MIL-HDBK-1011/1
airfields or in areas subject to hurricanes and typhoons. Where gravel
surfacing is used, it is recommended that it be "double surfaced" (an
additional surfacing of hot asphalt and aggregate placed over the original
asphalt and gravel surfacing). This provides additional protection against
lift-off and aggregate blowing during high winds. Note, however, that double
surfacing adds both substantial weight and cost to the roofing system.
d) Where insulation is required for a wood deck, install the
insulation inside the building under the roof instead of on top under the
roofing if possible. This is not recommended for a concrete deck.
e) Install the recommended built-up roofing system only on roofs
with a minimum slope of 1/2 inch in 12 inches. In new construction, provide a
slope to the structural deck of 1 inch per foot for positive drainage. For
existing roofs of less than 1/2 inch per foot slope, consider another roofing
system.
7.4
Single-Ply Roofing Systems. Sheet-Applied. Single-ply roofing
systems have been in place on roofs in tropical-humid environments for many
years. Failures generally have been limited to roofs of composite preformed
sheets with vinyl as part of their makeup. These sheets shrink and become
brittle under the intense tropical sun. On the other hand, rubber sheets of
EPDM have proven to be notably successful when applied directly to concrete
roof decks or over insulation by the fully adhered method.
7.4.1
EPDM (Ethylene Propylene Diene Monomer). This material is an
elastomeric rubber sheet specially formulated as a flexible, stretchable roof
covering. It is applied to the substrate by one or a combination of three
methods:
Fully-adhered with a bonding adhesive
a)
b) Mechanically fastened
Loose-laid and ballasted with concrete pavers
c)
Fully-adhered and mechanically fastened systems, only, are
recommended for use in the tropics and especially in the areas subject to
hurricanes and typhoons.
EPDM sheets are manufactured in 9 to 10 foot wide sheets which are
cut to length, allowed to relax, and then glued to the substrate. Laps are
glued with splicing cement. The black EPDM sheets are either manufactured
with a light-colored, factory-laminated reflective EPDM or Hypalon sheet or
can be coated with a reflective liquid coating after installation.
In the
tropics, coat the EPDM. Recoating will be necessary in 3 to 5 years to
maintain high reflectivity. The type with the factory-laminated reflective
surface is recommended as the life of the membrane will far out last the
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