How to Install a Shower in an Attic

Check with your local building department to see if a plumbing or building permit is required. Make a plan of the existing water supply and drainage system, and how the new shower will be connected to it, ensuring that the shower will be properly vented and drained. Most building codes have a maximum distance separation between the drain trap and the vent pipe that must be met. Make note of pipe sizes, fittings, connectors, materials and transitions. Plan the location of the shut-off valve and the access to it.

Shut off the water supply in the house. Install the hot and cold water supply piping, extending them from the existing supply lines up until the location of the new shower. Cut a hole in the subfloor and extend the water supply pipes through. Install shut off valves before turning the water supply back on. Extend the drain pipe from the existing drain to the exact location of the drain for the new shower. Cut an 8-inch by 8-inch hole in the subfloor, then install the P-trap and an extension through the floor. Stuff a rag into the drain pipe until you are ready to make the connection. Install a separate vent for the shower, if required.

Measure and mark out the location of the shower on the floor, placing the floor drain in the middle of the shower base. Build the side walls of the shower alcove out of 2 by 4 lumber at 16 inches on center (14 1/2 inches between the studs), and attach to the existing framing on the attic wall. Nail a 1 by 4 cross brace between the studs at the correct height from the floor as support for the faucet and the shower head. Position the cross braces at the back of the studs to allow sufficient room for the water supply lines and the fixtures. Extend water supply lines past the faucet to the shower head.

Attach water-resistant wallboard to the inside of the alcove with drywall screws. Attach shower base to the floor according to the manufacturer's instructions. Set it in 1-inch thick mortar. Press the base down into the mortar, carefully measuring it with a level and adjusting it as needed. Let the mortar dry for six to eight hours.

Apply ceramic tile to the water-resistant wallboard by first applying a thin layer of mortar. Start tiling from the bottom. Use the level to ensure that the tiles are laid accurately. Place tile spacers in between so that the alignment of the tiles is even. Cut holes in the tile to allow the faucet and the shower head to be installed. When all tiles are laid out with tile spacers in between, apply grout between the tiles and wipe away excess with a cloth. Install the faucet and the shower head last.