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Concrete sealer for laying tile on basement slab

smoke_teff | Posted in General Questions on


As part of an ongoing basement renovation, I am planning to lay tile on the concrete slab. I’ve read that it’s wise to use a concrete sealer between the slab and morter for moisture-proofing purposes–I’ve also read that this sealer should be flexible/elastomeric in order to help prevent cracks in the tile.

I sealed the walls in black liquid rubber foundation sealant and have a few gallons leftover. Would this work? One source said rubber was ideal, but another said a sodium silicate or lithium silicate based sealer was ideal. 

Any opinions/advice?

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  1. Expert Member
  2. smoke_teff | | #2

    Hi Malcolm,

    I assume that link means you're endorsing that product as one that would work in this situation. I can't tell, however, if you're suggesting that the product I mention is inappropriate or wouldn't work for some reason.

    That product can be found here:

    1. Expert Member
      MALCOLM TAYLOR | | #4

      Yes. Redgard is made for exactly what you are doing, and has a great track record. Keith has given you good advice about what you are suggesting as an alternative.

  3. gusfhb | | #3

    I think the problem with your idea is that it is not intended to lay tile on, or be indoors.

    There could be bonding issues.

    Or not

  4. rynoshark | | #5

    We are remodeling our basement, and the old concrete slab (poured in late 1970s) needs to have self-leveling concrete poured during a remodel. Would it make sense for concrete sealer to be used in this case, and if so, on the original concrete slab or the freshly poured self leveling compound? The floor was painted in areas previously, though it has flaked off.

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