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Technical Translation (National Research Council of Canada), 1961
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Rain Penetration of Brickwork
Amrein, E.
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Preface
Rain penetration of walls is a common and difficult problem in building which has been experienced in many countries. The Division of Building Research is one of
several bUilding research organizations investigating the problem. As part of the Division's contribution to
studies of it, translations are being prepared from time to time of foreign papers dealing with the SUbJect. The present translation is of the article "The Rain Penetra-tion of Brickwork" by E. Amrein. ·Dr. Amrein is with an
association of clay products manufacturers in SWitzerland, and his account of European experiences with the problem, and of his laboratory studies of it, forms a useful
contribution to the literature.
This translation was prepared by Mr. D.A. Sinclair of the Translations Section of the National Research Council, to whom the Division of Building Research records it thanks.
Ottawa, JUly 1961
B.F. Legget, Director
Technical Translation 968
Title: The rain penetration of brickwork
(Die SchlagregendurchlAssigkelt von Sichtmauerwerk) Author: E. Amrein
Reference: Die Ziegelindustrie, 12 (24): 726-730, 1959
THE RAIN PENETRATION OF BRICKWORK 1. Introduction
The rain penetration of brickwork has always been a problem of great importance for countries where brick masonry is the normal method of bUilding walls. It has been dealt with in various publi-cations. For this reason we first made a thorough study of the foreign literature before beginning our own tests. The following organizations participated in the investigations from 1957 to 1959:
Dachziegelwerk Frick;
Schmidheiny and Co. AG, Heerbruggj Prtlf- und Forschungsstelle VSZS.
At thiS point we would like particularly to thank the directors of these firms and their coworkers, especially Mr. Picard and Dr. Iberg, as well as Dipl.-Ing. P. Haller, EMPA, Zftrich, for their cooperation and valuable suggestions.
2. Literature
Thein's paper published in 1931(1) contains the following important information:
Brick ｦ｡ｾ｡､･ｳ are exposed to rain chiefly in the months of February - April. The autumn is less dangerous, since at this time walls are generally very dry. However, after a very wet summer
there may be some danger of rain penetration in the autumn as well. The following are the chief errors that may occur in the erection of brickwork:
1. Faulty surface qualities of the brick, e.g. irregularity of dimension, chipped corners, warping. Non-uniformity of the bricks inevitably leads to non-uniform filling of the jOints. 2. The masonry mortar is made of impure sand, which has too uniform
a grain. Too low a cement content results in a mortar with high porosity. The use of too little or impure water results in poor adhesion of the cement to the sand.
3. The joint mortar is too porous; unsuitable sand yields a highly water-absorbing mortar. Mortar which is too dry and too lean
is unsuitable.
4. The laying of bricks without wetting them interferes with the mortar setting process and leaves a water permeable gap between
the brick and the mortar.
5. The use of hydrochloric acid to clean the joints before finish-ing leads to separation of calcium chloride and prevents good bonding of the pOinting mortar. Before and after use the faqade in question must be washed well with clean water.
6. The following errors of execution may occur:
Non-uniform addition of water, depending on the particular requirements;
Use of mortar that has become segregated; Bed jOints not completely filled;
Inaccurate laying of bricks, sometimes referred to as piling (Stapeln) ;
Empty vertical jOints due to inadequate dabbing with mortar and inadequate pressure in bringing the bricks together;
The use of lean mortar leads to imperfect vertical jOints even when the utmost care is applied in the construction. These flaws can only be repaired by most careful grouting with jOint coating mortars;
Careless scraping of jOints before pointing;
Careless pOinting (uncontinuous, inadequate coating, lifting Off, excessively dry mortar, etc.).
