ob- 
 served and remedied, would have prevented the occur' 
 rences of efflorescence as illustrated by photographs, have 
 been mentioned. There are many more of such details and 
 it is assumed that the architect and builder are more 
 familiar with them than is any one else. 
 
 Efflorescence can become very noticeable on the wall of 
 a building composed of brick or other masonry materials 
 that are exceptionally low in soluble salt content if an 
 excessive amount of water enters that wall. 
 
 Any efflorescence appearing on the wall of a building 
 that is suitably designed, constructed and kept in repair 
 in order to avoid excessive water penetration, will be due 
 to rare and abnormal conditions. It will in time gradually 
 diminish and finally disappear. It will never recur under 
 normal conditions even though the soluble salt content of 
 the entire wall be higher than is normally the case. Pro- 
 longed and heavy wind-driven rains will bring out efflores¬ 
 cence on almost any wall, but this efflorescence is of the 
 temporary nature described, is usually of short duration, 
 and is generally unaccompanied by disintegration of joints. 
 
 The effort on the part of manufacturers of face brick 
 to develop products as free as possible from soluble salts 
 (even if the goal, complete elimination, could be attained) 
 will not in itself insure against the development of efflores¬ 
 cence on walls. Their work must be supplemented by a 
 concentrated effort on the part of architects, builders and 
 owners to keep the walls as dry as possible. It is also 
 very necessary that manufacturers of the other building 
 materials used in walls with the face brick be equally con¬ 
 cerned with the question of soluble salts in their materials. 
 
 Means of preventing efflorescence by keeping the walls 
 dry have been outlined. It is hoped that architects and 
 builders generally will proceed much further with this 
 study and that the face brick industry will have their 
 full cooperation in keeping dry the face brick walls of 
 buildings yet to be constructed. 
 
 EFFLORESCENCE ON FACE BRICK WALLS 
 
 (Publication Approved by the Director of the Bureau of Standards of the U. S. Department of Commerce) 
 
 ' I 'HE accumulation of salts, usually sulfates, upon the 
 -L outer surface of the wall of a building, is commonly 
 referred to as “white wash” or “efflorescence.” These 
 salts may exist in the mortar used with the face brick, in 
 the face brick themselves, and usually to a greater extent 
 in the softer burned brick and hollow tile backing. They 
 may be present in any concrete mortar materials, cement 
 block, etc., used in the backing. 
 
 Causes of efflorescence 
 
 During a cool and humid season of the year when the 
 wall is repeatedly exposed to rain, moisture penetrates 
 far back of the facing and takes into solution some of these 
 soluble salts from both the back-up and the facing ma¬ 
 terials. As soon as the weather becomes favorable for 
 evaporation of this accumulated moisture, as in the 
 spring of the year, these salts are carried outward and 
 are deposited on the face brick. A wall under process 
 of construction is particularly apt to absorb a considerable 
 amount of moisture. Every precaution should be taken 
 
 to keep an unfinished wall covered and protected from rain 
 or snow during the process of construction. Moisture 
 so accumulated in the wall brings the salts to the outer 
 wall surface to such an extent that the efflorescence be¬ 
 comes very noticeable before the building is even com¬ 
 pleted. The layman who sees only the visible salts on 
 the outer wall, may not consider any of the materials in 
 the wall, beyond what he actually sees, as contributing 
 factors. 
 
 Purpose of investigation 
 
 In order to get the essential facts concerning the 
 mechanism of the development of efflorescence, the Am¬ 
 erican Face Brick Association conducted an investigation 
 at the Bureau of Standards in accordance with that insti¬ 
 tution’s Research Associate plan. 
 
 Method of procedure 
 
 To obtain information concerning the development of 
 efflorescence, it was thought to be expedient to study 
 primarily the materials, brick and mortar. Whatever 
 
WET WALLS AND EFFLORESCENCE 
 
 25 
 
 facts were found with respect to intervening cement or 
 lime mortar joints in the outer wall of face brick as con' 
 cerns efflorescence would apply to such lime or cement 
 mortar if used with backup materials, provided of course 
 that water could penetrate into the backing. Whatever 
 factors there are in plant procedures that would tend to 
 introduce soluble salts in face brick would also obtain 
 in the process of manufacture of any heavy clay product 
 manufactured under similar conditions. 
 
 In order to study the parts that mortar materials as 
 well as face brick play in the development of efflorescence 
 on a wall, there were selected for the purpose four types 
 each of well known and extensively used limes, portland 
 cements and bricklayers’ cements. There were also 
 selected from various parts of the United States fiftyffive 
 different types of face brick. 
 
 The brick and mortar materials were used in test 
 panels made as follows: three brick of the same type were 
 laid up, one above another, with intervening joints of a 
 mortar prepared from one volume of lime or cement mixed 
 with three volumes of Standard Ottawa Sand. The 
 mortar joints were approximately ffff inch in thickness. 
 
