Cement Board

Cement board is a durable, water-resistant building material made from cement and reinforcing fibers, used primarily as a strong, stable backing (backerboard) for tile in wet areas like showers, kitchens, and floors, but also for exterior siding and countertops, resisting moisture, mold, and rot where drywall would fail. It provides excellent tile adhesion and impact resistance, though it's heavy and requires special tools for cutting.