Thein's recommendations for the erection of brickwork can be summed up as follows:
Only perfect bricks with maximum dimensional accuracy, unwarped and free of cracks and craters should be used. A lime cement mortar 1 : 3.5 or a cement mortar I : 4 with added waterproofing compound should be used. As a pOinting mortar a cement mortar 1 : 3 is
suitable. The mixture I : 2 is too fat and tends to produce shrink-age cracks. The sand should have the highest possible weight per unit volume and be without coarse grain. The addition of mortar densifying agents is to be recommended provided they are stable with respect to moisture. The bricks should be wetted before laying.
-5-The joints should be at least 1 em wide to permit adequate subsequent pointing. In bUilding walls the bricks should not merely be laid on top of a mortar course but should be pressed thoroughly into the
mortar. Damp mortars must not be used; the mortar must be thoroughly mixed, preferably with a mixing machine. Immediately after laying
the bricks the joints should be scraped out. Pointing must be
r
accompanied by the exertion of great pressure on the pointing mortar. First the bed jOints and then the cross joints are pointed •.
Cavity wall brickwork offers the best ｧｵｾｲ｡ｮｴｹ of impermeability
So much for Thein's suggestions. Shortly after his publication, one appeared by Meyer(2) in 1932 on the processing of clinker brick. This work dealt chiefly with the problems of pOinting mortar and the fOllowing conclusions were drawn.
For a pointing mortar the sand should be fine grained and as clean as possible. At least 70% of the sand should comprise grains of 0 - 1 mm. There should be no grains above 3 rom. The washable-out part should not exceed 2 percent (except for limestone flour). The pointing mortar should always consist of a Portland cement and
sand in a ratio of 1 part by weight cement to 2 parts sand. In mixing, care must be taken not to use more ｾ｡ｴ･ｲ than is needed ·to make a plastic, water-tight mortar. The water-cement factor must be about 0.5. Additions of clinker flour, dry hydrate or brickdust render the pOinting mortar permeable. It has also been found that in no case did the addition of a densifier ｾ･ｮ､･ｲ an otherwise
permeable mortar waterproof. The shrinkage mass of the 1 : 2 mortar after 12 weeks, for a water-cement factor of 0.45 to 0.5, is 0.5 to 0.8 percent. Increasing the water-cement factor results in a
considerable increase in the shrinkage factor up to 1.2 percent. POinting mortar of limestone flour with the following grain analySis data
5
-
3 mm, 4 percent 3-
1 rom, 30 percent 1-
0.2 mm , 27 percent 0.2-
0 mm, 38.5 percenthas proved its value everywhere even though the ｷ｡ｳｨ｡｢ｬ･ｾｯｵｴ content was 26 percent. However, the washable-out components did not
consist of clay, as is usually the case, but of brickdust and were therefore not harmful.
ｂｲｾ｣ｫ･ｲＨＳＩＬ
on the basis of Thein's works, finds that thedefinition of driving rain (Schlagregen) is not realized in practice and the conversion proposed by Thein is not an entirely correct way of depicting its effect. After thorough investigations and with the
"
aid of meteorological measurements Brocker arrives at the following definitions:
Driving rain is a precipitation combined with wind in such a way that a considerable portion of the rain is driven against a wall
standing perpendicular to the wind direction.
Standard driving rain is rain associated with wind of force 5; at this wind force the angle of 45° is exceeded, i.e. the vertical wall stops more rain than the horizontal.
Heavy driving rain is rain associated with a wind force of 8. The quantity of rain must be disregarded, since it has no effect on the wetting action.
For wind force, velocity and dynamic pressure the following table is used:
Wind force Veloci ty mls Dynamic pressure nun
.water 0 0.0 - 0.5 0 0.015 1 0.6 - 1.7 0.02
-
0.18 2 1.8 - 3.3 0.2 0.62 4 5.3 - 7.4 1.7 3.3 5 7.5 - 9.8 3.4 5.8 6 9.9 - 12.4 6.0 9.4 8 15.4 - 18.2 14.4 - 20.2 10 21.6 - 25.1 28.5 - 38.5 12 greater than 29 grea ter than 51.2Br8cker used a wind force of 9 for his experiments and the quantity of water was sufficient to produce a film of water on the wallo
It must be pointed out that ｂｲｾ｣ｫ･ｲＧｳ tests did not determine the rain penetration of ｢ｲｩ｣ｩｬｬｾｯｲｫＬ but only the effect of stuccoing.
