Page 153 - Construction Waterproofing Handbook

3.42 CHAPTER THREE
turn-ups, the product can be an effective barrier system. These systems make excellent
candidates for remedial application, as they can hide considerably more substrate imper-
fections than the liquid systems discussed previously. These systems can also be applied
to wood substrates and make excellent choices for residential applications including apart-
ment projects.
Many systems combine the properties of the liquid-applied systems with sheet good
reinforcing for “belt and suspenders” protection. The limiting factor is cost, as the more
material and layers a system requires for effectiveness, the more the final in-place cost
rises. Table 3.20 summaries the advantages and disadvantages of using sheet systems for
waterproofing applications.

DECK-COATING CHARACTERISTICS

Deck coatings bond directly to concrete, wood, or metal substrates. This prevents lateral
movement of water beneath the coatings, as is possible with sheet good systems. Once
cured, coatings are nonbreathable and blister if negative vapor drive is present. This is the
reason deck coatings, with the exception of acrylic and epoxies, are not recommended for
slab-on-grade applications. Specifically, moisture in soils is drawn up into a deck by cap-
illary action, causing blistering in applied deck coatings. In the same manner, blistering
occurs in deck coatings applied on upper deck portions of sandwich-slab membranes due
to entrapped moisture and negative vapor drive. In both cases, an epoxy vapor barrier
prime coat should be installed to protect deck-coating systems from being subjected to this
vapor drive.
Physical properties of deck coatings vary as widely as the number of systems available.
Important considerations to review when choosing a coating system include tensile
strength, elongation, chemical resistance, weathering resistance, and adhesion properties.
Different installation types, expected wearing, and weathering conditions require different
coating types.
High tensile strength is necessary when a coating is subject to heavy wear including
vehicular traffic or forklift traffic at loading docks. Tensile strengths of some deck coat-
2
ings exceed 1000 lb/in (tested according to ASTM D-412) and are higher for epoxy
coatings. This high tensile strength reduces the elongation ability of coatings.
Elongation properties range from 200 percent (for high-tensile-strength top coats) to
more than 1000 percent (for low-tensile-strength base coats). For pedestrian areas where
impact resistance and heavy wear is not expected, softer, higher elongation aromatic ure-
thanes are used. Sun decks subject to impact from lawn chairs and tables would be better
served by a coating between the extremes of high and low tensile strength.

TABLE 3.20 Sheet Systems

Advantages Disadvantages
Uniformity of material application Difficult applications in small areas
Forgiving of substrate flaws Repairs difficult
Applicable over wood substrates Water can travel under sheet systems