Installation Guide

Suitable for use under all major roof coverings - Tri-Flex® XT
mechanically-attached underlayment can be used under shingles,
tiles, slate, metal and cedar shakes. Refer to subsequent sections
for more details.
Custom Logo Available - The product can printed with a cus-
tomer logo. Minimum order amounts apply. Please contact the
GCP sales representative for details.
GCP technical support - Tri-Flex® XT underlayment is backed
by a team of local technical support personnel that help ensure
every application goes smoothly.
Installation Guidelines
1. The roof deck must be swept clean and be smooth and dry
before installation begins.
2. Tri-Flex® XT membrane is laid horizontally (parallel to eave),
starting at the bottom of the roof, with printed side up and with
4-inch side laps and 6-inch end laps. Side laps run with the flow
of water in a shingling manner.
3. Tri-Flex® XT underlayment should not be used at slopes less
than 2:12, provided the slope is also acceptable to the primary
roof covering. On slopes of less than 4:12, GCP membrane
should be half-lapped a full 24 inches over the underlying
course, shingle style.
4. Tri-Flex® XT underlayment is attached to the roof with roofing
nails or staples both having 1-inch diameter plastic/metal caps,
spaced at 8 inches on center (oc) on both side and end laps
in normal wind zones. In high wind zones or coastal applications,
double the fastening to 4 inches oc. In all cases fasten at
24 inches oc down the middle of the roll in the field of the roof.
Fasteners may be hand or machine applied. Staples without caps
cannot be used.
5. Where seams or joints require sealant or adhesive, use a high
quality, low solvent, asbestos free plastic roofing cement
meeting ASTM D4586 Type 1, Federal Spec SS-153 Type 1
(Asbestos Free). Consult your local GCP representative for
more details.
6. Install drip edge at eaves under underlayment and at rake over
underlayment.
7. Installation of the roof covering can proceed immediately
following underlayment application. Tri-Flex® XT underlayment
cannot be used as a primary roof covering. The product is not
designed for permanent outdoor exposure. The installation of
the final roof covering should take place within 6 months.
8. For additional protection lay a single length of Tri-Flex® XT
membrane vertically in valleys and on hips prior to installing
metal flashings (if used) and before installing horizontal
underlayment. Return Tri-Flex® XT roofing underlayment up all
abutments at least 12 inches (more in heavy snow areas).
Secure and trim to suit.
9. Prior to loading roofing materials on Tri-Flex® XT underlayment
it is recommended that roof jacks, toe-boards or a storage
platform be secured to the underlying roof deck to prevent
slippage of stored materials on steep sloped roofs. See OSHA
Regulations (Standards – 29 CFR), Fall Protection Systems
Criteria and Practices – 1926.502.
10. Check local building code to ensure compliance in your area,
as local building codes may vary.
Code Approvals
• Meets the requirements of ICC AC-188 (Acceptance Criteria for
Roofing Underlayments) and Miami Dade County requirements
• Complies with ASTM E108/UL 790 for use in the installation of
Class A asphalt glass fiber mat shingles and Class C asphalt
organic felt or metal shingles
• Meets ASTM D226 physical requirements of Type I and Type II
(# 15 and # 30 asphalt felt)
Precautions and Limitations
• Consistent with good roofing practice, always wear fall
protection when working on a roof deck.
• Slippery when wet or covered by frost, debris or dust.
• Do not fold over the roof edge unless the edge is protected by
a drip edge, gutter or other flashing material.
• Check with the manufacturer of the metal roofing system for
any special requirements when used under metal roofing. Do
not install directly under roof coverings especially sensitive to
corrosion, such as zinc, without providing proper ventilation.
• Do not install under copper, Cor-Ten®, or zinc metal roofing in
high altitudes or in the desert southwest. These roofs can reach
extremely high temperatures due to the low reflectivity, high
absorption, and high conductivity of the metals.
Used only capped nails or capped staples.
Lay with a minimum 6 inches end lap.
Use a 4 inch side lap. Follow printed
guidelines for easy installation.
Fasten at 24 inches oc in the middle of the roll.