Backer board can handle frequent contact with water, making it an effective substrate for tile. Workers install backer board by cutting it to size and attaching it to the wood frame. You must seal the seams between sheets of backer boards, as well as the seams between backer board and nearby drywall. Seal the seam between backer board and drywall with adhesive fiberglass tape if the tile will extend past the seam. Finish the seam using standard drywall finishing techniques if the tile will not extend past the seam, meaning the outer edge of the backer board will be exposed after the tile installation.
- Adhesive fiberglass tape
- Thinset mortar
- Trowel
- Joint compound
- Paper drywall tape
- 6-inch drywall knife
- 12-inch drywall knife
- 150-grit sandpaper
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Instructions
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1
Lay a section of adhesive fiberglass mesh tape over each seam where the backer board meets drywall.
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2
Apply a coat of thinset mortar — using a trowel — to embed each fiberglass tape.
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3
Smooth the thinset mortar until it is flat and free of ridges.
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4
Apply a layer of joint compound across the joint, using a 6-inch drywall knife. Lay paper tape along the joint, wiping it flat with the drywall knife. Immediately apply a thin coat of joint compound over the tape to hide it.
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5
Allow the joint compound to dry, which should take no more than 24 hours.
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6
Apply an additional coat of joint compound over the tape to hide it. Use a 12-inch drywall knife to apply a wide, smooth band of compound, hiding the tape completely. Let this coat dry and sand it smooth with 150-grit sandpaper.