TB-0008 — Use Over Fluted Metal Decks Technical Letter (US Version)
GCP’s self-adhered underlayments (GRACE ICE & WATER SHIELD®, GRACE ICE & WATER SHIELD® HT, GRACE ULTRA™, GRACE SELECT™, Roof Detail Membrane™ and GCP granular underlayment) are to be used as air and vapor barriers only, when installed on a clean, dry fluted metal deck where permitted by local building and fire codes. Care should be taken to make sure that all side laps are made over the tops of the flutes so they can be sufficiently pressed together for a good seal. It is recommended that sheet metal or some other smooth structural substrate be fastened to the metal in the areas where end laps will fall. This will allow the end laps to be pressed together.
Special care should be taken that foot traffic on the roof does not damage the membrane since it is especially susceptible to damage over the troughs of the flutes where it is unsupported.
Roof fasteners driven through the GCP self-adhered underlayment should be placed only over the crests of the flutes where the membrane is supported.
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Last Updated: 2021-02-05