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gkaro 12-15-2011 11:54 PM

flat roof construction.
Hi all. Building a flat roof -2.5% slope. The plans call for an air space between the insulation and the ply. Question....if I go with spray foam -2 lb...does the air barrier become irrelevant?
Do building codes allow for this compromise ?

jklingel 12-15-2011 11:56 PM

I believe that if it is closed cell spray foam, not open, you are correct because it will be an air/vapor barrier. Check on or

AndyGump 12-16-2011 12:26 AM

Yes, the International Residential Code does allow for some non-vented attic conditions like you are talking about.

I know it is a flat roof, cathedral type ceiling is not an attic area, but the code calls it that.

There are specific conditions that have to met though.


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