WALL & FLOOR
Cement backerboard is a strong, highly water resistant base for ceramic, porcelain & natural stone tile. Even in standing water, cement backerboard will not swell, decompose, decay, delaminate or deteriorate. It will not expand or contract due to changes in temperature or humidity like other underlayment materials. Because of its unique formulation of concrete and fiberglass, cement backerboard may be used as a sub-surface for tile on walls, floors, tub decks and countertops.
Cement Backerboard can be applied over 3/4” plywood when floor joists are 16” on center. When planning the floor, install the sheets of backerboard with joints staggered from existing sub-floor joints so that the new seams are not laid over the plywood seams. Prior to fastening the backerboard to the plywood, mix PROFLEX Mortar with water to a “mayonnaise consistency” (follow mixing directions on packaging). Trowel-out the PRO-FLEX Mortar to the plywood sub-floor with a Unotch trowel and lay the backerboard into the mortar. (By adhering the cement backerboard to the plywood with PRO-FLEX, you are fusing the two layers together to create a superior bond.)
Fit the cement backerboard closely together. Fasten the backerboard to the plywood sub-floor using 1 1/2” galvanized roofing nails or sheetrock screws spaced 8" on center; avoid floor joist. Nail heads should be flush with the surface. All seams of the cement backerboard must be taped using FIBRA TAPE (fiberglass net tape) and PRO-FLEX Mortar applied with a smooth putty knife. Any cutting of the backerboard can be made easily with a SCORE TOOL. After the cement backerboard is secured firmly into place (nail or screw), and all seams skim-coated with PROFLEX Mortar, allow to dry 24 hours prior to tiling.
Cement Backerboard may be installed over metal or wood studs spaced 16” on center. Exterior walls should be insulated properly prior to installation. For tub surrounds and stand-up showers, leave backerboard 1/4” off the lip of the tub or shower base (DO NOT install backerboard on stand-up shower walls until after the vinyl liner / “bladder” is in place) and fill with 100% Silicone Caulk or PRO-MASTIC in this 1/4” gap. Using galvanized sheetrock screws, secure the backerboard into place. Screw the backerboard to the studs every five inches. Allow an 1/8” gap between all backerboard sheets, sheetrock, and plaster. Using FIBRA TAPE, a smooth putty knife, and PRO-FLEX/PROMASTIC, patch all these 1/8” gaps.
To install cement backerboard on countertops or whirlpool tub decks, follow the same instructions as above: Floor Installation. For more detailed cement backerboard installation instructions, confer with one of our experts at the Tile Shop.