 Two such panels were constructed with each type of 
 brick laid up with a given lime, portland cement or brick' 
 layers’ cement mortar. Each pair of panels constituted 
 a single test. Twelve tests of twenty Tour panels were 
 made with each of the four limes and cements, thus bring' 
 ing the total number of panels tested to 288. 
 
 After the panels were constructed they were allowed 
 to set and dry on the floor of the laboratory before being 
 subjected to the test for efflorescence. At the end of three 
 weeks, each pair of panels was set in a separate pan con' 
 taining about one inch of distilled water, one panel of 
 each pair being set vertically and the other horizontally. 
 Water was added to the pans from time to time as required 
 to replenish loss by evaporation. The tests were con' 
 tinued for a period of six months. 
 
 Simultaneously with these panel tests individual tests 
 for efflorescence were made with the brick of the same 
 types as those used in the panels. Each lot of six brick 
 representing one manufacturer’s product was tested in a 
 pan separate from the others. The brick were set ver' 
 tically in the pan and in about an inch of distilled water 
 and the tests in all cases were continued for a period of 
 six months. 
 
 Results of tests for efflorescence 
 
 It must be realized that the tests above described were 
 such as to provide conditions most favorable for the de' 
 velopment of efflorescence. If the same brick and inter' 
 vening mortar joints had been placed in the outer wall of 
 a building, rainfall from time to time would have tended 
 to wash off the deposits of salts on the surface. However, 
 in this case there was in each individual test a steady 
 accumulation of such salts on the dry portions of the 
 panels and no removal of accumulated salts during the 
 
 six months’ period of the tests. 
 
 The total number of different types of face brick used 
 in the panels was thirty'two. Of this number fifteen did 
 and seventeen did not develop any noticeable efflorescence 
 during the six months’ tests made on the individual brick 
 themselves and not in contact with any mortar. The 
 seventeen types which did not develop any efflorescence 
 when so tested individually did develop noticeable 
 efflorescence with at least one of the various types of 
 mortars. Both the face brick and the cements and limes 
 used in these tests were so chosen as to be as nearly 
 representative as possible of such building materials as 
 used in the United States. The results should therefore 
 be very indicative of the contribution that each material 
 would make toward the development of efflorescence on 
 a wall. 
 
 The tests were rigorous and extended over a compara' 
 tively long period of time. The gradually accumulating 
 salts on the dry surfaces of the panels or of the individual 
 brick were not removed by rain, a condition which obtains 
 when such materials are used in the wall of a building. 
 In view of the fact that iff or fifty'three per cent of the 
 types of face brick developed no efflorescence during the 
 six months when tested individually (even though the 
 tests were much more severe than any actual conditions 
 existing in the wall), but did develop noticeable efflores' 
 cence when laid up with at least one type of mortar, it 
 must be concluded that the face brick manufacturers have 
 to a considerable extent reduced any tendency on the 
 part of their product to develop efflorescence. 
 
 Methods of reducing the extent to which lime and cement 
 materials may contribute to efflorescence 
 
 Theoretically, any possible contribution to wall efflores' 
 cence on the part of mortar materials may be prevented 
 or decreased if the mortar could be rendered more im' 
 permeable to water. It is not possible to fill all of the 
 voids, but it is possible that the presence of a certain 
 substance or substances introduced into such voids could 
 lessen the passage of water due to capillarity. It is rea' 
 sonable to assume that if little or no water can enter 
 mortar materials, there can be no leaching out to any 
 appreciable extent of any salts which they contain. 
 
 Experimental 
 
 A relatively soft and porous type of brick was used 
 throughout in all of the tests of mortars containing the 
 water repellent substances. Excepting those tests where' 
 in a cement was used which already contained the water 
 repellent substance, the mortars were made either with 
 portland cement or lime, or mixtures of lime and cement, 
 together with sand. The relative proportions of the 
 mortar materials were such that the volume ratio of cement 
 or of lime, or of the lime plus cement (if mixtures were 
 used), to sand was one to three. Excepting those trials 
 made wherein a cement was used to which the water 
 
26 
 
 WET WALLS AND EFFLORESCENCE 
 
 repellent material had already been added at the factory 
 and excepting also those trials in which diatomaceous 
 earth was substituted in part for sand, the amount of the 
 water repellent substance used was either that as sped' 
 fied by the manufacturer, if it had been purchased on the 
 market, or else (if it were not a material made solely for 
 this purpose) an amount of it equal to two per cent by 
 weight of the cement or of the lime or of the lime plus the 
 cement was used. 
 
 The water repellent materials were added directly to 
 the mortar materials at the time of mixing. Distilled 
 water was used in such quantities that upon thorough 
 mixing, the mortar had the desired consistency and was 
 thoroughly workable. 
 
