Permeability of ASTM D 3909 cap sheet; needing roof to dry to outside
4" of 2 lb closed cell spray foam will go on underside of roof sheathing....so roof needs to dry to outside; hence why I am using #30 felt/tar paper instead of a non-permeable ice & water shield.
However, to get my Class A fire rated system, I need to use an ASTM D 3909 cap sheet over the tar paper. How well is this system going to be able to dry to the outside and will there be any issues with this system?
The roofing material is a synthetic shake; Bellaforte by DaVinci.
Posted Aug 29, 2014 4:52 PM ET
Edited Aug 30, 2014 5:34 AM ET
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