How to Bed a Shower Base

To "bed a shower base" is to install a bed of mortar directly on top of the sub floor. It is the first step in building a waterproof shower base. This is a job that a handy do-it-yourself homeowner can do, but don't expect to finish the entire shower in a weekend. The mortar used to bed a shower base needs to set for at least 24, and preferably 48, hours before continuing.

Things You'll Need

• Roofing felt
• Wire mesh of the type used to reinforce stucco
• Staple gun
• Shower drain assembly

Instructions

1. Install a "slipsheet." This is a waterproof membrane, usually roofing felt, that is laid across the entire shower base. Cut the roofing felt (also known as tar paper) to the exact size of the shower base and lay it out. Carefully cut away the slipsheet around the edge of the drain.

2. Cut a piece of the type of wire mesh used to reinforce stucco to the exact size of the shower base. Lay the wire mesh on top of the roofing felt and cut away the mesh that falls over the drain, the same way that you cut away the roofing felt.

3. Use a staple gun to attach both the wire mesh and the roofing felt to the plywood base of the shower bed. The wire mesh will help the mortar grab the floor and the roofing felt will help to isolate movement of the wood shower bed to help keep the mortar or tile from cracking.

4. Attach the bottom part of the drain assembly. This is the doughnut-shaped portion of the drain. Fit it evenly over the drain opening and attach it with stainless-steel or brass screws.

5. Mix the mortar, following the manufacturer's instructions. The amount of mortar needed for a shower pan varies with the size of the shower. Follow the recommendations of the manufacturer of the mortar for the quantity of mortar needed to build a shower bed.

6. Lay or "bed" the mortar in the shower base. The idea is to create a slope from the sides of the shower base down to the drain, so that all water drains out. The ideal thickness of a shower base is about 1½ inches at the perimeter and ¾ to 1 inch near the drain. Use a concrete trowel to glob on mortar and then spread it out, building the perimeter slightly thicker than the center.

7. Pack the mortar down using a 1-foot length of scrap 2-by-4 lumber. It is important that the mortar be packed down well, so take a lot of time with this step. Angle the board so that the shower base slopes toward the drain.

8. Scrape the "mud" off the surface of the mortar bed with the side of the concrete trowel. Be careful not to remove the mortar, just the soupy "mud" that rises to the top.

9. Allow the mortar to cure for 24 to 48 hours before continuing with the shower installation.

References

• Read more about how to bed a shower base.