I have a two year old house that sits on an 8" concrete floating slab. The slab is insulated below and around the side. The floors in the house are unfinished. That is, the concrete slab is currently the floor.

To get some idea of whether there is moisture coming out of the slab, I taped a ~1'x1' sheet of plastic to a spot on the floor. When I removed it a couple weeks later there was no evidence of moisture either on the plastic or the slab itself.

I am looking at having finish flooring put in. I am considering linoleum (specifically, marmoleum click tiles). On an early site visit the installer seemed confident that a vapor barrier should be installed on the slab to keep the tiles dry.

Considering the details of this particular slab, is there reason to think the vapor barrier will be completely redundant? If the details are not sufficient, is there further information that can easily be gathered that would point to redundancy (or the opposite)?

1 Answer 1


Insulated slabs usually have vapor barrier underneath. Since you did a test and found no moisture, there should be no problem installing vinyl flooring on it.

  • 1
    I agree, I usually test a larger area but if damp it will show in 24 hours. I find the best time to test is in winter as you could get a negative in summer and have a positive or damp floor in winter. With that said I have not seen an insulated slab that was wet.+
    – Ed Beal
    Commented Jul 24, 2019 at 15:28

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