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The Right Backer Board for a Tile Floor

Choose the correct thickness at the start of a job to avoid a major headache later


I installed a ceramic tile floor and used a 1/4-inch backer board. Later
I heard that I should have used 1/2-inch backer board. Now a few tiles are coming loose. Is there a grout and thin-set that sticks and flexes more
than the standard mixes, or should I just load the bottom of the tile with liquid nails?

– Thomas, Mount Holly Springs, Pennsylvania


Tom Silva replies: Yes, there is a flexible product that you can actually mix with the thin-set, but it wouldn't solve your problem. The backer board is too thin. Quarter-inch backer board is used for tiling over an existing solid sub-floor. But if you're stripping a bathroom or a tub area back to the studs, you'll need to apply a 1/2-inch sheet of masonry board, seal all the seams, tape them, and then apply your tile to that. In short, you should have used 1/2-inch. The floor needs to be removed and you should start again.


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