SYSTEMS/MASONRY
Coatings and Sealants
A wide variety of coatings are available for waterproofing masonry walls, as discussed in NCMA-
TEK No.10A and the PCA Concrete Masonry Handbook. It is generally recognized that these
coatings alone will not prevent water leakage, although they are necessary when a single wythe of
concrete masonry constitutes the exterior facade. The other aspects of design and construction for
controlling water leakage discussed in this section, i.e., surface drainage, mortar joints and flashing,
must also be employed and in some cases can preclude the need for any surface coating. If these
control measures are not taken and the wall does not adequately control cracking, then coatings
alone will not prevent water leakage.
Surface coatings can be classified as opaque and clear. The opaque coatings can actually provide
waterproofing because of their higher content of solids. Clear coatings tend to be less effective
than opaque coatings, and are referred to as water repellents. Clear coatings employ a variety of
materials, and work by changing the capillary angles of the pores in the masonry (see BIA
Technical Note 7E). They will not normally fill cracks in masonry walls, and it is these cracks that
are associated with most water leakage. Clear sealants do have their applications, but the
inappropriate use of such materials can lead to problems. The performance limitations of clear
sealants include an inability to stop moisture penetration through cracks and incompletely filled
joints, the potential for contributing to spalling and/or disintegration of units; the inability to stop
staining and efflorescence followed by interference with its removal; and making the wall almost
impossible to tuck point. BIA recommends against their use except under very specific
circumstances. Before considering their use for controlling water leakage, BIA recommends a
careful inspection of the wall to investigate other potential sources of water leakage. Such an
inspection should include the design and current condition of caps, copings, flashing, weep holes,
sealant joints, and mortar joints. Any defects should be corrected, and these actions may control
water leakage without the use of a coating. BIA Technical Note 7E provides a thorough checklist to
use in determining the appropriateness of using a clear sealant. Many of these BIA limitations on
the use of clear coatings also apply to opaque coatings.
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