Page 156 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.45
For new concrete substrates, a light broom finish is desirable. Surface laitance, fins, and
ridges must be removed. Honeycomb and spalled areas should be patched using an accept-
able nonshrink grout material.
Coatings should not be applied to exposed aggregate or reinforcing steel. If present,
these areas should be properly repaired. Concrete surfaces, including patches, should be
cured a minimum of 21 days before coating application. Use of most curing compounds is
prohibited by coating manufacturers, since resins contained in curing compounds prevent
adequate adhesion. If present, substrates require preparatory work, including sandblasting,
or acid etching with muriatic acid. Water curing is desirable, but certain manufacturers
allow use of sodium silicate curing agents.
Substrate cracks must be prepared before coating application (Fig. 3.24). Cracks less
1
than 16 in wide should be filled and detailed with a 4-in band of nonflow base coat. Larger
cracks, from 2 in to a maximum of 1-in width, should be sawn out and filled with ure-
1
thane sealant (Fig. 3.25). Moving joints should have proper expansion joints installed with
coating installed up to but not over these expansion joints. Refer to Figs. 3.26 and 3.27 for
typical expansion joint detailing.
Substrates should be sloped, to drain water toward scuppers or deck drains. Plywood
surfaces should be swept clean of all dirt and sawdust. Plywood should be of A-grade only,
with tongue and groove connections (Fig. 3.28). Only screw-type fasteners should be used,

FIGURE 3.22 Mechanical removal of contaminants. (Courtesy of Coastal Construction Products)