vapour barrier above or below insulation?


Old 04-23-02, 06:21 AM
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vapour barrier above or below insulation?

Hi! I have asked this question in a different place in the forum but realize this is probably where I should be asking! We are installing a 3/4" T&G OSB floor above a wood frame (to raise the floor) with fiberglass insulation between the joists in a workshop in the basement. We know we need to add a vapour barrier. However, what we can't figure out is whether the vapour barrier should be under the wood frame and insulation or over it, just under the OSB. Can someone tell us please? We appreciate your help!
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Old 04-23-02, 06:44 AM
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If your wood frame floor is to be directly on the concrete basement floor, put the vapor barrier under the frame or use pressure-treated lumber (better).
If you're using p-t lumber on the floor, put the vapor barrier under the OSB and over the insulation.
Personally, I would put a vapor barrier under the framing and under the OSB both. I'm not a contractor, so this is just my opinion.
Good Luck!
Old 04-23-02, 06:29 PM
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Vapor barriers

Go to for helpful info regarding insulation and vapor retarders. You can also email resercon for additional info if you have additional questions.
Old 04-24-02, 06:03 PM
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Usually vapor barriors are applied to the heated side of the insulation. If applied to the wrong side, condensation build up in the insulation and actually conducts a better way for the dampness or cold through the insulation.

It is also a good way to get mold to start forming with the added moisture if applied incorectly

Kelli Anne Taylor Flooring
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