FM Approvals has revised its criteria for determining the uplift
resistances of membrane and liquid-applied roof assemblies. Because
many roofing professionals rely on FM Approvals' classifications
when designing and specifying low-slope roof assemblies, you should
be aware of the changes made and their effects on specific roof
FM 4470, "Approval Standard for Single-Ply, Polymer-Modified
Bitumen Sheet, Built-Up Roof (BUR) and Liquid Applied Roof
Assemblies for use in Class 1 and Noncombustible Roof Deck
Construction," is the basis for FM Approvals' determination of
1-60, 1-90, 1-120, etc., classifications used for low-slope
membrane and liquid-applied roof assemblies.
In June 2012, FM Approvals revised FM 4470; the effective date
of the new standard was Dec. 31, 2012. The revisions include adding
NFPA 276, "Standard Method for Fire Tests for Determining the Heat
Release Rate of Roofing Assemblies with Combustible Above-Deck
Roofing Components," to determine combustibility below the roof
deck; changes to the conditions of acceptance for wind uplift and
hail damage resistance testing; and adding an alternative test
method for determining fasteners'...
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