-7-His conclusions are nevertheless interesting and may be summarized as follows:
The most reliable protection against driving rain consists in the use of masonry with a continuous internal air gap, i.e. a
cavity wall design. This design is very widely used in the northern countries - Germany, Holland and England. Fairly good protection is obtained by the use of good stuccoing.
In addition to the above-mentioned studies the following
"
suggestion is also interesting: DUhrkop has found that great care must be taken in filling the cross jOints. A carelessly built wall cannot be waterproofed even by pOinting.
3. Tests
(a) Tests of the VSZS Testing and Research Station
All the spray tests of the first series clearly showed the basic need for exercising great care in determining the mortar composition and in building the wall. Some leaky walls of the first series were later pOinted, and while this retarded the water penetration it could not prevent it entirely.
The experience gained from these tests caused us to pay close attention in the later ones to the whole process of construction. We wish to determine further what would be the effect of a light driving rain simulated by spraying the wall and blowing against it with a fan. The data on the four walls tested were as follows: Bricks:
RN 1, cored, red, glazed. Glazed bricks were chosen in order to concentrate the rain penetration principally at the joints. Mortar:
Sch8nenwerd sand was used for the mortar with a maximum grain of approximately 6 mm, weight per unit volume 1.78 kg/dm3
, the grain
size curve lying between the EMPA and the Fuller curve. The cement component was 350 kg/m3 mortar. Siggenthaler cement was employed.
0.2 percent Sikanol relative to the weight of the cement was added to the mortar. The water content was established at between 12.0
and 12.97 percent, the water-cement factor at approximately 0.65.
Brickwork:
Wall sections 1 m wide and 1.2 m high were tested. The wall thickness was 12 cm, bed-joint thickness 15 mm, crOss-joint thickness
10 mm. The jOints were executed as continuous joints. Spraying:
The test surfaces of about 1 m2 were sprayed at the rate of
about 10 litres per minute. In the second series of tests the spray was driven by a wind velocity of 6 to 8 m/sec.
POinting mortar:
The pointing mortar had the following composition: Sand 0 - 2 mm, 1 part by vol. sand and 1 part cement + 2 percent Sikalit
relative to the weight of the cement. The pointing mortar was worked in well.
The differences between the four specimens can be summarized as follows:
Wall A
An additional two percent Sikalit relative to the weight of the cement was added to the masonry mortar; the jOints were trimmed with the trowel only.
Wall B
Again 2 percent Sikalit was added; the jOints were smoothed carefully with an iron.
Wall C
After erection the specimen was pointed. The pOinting mortar composition has already been described.
Wall D
Four percent Bayer F-silicon relative to the weight of the cement was added; the joints were trimmed.
The results can be summarized as follows:
1. The mortar employed was of standard plasticity, which we believe, however, could be considerably improved by suitable grain
composition. Mortar made with the sand available to us, but
without the addition of Sikanol, did not show sufficient plastic-ity. The tests demonstrate, therefore, that the mortar can be
-9-improved by the addition of ｰｬ｡ｳｴｩ｣ｩｺ･ｲｳｾ but only to a limited degree. We believe that the plasticity must be attained by proper grain size control and that the maximum size should be 5 mm.
2. Cross joints and bed jOints should be continuous. Cross jOints must not be filled from above. When the bricks are laid mortar
should ooze out from the cross and bed joints.
3. Improvement by pOinting is possible only if the masonry construc-tion is correct. Poorly built walls are protected by pointing only against very light driving rain. As soon as the wind force increases pOinting no longer protects the wall adequately. The pointing must be done very carefully.
