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How to Lay Tile on Hardibacker Board

Kevin McDermott

HardiBacker is a top brand of cement board, which is used as underlayment for hard tiles like ceramic or marble. The boards look like hard, heavy drywall and are almost as easy to cut and install, but once in place they provide the stability of a concrete floor. Proper installation of the HardiBacker board is crucial to the tiling process, because any loose areas, dips or obstructions in the underlayment will cause problems later with the tiles. Start with a clean, dry subfloor or wood floor with no trim and no obstructions.

Lay Tile on Hardibacker Board
  1. Set a sheet of HardiBacker board in one corner of the room. Mark around the border of the board onto the subfloor, with your pencil. Remove the board, spread thinset mortar over the area with a mortar trowel, and set the board back in place.

  2. Screw the board down with galvanized screws (1 1/2 inch) into the board's surface, sinking a screw at each of the dots that are visible across the board's surface. Repeat the process for each of the other HardiBacker boards, laying them in rows with the joints staggered, and cutting them at the ends with a jigsaw as necessary to fit by the perpendicular walls. Cover the whole floor.

  3. Press fiberglass drywall tape over the lengths of the seams between the boards. Spread thinset mortar over the tape with the flat side of the mortar trowel. Smooth out the seams completely. Let the installation dry overnight.

  4. Stretch a chalk snap line across the floor in one direction and snap the line, cutting the room in half. Stretch the string in the perpendicular direction, intersecting the first line in the middle. Square the string to the first line using a carpenter's square, then snap the line, dividing the floor into four squares.

  5. Apply thinset mortar over the intersection of the two lines, using the notched side of the mortar trowel. Set four tiles into place at the intersection, putting spacers between them. Build off the center tiles toward the walls, spreading more mortar, putting spacers between them, and cutting the end tiles by the walls on a tile cutter as needed. Let the tiles set overnight.

  6. Take out the spacers. Spread grout over the floor with a grout float, pressing it into the lines between the tiles and scraping it off the surface. Use a sponge to wipe off the excess grout. Let the grout cure for four or five days before resuming use of the area.