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Sealing Crawl Space floor

BobHr | Posted in General Questions on

What is the recommended material for sealing a crawl space floor. How is it attached to the block wall.

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  1. Riversong | | #1


    There are a number of vapor barriers designed for such applications. Some are just thick poly (10 mils), and others are cross-laminated or otherwise reinforced to increase tear resistance. I use Tu-Tuf, which comes in a smooth white version (#4) or a slightly ribbed translucent version (XF), which is a little more pliable and better for traction. They are only 4 mils thick but much more tear and puncture resistant than conventional poly, and have no pinholes.

    They're available from Energy Federation ( and other suppliers.

  2. Riversong | | #2

    I forgot the second half of your question.

    The best way to seal the VB to the block walls is with Tremco acoustical sealant, which is a non-hardening butyl rubber caulk, or any other polyethylene-compatible adhesive caulk such as urethane (PL Premium). With the Tremco, you'll have to attach wooden strapping over the edge of the VB and nail with a powder-actuated nailer to hold it in place. With the construction adhesive, it should be secure without strapping. Obviously, the block will have to be clean and dust-free.

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