Page 63 - Construction Waterproofing Handbook

BELOW-GRADE WATERPROOFING 2.27

FIGURE 2.35 Negative application of cementitious water-
proofing. (Courtesy of Vandex)

finishes applied over waterproofed areas. To prevent excessive wear, concrete toppings
are installed over horizontal exposed surfaces subject to pedestrian or vehicular traffic.
If drywall or paneling is installed over the waterproofing, furring strips are first applied
by gluing them directly to the cementitious system. This eliminates nailing the boards
through the cementitious membrane. Carpet perimeter tracks should be applied in the same
manner to prevent damage.

Capillary/crystalline systems
Capillary/crystalline systems are mixtures of cement and sand in combination with pro-
prietary chemical derivatives in dry or liquid form. The systems are applied in trowel,
brush, or spray applications. Unlike other cementitious systems however, capillary have
the additional advantage of an application using only the dry mix product that is broadcast
directly over concrete that has not yet reached final set and cure. This is referred to as the
“dry-shake” method, commonly used on slab components as a vapor barrier, as additional
protection with below-grade slab waterproofing systems, or as a stand-alone waterproof-
ing system. A typical dry-shake application is shown in Fig. 2.36.
A capillary/crystalline system not only waterproofs, as a system itself; the chemical
additives are able to penetrate into the concrete wall or slab and react with the calcium
hydroxide and available capillary water present to form crystalline structures within the
concrete itself. These crystalline structures block transmission of water through the sub-
strate, adding additional water repellency to the envelope components.
The chemical process begins immediately upon application of the waterproofing sys-
tem but can take as many as 30 days to fully reach maximum repellency. Once fully cured,
capillary/crystalline systems have been tested to withstand hydrostatic pressures as great
as 400 ft of water head. These systems have other advantages compared to other cementi-
tious systems, including the following: