A cement board is a combination of cement and reinforcing fibers formed into sheets, of varying thickness that are typically used as a tile backing board. Cement board is usually screwed to wood or steel studs. It can be used on the exterior of buildings as a base for exterior plaster and sometimes as the finish system itself. Cement board adds impact resistance and strength to the wall surface as compared to water resistant gypsum boards. Cement board is also fabricated in thin sheets with polymer modified cements to allow bending for curved surface
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. It absorbs moisture as well, but it has excellent drying properties.