Instructions / Assembly
®
4
Nailing of Base Sheet Directly to Deck
All nailing must be done through flat metal caps or acceptable nails with
1 inch 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 pounds.
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 inches and stagger-nail down the center of sheet in two rows with nails
spaced at intervals not to exceed 18 inches in each row with each row
12-13 inches 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
1
/
2
inch per foot or more unless supplemental nailing is used. If the roof
slope is less than
1
/
2
inch per foot, nailing is not required.
If the slope is greater than
1
/
2
inch but less than 2 inches per foot, use
wood nailers at the eave, at the ridge and at intermediate spacing of no
more than 16 feet. If the slope is 2 inches to 3 inches per foot, use wood
nailers at the eave, at the ridge and at intermediate spacing of no more than
8 feet. All dimensions are from inside face to inside face of the wood nailers.
Ensure a snug fit with the courses of insulation, but avoid cutting the insula-
tion. 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 inches 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 TRIPLY base and ply sheets vertically on slopes
1
/
2
inch per foot or more and back-nail them into wood nailers or nailable decks
approximately 4 inches 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 inch centers. Use nails with
integral metal heads at least 1 inch round or square.
Install TRIPLY membranes vertically on slopes
1
/
2
inch per foot or more.
Terminate at wood nailer and fasten the top edge of each sheet with TRIPLY
screws and plates, placing 4 fasteners evenly spaced across the top of the
sheet. The overlapping sheet must extend at least 9 inches past the top of
the underlying sheet. All end laps must be staggered to the closest wood
nailer, spaced a minimum of 4 feet. On slopes of 2 inches to 3 inches per
foot, the TRIPLY sheets must be cut into lengths not to exceed 17 feet. For
non-insulated wood decks, terminate and fasten the end of the TRIPLY
sheets to the deck with the same fasteners, on the same spacing indicated
above.
ASTM 312, Type IV, HT Steep Asphalt must be used to install all base
sheets, ply sheets and TRIPLY Mop membranes on slopes of
1
/
2
inch per
foot or above.
For cold applied specifications, starting at
1
/
2
inch per foot or greater, the
above referenced fastening requirements must be followed, except wood
nailers must be used at intermediate spacing of no more than 8 feet.
For roofs with slopes greater than 3 inches per foot, contact GAF
Materials Corporation Contractor 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 flash-
ing type, examine the many factors that may affect the optimum trouble-
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.
Recover
For reroofing projects, it is always best to remove the old roof system.
This will show the deck condition, allow for up-grading 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 recovering an existing BUR
or any modified bitumen roof. Any deviations must be addressed in writ
-
ing from GAF Materials Corporation Technical Services.
Recovering single-ply membranes present unique problems;
contact GAF Materials Corporation 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 recov-
ered with a new roofing membrane. GAF Materials Corporation assumes
no responsibility for determining the suitability for recovering or the com-
position of the existing roof system. The Company’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 prob-
lems include, but are not limited to, problems in the new roof system that
result from roofing over wet materials in the old roof.
The preparation for recovering the old roof should include:
A. Establishing the history of the old roof system.
B. Determining and correcting the cause of any premature roof failures.
C. Determining that the deck is structurally sound to receive the
new system.
D. Taking test cuts to verify the old roof construction and condition.
Three test cuts should be made for roofs under 100 squares and one
test cut per 100 squares above the minimum amount.
Note: Roof systems having existing vapor retarders must be addressed
with GAF Materials Corporation Technical Services.
E. Confirming that the old system is securely fastened to the roof deck.
F. Removing all wet roof insulation and old, wet membrane. Replacing
with dry materials. The existing roof membrane must be in a condi-
tion suitable to receive the new roof assembly.
Note: It is highly recommended that a moisture survey be made to deter-
mine the extent of wet insulation and moisture entrapment.
G. Providing for proper drainage of the new roof system to eliminate
ponding. Provisions must be made to ensure the new roof system
has proper drainage, i.e., placement of additional roof drains, use of
tapered insulation, use of crickets, etc., as appropriate.
H. Complying with all code requirements.
I. GAF Materials Corporation recommends recovering over only one
existing roof system. The Company will not issue a guarantee for a
new GAF Materials Corporation roof membrane installed over more
than one pre-existing roof system.
TRIPLY
®
Design and Application Instructions
Nailable
Deck
TRIPLY Base Sheet
18
"
Max.
12
"
-13"
12
"
-13"
9
"
Max.
2
"
Min.
Side Lap