Instructions / Assembly

2
None of the foregoing factors is the responsibility of GAF, which under no
circumstances will assume such responsibility.
If the roof is sloped ½:12 or more, see “Installation on Steep Slopes.”
Non-Nailable Decks (Steel Decks)
Any of the Tri-Ply
®
specifications for use over insulation may be applied
over a steel deck. A steel deck must be covered with rigid insulation that
is firm, capable of withstanding traffic, and is thick enough to span the rib
opening of the deck. The insulation must be mechanically attached using
Tri-Ply
®
Screws and Plates to meet at least FM I-60 uplift resistance.
When two layers of insulation are to be installed, solidly mop the second
layer of insulation to the first layer.
A steel deck must be no lighter than 22 gauge and conform to the recom-
mendations of the latest Factory Mutual Bulletin I-28.
Nailable Decks (Wood Decks—Plywood Decks)
Wood boards must be at least 1" (25 mm) nominal thickness and have a
nominal width of 4" to 6" (102 to 152 mm). All boards must have a bear-
ing on rafters at each end and be securely nailed.
Plywood sheathing shall be exterior grade, minimum 4 ply, not less than
15/32" (11.9 mm) thick. Plywood decks must be designed and fabricat-
ed in accordance with the recommendations of the American Plywood
Association. All four sides of each plywood panel shall bear on and be
securely nailed to joists and cross blocking between joists. “H” clips are
not acceptable. Plywood decks must be installed with a 1/8" – ¼"
(3 – 6 mm) gap between sheets and must match vertically at joints to
within
1
/
8
" (3 mm).
Wood and plywood decks must be dry prior to roofing. Cover cracks
wider than ¼" (6 mm) and knot holes larger than 1" (25 mm) with secure-
ly nailed sheet metal. When light metal wall ties or other structural metal
are exposed on top of the wood deck, cover them with a heavy ply of
roofing membrane, such as inverted Tri-Ply
®
BUR Granule Cap Sheet,
extending 2"– 6" (51 – 152 mm) beyond the metal in all directions. Nail in
place before applying the base ply.
If Tri-Ply
®
Ply 4 or Tri-Ply
®
FlexPly
™
6 is used as a base sheet over a wood
deck, a sheathing paper is required.
Nail the base sheet through flat metal caps or use nails with attached
1" (25 mm) square or round metal caps that have a minimum withdrawal
resistance of 40 lb (18 kg) each.
Tape-and-staple fastening systems may be used on wood decks when
they comply with local building codes and agencies such as FM and UL.
ROOF DRAINAGE
Proper and adequate drainage of the roof surface is required, and is the
responsibility of those involved in the design and construction of the roof
substrate and supporting structure. GAF recommends at least ¼:12 slope
with proper grading to and placement of outlets. Guarantees will not be
valid for areas of a roof that pond water. Ponding water is defined as water
that does not drain or dissipate from the roof surface within 48 hours after
precipitation. Ponding can also result from other water sources, including
improperly piped air conditioning condensate and steam condensate lines.
Perlite tapered insulation may be used to create proper drainage. For
recommendations on tapered insulations or fills to provide slope for
drainage, contact the GAF Tapered Design Group at 1-800-766-3411.
EXPANSION JOINTS
Separate building units from adjacent units by expansion joints to allow
for structural expansion and contraction. Although requirements may
vary depending on structural and climatic conditions, expansion joints
are strongly recommended. The exact location and number of expansion
joints are the responsibility of the building designer.
VAPOR RETARDERS
A vapor retarder installed to the deck beneath the pre-formed roof insula-
tion is not a part of the roofing specification; its use must be determined
by the architect, design engineer, or building owner.
ASPHALT
Heating of Asphalts
ASTM D312 Type III Steep or Type IV High Temperature Steep Asphalts
should be used to install mop-applied Tri-Ply
®
BUR Cap and Ply Sheets
and Tri-Ply
®
SBS Membranes.
Field experience has demonstrated that proper temperatures in the kettle
and at the point of application are essential to obtain a satisfactory roof.
Kettle temperatures in excess of those indicated below may result in
changing of the asphalt while temperatures below specified minimums
can result in lack of adhesion. Every effort should be made to maintain
the temperature limitations indicated below. It is essential that the fore-
man of the roofing crew be provided with an accurate thermometer to
check temperatures at the kettle and at the point of application.
Prolonged heating, at 500 °F (260 °C) or more, of roofing asphalts may
cause changes in their physical properties that can affect roof membrane
performance and must be avoided. Unless roofing asphalt is being
continuously used, the temperature of the kettle should be reduced
to below 500 °F (260 °C).
Recommended kettle and asphalt application temperatures:
Steep Asphalt ASTM D312 Type III
Kettle —Not over 500 °F (260 °C)
Time of Application —EVT, but not less than 400 °F (204 °C)
HT Steep Asphalt ASTM D312 Type IV (High Temp.)
Kettle —Not over 500 °F (260 °C)
Time of Application —EVT, but not less than 400 °F (204 °C)
Safety Note: Asphalt should be heated to provide the EVT at the time of
application, but should not be heated above the final blowing temperature
or the flash point of the asphalt.
GAF supports NRCA’s position of two EVTs, one for mop application and
one for mechanically applied asphalt. For mop applications, the optimum
asphalt viscosity of 125 centipoise has been established. The optimum
asphalt viscosity of 75 centipoise has been established for mechanical
applications.
The same asphalt will need to be heated to a higher temperature to
achieve the lower optimum viscosity when it is applied with a mechanical
spreader.
Application of Asphalt
Low-density roof decks and insulation material tend to absorb the bitu-
men. It is important, therefore, that the layer of bitumen used to secure
either the insulation material to the roof deck or the first ply of felt in the
roof system be applied in sufficient quantity to ensure adequate adhesion.
Interply moppings of asphalt must be applied in a continuous film and
consist of approximately 25 lb (11.3 kg) per 100 square feet (9.2 sq. m)
of roof area, with a tolerance not to exceed 20% plus or minus.
TRI-PLY
®
Design and Application Instructions