USG. Durock Next Gen Cement Board’s advanced cement technology reduces the board’s weight by up to 25%, making it the lightest cement board available, according to the maker. Designed as a water-durable and mold-resistant substrate for high-moisture areas in both interior and exterior applications, the board has a rough side for thinset mortar and Portland cement basecoat applications and a smooth side for ceramic tile and mastic applications. Easy to score and snap, the board will not rot, warp, delaminate, or disintegrate, and is noncombustible. 800.874.4968.