TI 809-53
CEMP-ET
Appendix 2-1. Roof Slopes and Fire Ratings for Various Materials
01 May 1999
Slope (Inches/Foot)
Comments
Ratings
1/4
1
2
3
4
5
6
7
8
9
Low Slope (Hydrostatic)
Slope %
Membrane Roofing (cont'd)
2
8
17 25 33
50
Modified Bitumen (cont'd)
Modified bitumen - granular
Minimum slope on new roofs is 4%
Class A or B rating can be achieved for use over
(1/4 in./ft). Torched or adhesively
noncombustible decks generally up to 8.3%
bonded systems required at slopes
(1:12). Class A or B rating can be achieved for
above 8.3% (1:12).
use over combustible decks with additional
ply sheets and/or insulation generally up to
4% (1/2 in./ft) slope.
Single Ply
EPDM - smooth surfaced/
Class A or B rating can be achieved over non-
Minimum slope on new roofs is 2%
mechanically attached or fully adhered
1/4" in 12).
combustible decks with fire retardant
formulated grades generally to a slope of 8.3%
(1:12). Class A or B rating can be achieved for
use over combustible decks with ply sheets and/
or insulations generally up to 4% (1/2 in./ft).
EPDM--ballasted
Minimum slope onnew roofs is 2%
Ballast provides Class A rating for non-
(1/4 in./ft). Ballast movement limits
combustible and combustible decks when used
in excess of 39 Kg/m2 (8 lbs/ft2).
slope to 17% (2:12).
Reinf. PVC, Hypalon, Thermoplastic
Minimum slope on new roofs is 2% (1/4 lias/s A or B rating can be achieved for PVC and
C n.
Polyolefin (TPO)
ft). Hypalon products with water absoirp-retarded TPO for use over non-combustible
f e
smooth surfaced/
tion > 3% require minimum slope of 4%ecks generally up to 1 in./ft. Class A or B rating
d
mechanically attached or fully adhered
(1/2 in./ft).
can be achieved over combustible decks with
special underlayments and/or insulations
generally up to 8.3% (1:12). Class A or B rating
can be achieved for Hypalon for use over non-
combustible decks generally up to 2 in./ft max.
slope. Class A or B rating can be achieved over
combustible decks with special underlayments
and/or insulations generally up to 17% ( 2 in./ft)
maximum slope.
2-29
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