Although water resistant sheetrock is an acceptable covering for walls exposed to a limited amount of moisture (above a kitchen sink and bathroom ceilings and walls), it should not be used in areas that will be subjected to heavy wetting, as it will eventually disintegrate. These areas include but are not limited to shower stall walls and tub surrounds and enclosures. Instead, a cement based, or specialized gypsum-core board should be used as the backing on which wall and floor tile is installed.
Much like sheetrock replaced the labor intensive lathe and plaster wall finish, tile backer board has rendered the old fashioned cement and metal-lathe tile backing obsolete. While more difficult to cut, tile backer board can be installed in the same manner as drywall; only a more aggressive screw pattern should be employed (to prevent movement which causes tiles to crack), and special water resistant screws used. Typically, 1/2-inch backer board is used behind wall tile, and 1/4-inch backer board is used as the substrate for floor tile.
At 753, there is a half bath, and two full bathrooms on each floor (guest and master bath). Our designers called for wall and floor tile to be used throughout both guest and master bathrooms, so it was necessary to install backer board on the bathroom walls and floors. For this particular remodeling project, we opted to use the Durock brand cement board in all four bathrooms, which we glued and screwed to the wall framing and plywood subfloor. Since both master baths were designed with custom shower pans (poured from concrete), we were not required to lay backer board on the floor of the actual shower. (Pouring and waterproofing the shower pan will be covered in a future post.) After all the Durrock was glued and screwed, we applied the finishing touch by sealing the joints with fiberglass tape and thin-set mortar.