Project Guide

How to Install a Cement Backerboard

1
SNAP A GRID OF CHALK LINES TO MARK THE LOCATION OF BACKERBOARD
chalk lines mark location - Installing Cement Backerboard
  • 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.
2
WHILE THE MORTAR IS STILL WET, PLACE A SHEET OF BACKERBOARD ONTO IT
Place a sheet backerboard - Installing Cement Backerboard
  • 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.
3
SECURE BACKERBOARD WITH SCREWS
Secure backerboard with screws - Installing Cement Backerboard
  • 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.
4
FILL THE JOINTS WITH MORTAR
Fill joints with mortar - Installing Cement Backerboard
  • 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.
5
COVER JOINTS WITH FIBERGLASS TAPE
Cover joints fiberglass tape - Installing Cement Backerboard
  • 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.
6
COVER EACH LENGTH OF TAPE WITH A THIN LAYER OF MORTAR
Cover each length tape - Installing Cement Backerboard
  • Spread the mortar with the flat side of your trowel and feather the edges.
  • Transition from board to board so it is as smooth as possible.