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Roofing Underlayment as WRB on Side Wall

J L | Posted in General Questions on

What are the problems, if any, with using Roofing Underlayment on the side wall as a weather-resistant barrier, provided that the product has the desired physical characteristics (perm rating, etc…)?

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  1. GBA Editor
    Martin Holladay | | #1

    J.L.,
    All building codes require that a layer of asphalt felt, a roofing underlayment, be installed on walls as a water-resistive barrier (WRB). Other products, including plastic housewrap, have been approved as acceptable substitutes for the code-required layer of asphalt felt.

    More information here: All About Water-Resistive Barriers.

    Whatever you do, don't install synthetic roofing underlayment as a WRB on wall. Most synthetic roofing underlayments are vapor-impermeable. That's bad.

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