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Community and Q&A

Regarding the November 2011 article on Synthetic Roofing Underlayments

TVWTGDkL4L | Posted in General Questions on

Should synthetic roofing underlayment be used on a roof with open cell foam sprayed against the roof deck with shingles in North Carolina? I sure hope so as we just did it with a house I am having built.

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  1. GBA Editor
    Martin Holladay | | #1

    According to manufacturers recommendations, almost all synthetic roofing underlayments can only be used over ventilated spaces (that is, vented cathedral ceilings or vented attics).

    The only exceptions are vapor-permeable synthetic underlayments like Deck-Armor, Delta-Maxx Titan, VaproShield SlopeShield, Cosella-Dörken Vent S, Nemco Industries RoofAquaGuard BREA, or Cosella-Dörken Delta-Foxx. If you chose one of these vapor-permeable products, you probably know you did, because they cost an arm and a leg.

    Your roof assembly is not ventilated, so if you used a typical brand of synthetic roofing underlayment, your installation violated the manufacturer's recommendations. It is also a code violation, since almost all building codes require all products to be installed according to manufacturer's recommendations.

    So, you made a mistake. But now that the roof is built, I wouldn't lose much sleep, since it's too late to solve the problem. Your roof will probably work.

    However, it you want to pursue a case against your builder, it certainly sounds as if your builder might have made a mistake.

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