Masonry Magazine August 1982 Page. 17
"Moisture Control in Brick and Tile Walls" (Ref. 3).
Caulking and Sealants. Too frequently caulking is considered a means of correcting or hiding poor workmanship, rather than as an integral part of construction which should be designed and installed in the same manner as other elements of the structure.
Joints between masonry and door and window frames, expansion joints and other locations where caulking may be required are the most frequently encountered sources of openings which permit rain penetration into the masonry. These vulnerable spots should be given attention during design and during construction. Also, maintenance programs should be provided to inspect and replace sealants or caulking which may have dried out, or may have otherwise become ineffective.
Construction Practices
As previously discussed, it is apparent that construction practices and the workmanship employed in the building of masonry walls can seriously affect the wall's tendency towards efflorescence. Some discussion and recommendations for proper construction practices follow.
Workmanship. Workmanship characterized by the complete filling of the mortar joints is desirable in preventing moisture penetration to the interior of masonry structures. It is also of paramount importance in preventing the occurrence of efflorescence, Technical Notes 7B, "Rain Penetration", discusses the workmanship practices which should be employed in the construction of masonry walls.
Protection. Partially completed masonry walls exposed to rain and other elements during construction may become so saturated with water that it will require weeks or even months (depending upon climatic conditions) after the completion of the building for the masonry to dry out. This prolonged saturation may cause many of the only "slightly" soluble salts as well as the highly soluble salts to go into solution. Such conditions may also contribute to the contamination of the masonry with soluble salts from elsewhere in the construction (concrete, plaster, trim, etc.).
During erection, all walls should be kept dry by covering with a strong waterproof membrane at the end of each day or shutdown period. Covering should overhang the wall at least 2 ft on either side and should be secured against displacement by wind. For masonry construction during cold weather, see Technical Notes 1, 1A, 1B and IC, for winter protection recommendations and construction procedures.
Storage of Materials. The manner of materials storage at a construction project site may have influence on the future occurrence of efflorescence, or the lack thereof. Materials should be stored in such a manner as to avoid their saturation by rain and snow, and also avoid their contamination from salts or other matter which may contribute to efflorescence.
Masonry units should be stored off the ground to avoid contamination by dirt and by ground water which may contain soluble salts. They should also be covered by a waterproof membrane to keep them dry.
Cementitious materials for mortar should be stored off of the ground and inside under cover.
Sand for mortar should also be stored off the ground to prevent contamination from dirt, plant life, organic materials and ground water, any of which may be a contributor to efflorescence. In addition, it is advisable to store sand and other aggregates under a protective membrane cover, if possible. This will avoid saturation and freezing in cold weather.
ANALYSIS OF EFFLORESCENCE PROBLEMS
When efflorescence salts appear on a masonry structure the causes may be many and varied. To determine causes, it is necessary to analyze the conditions carefully, based on a full understanding of the mechanisms which may be involved (see Technical Notes 23, "Efflorescence Causes"). The following check list is offered as a step-by-step procedure for the analysis of such problems. Its purpose is to aid in the identification of causes of the efflorescence and making determinations for repair or alleviation of the problem.
Analysis Procedure
An examination with the following check list may be sufficient to determine the cause and extent of the problem, and suggest methods for its repair and alleviation.
1. Determine the age of the structure at the time when the salts first appeared. If "new-building bloom" is involved (structures less than one year old), the source of the salts is often the cement in the mortar, and the source of the moisture is usually the construction water. If, however, the building is over a year old, other sources must be considered.
If the structure showing efflorescence is over two years old, construction details should be examined for possible leaks in the wall or in the surrounding construction. The appearance of efflorescence on an established building, which has been free of efflorescence, is usually attributable to a new entry of water into the construction assembly. It is assumed, in this instance, that the soluble salts are present in the construction and that the addition of moisture makes them appear.
2. The location of the efflorescence, both on the structure and on the individual units or mortar joints, should also be carefully noted. The location on the building may offer some information as to where the water is entering. The location of the salts crystals on the joints or the units may be of help in determining the source of the salts. The recent use or occupancy of the building may also be noted. For example, has it been vacant for some time, has new construction been going on? In short, what has changed that might cause, or trigger, the appearance of the efflorescence?
3. The condition of the masonry should be carefully examined. The profile of the mortar joints, the condition of the mortar, the type of workmanship which was employed, the condition of caulking and sealant joints, the condition of flashing and drips, any deterioration or eroding of mortar joints in copings or in sills all should be carefully noted. This information should offer clues as to the entry paths of moisture into the construction.
4. The wall section and details of construction should be examined for an indication of possible paths of moisture travel, and for possible sources of contamination by soluble salts. A careful examination of roof and wall juncture and flashing details should be made. A comparison of "contract drawings" with "as built drawings" may also be helpful. This examination will also be useful for the later determination of steps for repair to eliminate the efflorescence.
5. Laboratory test reports on the materials of construction should be examined, if they are available. This will help determine the source of the soluble salts, and may be of use in analyzing and making repair judgements.
6. The identification of efflorescing salts is sometimes of use. This can be done by commercial testing laboratories. X-ray defraction analysis is sometimes used. Petrographic analysis or chemical analysis is also possible. In some instances it is useful to know both the type of the salts present and their relative quantity. According to Brownell (Ref. 1):
"It is most unusual to find two or more salts comprising the efflorescence.... The presence of carbonate indicates mortar contamination, soluble sulfates place the brick in suspect, and potassium chloride most certainly is the result of cleaning the structure with muriatic acid. Sodium chloride efflorescence may very well be traced to sea water, either from the sea itself, mist in the air, or absorbed up from the ground."
Table 1 is taken from Brownell's report (Ref. 1) and is described as a table of "Most Probable Source" of salts.
TABLE 1
Common Sources of Efflorescence
| Principal Efflorescing Salt | | Most Probable Source |
| --- | --- | --- |
| Calcium sulfate | CaSO4+2H2O | Brick |
| Sodium sulfate | Na2SO4+10H2O | Cement-brick reactions |
| Potassium sulfate | K2504 | Cement-brick reactions |
| Calcium carbonate | CaCO3 | Mortar or concrete backing |
| Sodium carbonate | Na2CO3 | Mortar |
| Potassium carbonate | K2CO3 | Mortar |
| Potassium chloride | KCI | Acid cleaning |
| Sodium chloride | NaCl | Sea water |
| Vanadyl sulfate | VOSO4 | Brick |
| Vanadyl chloride | VOCI2 | Acid cleaning |
| Manganese oxide | Mn304 | Brick |
| Iron oxide | Fe203 or Fe(OH)3 | Iron in contact or brick with black core |
| Calcium hydroxide | Ca(OH)2 | Cement |
7. Miscellaneous sources of water should also be considered, if all other sources seem to be eliminated. Some of these sources are: condensation within the wall, leaky pipes, faulty drains and condensation on heating or plumbing pipes. Although rather rare, if such condensation analyses are necessary, the methods are described in Technical Notes 7C and 7D, "Moisture Control in Brick and Tile Walls-Condensation and Condensation Analysis".