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Question and Answer ArticleCuring Damp Floors

By Jennifer T. Derrick
Published: January 27, 2010

Q: How can I keep my floors from feeling damp in my cabin on the north shore of Lake Michigan? I have a “crawl-less” crawl space (less than 12 inches from the sand to floor joists). I am going to put new subflooring down next spring, but I would like to do something to reduce the dampness you can feel in the flooring. The cabin is built on a sand dune so the moisture is probably from the coolness of the lower levels of sand. – Lonnie Cross; via e-mail

A: It’s good you’re installing new subflooring, as this will allow you to see what’s actually going on down there. Nowadays, most crawl space homes are fitted with a vapor barrier. This may have been omitted when your cabin was built.

Vapor barriers are especially important if a crawl space isn’t well ventilated. Even with vents in place, however, it’s wise to install a vapor barrier as an extra precaution. Floors shouldn’t feel damp with a proper barrier and new subflooring installed.

The best way to install a vapor barrier is to staple the barrier directly under the floor joists. Another method is to put the sheeting on the ground beneath your cabin, sealing it well on all sides with a special moisture-barrier tape. You can do both too.

The barrier itself isn’t difficult to put in, but may prove more challenging since all the floor joists are already in place.

Sheeting of black polyethylene (6-mil gauge or thickness) is what’s normally used, but if you want, you can track down high-performance polyethylene. It’s not likely you’ll find it at a big box home center, but local contractors will be able to point you in the right direction.  

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