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Community and Q&A

Vapor Barrier for Existing Slab

severaltypesofnerd | Posted in Green Products and Materials on

I’m seeking product recommendations for topically applied above slab concrete vapor barrier for old existing slabs, achieving a documentable .06 Class I vapor barrier per ASTM E96  .  I’m stuck with the .06 requirement, and can’t make any form of compromise there.  And I’m stuck with the old slabs.  California  Climate Zone 3

Thanks to Martin, I’m aware that:

perm[total] = 1 / (1 / perm[layer 1] + 1 / perm[layer 2]).

What would you use on top of such slabs?

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  1. Aaron_P2 | | #1

    Here is what we usually specify around for commercial projects. I'm sure there are other alternatives if you dig through some data sheets for specific perm ratings. This product is usually installed on top of the slab before a self-levelling underlayment is poured on top. Not sure what your finished flooring will be or if you have issues with head height. Also per your photo, they require the cracks to be treated - assuming that crack is no longer moving they instructions require Ardex Ardifix.

    1. severaltypesofnerd | | #4

      The pictured cracks are dynamic. The corresponding redgard instructions say backer rod, elastomeric caulk, then redgard on top of the caulk. redguard

  2. Expert Member
  3. Deleted | | #3


  4. severaltypesofnerd | | #5

    OP here: how about glue down 6 mill poly? Does anybody do that?

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