A.Contributing editor Michael Byrne, a tile-setter and consultant in Los Olivos, Calif., and moderator of JLC Online's tile forum, responds: If the old tub-surround tiles are uncracked and in good shape and you're confident they've been installed over a sound mortar bed or cement backerboard substrate, you can install new tiles directly over the old. But be sure to verify that the faucet valve stems are long enough to accommodate the old escutcheons, and that your client won't mind the slightly diminished ledge around the tub.

You'll need to abrade the surface of the old tile before installing new tile (for proper adhesion, 95 percent of the tiles' surface should be abraded). First, though, thoroughly clean the tile and grout with a tile cleaner containing phosphoric acid to remove soap and other films; rinse with clear water. Then mask off the tub ledge with heavy...

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