MIL-HDBK-1001/SA
Section 11: FIRE RESISTANCE
11.1 General. Fire hazards to roof systems are broadly classified as follows:
a) External, above-deck fire exposure from flying brands or burning debris blown over from neighboring buildings on fire;
b) Internal, below-deck fire exposure from interior inventory or equipment fires;
c) Time-temperature or fire resistance classifications.
11.2 External Fire Resistance
11.2.1 Membranes. Roofing membranes are tested and rated for their resistance to external fire. They should not spread flame rapidly, produce flying brands endangering adjacent buildings, or permit ignition of supporting roof decks.
11.2.2 Tests and Ratings. According to the industry standard for rating roof coverings, ASTM E 108, Fire Tests of Roof Coverings, classified roof coverings "are not readily flammable, do not slip from position, and possess no flying brand hazard." Their performance is rated as Class A, B, or C, depending on
their resistance to external fires of varying intensity. Class A
coverings provide the greatest resistance, Class C the least.
11.3 Internal Fire Hazards
11.3.1 Background Research. Research on acceptable fire
spread from internal (i.e., below-deck) fires has focused chiefly
on steel-deck roof assemblies. Because of its extremely high
thermal conductivity, steel deck immediately transmits the heat
energy of an interior fire to the above-deck roof components.
11.3.2 Safeguard. The chief safeguard required against internal fire is limitation of flame spread along the underside of the roof assembly.
11.3.3 Steel Deck. A steel deck roof assembly with 1-inch
(2S-millimeter), mechanically anchored, plain vegetable
fiberboard insulation and a four-ply, aggregate-surfaced built-up
membrane has become the standard roof construction for both UL
and FM; the criteria for evaluating other roof-deck assemblies.
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