What is Cement Board?

Cement boards are sheets made of cement and fibers containing cellulose. Boards are typically 4 ft by 8 ft in dimension and vary between ¼ and ½ inch in thickness. The primary purpose of cement boards is to serve as backing for tile and is superior to paper-covered gypsum at this task because of its resistance to water – as tile is typically used in areas prone to water exposure, it is important to have a backing that will not develop mold and mildew or disintegrate after prolonged exposure to moisture. This board is heavy and usually requires two people to lift and move. Only a carbide-tipped blade can cut a board. This can produce a lot of dust and is best done in a well-ventilated workshop area.

Where is Cement Board Used?

Cement board is used anywhere tile is installed to add strength to the supporting structure. Cement board may be applied to an existing wood floor to make way for new tile, on top of cabinets to create countertops, or installed horizontally on a wall to create a backsplash or provide a substrate for the application of plasters such as stucco. It can be used in exteriors or interiors and can be attached to both wood and steel studs.

How to Install Cement Board

Cement board installation is very similar to that of drywall. It is important to first install a vapor barrier to the surface to which the cement board will be attached; although cement board is touted for its quick drying times and resistance to absorbing water, it is wise to protect the studs behind cement board from corrosion or mildew growth. Next, apply a thin layer of adhesive mortar to the surface you wish to install the board on. Then attach the board to the stud, wall, or floor using ring-shank nails or drywall screws. Be sure that the screw or nailhead is indented slightly into the wall for a firm hold. Allow slight gaps – approximately 1/8 inches – between cement boards to account for any expansion due to heat. When installing above a bath, leave at least a ¼ inch gap between the tub and cement board to prevent the wicking of moisture. Once all the boards are nailed to the surface, fill the joints with a silicone-based caulk or taping compound that is water-resistant. You are now ready to install tile to your cement board. Be sure to only apply cement board to areas that will be tiled or plastered. Exposed board can not be disguised with paint!