 Six brick laid up with the mortar, giving five mortar 
 joints, constituted a panel. After being constructed, 
 the panel was allowed to set and dry on the laboratory 
 floor for a period of three weeks prior to beginning the 
 test. After this length of time, the panel was set (brick 
 flatwise) in a shallow pan, the joints being parallel to the 
 base of the pan. The lower brick was about half sub' 
 merged in a saturated solution of sodium sulfate which 
 was poured into the pan upon beginning the test. For 
 a period of six months the level of the solution of sodium 
 sulfate was kept fairly constant and observations were 
 taken from time to time, noting any upward progress of 
 the salt solution through the mortar joints. When pene' 
 tration did occur, the crystals of sodium sulfate appeared 
 upon the second, third, etc., brick from the bottom 
 according as the rate of penetration was slow or rapid. 
 The test was continued over a period of six months. 
 
 Results of tests on water repellent materials 
 
 For the most part, all of the compounds used tended 
 to decrease the rate of penetration of the salt solution 
 through the mortar joints. The inert materials, clay 
 and diatomaceous earth did not entirely prevent penetra' 
 tion in all cases, but were, however, more or less effective. 
 Ammonium, aluminum, and calcium stearate were equally 
 effective and no salts penetrated beyond the first mortar 
 joints in any panel in which any one of these substances 
 was used. 
 
 A wall in which these water repellent substances have 
 been used must not be considered as being thoroughly 
 waterproof. Rain may penetrate through face brick to 
 the backup materials, take salts in these materials into 
 solution and then carry them back to the outer wall dun 
 ing the subsequent process of the drying of the wall. 
 The purpose of the stearates is only to render less likely 
 the contributing of the various mortar materials used in 
 the entire wall to the development of efflorescence on the 
 outer wall. Furthermore it is evident that in order for 
 this condition to be realized, the water repellent substances 
 
 must be used in all of the mortar in the wall, in the backing 
 as well as in the mortar used with the face brick. 
 
 Other means of reducing efflorescence 
 
 Since two conditions must exist for efflorescence to 
 appear on the outer wall, it is obvious that there are two 
 means of reducing efflorescence. One of these conditions 
 is the presence of salts in the materials in the wall, from 
 front to back. The other condition is the penetration of 
 moisture into the wall, taking these salts into solution. 
 The manufacturer should concern himself with the first 
 condition mentioned. The architect and builder can 
 relieve the second, penetration of water into the wall, to 
 some extent at least. 
 
 The use of the stearates as watenrepellent substances in 
 the mortar is suggested. In addition to this, careful and 
 prompt pointing and waterproofing of parapet walls, 
 copings, etc., and flashing to prevent the penetration of 
 water into the walls will also help. In the case of parapet 
 walls, it is well to carry the flashing completely through 
 the wall at one or two courses above the roof level. The 
 parapet wall is then completely separated by an impervious 
 membrane from the other portion of the wall and conse' 
 quently water can not penetrate down into the wall and 
 later be drawn up to the top of the parapet by capillarity. 
 Architects should seek still further to avoid trouble by 
 waterproofing the entire inner side of the wall and should 
 use impervious coping with carefully pointed joints. 
 
 The manufacturers of face brick are able to reduce to a 
 negligible quantity soluble salts in their product, chiefly 
 by means of special burning procedures. Often, also, 
 they have made use of barium compounds, adding them 
 to the clay to render the sulfates insoluble. To a lesser 
 degree, perhaps, such measures can be used in the manu' 
 facture of the clay products used as back'up materials, 
 although the selling price of such products does not war' 
 rant the application of the comparatively expensive mea' 
 sures as used in the manufacture of face brick to eliminate 
 any soluble salts. 
 
 The builder who would guard especially against the 
 occurrence of efflorescence on the outer wall should take 
 into consideration each and every material that is to com' 
 pose the entire wall. If any tests are to be made to de' 
 termine the presence of soluble salts, every material in 
 the wall should be so tested and it is equally important 
 that every necessary precaution be taken to reduce pene' 
 tration of water into the wall to a minimum. 
 
 A more detailed report covering the work done has been 
 published by the Bureau of Standards as Technologic 
 Paper No. 370, under the title “Cause and Prevention of 
 Kiln and Dry'House Scum and of Efflorescence on Face 
 Brick Walls.” 
 
 16,500 10-28-1 PRINTED IN U 8. A 
 

 
 ' '' V 
 
 .V?'V 
 
 
 
 
 
 
 
 ■ 
 
 
 
 gsp*£ m 
 
 . .. _ 3ftft:.'. St8 
 
 - - . ‘ - , 
 
 - 
 
 
 ; -y*$ 
 
 v' ' *•■. 
 
 .. ft., • ' • ' '? '• • • - ' •• 
 
 ' 
 
 . 
 
 . ; i - - - : j*- t. .. 
 
 SJ <$ t‘ * * 5 ® • f tsmL ' ! 
 
 ' 
 
 . ■ 
 
 ■ 
 
 ■ 
 
 '■ ‘ > 
 
 :• re ..v.. 
 
 ■’ . • . . • •• • y Vt* 
 
 
 
 
 
 
 
 W’ •V* S