Base sheets with perforations are rolled into place
and then top mopped with hot asphalt. Base sheets
without perforations are mechanically attached to
nailable substrates.
**************************************************************************
[
a. Venting Base Sheet: ASTM D 4897, Type II, [without][with]
perforations and as approved by the modified bitumen roof membrane
manufacturer.]
[
b. Fiberglass Felt Base Sheet: ASTM D 4601, Type II, [without][with]
perforations and as approved by the modified bitumen roof membrane
manufacturer.]
**************************************************************************
NOTE: When specifying a two-ply membrane system or
application over a fiberglass felt base sheet,
delete any reference to Interply sheet. Use
modified bitumen base sheet and cap sheet.
Specify polyester-reinforced membrane for high
traffic roofs and where enhanced puncture resistance
and overall durability are required. Where
polyester reinforced sheet is required, delete any
reference to ASTM D 6163.
Do not specify fiberglass membrane layer over a
polyester-reinforced membrane layer.
Specify Type II modified bitumen materials for all
two-ply membrane installations, heavy-duty or high
traffic service conditions and for all instances
where fiberglass reinforced modified bitumen cap
sheets are permitted.
**************************************************************************
[
c. SBS Base Sheet: [ASTM D 6162] [or] [ASTM D 6164] [or] [ASTM D 6163
], Type [I or] II, Grade S, minimum 2.0 mm (80 mils) thick.]
[
d. SBS Interply Sheet: [ASTM D 6162] [or] [ASTM D 6164] [or] [ASTM D
6163], Type [I or] II, Grade S, minimum 2.0 mm (80 mils) thick.]
**************************************************************************
NOTE: Specify Grade S cap sheet only with the
approval of the Government and when gravel surfacing
or field applied coating is required in lieu of
factory-applied mineral granule surfacing.
Specify 3.7 mm (145 mils) minimum thickness for SBS
cap sheet unless directed otherwise by the
Government.
**************************************************************************
[
e. SBS Cap Sheet: [ASTM D 6162] [or] [ASTM D 6164] [or] [ASTM D 6163];
Type II, Grade [G][S], minimum [3.7 mm (145 mils)] [
] thick
at selvage edge, and as required to provide specified fire safety
rating.]
**************************************************************************
SECTION 07550
Page 17
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