Check the Area

Ensure that the subfloor is sound and not loose, warped or damaged. Ensure that it's clean and flat.

Step 1

make necessary cuts on backer board

make necessary cuts on backer board

Make the Necessary Cuts

Use a straightedge to score the material and then snap to break it apart. Make large cuts with a circular saw. You can also use a drill with a masonry bit to make pilot holes – for such cut-outs as circular patterns and then hit it out using a hammer.

Note: Cement backer board can be cut with a carbide tip scoring tool, circular saw with a carbide tip (set saw for thickness of board) or mechanical Snapper Steelhead Shear.

Step 2

Lay the Backer Board

Lay the backer board in a "brickwork" type pattern–meaning that sheets are offset. No four corners should meet at any point. Do not align sheet joints with subfloor joints. In a narrow hallway, the boards can be installed in a line.

Step 3

Apply the Mortar

Using a notched trowel, apply a leveling bed of thinset mortar over the subfloor and embed the backer board sheets into the adhesive. Spread the mortar to about 3/16" thickness. Add more mortar as necessary to fill sunken areas in. Lay the backer board according to the manufacturer's instructions. Many have a nailing pattern that should go face up–with a nailing pattern every 8" on center.

Step 4

fasten backer board to floor

fasten backer board to floor

Attach the Backer Board

Fasten the backer board to the floor using proper nails or screws, as recommended by the manufacturer, every 8" around the perimeter and all supporting the studs. Keep fasteners between 3/8" and 3/4" from sheet edges and 2" in from sheet corners. Make sure that the nail or screw heads are not sticking up above the board surface.

Note: In some cases, you can attach the backer board joints using 2" wide glass fiber mesh cementitious alkali-resistant backer unit reinforcing tape (see product instructions – usually needed for wide areas). The tape will help disperse any movement of the boards and decrease the probability of popping or cracking tiles along the seams.