CEMP-ET
TI 809-53
01 May 1999
Table 2-8. Fire Ratings and Required Underlayments for Low-Slope Roof Systems
ASTM E108 Class
Metal
Deck
ASTM E108 Class A,
A, B, C
B, C
Construction
Combustible
Noncombustible (e)
Decks (c)
Built-Up Roofing
Smooth
B
A
Isoboard/Perlite/Glass Fiber
Capsheet
B
A
Isoboard/Perlite/Glass Fiber
Aggregate
A
A
Isoboard/Perlite/Glass Fiber
Modified Bitumens
Unsurfaced
B-FR. (d)
A-FR.
Isoboard/Perlite/Glass Fiber
Capsheet
B-FR.
A-FR.
Isoboard/Perlite/Glass Fiber
EPDM
Adhered
C-FR.
A-FR.
Isoboard (b)
Mechanically Fastened
C-FR.
A-FR.
Isoboard/Perlite/Glass Fiber
A
A
Isoboard/Perlite/Glass Fiber
PVC Plasticized
Mechanically Fastened
B
A
Isoboard/Perlite/Glass Fiber
Fully Adhered
B
A
Isoboard (b)
Weldable Unplasticized
Mechanically Fastened
C-FR.
A-FR.
Isoboard (b)
Fully Adhered
C-FR.
A-FR.
Isoboard (b)
A
A
Isoboard (b)
A
A
Some Listed Systems
SPF
(a)
A
Not Required
Hydrostatic Metal
(a) Depends on underlayment/(gypsum board?)
(b) Perlite/glass fiber may not be acceptable to single-ply systems because of asphalt content or
dusty/solvent-degradable surface.
(c) On combustible decks, mass of surfacing or underlayment is important to prevent ignition of the
deck.
(d) FR. means Fire Retarded Sheet required.
(e) Non-Combustible decks include steel, concrete and gypsum.
2-11
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