Install backer board by laying a thin-set mortar bed, embedding each sheet, screwing it down every 8 inches, and taping the seams before tiling.
For the full breakdown, see our best Backer Board Screws guide.
Tile failures almost always start beneath the tile, which is why learning how to install backer board the right way is the real project. The board is only half the job — the mortar bed under it, the screw pattern, and the taped seams decide whether the tile cracks or stays put for decades.
The steps below follow current James Hardie and MiTek installation guidance for cement backer board over wood subfloors and on walls around tubs and showers. Drywall and gypsum board are not substitutes, and the work assumes a flat, clean, structurally sound surface underneath.
Prep the Subfloor and Dry-Fit Every Sheet
Cut and dry-fit every sheet before any mortar goes down, and stagger the joints so they never line up with seams in the subfloor or the sheets beside them. Warped or damaged sections get replaced, and a leveling compound fixes low spots before installation starts.
Leave a 1/4-inch gap at walls and a 1/8-inch gap between sheets. Board edges and corners should never touch anything — the gaps are what stop movement and cracks from transferring up into the tile. On walls, stagger the vertical seams between rows.
Install Backer Board: Mortar, Set, Screw, Repeat
Spread polymer-modified thin-set on a wood subfloor, comb it in one direction, and set each sheet into the wet mortar with a sliding motion before fastening anything. The mortar bed provides support, not adhesion — the board is still mechanically fastened, and omitting the bed is the classic setup for cracked tile.
- Comb the thin-set in one direction so the bed is even and fully supports the sheet.
- Set the first sheet into the wet mortar and embed it with a sliding, pressing motion.
- Fasten with corrosion-resistant backer-board screws or nails — every 6 to 8 inches on floors, with perimeter screws driven every 8 inches, and a maximum 8 inches on center on walls.
- Keep floor fasteners 1/2 inch to 2 inches from board edges, wall fasteners 3/8 inch