I'm planning on tiling my kitchen floor which is bare concrete. However, I did a water test on the concrete and it's soiled to the point that water beads up on the surface. The floor most likely needs to be treated to ensure a proper bond with the tile, but I cannot seem to find any information on treating concrete indoors, particularly in a small kitchen. My concern is using any powerful acids indoors due to the fumes, pets in the home, and having large amounts of water on the floor to wash it off. I have read about grinding concrete but that would generate a lot of fine dust which I don't want to get into other parts of the house.

What is the safest way to get the concrete clean enough for tiling? For reference I do have large doors leading outside from the kitchen which helps for any ventilation needs.

  • try using dish washing soap on a small area (soap that you add to water in the sink, not soap for a dishwasher) – jsotola Apr 6 '19 at 0:25

I'd go with a decoupling membrane - like ditra. The membrane technically requires the substrate to be clean for bonding as well but the failure is less likely for the whole membrane vs a single tile. If you bond the membrane to the floor using the recommended thinset and then bond the tiles to the membrane the tiles will be held tight. If the membrane bond isn't perfect that shouldn't really matter as it will move as a whole and derive strength from the overall bond and weight of the tile on top of it.

I'd still scrape the concrete with a floor scraper. I don't know if I'd do much more than that.

You could grind but as you mention it can be dusty and expensive.

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  • Funny, I was looking to use ditra when I retile my bathroom. This sounds like a solid solution. Membrane is a good idea since the kitchen is small, water could fall from the sink, etc. More protection for the floor. Thanks! – vixere Apr 6 '19 at 13:27

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