We will be installing ceramic tile (12" sq.) in the kitchen of our 1947 bungalow. After pulling up the previously laid ceramic tile and 1/4" luan (ugh), we've found a couple more layers.
Below that we've found 1/4" hardboard (nailed down), with what appears to be the original linoleum that has a bit of foam backing laid on top of two layers of plank sub-flooring.
We're wondering what would be best to remove and what to add before laying the the cement board with mortar. We can get the hardboard and linoleum layers off fairly easily, but the linoleum leaves a layer of foam on the sub-floor.
We assume it is not a good idea to attach the cement board directly to the black foam residue on the planking. We are considering removing the linoleum, leaving the foam and screwing down a thin layer of plywood before adding the cement board. Is this a reasonable plan? Is the plywood necessary? Is there a better or easier option?
We were hoping to get this project done this weekend (140 sq. ft), but that now depends on the next steps.
Craig and Kim
You will need a minimum 0f 1/2" of BCX grade plywood screwed into the planking then add a 1/4" cement board set in thinset combed with a 1/4" square notch trowel and anchored with galvanized roofing nails or backerboard screws. Try to get as much of that foam off as possible as that stuff can cause floor movement if it compresses under a heavy weight load. When installing the ply leave a 1/8" gap between sheets and fill this seam with a cheap latex caulk. Keep the edge of the ply off the walls about 1/4" to allow the wood in the walls to move due to seasonal weather changes. After the cement board is installed use a mesh tape to seal the seams and use modified thinset to put one coat on the tape just as you would use spackle to coat the tape on wallboard. Use at least the same size trowel to comb the modified thinset all in a side to side (left to right) direction when setting the tile. Keep a bucket of water and a sponge handy to clean out the grout joints of any oozing thinset as you go.