Grade 1, standard; Grade 2,
Liquid-Applied Coatings. Liquid-applied coatings are a
special class of fully adhered membranes. Chemically, they are
Uses. A major use of liquid-applied coatings is on a
substrate of sprayed polyurethane foam (PUF) roofs, which require
a waterproof coating. Liquid-applied coatings for sprayed PUF
roofs include polyurethane, neoprene, hypalon, acrylic, and
silicone. Other acceptable substrates for these coatings are bare
concrete and plywood.
Advantages. Within their narrow range of
applicability, fluid-applied membranes have these notable
a) conformance to irregular roof surfaces with good
adhesion and little waste;
b) continuous, seamless waterproofing (including base
flashing at penetrations and edges for some systems).
a) Overwhelming dependence on high-quality field work.
In a concrete deck, cracks must be located, marked, and either
sealed or taped. Cracks and seams greater than 1/64 inch (0.4
millimeters) must be sealed. A viscous mastic and seams greater
than 1/64 inch (0.4 millimeters) must be sealed. A viscous
mastic material seals cracks between 1/64 and 3/8 inches wide
(0.4 and 9.5 millimeters), and because of mastic shrinkage,
satisfactory joint filling may require two mastic applications.
Cracks or joints over 3/8 inches (9.5 millimeters) require
b) Cast-in-place concrete decks must be steel-troweled
and then cured for at least four weeks to reduce repairs of post-
application shrinkage cracks.
c) To prevent moisture entrapment in the liquid-
applied membrane, at least two days must be allowed between the
latest rainfall on the substrate and membrane application.
Perimeter Anchorage. With the possible exception of
liquid-applied systems, single-ply systems are anchored at their