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Drywall on top of house-wrapped OSB?

DaBearsFTP | Posted in General Questions on

Hello everyone! I am finishing the interior of an add-on garage in central NC. It was constructed professionally about 10 years ago but the interior is just studs.

I’m still deciding on OSB or sheet rock but my question is about the wall pictured.

This wall used to be the exterior of the original garage, but it is now a shared wall between the original and the new add-on garage. It is insulated, and there is OSB under that house-wrap. There used to be vinyl siding on there, before the add-on.

The add-on will be air conditioned. Cooled in the summer and heated in the winter. The original garage will not be.

Can my new wall material go right on top of that house wrap, or should I be concerned about moisture in that space?

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  1. Expert Member
    NICK KEENAN | | #1

    I'm trying to get a handle on what you're describing. The original garage is insulated but not conditioned? Is it attached to a house?

    I think that wall is now the de facto exterior wall of your new garage. In upstate New York, an exterior wall should have a vapor barrier on the interior and dry to the exterior. If it was built properly to begin with the vapor barrier is now on the wrong side. The Tyvek isn't a problem, it's vapor permeable. The problem is you've got nothing to keep moist air from getting into that wall and condensing when it gets to the cold side. And no way for that moisture to escape.

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