The purpose of this Technical Bulletin is to clarify Holcim Building Envelope position on existing metal roofing system recovers. Firestone currently has the following EPDM and TPO adhered and mechanically fastened purlin attached single-ply roof systems over existing metal roofing systems:
- RubberGard™ EPDM and UltraPly™ TPO membrane systems are adhered to an appropriate cover board that is mechanically attached over appropriate flute filler to the existing metal roof panels. A minimum of 16 fasteners and plates per 4′ x 8′ board ensures that the wind uplift loading is distributed evenly throughout the roof system.
- The RubberGard EPDM R.M.A. system utilizes R.M.A. strips that are mechanically attached to the structural purlins and the membrane is adhered to the R.M.A. strips.
- The standard UltraPly TPO or RubberGard EPDM MAX mechanically attached system utilizes seam plates located within the membrane overlaps and fastened directly into the structural purlins.
- The UltraPly TPO InvisiWeld™ System consists of UltraPly TPO membrane that is induction welded to UltraPly TPO InvisiWeld Plates located under the membrane and fastened directly into the structural purlins.
Although Firestone does not have specifications for mechanically fastened systems attached into the existing metal roof panels rather than into the purlins, this practice has been utilized over the years. Installing roofing systems for which there is no published specifications does not always result in consistent reliable and warrantable roofing systems. Moreover, fastening mechanically attached systems into the metal roof panels can result in an inherently weak roof system that may unevenly load the building structure.
In an effort to promote roofing systems where long term reliability has been tested and proven and also to align with the commercial roofing industry, Firestone will no longer approve PINS for mechanically fastened roofing systems attached directly to metal roofing panels beginning Jan. 1, 2016. Any outstanding projects that have been bid and contracted must have PINs submitted for review by the end of this year. Metal roofing recover system PIN’s submitted beginning January 1, 2016 must utilize one of the specified adhered or mechanically attached purlin fastened systems listed above.
Thank you for your support of Holcim Building Envelope.
National Technical Manager, Single-Ply Systems
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