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Community and Q&A

Flooring on top of under-insulated slab

smalmo2 | Posted in General Questions on

Our new home will have 2″ of rigid foam under the basement slab and a poly vapour barrier. We are using cork plank flooring for 90% of the floors and tile in the washrooms. Given that the concrete itself contains moisture and the cork manufacturer states a vapour barrier must be used over concrete what is the most cost-effective method to install the flooring? I am considering a dimpled membrane like Delta FL and installing the cork directly over top or possibly 1″ rigid foam and again installing directly over top. I don’t see the need to utilize plywood or OSB for a floating cork floor although the tile will get plywood over whichever method I go with.

Or am I overly concerned about slab moisture and should install directly over the slab?

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  1. wjrobinson | | #1


    Google it.

  2. GBA Editor
    Martin Holladay | | #2

    Before you install any finish flooring over a fresh concrete slab, you have to wait for the concrete to cure and the moisture content of the slab to drop to an acceptable level. There are several ways to test slabs to see if they are dry enough for flooring installation.

    Once your slab is dry, it should stay dry -- especially if you have 2 inches of rigid foam and poly under the slab. (Of course, you need proper grading around the perimeter of your home, and you need to be careful when you run your lawn sprinklers so you don't saturate your slab.)

    Once your slab is dry, follow the flooring manufacturer's instructions.

  3. anthonyc12 | | #3


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