**************************************************************************
NOTE: Delete foil-faced board when fully adhered,
cold-applied single ply roofing is specified.
Blistering of roofing membranes has occurred over
some polyurethane and composite (polyurethane) board
insulation, possibly due to either release of gases
from polyurethane, moisture entrapped in facing or
plying felt, differential movement between roofing
membrane and polyurethane resulting from thermal
stresses on the materials, or inadequate brooming
and mopping. When hot-applied built-up, modified
bitumen sheet, or PIB sheet roofing is installed
over insulation, it is recommended that thin layer
of mineral fiber, wood fiberboard, expanded perlite
board insulation, or glass mat gypsum roof board be
placed over top surface of polyurethane board,
embedded in solid asphalt mopping with joints of
mineral fiber, wood fiberboard, or perlite board, or
glass mat gypsum roof board staggered in both
directions with respect to polyurethane board below.
The same precautionary procedure should be followed
when polyisocyanurate foam boards are specified even
though there may not be documentation of similar
problems with these types.
**************************************************************************
b.
Polyisocyanurate Board: ASTM C 1289 [Type I -- foil faced both
sides] [or] [Type II, fibrous felt or glass mat membrane both
sides], except minimum compressive strength shall be 140 kPa 20
pounds per square inch (psi).
**************************************************************************
NOTE: Delete polystyrene composite board when
insulation will be applied with hot asphalt.
**************************************************************************
c. Composite Boards: ASTM C 1289, [Type III, perlite insulation
board faced one side, fibrous felt or glass fiber mat membrane on
other side.] [Type V, oriented strand board or waferboard on one
side and fibrous felt or glass fiber mat membrane or aluminum foil
on the other.]; ASTM C 984 (Polyisocyanurate-perlite) [; or ASTM C
1050 (Polystyrene-wood fiberboard), Type III, Grade 1, Class A].
d.
Cellular Glass Boards:
ASTM C 552, Type IV.
**************************************************************************
NOTE: Delete non-composite polystyrene board when
insulation will be applied with hot asphalt or used
under hot asphalt-applied roofing. This type of
insulation is sensitive to hot asphalt, various
solvents, and certain single ply roofing membranes.
**************************************************************************
**************************************************************************
NOTE: Expanded or extruded polystyrene insulation
board is flexible enough for use on arched roofs.
For this application, each layer must be thin enough
to permit the required bending and each layer must
SECTION 07220
Page 12
Previous Page
