Page 77 - Construction Waterproofing Handbook

2.40 CHAPTER TWO
Polyvinyl chloride
Solvent-based PVC or plastics are not extensively used in liquid-applied waterproofing
applications. These derivatives are more often used as sheet membranes for roofing. Their
elastomeric capabilities are less than other fluid systems and have higher material costs.
They do offer high resistance to chemical attack for below-grade applications.

Hot-applied fluid systems
Hot-applied systems are improvements over their predecessors of coal tar pitch and felt
materials. These systems add rubber derivatives to an asphalt base for improved perfor-
mance, including crack-bridging capabilities and chemical resistance.
Hot systems are heated to approximately 400°F in specialized equipment and applied
in thickness up to 180 mil, versus urethane millage of 60 mil (see Fig. 2.50). Asphalt exten-
ders keep costs competitive even at this higher millage. These materials have a consider-
ably extended shelf life compared to solvent-based products, which lose their usefulness
in 6 months to 1 year.
Since these materials are hot-applied, they can be applied in colder temperatures than solvent-
based systems, which cannot be applied in weather under 40°F. Manufacturers often market their
products as self-healing membranes, but in below-grade conditions this is a questionable char-
acteristic. Properties of typical fluid-applied systems are summarized in Table 2.5.

FLUID SYSTEM APPLICATION

Substrate preparation is critical for proper installation of fluid-applied systems. See Fig.
2.51 for typical fluid system application detail. Horizontal concrete surfaces should have
a light broom finish for proper bonding. Excessively smooth concrete requires acid etch-
ing or sandblasting to roughen the surface for adhesion. Vertical concrete surfaces with
plywood form finish are satisfactory, but honeycomb, tie holes, and voids must be patched,
with fins and protrusions removed (Fig. 2.52).
Wood surfaces must be free of knotholes, or patched before fluid application. Butt
joints in plywood decks should be sealed with a compatible sealant followed by a detail
coat of membrane. On steel or metal surfaces, including plumbing penetrations metal must
be cleaned and free of corrosion. PVC piping surfaces are roughened by sanding before
membrane application.
Curing of concrete surfaces requires a minimum of 7 days, preferably 28 days. On sub-
slabs, shorter cure times are acceptable if concrete passes a mat dryness test. Mat testing
is accomplished by tapping visquene to a substrate area. If condensation occurs within
4 hours, concrete is not sufficiently cured or is too wet for applying material.
Blistering will occur if materials are applied to wet substrates, since they are non-
breathable coatings. Water curing is the recommended method of curing, but some manu-
facturers allow sodium silicate curing compounds. Most manufacturers do not require
primers over concrete or masonry surfaces; however, metal substrates should be primed
and concrete if required (Fig. 2.53).
All cold joints, cracks, and changes in plane should be sealed with sealant followed by
a 50–60-mil membrane application, 4-in wide. Figure 2.54 details typical locations where
additional layers of membrane application are required for reinforcement.