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Vapor barrier over plywood subfloor?

Posted by cdirmann (My Page) on
Tue, Aug 21, 12 at 15:23

I purchased a laminate floor that I want to use in my house to replace worn carpet. The subfloor is plywood and it is over an unconditioned crawlspace and the home is located in North Florida so humidity/ moisture are a factor. I've heard that the 6 mil polyethelene should not be used as it would trap moisture in the plywood which may lead to rot or mold; however, that is what the manufacturer of the flooring is suggesting.
What kind of vapor barrier/retarder should I use between the plywood and laminate? Would 15# tar paper work? Or is there something more suited to this installation?


Follow-Up Postings:

RE: Vapor barrier over plywood subfloor?

Tough question. I am familiar with what the North Florida environment can do to most anything made of wood, so you are right to be concerned. Moisture passing through a material that then condenses on a barrier is where there could be a problem. Since the crawlspace is unconditioned, then I would assume that you at least have some means for air exchange or venting and that the ground is covered with a moisture barrier.

Very interesting question. Have you consulted with the flooring manufacturer directly about this?

RE: Vapor barrier over plywood subfloor?

I would love to hear what you found out... I am not in North Florida (but the Pacific Northwest). We don't have nearly as high humidity, but we do have a lot of moisture at certain times of the year. I am looking to put laminate over an unconditioned, vented crawlspace as well, and wondering about the use of a vapor barrier between the subflooring and the laminate... Hope you post back if you got an answer!

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