Thinner barrier effective for home use

Q. I want to cover my crawlspace with a plastic moisture barrier, but I can only buy the 6 mil. I have tried to buy the new 20 mil kind but the companies won't sell it to me. What do I do?

A. Companies that sell the 20 mil (20 thousandths of an inch in thickness) plastic vapor barrier material do their own installations. If your moisture problem in your sub-area crawl space is normal damp soil and random water puddling -- even if it is year-round -- you would do just as well to install 6 mil material. It may not last as long if you find yourself repeatedly crawling in the sub-area, but it will hold back the moisture every bit as effectively as 65 mil.

By covering the ground in your crawl space with a sheet of plastic you contain damaging evaporation, thus preventing it causing rot to the wood floor immediately above. If you live in a particularly wet area you should cover the entire sub-area all the way up to the foundation; however, if you live in a drier climate, it is wise to hold the plastic about 6 inches away from the foundation so the earth can breathe. The floor of your home does require a small amount of moisture.