Page 143 - Construction Waterproofing Handbook

3.32 CHAPTER THREE
TABLE 3.13 Elastomeric Coating Properties

Advantages Disadvantages
Excellent elastomeric and Uniform application thickness difficult to control
crack-bridging capability
Wide range of colors and Life cycle shorter than cementitious
textures available
Breathable No below-grade usage
Applicable over wood Masonry substrates may require extensive repairs
and metal substrates before application
Resistant to acid rain and May fade over time
other pollutants

ELASTOMERIC COATING APPLICATION

Successful application of elastomeric coatings depends entirely on proper substrate prepa-
ration. Although they are effective waterproof materials, they should not be applied over
cracks, voids, or deteriorated materials, as this will prevent cohesive waterproofing of the
building envelope. Coatings chosen must be compatible with any existing coatings,
sealants, or patching compounds used in crack repairs. Coating manufacturers have patch-
ing, sealing, and primer materials, all compatible with their elastomeric coating.
Applying elastomeric coating requires applicator knowledge beyond a typical paint job.
Most painting contractors do not have the experience or knowledge to apply these coatings.
Existing substrates must be cleaned to remove all dirt, mildew, and other contaminants. This
is accomplished by pressure-cleaning equipment with a minimum capability of 1500 lb/in 2
water pressure. All grease, oils, and asphalt materials must be removed completely.
Mildew removal with chlorine should be done where necessary. Chemical cleaning is
also necessary to remove traces of release agents or incompatible curing agents. If chem-
icals are used, the entire surface should be rinsed to remove any chemical traces that might
affect the coating bonding.
Previously painted substrates should have a duct-tape test for compatibility of the elas-
tomeric coating application. A sample area of coating should be applied over existing
materials and allowed to dry. Then duct tape should be sealed firmly to the substrate then
pulled off quickly. If any amount of coating comes off with the tape, coatings are not prop-
erly adhering to existing materials. In that case, all existing coatings or paints must be
removed to ensure adequate bonding. No coating can perform better than the substrate to
which it is applied, in this case a poorly adhered existing coating. Either excessively chalky
coatings must be removed or a primer coat applied. Primers will effectively seal the sur-
face for proper bonding to a substrate.
High-alkaline masonry substrates must be checked for a pH rating before installation.
The pH rating is a measure of substrate acidity or alkalinity. A rating of 7 is neutral, with
higher ratings corresponding to higher alkaline substrates. A pH of more than 10 requires
following specific manufacturer’s recommendations. These guidelines are based upon the
alkali resistance of a coating and substrate pH.