How to Install a Cement Backer Board Bathtub

Tiling your bathtub surround is a great way to protect the wall from moisture, but the tile alone isn't enough. Some moisture still gets through the grout, and if the wall behind it is plaster or drywall, that moisture can soften the wall and cause the tiles to loosen. Covering the wall in moisture-proof cement backer board will prevent that, and will give you a solid surface to begin tiling.

Things You'll Need

• Electronic studfinder
• Level
• Pencil
• Cement backer board
• Jigsaw
• Carpenter's glue
• Screwgun
• 1 and 1/4-inch galvanized drywall screws
• Mesh drywall tape
• Thin set mortar
• Drywall knife

Instructions

1. Find the studs in the walls around the tub with an electronic studfinder. Use a level and pencil to mark them out vertically on each of the walls.

2. Measure one wall, at the bottom (just above the tub) for the first piece of backer board. If the wall is narrower than the length of a board (generally, 5 feet), then measure the whole wall and cut the board to that size, using a jigsaw. If the wall is longer than a piece, then measure to the stud that's closest to the size of the piece (without being longer), and cut the piece to that size.

3. Apply carpenter's glue over the back of cut backer board. Set the piece lengthwise on the bottom portion of the wall. If it's going to a stud instead of all the way across, make sure the edge runs along the middle of the stud. Shoot in galvanized drywall screws every 8 inches or so along each stud that's behind the board.

4. Repeat the procedure for each board, working your way up the wall. Avoid any four-way intersections between the boards, taking them to different studs between courses. Use your jigsaw to cut holes in the boards to go around plumbing fixtures in the walls as necessary.

5. Press mesh drywall tape along all the seams. Use a drywall knife to spread thinset mortar over the tape. Get it very flat and smooth. Let if set for a day. Tile the wall.

Tips & Warnings

• Wear goggles when you cut the boards.

References

• RD.com: Cement Board Installation