MIL-HDBK-1011/1
flashing and can be sprayed up vertical surfaces. Apply the coating to a
minimum thickness of 60 mils, but 60 mils to 90 mils is recommended as a
minimum if the liquid coating is over topside insulation such as sprayed in-
place polyurethane foam (PUF).
Achieve the recommended thickness by applying successive coats of
approximately 20 mils each. Vary each coat slightly in color (grey, tan, and
white for example) so that the final coat is of the desired color and the
covering of the preceding coat can be observed and measured.
7.5.3
Acrylic Elastomers. These are usually water based, which makes
them easy to apply and to clean up; and they are relatively inexpensive.
Select material that has a short cure time.
7.5.4
Polyurethane Elastomers. These materials can be either one- or
two-component and are usually spray applied. Granules are often added to the
final coat to provide traction (silicone can be slippery) and to harden the
final coat. These coatings are prone to pinholing when applied in thick coats
(over 30 mils wet).
7.5.5
Vinyl, Hypalon, and Neoprene. These coatings are not recommended
because of their low volume solids. Butyl coatings are not recommended
because they are not resistant to high levels of ultraviolet light.
7.6
Shingle and Tile Roofing. Wood shingles and shakes, clay tile, and
similar roofing materials are not recommended for consideration in tropical-
humid environments for various reasons, including high initial cost and short
life due to rapid deterioration. Asphalt shingles, with lower initial cost,
can require frequent maintenance and repair in high-wind areas.
7.7
Fiber-Reinforced Cement Roofing. Cement-asbestos roofing and
siding has been a long-life, maintenance-free material which has been used
successfully throughout the tropics and elsewhere. However, because of the
health and environmental problems with asbestos it is no longer available.
Non-asbestos similar products are now being manufactured in shingle and
corrugated sheet forms and perform well in a tropical-humid environment.
7.8
Corrugated Metal. Corrugated metal roofing, as used herein,
includes galvanized metal and aluminum. The material may be factory coated or
unfinished.
This material is generally utilized as roofing and siding for
prefabricated warehouse type structures but also have been used on commercial
and residential structures. Provide adequate fastenings and building tie-
downs in hurricane and typhoon areas.
7.8.1
Galvanized Steel. Use 24 gauge minimum and coat on both sides to
provide an acceptable long life. Factory finishing is recommended. The
coating must be of adequate thickness and be ultraviolet resistant.
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