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Crawlspace vapor barrier product?

user-2575529 | Posted in General Questions on

The local home centers don’t have anything much thicker then 6 mil for poly that I could easily pick up and use for a crawlspace vapor barrier. I have a very small area, less than 100 sq ft, and the proper 10-20 mil thick products I see online have way more material then I need. They also cost quite a bit as well!

I was wondering if it would be a problem to use a EDPM rubber roofing material? I can get a 10×20′ roll for $100 and it is 45 mils thick and in stock at the local home center…

Does anyone think that this would be a bad choice for use in my crawlspace as a vapor barrier on the floor?

Thank you

William

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Replies

  1. LucyF | | #1

    William,
    EPDM is used as an "underground roof" to go around a house for people who have drainage problems in the basement. I can't see that it would be any kind of problem to use it as a crawlspace liner. I reviewed some forums where other people asked if they could do that and it certainly sounds reasonable.

    Here is a GBA discussion of the underground roof or inground gutter.
    https://www.greenbuildingadvisor.com/green-basics/inground-gutters

    JLC discussion on crawlspace liners - one suggestion to use EPDM as the liner
    http://forums.jlconline.com/forums/archive/index.php/t-47770.html

    Home Energy Pro discussion on crawlspace liners - another suggestion to use the EPDM as a liner
    http://homeenergypros.lbl.gov/forum/topics/sealing-vapor-barriers-to-concrete-foundations?xg_source=activity

    Insulating crawlspaces on the Oak Ridge National Lab site - they use the EPDM on the outside of the wall, rather than as the crawlspace liner.
    http://web.ornl.gov/sci/roofs+walls/insulation/fact%20sheets/crawlspace%20insulation%20technology.pdf

  2. Expert Member
    MALCOLM TAYLOR | | #2

    William, Are you providing some protection for the Poly? If so there is no reason to use anything thicker than 6 mil.

  3. agurkas | | #3

    Malcolm, if there is no need to ever get into crawlspace and you live in the area not known for radon - sure. But if you have anything that needs to be maintained down there and soil with bunch of rocks (some sharp, as always) - you need felt and then properly reinforced poly.
    I am not even getting into radon issues

  4. Expert Member
    MALCOLM TAYLOR | | #4

    Apollo, That's why I asked if he was providing protection. Relying on a more robust vapour barrier for mechanical protection is a suckers game. Put down a smooth substrate and cover the VB with a rat slab. 6 mil a perfectly adequate in those circumstances.

  5. user-2575529 | | #5

    Lucy, thank you for all the wonderful links. Very helpful!

    Malcom, There will not be any protection for the Poly for the near future that is why I wanted to go with something thicker. There is also already a Radon mitigation system in place. The poly that is in this area is in poor condition and needs to be replaced.

    I should add that there is a full basement with a partial crawl accessible from the basement.

    Looks like I will be giving the EDPM material a try!

    Thanks for the help everyone.

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