A cement board is a combination of cement and reinforcing fibers formed into sheets, 4'*8' (6 to 12 mm) thick that are typically used as a tile backing board. Cement board can be nailed or screwed to wood or steel studs to create a substrate for vertical tile and attached horizontally to plywood for tile floors, kitchen counters and backsplashes. It can be used on the exterior of buildings as a base for exterior plaster (stucco) systems and sometimes as the finish system itself.
As a tile backing board, cement board has better long-term performance than paper-faced gypsum core products because it will not mildew or physically break down in the continued presence of moisture or leaks. Also cement board provides a stronger bond and support with tiles than typical gypsum board. Cement board is not waterproof. It absorbs moisture as well, but it has excellent drying properties. In areas continually exposed to water spray (i.e. showers) a waterproofing material is usually recommended behind the boards (i.e. plastic barrier) or as a trowel-applied product to the face of the boards behind the finish system.
Cement board is hung with corrosion resistant screws or ring-shank nails. Cement board has very little movement under thermal stress, but the boards are usually installed with a slight gap at joints in shower pans, bathtubs, and each other. These joints are then filled with silicone sealant or the manufacturer's taping compounds before applying a finish. The filled joints are taped like conventional gypsum board, but with fiberglass tapes that provide additional water resistance. Combined with a water impermeable finish, cement board is a stable, durable backing board.
CEMENT FIBER BOARD
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