Instructions / Assembly

4
Nailing of Base Sheet Directly to Deck
All nailing must be done through flat metal caps or acceptable nails with
1" (25 mm) square or round metal caps. The proper nail or fastener must be
selected in accordance with the recommendations of the deck manufacturer
or as recommended for specific type decks in this catalog. The fastener
used must have a minimum withdrawal strength of 40 lb (18 kg).
Some buckling of the base sheet may occur during its installation if it is not
permitted to relax sufficiently. The base sheet must be unrolled and allowed
to relax before fastening. It is suggested that the base sheet be stretched
just prior to nailing. This is usually accomplished by a shuffling motion of
the feet of the mechanic installing the sheet just ahead of nailing.
Nail along the side lap of the base ply at intervals not to exceed 9" (229 mm)
and stagger-nail down the center of sheet in two rows with nails spaced at
intervals not to exceed 18" (457 mm) in each row, with each row 12" – 13"
(305 – 330 mm) in from the edges of the sheet.
Installation on Steep Slopes
Slippage of mop-applied or torch-applied roof systems may occur on slopes
of ½:12 or more unless supplemental nailing is used. If the roof slope is
less than ½:12, nailing is not required.
If the slope is greater than ½:12 but less than 2:12, use wood nailers at
the eave, at the ridge, and at intermediate spacing of no more than 16'
(4.8 m). If the slope is 2:12 to 3:12, use wood nailers at the eave, at the
ridge, and at intermediate spacing of no more than 8' (2.4 m). All dimen
-
sions are from inside face to inside face of the wood nailers. Ensure a
snug fit with the courses of insulation, but avoid cutting the insulation. For
non-insulated wood decks, back-nail the plies directly to the deck at the
intervals listed above.
If insulation is to be installed, mechanically attach insulation or mop
between wood nailers with the long dimension in the same direction as the
roof slope. Use wood nailers treated with water-based preservative to hold
the insulation in place. Use wood nailers at least 2" (51 mm) wide and the
same thickness as the insulation. Install on top of the vapor retarder
(if used) at right angles to the direction of slope. Mechanically attach
wood nailers to the deck with nails, screws, or bolts.
Install all plies of Tri-Ply
®
Base and Ply Sheets vertically on slopes ½:12 or
more and back-nail them into wood nailers or nailable decks approximately
4" (102 mm) from the back edge of the sheet. All end laps must be at wood
nailers, and the top edge must be at wood nailers, and the top edge must be
nailed into the wood nailer on 6" (152 mm) centers. Use nails with integral
metal heads at least 1" (25 mm) round or square.
Install Tri-Ply
®
Membranes vertically on slopes ½:12 or more. Terminate
at wood nailer and fasten the top edge of each sheet with Tri-Ply
®
Screws
and Plates, placing 4 fasteners evenly spaced across the top of the sheet.
The overlapping sheet must extend at least 9" (229 mm) past the top of the
underlying sheet. All end laps must be staggered to the closest wood nailer,
spaced a minimum of 4' (1.22 m). On slopes of 2:12 to 3:12, the Tri-Ply
®
Sheets must be cut into lengths not to exceed 17' (5.2 m). For non-insulated
wood decks, terminate and fasten the end of the Tri-Ply
®
Sheets to the deck
with the same fasteners, on the same spacing indicated above.
ASTM D312, Type IV, HT Steep Asphalt must be used to install all base
sheets, ply sheets, and Tri-Ply
®
Mop Membranes on slopes of ½:12 or above.
For cold-applied specifications starting at ½:12 or greater, the above refer
-
enced fastening requirements must be followed, except wood nailers must
be used at intermediate spacing of no more than 8' (2.4 m).
For roofs with slopes greater than 3:12, contact GAF Technical Services.
FLASHING
The juncture of the roof deck and a vertical surface is probably the most
vulnerable moisture infiltration point on any roof. Before selecting a
flashing type, examine the many factors that may affect the optimum trou-
ble-free joining between the roof deck and vertical surface. The potential
for differential movement between deck and vertical surfaces must be
addressed in the flashing design.
RE-COVER
For reroofing projects, it is always best to remove the old roof system.
This will show the deck condition, allow for upgrading roof insulation,
eliminate moisture entrapment, allow proper addition of new units and
curbs, and give greater confidence in the new roofing system.
Follow the recommendations below when re-covering an existing BUR or
any modified bitumen roof. Any deviations must be addressed in writing
from GAF Technical Services.
Re-covering single-ply membranes present unique problems; contact GAF
Technical Services for guidance.
Preparation
A proper analysis of the old system, including determining the cause of its
failure, must be made. A proper preparation of the old system and the roof
insulation (if any) must be done.
It is the responsibility of the building owner or its agent, roof designer, or
roofing contractor to determine if the old system is suitable to be re-cov-
ered with a new roofing membrane. GAF assumes no responsibility for
determining the suitability for re-covering or the composition of the exist-
ing roof system. GAF’s responsibility under the term of the guarantee does
not include problems with the new system caused by the substrate, in this
case, the old roof system. These problems include, but are not limited to,
problems in the new roof system that result from roofing over wet materi-
als in the old roof.
The preparation for re-covering the old roof should include:
1. Establishing the history of the old roof system.
2. Determining and correcting the cause of any premature
roof failures.
3. Determining that the deck is structurally sound to receive the
new system.
4. Taking test cuts to verify the old roof construction and condition.
Three test cuts should be made for roofs under 100 squares
(929 sq. m) and one test cut per 100 squares (929 sq. m) above
the minimum amount.
Note: Roof systems having existing vapor retarders must be addressed
with GAF Technical Services.
5. Confirming that the old system is securely fastened to the
roof deck.
TRI-PLY
®
Design and Application Instructions
Nailable
Deck
Try-Ply
®
Base Sheet
18" (406 mm) Max.
18" (457 mm) Max.
18" (406 mm) Max.
12"-13"
(305 mm - 330 mm)
12"-13"
(305 mm - 330 mm)
9" Max.
(229 mm)
2" (51 mm) Min.
Side Lap