4. Expertly built brickwork is proof against driving rain provided the jOints are well smoothed.
5. It is our opinion that if the mortar is further improved (ideal grain composition) trimmed joints can be employed. However this must still be proven.
6. Further investigations are needed to determine whether sands with an EMPA or Fuller curve of grain composition are ideal for use in masonry mortar. The Picard investigations dealt with below give some new suggestions (see figures).
(b) Tests of Schmidheiny and Co. AG, Heerbrugg Dr. Iberg found:
1. Penetration always takes place through non-watertight cross and bed joints. The water running down the exposed face of the test wall seeps mainly through gaps and pores in the mortar joints. The weakest places were generally the points where cross and bed
jOints met.
2. All walls of which the joints had not been pointed ｾｬｩｴｨ a special mortar were permeable. Quite often penetration through the wall
took only a few minutes.
3. Quarry sand of poor grain composition always resulted in very permeable mortars. Even when the proportion of cement was increased it was impossible to produce a plastic mortar that
was ready to spread.
4. The addition of a waterproofing agent such as Sika or sealing oil 1n conjunction with a good sand delayed the penetration of the water 1 to 3 hours, but could not prevent it.
5. In these test additions of plasticizers such as VR and Sikanol had no effect. It was found, in fact, that mortars with VR or Sikanol absorbed more water than a mortar with none at all. Thus the use of plasticizers 1s of very dubious value.
6. Pure PC mortar with good sand generally absorbs water less rapidly than a cement mortar slaked with hydraulic lime.
7. The walls whose jOints were pointed in a second work step with a special mortar PC 400 + Sika and a sand of grain size 0 - 3 mm were impermeable. It must be assumed, however, that there were no gaps to speak of in the masonry mortar and the jOints were
filled full.
(c) Tests of Dachziegelwerk Erick
The detailed tests were carried out on walls 12 cm thick built of bricks showing a maximum capillary height of rise of 10 cm in 9 hours, using mortars, all of which contained 350 kg Portland cement/m3
• It was found that:
1. ｾ｢･ｮ･ｶ･ｲ the cross jOints are filled from above the masonry is
never proof against driving rain.
2. Cross-joint mortar must be applied in dabs on the end of the brick and must be trimmed off with the trowel towards the bottom of the last brick laid. A sufficient excess of mortar must be used so that when the brick is pushed into place the mortar oozes out in all directions, but especially at the top of the cross joint. Lean, short ｾｯｲｴ｡ｲｳ cannot be applied in this way and must be rejected for this reason alone.
3. It was found that good mortar properties enabling dab masoning to go forward rapidly could be obtained only with washed sand of very favourable grain composition and possibly also with chemical additives. However, since commercial sands often lose all their fine-grained components in the washing and often
-11-possess excess grain in one fraction it isoextremely difficult to find a boundary for practical purposes. These statements are based on a cement content of 350 kg/m3
•
4. Because of the poor workability of this mortar a search is now being made for a clean, fine-grained substance to add to the washed sand as a fines ｣ｯｭｰｯｮ･ｮｴｾ The addition of crushed
lime-stone 0 - 2 mm with a fine-grain component of 24 percent below 0.2 mm brought a remarkable improvement in the mortar properties. For laying Frick bricks of low water-absorption value the
addition of a flour lime of approximately 30 percent to any given washed sand was advantageous. The water retention of the mortars thus produced increases, efflorescence at the edges ceases and the mortar hardens better.
5. The specimens built with the composite sand showed the lowest penetrability. Since sands of this composition are not
commercially attainable, we must try to procure them. In any case because of the high litre weight it is clear that mortar impermeability depends on the grain shape and grain composition of the sand employed.
6. Tests that are still going on indicate that if the sand mixture is suitable even roughly trimmed joints are watertight, rendering subsequent smoothing or grouting unnecessary.
