Is Ventilation & Vapor Barrier required

John Windolf
we have a project wth a cast in place concrete frame. We have a lower sloped (2.25:12) roof, that is cast in place concrete, that the owner wants to install a standing metal seam roof in lieu of the PVC membrance. We looked at fully adhered polyiso with 5/8" OSB for nailing the Firestone UC-3 to. Do you recommend a vapor barrier over the concrete deck? Do you need an airspace for ventilation under the OSB?
Eric Novotny
An informed customer is the Best Customer!
What is the size of the roof? You will need to check with your current code but any sort of faced ISO board (foil or poly) will qualify as the vapor retarder as well. Not sure that you need full plywood as well and it would be easier to look at something like a nailbase product.

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