Ceramic Tile Floor Cement Board Installation

If you are installing a ceramic tile floor it is imperative that you consider a ceramic tile floor cement board installation first.  For the most successful ceramic tile floor project a fibrous cement backer board or cement board that is mesh-reinforced needs to be installed first with special backer board screws. The same backer board should be installed for tie wall tile and shower tile.

If the sub-floor is 3/4 inch plywood it is not necessary to attach the backboard to the floor joists. Simply screwing the backer board, cement board, to the plywood sub–floor is adequate. However, screwing the cement board to the floor joist is an acceptable method for sub-floors that are not ¾ inch plywood. Start by locating where the floor joist and snap chalk lines to indicate their location.  Arrange the sheets to avoid four corners meeting in the same place. Leave 1/8 inch between backer board sheets and 1/4 inch between the sheets and the base of the wall.

Installing the cement board: 

1. Sweep the floor until it is free of dirt and debris. Lay down a backer board sheet, measure and mark it top to bottom for the cut, and then subtract 1/4 inch. With a straightedge against the mark, score the line with a cement-backer board knife.

2. Turn the sheet over, hold one side down, and pull the other side up. Place the sheet on its side and score the reverse side along the same line as the first. Snap the sheet back to separate the two pieces. Sand the edge with a tile stone if it is very rough.

3. Screw the backer board to the sub-floor using 1 inch screws. Where there are joists below, drive screws every 6 inches or as specified by the manufacturer, through the backer board into the joist. If the sub-floor is 3/4 inch plywood drive the screw through the backer board into the sub-floor. Drive screws along the edges every 6 inches (or as recommended). Mix thinset mortar and, after sweeping up, apply it to the joints separating the backer board with a trowel.

4. Let dry thoroughly before beginning to install tile.