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Saving a Soggy Shower Wall

When water seeps behind a tiled wall in the bath, some delicate surgery can save the day.

soggy shower wall and scraper
Photo by Merle Henkenius
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For all its good looks and glazed durability, ceramic tile is far from invincible around water. Tub or shower surrounds require routine care to keep grout joints waterproof and seams between tile and shower base or tub sealed with caulk. If the tiles are mounted on drywall, the moisture will eventually turn the drywall to a messy mush. But that doesn't mean you'll have to tear all the tiles off the wall and replace them. DAMAGE CONTROL
The first step in the repair is to assess the damage to determine how much of the wall has gotten wet. Leaks typically start along the bottom of the wall where the tile meets the top of the tub or shower pan. Those areas are exposed to the most water, so damage tends to spread quickly. The longer the leak has gone unnoticed, the larger the repair will be. The tiled wall shown on these pages is only a few years old, but water had seeped in through grout joints and ruined the drywall. The damage had spread about 9 in. up the wall, so we had to remove three courses of 4-in.-sq. tile to reach sound drywall. Although the rot was limited to an area approximately 3 ft. wide, we removed a 5-ft.-wide section all the way across the back wall of the tub so we could install a continuous piece of substrate with no vertical seams. To prevent any future leak from causing so much damage, we used cement backerboard instead of water-resistant drywall. Backerboard essentially is 1/2-in.-thick cement covered on both sides by a fiberglass mesh. Because it's completely impervious to moisture, backerboard is the ideal substrate for tile; it is now required by code in many areas for new work if you don't opt for a full mortar (mud) job. A 32x60-in. sheet costs about $15.
For all its good looks and glazed durability, ceramic tile is far from invincible around water. Tub or shower surrounds require routine care to keep grout joints waterproof and seams between tile and shower base or tub sealed with caulk. If the tiles are mounted on drywall, the moisture will eventually turn the drywall to a messy mush. But that doesn't mean you'll have to tear all the tiles off the wall and replace them. DAMAGE CONTROL
The first step in the repair is to assess the damage to determine how much of the wall has gotten wet. Leaks typically start along the bottom of the wall where the tile meets the top of the tub or shower pan. Those areas are exposed to the most water, so damage tends to spread quickly. The longer the leak has gone unnoticed, the larger the repair will be. The tiled wall shown on these pages is only a few years old, but water had seeped in through grout joints and ruined the drywall. The damage had spread about 9 in. up the wall, so we had to remove three courses of 4-in.-sq. tile to reach sound drywall. Although the rot was limited to an area approximately 3 ft. wide, we removed a 5-ft.-wide section all the way across the back wall of the tub so we could install a continuous piece of substrate with no vertical seams. To prevent any future leak from causing so much damage, we used cement backerboard instead of water-resistant drywall. Backerboard essentially is 1/2-in.-thick cement covered on both sides by a fiberglass mesh. Because it's completely impervious to moisture, backerboard is the ideal substrate for tile; it is now required by code in many areas for new work if you don't opt for a full mortar (mud) job. A 32x60-in. sheet costs about $15.
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soggy shower wall
USE A FLAT PRY bar to remove tiles that are firmly stuck to the wall. Don't pry under the corner of a tile or you'll crack it.
Out with the Old
Start by pulling off loose tiles by hand. You'll probably have soggy chunks of drywall fall out, too. When you get to a tile that's firmly adhered, pry it off with a putty knife, wide chisel or flat pry bar (photo 1). Work carefully to keep from scratching or breaking the tiles you remove; finding replacements that match perfectly often is impossible. To remove tiles that won't budge, reach into the wall and use a utility knife to score the drywall from behind. Then pull the tile and small squares of drywall out together. Drop those pieces into a bucket of hot water to separate the gypsum backing from the tiles. Leave some of the old drywall exposed where it will meet the new backerboard. That way, the top row of replaced tiles will bridge the two surfaces, making a stronger joint. You'll probably need to trim the jagged edge of the existing drywall with a drywall saw (photo 2) to create a straight, level line. With the tiles removed and the drywall edge trimmed, slice all remaining caulk from the top edge of the tub or shower (photo 3). Then use a grout saw to scrape the grout from all joints immediately above the repair (photo 4). Also remove the grout from any joints that are cracked or discolored by mildew. The next step is the most tedious: preparing the tiles you removed for reinstallation. It entails scraping off all the old grout and caulk and removing the mastic and drywall paper. Don't sand the mastic—it could contain asbestos. Instead, use a sharp knife to clean around the edges.
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trimming the edge of the gypsum wallboard
TRIM THE BROKEN edge of the existing gypsum wallboard with a drywall saw to create a neat, straight horizontal seam.
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.
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Where To Find It:

 

Where To Find It:

scraping caulk and soap residue from the shower base
USE A SHARP RAZOR knife to scrape off any old, dried caulk and soap residue from the top edge of the bath or shower base.
United States Gypsum (Durock cement backerboard)
125 S. Franklin
Chicago, IL 60606
800/874-4968
www.usg.com
 
 

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