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  1. #1
    Join Date
    Apr 2007
    Location
    Chicago
    Posts
    57

    Question Vapor Barrier Needed?

    Does a dirt floor crawlspace still need a vapor barrier if there are concrete joists and a concrete floor above the crawlspace area? Would moisture still evaporate through the concrete floor into the living space above? My thinking would be no, but I'm not sure.

    Thanks

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  2. #2
    Join Date
    Aug 2007
    Location
    Memphis TN.
    Posts
    4,311

    Default Re: Vapor Barrier Needed?

    Mr. Bacon,

    Isn't concrete porous, wick water? Poured slabs have a continuous vapor barrier. Is the concrete water sealed underneath?

    Last edited by Billy Stephens; 08-28-2007 at 08:42 AM. Reason: spelling

  3. #3
    Join Date
    Mar 2007
    Location
    Healdsburg, CA
    Posts
    1,741

    Cool Re: Vapor Barrier Needed?

    All concrete slabs below habitable areas/spaces should be provided with a vapor barrier. A concrete slab sitting on grade is nothing more than a very large tampon when it comes to wicking moisture out of the sub-soil. There is a jurisdiction in my area that has for years required a 2-ply asphaltic hot-mop VB below garage slabs due to the propensity of folks for eventually converting their garages to family rooms and/or sleeping rooms.

    Jerry McCarthy
    Building Code/ Construction Consultant

  4. #4
    Join Date
    Aug 2007
    Location
    Memphis TN.
    Posts
    4,311

    Default Re: Vapor Barrier Needed?

    Quote Originally Posted by Jerry McCarthy View Post
    All concrete slabs below habitable areas/spaces should be provided with a vapor barrier. A concrete slab sitting on grade is nothing more than a very large tampon when it comes to wicking moisture out of the sub-soil. There is a jurisdiction in my area that has for years required a 2-ply asphaltic hot-mop VB below garage slabs due to the propensity of folks for eventually converting their garages to family rooms and/or sleeping rooms.
    Man and I thought everything was big in Texas


  5. #5
    Join Date
    Mar 2007
    Location
    Dallas, Texas
    Posts
    4,112

    Default Re: Vapor Barrier Needed?

    Jerry, very... er... descriptive explanation.
    Jim

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  6. #6
    Join Date
    Mar 2007
    Location
    Connecticut
    Posts
    1,822

    Default Re: Vapor Barrier Needed?

    Jerry, My wife flipped last night when I hot mopped her box of Tampons. That was bad advice. Thanks alot


  7. #7
    Join Date
    Mar 2007
    Location
    Healdsburg, CA
    Posts
    1,741

    Default Re: Vapor Barrier Needed?

    I apologize if I offended anybody with my description of what a slab foundation is capable of related to women’s hygiene products.
    However, let's take another example. You ever notice when a newspaper is left on your lawn for any length of time and when you pick it up it's all wet where it was in contact with the grass?
    Or, how about when you stand on the sandy beach and after a couple of minutes you move your foot and where your footprint was fills with liquid?
    This is a natural phenomenon and slab foundation are notorious in drawing moisture from the soils.


    Jerry McCarthy
    Building Code/ Construction Consultant

  8. #8
    Join Date
    Aug 2007
    Location
    Memphis TN.
    Posts
    4,311

    Smile Re: Vapor Barrier Needed?

    Mr. McCarhy,

    Just poking a little fun. You were direct and accurate both good qualities. I was trying to
    get Mr. Bacon to think about his question. Could have added to my post wasn't half of
    Chicago built on a drained swamp?


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