How to Hang Sheetrock Over a Shower Valve

Measure the wall where the cement backer board will be hung over the shower valve. Allow a 1/4-inch gap between the bottom of the backer board and the top of the shower base. Leave a 1/8-inch gap between multiple backer board panels, as well as around the sides and along the ceiling.

Use a straight edge and pencil to draw lines on the backer board where it needs to be cut. Score the backer board along the pencil lines five or six times with a utility knife.

Slide a 2-inch-by-4-inch board under the backer board so that the part to be removed is up off the floor. Snap off the excess pieces of backer board by pressing down along the edge. Clean up any rough edges with a wood rasp or the utility knife.

Measure from the adjoining wall to the center of the shower valve and add the 1/8-inch gap. Measure from the top of the shower base to the center of the shower valve and add the 1/4-inch gap. Take these measurements at least twice to make sure they are correct.

Determine which side of the cement backer board will be facing in toward the shower. Hang it with the rough side facing the shower when thin-set mortar will be used and with the smooth side facing the shower for latex mastic. Mark the shower valve location on the cement backer board and check the measurements again.

Drill a hole in the backer board for the shower valve with a carbide-grit hole saw or an old spade bit if the hole needs to have a diameter of 1 1/2 inches or less. Make a circle cutter from a scrap piece of wood and two screws if the hole needs to be larger than 1 1/2 inches. Drill a hole at one end of the scrap wood. Attach it to the backer board with a screw at the center of where the hole needs to be cut. Drive a screw through the scrap wood where the backer board needs to be scored. For a 4-inch hole, drive the screw through the scrap wood 2 inches from the screw holding the wood to the backer board.

Press down on the scrap wood so that the screw digs into the backer board. Move the scrap wood around in a circle several times to score the backer board. Score the backer board the same way on the other side. Remove the scrap wood and pound the hole out with a hammer.

Staple heavy plastic sheeting to the wall studs. Set the backer board on the wall where it will be installed. Place 1/4-inch shims between the shower base and the bottom edge of the backer board. Make sure there is a 1/8-inch gap along the top and sides.

Drive screws through the backer board into the wall studs every 8 inches. Place fiberglass mesh drywall tape over all of the gaps between the backer board panels and between the panels and adjoining walls.

Apply a layer of thin-set mortar to the mesh tape with a putty knife. Use firm pressure on the putty knife to push the mortar into the tape and the gaps below the tape. Make sure the tape is covered uniformly and the mortar is as smooth as possible.