Page 138 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.27
Cementitious coatings may be applied by brush, trowel, or spray. Stiff, coarse, or fiber
brushes are used for application. Brush applications require that the material be scrubbed
into a substrate, filling all pores and voids. Finish is completed by brushing in one direc-
tion for uniformity.
Spray applications are possible by using equipment designed to move the material once
mixed. Competent mechanics trained in the use of spray equipment and technique help
ensure acceptable finishes and watertightness (Fig. 3.11).
Trowel applications are acceptable for the second coat of material. Due to the applica-
tion thickness of this method, manufacturers recommend that silica sand be added to the
mix in proper portions. The first coats of trowel applications are actually brush applica-
tions that fill voids and pores. Finish trowel coats can be on a continuum from smooth to
textured. Sponge finishing of the first coat is used to finish smooth concrete finishes
requiring a cementitious application.
With textured masonry units such as split face or fluted block, additional material is
required for effective waterproofing. On this type of finish, spraying or brush applications
are the only feasible and effective means.
The amount of material required depends upon the expected water conditions. Under
normal waterproofing requirements, the first coat is applied at a rate of 2 pounds of mate-
rial per square yard of work area. The finish coat is then applied at a coverage rate of 1
2
lb/yd . In severe water conditions, such as below-grade usage with water-head pressures,
2
2
materials are applied at 2 lb/yd . This is followed by a trowel application at 2 lb/yd . Clean
silica sand is added to the second application at 25 lb of silica to one bag, 50 lb, of premixed
cementitious coating.

FIGURE 3.11 Spray application of cementitious membrane on negative side. (Courtesy of LBI
Technologies)