(Also see Substrates)
Cement board is a good choice for most installations of tile and stone on shower walls, tub walls and floors. It is important to install cement board in strict accordance to the cement-board manufacturer’s written instructions.
Floors: Installation instructions for cement board on floors typically include applying cement-based thin-set between the exterior-grade plywood and cement board. The cement board is then screwed into the plywood while the thin-set is fresh/wet. MAPEI recommends the use of MAPEI’s Ultraflex 1, MAPEI’s Keraflex SG or MAPEI’s Ultraflex LHT SG as thin-set under the cement board. If leveling is needed on interior cement-board floors, MAPEI recommends the use of a pourable leveler, such as MAPEI’s Ultraplan 1 Plus, over the cement board. MAPEI’s Primer T should be used to prime the cement board before the use of a pourable leveler.
Walls: Installation instructions to treat corners and seams on cement board that is on walls typically include using a self-adhesive mesh tape and thin-set. MAPEI recommends the use of MAPEI’s Ultraflex 1, MAPEI’s Keraflex SG or MAPEI’s Ultraflex LHT SG in conjunction with mesh tape that is recommended by the cement-board manufacturer.