How to Install Cement Board Behind Tub and Shower Enclosures

1. Check to make sure the wall frames are plumb. This will ensure that the cement board is plumb and that the ceramic tile or other surface finish will install correctly.
2. If the tub or shower is on an exterior wall, make sure that any piping or wiring penetrations through the walls behind the tub and enclosure are air sealed and that the wall cavities are insulated before installing cement board or equivalent. See Walls Behind Showers and Tubs for air sealing and insulating guidance.
3. Measure the area for the tub or shower surround.
4. Trim the cement board to fit the measured space. Use a circular saw fitted with an abrasive blade or a hand tool specific to the job and fitted with a carbide tip. Apply a fluid-applied waterproofing to the board including the edges.
5. If the tub or shower is on an exterior wall and the cement board will serve as an air barrier over the insulation, apply a thick bead of caulk to the surface of the exposed studs, wood blocking, and tom and bottom plates. Nail or screw the thin-profile air barrier material to the studs.
6. Tape and mud any seams per manufacturer’s specifications.

Selected from: https://basc.pnnl.gov/resource-guides/cement-board-installed-behind-tile-and-panel-tub-and-shower-enclosures#quicktabs-guides=1