Cement backer-board or commonly referred to as tile backer-board, is a type of drywall made with cement and fiberglass which gives it long lasting strength. Cement backerboard is primarily used for kitchen backsplashes, bathrooms and ceramic tile showers because this type of drywall will not absorb water. Water absorption from standard gypsum drywall can and oftentimes does result in mushy walls, rotting beams, falling tile and toxic mold because standard drywall or sheetrock is not waterproof. Cement backer-board is also used as a wall base for tile around fireplaces and wood stoves because it is fire resistant.
For a home improvement project, remove old tiles and drywall so you have bare studs showing. Do not hang tile backer-board over existing drywall because you will degrade the strength and integrity of the backer-board by not providing it with an optimal base. Even if you have existing Wonderboard or green board, remove it because the cement backer-board is much more enduring.
Measure your open area and determine how much tile backer-board you will need. Cement board is available in a standard 4' x 8' sections. It can be purchased at hardware stores, lumber yards or home improvement stores such as Home Depot or Lowe's.
Hang a vapor barrier which is a plastic like sheeting to protect wood studs from moisture. Staple the vapor barrier in place with galvanized staples.
Use roofing nails or galvanized screws to fastened the cement backer-board to the wall. Do not use other types of nails or screws because they will rust away from the moisture.
Butt the backer-boards tightly up to each other. Cement backer-board requires a tighter fit than standard drywall because you don't want any openings that water can leak through.
Leave about an 1/8" gap at the bottom of your backer-board and the edge of the tub, bottom of the shower or bottom of the backsplash. Leaving a gap at the bottom of the wall stop water from travelling up the wall and to the beams which is called capillary action.
Use a circular saw to cut the backer-board to fit your open area. Wear goggles and a dust mask because cement backer-board is very, very dusty when it is being cut. Be sure to use a carbide saw blade. You can also cut it with a utility knife that has a carbide blade which becomes a lot of time consuming work.
After your backer-board is hung, use mortar to fill in the seams and gaps especially in corners.
Apply fiberglass mesh tape over the seams.
Apply a very thin coat of mortar over the fiberglass mesh tape.
Allow the mortar to dry and set up before tiling.