TL-0003 — Exposure Guidelines for Roofing Underlayments Technical Letter (US Version)
GCP’s underlayments (GRACE ICE & WATER SHIELD®, GRACE ICE & WATER SHIELD® HT, GRACE ULTRA™, GRACE SELLECT™, GCP granular underlayment, Roof Detail Membrane™, TRI-FLEX® and TRI-FLEX® 15) are not meant to be left permanently exposed to the sun. In general, the membrane should be covered with the final roof covering as soon as possible. However, GCP’s underlayments may be left exposed (as described in the general exposure guidelines below) if necessary, to accommodate construction scheduling or weather problems.
To extend the exposure period for GCP’s self-adhered underlayments, TRI-FLEX® can be applied over these membranes, provided it is acceptable for use in the specific roofing application (i.e. roof design and region).
During the time period the product is left exposed there are two primary factors at work on the membrane: heat and ultraviolet (UV) radiation. UV radiation will not affect the membrane in any significant way during its maximum exposure limit. Heat will not likely affect the performance of the product either, but there may be some changes in appearance depending on the climate and length of exposure.
|GCP Underlayment||Maximum Exposure Guidelines (Days)|
|GRACE ICE & WATER SHIELD®||90|
|GRACE ICE & WATER SHIELD® HT||120|
|GCP granular underlayment||30|
|Roof Detail Membrane™||90|
After the maximum exposure period, it is normal for the self-adhered membranes to appear slightly wrinkled. It is also normal to see a slight color change in the non-slip coating on the membrane surface. There may be a small amount of curling at the edges of the membrane as well. None of these issues will affect the performance of GCP’s self-adhered underlayments once covered. For information on performance of TRI-FLEX® and TRI-FLEX® 15 during exposure period, refer to Technical Letter 14, Drying-In Roofs with TRI-FLEX®.
Before covering the membrane after a long exposure, it should be inspected to ensure that any wrinkling or other movement that has taken place has not affected any of the lap areas. If a wrinkle forms that extends to the edge of a lap, it must be cut, pressed down, and patched before the roof is covered. Use a round patch of membrane extending past the damaged area 6 inches (150 mm) in all directions. Any curling at the edges or corners must be cut and patched if the affected area is more than 1/2 inch (13 mm) wide. If exposures longer than the maximum exposure period are anticipated, please contact your local GCP technical sales representative.
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This document is only current as of the last updated date stated below and is valid only for use in the United States. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on www.gcpat.com. Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.
Last Updated: 2021-02-05