Page 141 - Construction Waterproofing Handbook

3.30 CHAPTER THREE
Typical properties of a high-quality, waterproof, and elastic coating include the following:

● Minimum of 10-mil dry application
● High solids content (resins)
● Good ultraviolet weathering resistance
● Low water absorption, withstanding hydrostatic pressure
● Permeability for vapor transmission
● Crack-bridging capabilities
● Resistance to sulfites (acid rain) and salts
● Good color retention and low dirt pickup
● High alkali resistance
Acrylic coatings are extremely sensitive to moisture during their curing process, taking
up to 7 days to cure. Should the coating be subjected to moisture during this time, it may
reemulsify (return to liquid state). This becomes a critical installation consideration when-
ever such coatings are used in a horizontal or slightly inclined surface that might be sus-
ceptible to ponding water.

Elastomeric coating installations
Elastomeric coatings, which are used extensively on stucco finish substrates and exterior
insulation finish systems (EIFS), are also used on masonry block, brick, concrete, and
wood substrates. Some are available with asphalt primers for application over asphalt fin-
ishes. Others have formulations for use on metal and sprayed urethane foam roofs.
Elastomeric coatings are also successfully used over previously painted surfaces. By
cleaning, preparing the existing surface, repairing cracks (Fig. 3.12), and priming, coatings
can be used to protect concrete and masonry surfaces that have deteriorated through weath-
ering and aging (Fig. 3.13).
Proper preparation, such as tuck-pointing loose and defective mortar joints and inject-
ing epoxy into cracks, must be completed first. In single-wythe masonry construction, such
as split-face block, applying a cementitious block filler is necessary to fill voids in the
block before applying elastomeric coating for effective waterproofing.
Aesthetically, coatings are available in a wide range of textures and are tintable to any
imaginable color. However, deep, dark, tinted colors may fade, or pigments added for col-
oring may bleed out creating unsightly staining. Heavy textures limit the ability of a coat-
ing to perform as an elastomeric due to the amount of filler added to impart texture.
Because elastomeric coatings are relatively soft materials (lower tensile strength to impart
flexibility), they tend to pick up airborne contaminants. Thus lighter colors, including
white, may get dirty quickly.
Uniform coating thickness is critical to ensure crack bridging and thermal movement
capabilities after application. Applicators should have wet millage gages for controlling
the millage of coating applied. Applications of elastomeric coatings are extremely labor-
sensitive. They require skilled application of the material. In addition, applicators must
transition coating applications into adjacent members of the building envelope, such as
window frames and flashings, for effective envelope waterproofing. (See Table 3.13.)