DEXcell® Cement Roof Board is a high-performance roof board for use in low-slope roofing systems. It enhances the roofing system's durability when used as a coverboard in adhered or mechanically attached systems. DEXcell® Cement Roof Board is a fire barrier and thermal barrier manufactured of Portland cement, lightweight aggregate, and glass mesh that provides a tough, durable surface that can withstand prolonged exposure to moisture.