The two faces of backerboard
Recently, a friend and I installed some cement backerboard for the tile in his shower, and we came across a dilemma. The backerboard is smooth on one side and rough on the other, and there were no instructions indicating which side should face out. Is there a proper side to face out for cement backerboard?
Patrick Grieco, Toronto, None
Former associate editor Roe A. Osborn replies: The answer to your question seems to depend on the specific product you’re using (or on whom you ask). According to information in U.S. Gypsum’s Web site (www.usg.com), the smooth side of their Durock product is for mastic, and the rough side is for mortar applications. The textured surface enhances bonding and reduces tile slip.
Jackie Wright of Custom Building Products (www.custombuildingproducts.com), makers of another cement backerboard product called Wonderboard, told me that it makes no difference which side of their product faces out. She added that installing some sheets with the rough side out and some with smooth side out also will not affect the performance of Wonderboard.