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Vaopr Barrier Install Details

Dennis Brown | Posted in General Questions on

Question on vapor barrier install: For a crawlspace, one can take 6mil polyethylene and run it up the wall 6-8 inches. My question is the attachment method. Acoustical sealant can work for this but I read on a barrier supplier’s website that a polyethylene should not be used with an acoustical sealant. This is for material called Tenoarm. The link is here if you want to go to it:

http://www.conservationtechnology.com/building_films.html

or here is the portion I want to focus on:

“We do not recommend the use of construction tapes, caulks, or acoustical sealant in contact with any quality polyethylene since these can cause premature deterioration and are often short-lived.”

Is their statement true that a poly material should not be used with an acoustical sealant? Are all acoustical sealants made similarly? Are they petroleum based? Looks like the USG version is water based. Is it an oil based product that “destroys” poly?

Would there be any need to use more than just the acoustical sealant for attachment to walls? Would there be any reason to use a nylon expansion fastener drilled into block or concrete? Something like this product:

http://crawlspaceinfo.com/DrySpace_Tapes_Fasteners.htm

Is this overkill?

Thanks

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Replies

  1. Riversong | | #1

    First, I would not use standard 6 mil poly, which is far too vulnerable to tearing. There are many products specifically designed for subslab or crawlspace installation. I use Tu-Tuf.

    Tenoarm is a good product and they market their own adhesive, Tenoseal. But I know of no evidence of deterioration of poly films by any kind of caulk. Acoustical sealants are non-hardening. If the caulk will be the only attachment of the vapor barrier to the wall, then I would suggest a hardening adhesive caulk, such as Phenoseal or Polyseamseal.

  2. GBA Editor
    Martin Holladay | | #2

    Dennis,
    Canadians have been using Tremco acoustical sealant to seal the seams of poly for decades, and I've never heard of a problem or failure due to the Tremco.

    The best installation would be to install Tenoseal between the crawl space wall and the edge of the Tenoarm, and to install a horizontal wood batten on top of the seam, secured to the wall with concrete or masonry fasteners.

  3. Dennis Brown | | #3

    I was being a bit flippant just saying using 6mil poly. Let me update the correct vapor barriers here to use, or to consider using:

    1) Tu Tuf
    2) Tenoarm
    3) Raven Industries (http://buyplasticnow.com/vaporretarders.aspx)
    4) DrySpace (http://crawlspaceinfo.com/12MilDrySpace.htm)
    5) Stego

    Those are five I can think of at the moment. I think all of them would work but it is always the details that matter in installation. Sounds like you guys want mechanical fastening as well as acoustical sealant? I think I understand your install idea Martin. In your case, you would only use the Tenoseal (is that their version of some kind of acoustical sealant?) and not really use acoustical sealant at all. You would use the sealant on the wall, attach the vapor barrier to the sealant, and then board over the tape/sealant combo and effectively make a "sandwich" to keep it altogether.

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