MIL-HDBK-1011/1
Flashing and Sheet Metal. Many roofing systems are self-flashing
7.9.6
or flashing materials are provided by the roofing material manufacturer.
7.9.6.1
Flashing. Gutters. and Downspouts. In an atmosphere laden with
salt spray, stainless steel is recommended. Where salt spray is not severe,
flashings, gutters, and downspouts may be of stainless steel, aluminum alloy
(3003-N14), or copper. Where aluminum is specified, ensure thickness is not
less than 0.032 inches. In hurricane and typhoon areas, ensure aluminum
thickness is not less than 0.065 inches where exposed to the direct wind.
Aluminum may be used over concrete construction, provided that required
reglets are of stainless steel and aluminum surface in contact with concrete
or masonry is coated with bituminous paint or zinc chromate primer.
Use stainless steel nails, screws, bolts, and fasteners. Also,
secure flashing at one-half the normal interval to ensure a wind-resistant
installation. Galvanized steel sheet is not recommended for flashing or for
gutters and downspouts.
7.9.7
Vent Flashing. Lead sheet is recommended for plumbing vents and
other pipe penetrations through the roof.
7.10
Sealants
7.10.1
General. Because of the constant threat to structures in the
tropics caused by the intrusion of moisture and salt-laden air, incorporate
adequate control joints in the structure design and properly detail joints to
be sealed on the drawings.
7.10.2
Selection. There are only three unique considerations for
selection of sealants and seals (preformed tapes, foams, and extrusions) for
use in the tropics. They are resistant to ultra-violet light, immersion in or
prolonged exposure to water, and extreme high temperatures.
7.10.2.1
UV Resistance. Rubberized bituminous material, polysulfide and
polyurethane sealants, and styrene butadiene rubber closure strips all show
only fair to poor UV resistance. Do not consider these materials for exterior
applications where they are exposed to direct sunlight.
7.10.2.2
Water Immersion. Bituminous, butyl, polybutene, polyvinyl acetate
latex, polyurethane, poly mercaptan, and polyisobutylene sealants all show
poor service characteristics when immersed in water. Consider this in joints
which might be subjected to periodic flooding, or which might be exposed to
constant, prolonged rainfall or wind-driven spray.
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