Q: We're remodeling our kitchen and want to install a stone-tile floor. Anything we need to know before we begin?
Meghan Fouracer, Ithaca, N.Y.

A: If you're going directly over subfloor, tiles are likely to crack or pop loose unless you take two extra steps. First, stiffen the subfloor by gluing and screwing a second layer of ¾-inch sheathing to the existing layer. Second, install what's called an uncoupling membrane to isolate the rigid stone or ceramic from the subfloor's flexing joints and seasonal movements. Here, we used Ditra (, a dimpled plastic sheet that resembles a thin orange waffle. Although many tilers still slap stone directly onto the subfloor, I won't guarantee any of my jobs without the membrane.

Once the membrane is cemented in place, the tiling proceeds as usual. Be sure to use unmodified thinset, as the latex-modified kind won't harden properly when sandwiched between the tile and the membrane.
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    Tools List

    • utility knife with hook blade
      Utility knife
    • mixing drill
      Corded drill with mixing paddle to mix thinset and grout
    • small plastic bucket
      Buckets for thinset, grout, and rinse water
    • notched trowel
      ¼-inch notched trowel
    • grout float
      Grout float
    • margin trowel
      Margin trowel to spread thinset on back of stone
    • plastic putty knife
      Putty knife
    • sponge
    • Cheesecloth

    Shopping List

    Uncoupling membrane
    Thinset, modified and unmodified
    Muriatic acid
    Slate tiles
    Penetrating stone sealer
    Sanded grout