Saving a Soggy Shower Wall

In With The New
Then loosen the mastic by immersing the tiles for a few minutes in boiling water. Put on thick leather gloves to protect your hands, and use tongs to pick up the hot tiles. Place each tile on a solid surface - drive two screws into the work surface to keep the tiles from slipping - then scrape off the mastic using a stiff-blade putty knife (photo 5).

Measure and mark the cement backerboard to fit into the wall opening. Next, score along the cut line with a utility knife, cutting completely through the fiberglass mesh. Then, snap the board along this line and slice through the mesh on the back side (photo 6).

Install the backerboard smooth-side out. Leave about a 1/8-in. space between the board and the top edge of the bathtub or shower. Then fasten the backerboard to the wall studs using either roofing nails or galvanized screws (photo 7).

Spread a generous coat of mastic over the surface of the backerboard with a notched trowel (photo 8). Then press each tile into place, being careful to maintain uniform joints (photo 9). Wait at least three days for the mastic to cure before grouting. If you grout too soon, gases from the solvents in the mastic will produce tiny pinholes in the new grout, creating a way for water to seep in.

Mix powdered grout with latex additive, and force it into the joints with a rubber trowel. Wipe off excess grout with a damp sponge. After a couple of hours, buff the tile clean with a soft cotton cloth. Finally, fill the gap along the top of the tub or shower with silicone caulk and protect all grout joints with a liquid silicone sealer.