How to Install a Cement Backerboard
Time Required: Over 1 day
For a tile floor that lasts for years without cracking, a cement backerboard is crucial.
Backerboard is a thin layer of concrete with fiberglass mesh on both sides. It is available in a range of sizes, but 3 x 5-foot sheets are most common.
This project guide shows how to properly lay out your backerboard with a chalk line and using mortar to secure and level your floor before installing tile.
Tip: Do not install new tiles over existing tiles or over a wood or plywood floor.
- Plan so the joints in the backerboard won’t line up with the joints in the subfloor.
- With the smooth side of the ¼-inch notched trowel, spread enough mortar for one sheet.
- Ridge the mortar with the notched side of the trowel.
- Leave a ¼-inch gap between the backerboard and the wall and a 1/8-inch gap between the backerboard sheets.
- Position the sheets so you don’t have four corners that meet.
- Drive screws every 6-8 inches once the backerboard is in position.
- Around the perimeter, position the screws no more than 2 inches from the edge, but at least ½ inch in.
- Use the flat side of your notched trowel to smooth the mortar so it extends about 1 ½ inches on each side of the joint.
- The extra mortar makes it easier to bed the fiberglass tape.
- Cut the tape to length with the thin side of your trowel.
- Push the fiberglass tape into the mortar.
- When the tape is embedded, scrape off any excess mortar from both sides.