unfinished crawlspace


Old 05-23-05, 09:22 AM
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unfinished crawlspace

Part of our house is over an unfinished (dirt) crawl space with 2 foundation vents. The house has a a musty odor during the spring and fall season, which I imagine is due to the unfinished crawl space. As such, I have a dehumidifier for the home.

I want to seal the crawl space, but I have a couple of questions, they are:

What strength polyethylene liner should I use? I read that the standard is 6 mil, but some sites advise stronger than this. Please advise.
Should I seal the vents in the crawl space? I live a Arlington, VA, so we have both hot and cold exptremes.
How do vapor barriers impact radon levels?
Is this something that a DIY should take on?
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Old 05-24-05, 08:47 PM
Join Date: May 2005
Location: USA
Posts: 27
I'm not an expert, but I would think that insulating the floor from underneath would be a great idea, and then putting some poly over it as a vapor barrier, but to totally seal off the crawlspace might not be a great idea, especially if it's prone to moisture. Sealing it off from the world would mean the moisture would have nowhere to go, making it a breeding ground for mold and centipedes and God-only-knows, which you would no longer be able to access.

Radon is a gas so I would think the poly would be impermeable to it, but the problem would be around all the edges, unless you did a top-notch job sealing every edge of the poly, any radon or moldy air would be able to vent up into the walls.
Old 05-25-05, 05:19 AM
pgtek's Avatar
Join Date: Oct 2004
Location: north Carolina
Posts: 1,391
insulate the floor from undernea is a good ideal and cover it with a vapour barrier.
as for the ground lay a 6 mil vapour barrier and cover it with 6 inches on gravel.make sure the vapour barrier go up at least 12 inches on the wall so the gravel is below that part.

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