How to Repair Water-Damaged Shower Walls

Shower head with wet tiles
Maciej Toporowicz/Getty Images

Moisture that seeps behind wall tile quickly ruins drywall backing and can lead to mold, rot, and even subfloor and ceiling leaks. But typically only part of a shower wall is affected, and usually, it's near the shower base. If the problem is localized—and you get to it early enough—you can minimize the repair work by removing the tiles in the affected area, cutting out the damaged drywall, and replacing the drywall with new cement board before reinstalling the original tiles.

Tools and Supplies You Will Need

  • Putty knife
  • Flat pry bar
  • Utility knife
  • Bucket
  • Drywall saw
  • Razor scraper
  • Cement board
  • Cement board screws
  • Cement board joint tape
  • Thinset tile adhesive
  • 6-inch drywall knife
  • Notched trowel
  • Grout and grouting tools
  • 100 percent silicone caulk

Assess the Damage

Locate the source of the water intrusion. Many leaks begin at the bottom of the shower wall, where the tile meets the top of the shower pan or floor. Begin your assessment of the shower here. Moldy, discolored grout, loose tiles, and peeling caulk are signs that moisture could be getting through the tile to the area behind your shower wall.

Remove the Tiles

Remove the tiles in the affected area. You may be able to remove many of the tiles by hand. Otherwise, use a putty knife or a small flat pry bar to pry up stuck tiles. If necessary, scrape out the old grout with a utility knife or grout saw to expose the tile edges. Be careful not to pry at tile corners, which easily cracks the tile. Matching existing tiles can be very difficult (if not impossible), so take care not to break or chip tiles as you remove them. Place any tiles with drywall residue in a bucket of warm water to break down the drywall for easier removal.

Cut Out the Drywall

Break off any water-damaged drywall by hand. Once the saturated drywall is gone, cut a line across the intact drywall, half of a tile height below the remaining tile, using a drywall saw or a utility knife. This will give you a fresh starting point to install new drywall. Remove the drywall and all fasteners in the damaged area. Inspect the exposed studs for moisture, mold, and rot. If any wood is wet and/or moldy but not rotted, you can scrub the mold with a bleach solution, and let the studs dry completely. However, all rotted wood must be replaced. Also, replace any wet or moldy insulation after the wall has dried out. Scrape off all old caulk from the shower pan or floor, using a razor scraper.

Clean up the Old Tiles

Scrape the removed tiles with a putty knife or an old wood chisel to remove drywall residue and old adhesive. If the adhesive is mastic (non-cement-based), you can soak the tiles in boiling water for a few minutes to soften the adhesive before scraping. Wear gloves to protect your hands from the hot tiles.

Install Cement Board

Cut cement board to fit the wall cutout, allowing for a 1/8-inch gap below the drywall. Fasten the cement board to the studs with cement board screws, leaving a 1/8-inch gap between the cement board and the drywall. The cement board should be the same thickness as the drywall to ensure that the tile will lie flat across the joint.

Tape and Mud the Joint

Apply self-adhesive mesh cement board joint tape (do not use standard drywall mesh tape) to the drywall-cement board joint. Mix thinset adhesive, following the manufacturer's directions. Fill the gap and cover the tape with thinset, using a 6-inch drywall knife. Make sure the thinset is flat and smooth so the tile will lie flat. Let the thinset dry completely.

Install the Tile

Mix more thinset and apply it to the wall with a notched trowel. Set the salvaged tiles into the thinset, as with a standard tile installation, aligning the grout joints with the existing tile. Let the thinset cure, as directed, then grout the tile with a grout that matches the original tile. Do not grout between the bottom row of tiles and the shower pan or floor. Let the grout cure as directed.

Caulk the Tile Joint

Seal the gap between the tile and the shower pan or floor with a continuous bead of 100-percent silicone caulk. This caulk joint is critical to keeping water out of the shower wall, so it is important to use high-quality caulk and to ensure a complete seal. Do not use standard latex/acrylic caulk, even if it is labeled "tub and tile." Pure silicone caulk is much more durable than latex/acrylic formulas.