How to Install a Mortar Bed Shower Drain

If you're building a new shower and not using a pre-fab shower enclosure, you'll need to install a mortar bed shower drain--a giant sloped mass of mortar surrounding the drain pipe. The mortar bed shapes the bed of the shower and creates the slant that's necessary for the water to completely drain. Once you install the mortar bed for the shower drain, you can then install ceramic tile on the shower's floor.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Roofing felt
• Reinforcing wire mesh
• Hammer-type staple gun
• Shower drain assembly rough-in installed in sub floor

1. Ensure that the drain rough-in and the wood sub floor are clean and dry. The shower walls should also be roughed in and covered with waterproof backer board. Place a piece of roofing felt or other waterproof membrane across the entire shower floor. Cut the roofing felt so that the edges come up the shower walls about 4 to 6 inches. Cut out the felt from around the drain.

2. Install a piece of reinforcing wire mesh over the top of the roofing felt. The best reinforcing wire mesh is the kind used to apply stucco. The mesh will help reinforce the mortar bed shower drain, much like reinforcing wire reinforces concrete. Cut it to the exact size of the shower bed and lay it on top of the roofing felt.

3. Attach the reinforcing wire mesh and roofing felt using a staple gun. Apply staples approximately every 4 to 6 inches all over the shower bed.

4. Install the doughnut shaped bottom of the drain assembly. (The top will be attached after the mortar bed and tiles are installed.) Use stainless steel or brass screws to minimize corrosion.

5. Follow the manufacturer's directions when mixing the mortar. The manufacturer will state the amount of mortar needed relative to the size of the mortar bed shower drain area that you are installing.

6. Install the mortar bed shower drain area. The purpose of this is to create a slanted mortar bed from the walls of the shower to the drain area, which will drain out the water. Use a concrete trowel and create a mortar bed that is approximately 1 ½ inches thick near the walls, and tapers down to about ¾ to 1 inch thick near the drain. Begin at the perimeter, placing more mortar there and less near the drain.

7. Use a scrap piece of two-by-four lumber that's about 1 foot long to pack down the mortar. Use the larger side of the board and press down the mortar hard to form a solid mass. Hold the board at an angle so the mortar bed slopes down to the drain.

8. If water or mortar mud rises to the surface while you are packing down the mortar, use the side of the trowel to scoop it up, being careful not to scoop up any of the mortar itself.

9. Let the mortar bed cure for at least 24 hours (up to 48) before beginning the tile installation.

References

• Installing Mortar Bed Shower Drains