Choosing the best means for extending roof system service life
involves a number of factors. Coatings are one option and can be
cost-effective, but their varying performances can create
limitations. The reasons a particular coating works in one
situation but not another often are complex and difficult to
determine. Some limitations of coatings are related to climatic
In the U.S. and Canada, two primary factors seem to dominate
regional roofing practices: total annual precipitation and
freeze-thaw cycles associated with cold climates. Secondary factors
include Hail Belt conditions east of the Rockies, afternoon rain in
the Gulf states and Midwest, Florida's tropical characteristics,
intense summer temperatures in the Southwest and high winds.
Coatings, particularly those that are water-based, can be
affected by moisture in at least two critical ways: They can be
worn away by rain or heavy dew or can experience diminished
adhesion to damp surfaces. In the eastern half of the U.S., these
risks are reduced by using silicone coatings and bituminous-based
coatings. ASTM D16, Type V urethanes and new generation polyureas
are high-performance and environmentally compliant options when
rain is typical or a tough, traffic-bearing...
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