Page 152 - Construction Waterproofing Handbook

ABOVE-GRADE WATERPROOFING 3.41
Aliphatic materials have up to three times the tensile strength of aromatics but only
50 percent of aromatic elongation capability. Many manufacturers use combinations of
these two materials for their deck-coating systems. Aromatic materials are installed as base
coats for better movement and recovery capabilities; aliphatic urethane top coats make for
better weathering, impact resistance, and ultraviolet resistance.
Epoxy urethane systems are also used as top coat materials. These modified urethane
systems provide additional weathering and wear, while still maintaining necessary water-
proofing capabilities.
Urethane coatings are applied in two or more coats, depending upon the expected traf-
fic wear. Aggregate is added in the final coating for a nonslip wearing surface. An instal-
lation advantage with urethane systems is their self-flashing capability. Liquid-applied
coatings by brush application are turned up adjoining areas at wall-to-floor junctions, pip-
ing penetrations, and equipment supports and into drains.
Urethane coatings are manufactured in self-leveling formulations for applications con-
trol of millage on horizontal surfaces. Nonflow or detailing grades are available for verti-
cal or sloped areas. The uncured self-leveling coating is applied by notched squeegees to
control thickness on horizontal areas. At sloped areas, such as the up and down ramps of
parking garages or vertical risers of stairways, nonflow material application ensures proper
millage. If self-leveling grade is used in these situations, material will flow downward and
insufficient millage at upper areas of the vertical or sloped portions will occur.
Nonflow liquid material is used to detail cracks in concrete decks before deck-coating
application. Cracks wider than 16 in, which is the maximum width that urethane materi-
1
als bridge without failure, are sawn out and sealed with a urethane sealant. This area is then
detailed 4 in wide with nonflow coating.
In addition, urethane coatings are compatible with urethane sealants used for cants between
vertical and horizontal junctions, providing a smooth transition in these and other changes of
plane. This is similar to using wood cants for roof perimeter details (see Table 3.19).

Sheet systems
While they do not fit the description of a deck coating per se, there are balcony and deck
waterproofing systems that are available in sheet materials that provide waterproofing
capabilities. There are a variety of systems available, including those that require the sheet
embedded in a trowel- or spray-applied acrylic or resin material, and those that are act as
a complete system.
The latter is a vinyl product, similar to a typical interior vinyl flooring product with the
exception that the product is improved to withstand exterior weathering and of course
water infiltration. The system is vulnerable for leakage at the seams, following the
90%/1% principle. If seaming is adequately addressed, including the necessary vertical

TABLE 3.19 Urethane Deck-Coating Properties

Advantages Disadvantages
Excellent crack-bridging capability Limited color selection
Simple installations Low chemical resistance
Expanded product line Maintenance required with heavy traffic