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Thread: vapor barrier

  1. #1
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    Default vapor barrier

    I have a question concerning vapor barriers.

    I am remodeling my bathroom and Im not sure if I should add a 6mm plastic (vapor barrier) to my outside wall if the insulation has faced paper (vapor barrier). I have black fiber board on the outside wall, then R-15 pink insulation w/faced paper (vapor barrier), and then I want to put 6mm clear plastic, then Hardie board, and then grout and tiles.

    Do you think that I will be getting condensation in between the insulation and the plastic vapor barrier?

    Even if the insulation has a vapor retarder would it matter if there is another vapor on top of it?

    thanks for your help.

  2. #2
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    Default Re: vapor barrier

    In my corner of the world this is what we do:
    Inside: black thin tar paper (60 minute paper) over the studs, CBU (like hardieback), then tiles. The insulation is not a barrier.
    Outside: 2 layers of black paper, then chicken wire for stucco (3 layers) or just siding (rarely used).
    No 6mm plastic needed. We use 6mm plastic under slabs.

  3. #3
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    Default Re: vapor barrier

    dj1 uses teh correct method. If you really want to use 6 mil plastic, then you can put a few slits in the backing paper of the insulation. I would recommend that you do it the conventional way though. The advantage is that the tar paper will shed any moisture that gets through the tile and backerboard, but still breath, and the vapor barrier on the insulation will do its job.

    Do you have a tub or shower against this wall?

  4. #4
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    Default Re: vapor barrier

    dj1, you wouldnt happen to know what vapor barrier is used for denver co? Would it be the same process that is used in SoCal?

    Kieth3257, I have a tub against the wall.

    I did a little research ****** and found this information below in regards to R-15 FACED Paper. It doesnt specify what kind of vapor barrier to use. let me know what you think, thanks guys!

    -Owens Corning recommends
    that a vapor retarder should be
    used in most climates.
    In climates requiring winter
    heating, the vapor retarder
    should be placed toward the
    warm-in-winter side. (In humid
    climates, like the Gulf Coast,
    follow local building practices
    for vapor retarder placement.)
    In all applications using a vapor
    retarder, maintaining the facing
    integrity is important for
    effective moisture/humidity
    control. Repair any punctures
    or tears in the facing by taping.

  5. #5
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    Default Re: vapor barrier

    Vincentx,

    I'm not familiar with the code in Colorado, but it's can't be that much different than the code in LA.

    The vapor protection that the manufacturer is calling for is the thin black tar paper I mentioned (aka "60 minute paper"). It comes in a roll, 36" or 42" wide.

  6. #6
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    Houston Texas
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    Default Re: vapor barrier

    The vapor barrier is placed on the hot side of the wall. That depends on your location. In the area directly behind your tile assembly you want only 1 vapor barrier. That depends on how your tile assembly is constructed.

    How were you fixin to tile your walls? and by that I mean waterproof them?

  7. #7
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    Default Re: vapor barrier

    If you haven't installed the insulation yet, I would recommend that you staple the flanges to the ends of the studs, not to the faces as most people do. You can overlap the flanges a little so that makes a better vapor barrier.

    You do not want two layers of vapor barrier, but you do want to keep water off the barrier. For this, you use the tar paper, mounted horizontally, starting from the bottom with some overlap. Any water on the tar paper will shed down the wall.

    Now install the cement board around the tub. Fill the gaps with thinset and fiberglass cloth tape. Then install the tile and grout it.

    Keep in mind that any water that hits the wall should shed down into the tub. Any that gets behind the tiles should shed down the tar paper to the lip of the tub.

  8. #8
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    Default Re: vapor barrier

    Quote Originally Posted by Vincentx View Post
    I have a question concerning vapor barriers.

    I am remodeling my bathroom and Im not sure if I should add a 6mm plastic (vapor barrier) to my outside wall if the insulation has faced paper (vapor barrier). I have black fiber board on the outside wall, then R-15 pink insulation w/faced paper (vapor barrier), and then I want to put 6mm clear plastic, then Hardie board, and then grout and tiles.

    Do you think that I will be getting condensation in between the insulation and the plastic vapor barrier?

    Even if the insulation has a vapor retarder would it matter if there is another vapor on top of it?

    thanks for your help.
    This is a tricky one.
    The paper face on that insulation is only a vapour retarder ( not a barrier ) and considering the method of installation doesn't provide an airtight seal --- combined doesn't provide a very strong barrier for vapour drive into the wall cavity if you are in a cold winter zone.
    Tar paper is not a vapour barrier since it highly vapour permable which is why it is used on exterior sheathing. Also , tar paper will disintergrate once it becomes saturated with water and can actually increase potential for mold because of it's paper base.

    Considering the insulation is also behind the tub ( running down to the floor ) then putting any type of vapour barrier above the tub really will be useless --- since only half the wall would be sealed. Ideally completely removing the tub and installing a complete vapour barrier over the entire wall would be best, otherwise you're best to leave things as is and use the Kerdi - Board.
    http://www.schluter.com/7757.aspx

    This product will be the substrate -- water proofing system for the walls.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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