Basement tiling questions

Discussion in 'Ceramic and Stone Q&A' started by Flying J, May 29, 2020.

  1. Flying J

    Flying J New Member

    Pulling up all loose vinyl flooring due to mold growth underneath. Huge mess and a big basement.

    How should I treat moldy concrete slab prior to tiling.

    What is the best Tile to use on a damp concrete slab, Ceramic or Porcelain.

    I read I should use an uncoupling/waterproof membrane under layment but I also read to apply the tile directly to the concrete to allow natural moisture evaporation through grout lines.
  2. If it were me.. Id want to know why I have all the moisture in the slab.
    pour grading around house, downspouts ran away from foundation, etc..

    I would think no membrane in this case but I'm not a tile expert..You'll get some good advise on here though.
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  3. Loose sheet vinyl that was glued down?

    When was it built?

    I suppose we don’t know how much moisture will travel through your slab if no moisture barrier is under slab.

    Few questions at a time for me.
  4. Daris Mulkin

    Daris Mulkin The One and Only Charter Member I Support TFP Senior Member

    One thing to keep in mind. If there are any cracks, even hairline cracks they could crack the tile also. Concrete crack, it is natural, so a membrane may be the thing. I'm not a ceramic person either but have had some training on it and did my daughter bath in her basement and was advised to used the membrane. House built in the 60's.


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  5. Is it loose vinyl asbestos tile with black cutback asbestos adhesive/mastic?

    The moisture movement will bring minerals up through the grout joints if no membrane is used, specifically Schluter Ditra, Ardex Flexbone, or similar uncoupling membrane makers.

    If there’s black mastic, bonding to that is an issue.

    There’s pros and cons, and specific issues that should be addressed for planning prior to choosing a system.
  6. John S

    John S Pro Member

    Ardex flexbone UI 720 is the way to go because it doesn't require adhesion to any substrate and you can tile right over it and with its mesh tape, it can also be a waterproofing substrate. However, it is advised that you get to the root issue of your mold because typically that's indicative of a moisture issue. Once you have done that, remove all mold, scrape and clean your slab, then put the floating flexbone over it. The great thing about this product is if you decide to change out your tile, you can cut it out in sections since nothing will be bound to the concrete slab itself.
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