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What Mil vapor barrier will stop radon too?

99IdoDIY | Posted in General Questions on

I am going to install new plastic over the gravel in my crawl space. My primary goal is to reduce humidity. I was reading about radon and I might as well put down a plastic that will block both.

How thick of plastic do I need to stop humidity and radon?

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  1. Expert Member
    Dana Dorsett | | #1

    It's really about gas-tightness. It doesn't have to be very thick- 6 mils is fine if it's going to be under poured concrete (which would pretty much block any pin-holes, etc.) But if it's going over gravel and will be walked/crawled on from time to time, thicker is better. Most polyethylene would want to be at least 10mils or thicker to have sufficient long term ruggedness. EPDM membrane works too.

  2. GBA Editor
    Martin Holladay | | #2

    First of all, can you tell us your name?

    Ordinary 6-mil polyethylene will stop water vapor and radon, as long as it has no holes or rips. The thicker and tougher the polyethylene, the less likely it will get holes when it is installed.

    My article on crawl spaces recommends a tough product like a 20-mil pool liner or Tu-Tuf poly if the poly will be left exposed.

    For more information, see these two articles:

    Building an Unvented Crawl Space

    All About Radon

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