7. It is impossible at the present time to assess the value of the so-called waterproofing additives.
4. Conclusions
To ensure maximum impenetrability of brickwork to rain the following recommendations are noted:
1. The primary reqUirement is the use of a thick, plastic mortar. Such a mortar can only be obtained by using a sand of sUitable grain fOrm and size distribution. The investigations have shown that most Swiss sands lose their fine component by washing.
This component must be replaced, e.g. by the addition of lime-stone flours 0 - 2 mm, so that a fines component of about 20 to 25 percent below 0.2 mm is obtained. The maximum grain size
should be 5 mm. One should try to reduce this to 4 mm. These data apply primarily to mortars uSing a cement proportion of 350 kg/m3, which is the one most frequently applied. No other
binding agents should be used. Grain composition
0.0 - 0.5 mm 1 part by weight
(of this approximately 60 percent 0 - 0.2 mm) 0.5 - 2.0 mm 1 part by weight
2.0 - 5.0 mm 1 part by weight
2. Only thick, plastic mortar permits expert bricklaying. Great care is needed in forming the cross joints, since these are of the utmost importance in producing a watertight brickwork. The best of mortars is of no avail if the masonry is poor. In
executing the cross joints the end of the brick must be dabbed with the mortar. Before laying, the cross-joint mortar should be trimmed off with the trowel towards the underside of the last brick. A sufficient excess of mortar should be used so that mortar should be forced out in all directions, including the top of the cross jOint. Filling the cross joint from above must be strictly avoided. The bed joints should also be executed with sufficient mortar so that it is pressued out. The bricks should be laid only once and should not be tapped vigorously on one side or rocked. Removal and relaying of the brick without adding
fresh mortar is absolutely prohibited. Before the mortar has hardened too much the bed joints and then the cross joints should be smoothed with a sUitable iron instrument.
3. Waterproofing and plasticizing agents should be applied with extreme care. A poor mortar cannot be converted into a good one by either. Under certain circumstances good mortars can be
improved still further by the addition of these agents, provided suitable quantities of the additives are employed.
4. If suitable mortars cannot be produced by the contractor or the masonry work cannot be carried out according to the above
instructions. brickwork on the weather side has to be pointed. The pOinting mortar should contain sand of grain size 0.3 mm and
-13-a content PC 400, possibly with w-13-aterproofing -13-agents. Immediately after erection the joints should be scraped out and then pointed. This method is, of course, not an absolute guarantee of imperme-ability in heavy driving rain.
5. After erection the brickwork should be protected against penetra-tion and driving rain for some time.
6. Perforation of the bricks should also be executed carefully. Perforations on the longitudinal side should be set back
sufficiently far. Tests made abroad have shown that walls made with perforated bricks are more susceptible to rain penetration than those made with solid bricks, since the water finds its way to the back of the wall through the holes.
7. To prevent damage due to frost and moisture the bond should be so chosen that no water can Bet into the masonry as a result of poor jOint execution.
Fig. 1
Test wall being sprayed with apprOximately 10 litres
water per minute
Fig. 2
First test series, BN 1, red, untreated; jOints of mortar
PC 350, trimmed, poor masonry; picture taken
after 1-3/4 hours spraying
Fig. 3
First test series RN 1, red, untreated; jOints of mortar hydraulic lime 250 + PC 125, smooth, poor masonry; picture
taken 14 minutes after start of spraying
Fig. 4
Second test series, wall B, RN 1 red, silicon treated; jOints of mortar
PC 350 with waterproofing and plasticizer added, smoothed;
picture taken after 2-1/2 hours spraying
I
Fig. 5
Second test series, wall C, EN 1, red, silicon treated, jOints of mortar PC 350 + plasticizer, pointing mortar of 1 part by vol. sand 0 - 2 mm and 1 part Portland
cement + waterproofing agent 2 percent. Picture taken after 9-1/2 hours spraying, windblown
Fig. 6
Second test series, wall C, EN 1, red, silicon treated; joints of mortar
PC 350, plasticizer additve + silicon in powdered form; picture taken after 7-1/2 hours spraying, windblown
