How to Build a Shower Base for a Walk-In Shower in 8 Steps

Mortar and tile products are heavy. Ensure your floor joists and subfloor are up to the job before moving forward. If your new shower requires new wall construction or moving the plumbing, call a local plumber and drywall contractor to complete that before moving forward. When the room is ready, do the following prep work:

1. Remove your tub (if converting a tub to a walk-in shower).

2. Make any necessary subfloor or joist repairs. 

3. Outline your new shower on the floor in pencil. 

4. Remove the drywall to about 6 feet above the subfloor in and near the shower.  

5. At floor level, cut and install 2-by-6 blocking between each exposed stud space. Then, secure the blocks with exterior-grade screws.

The curb defines the shower’s outline and keeps water from immediately escaping the area if the drain clogs. 

• Using exterior-grade screws, affix two-by-four lumber lengths at the shower curb location that you drew out earlier. 

• Stack and secure two more layers of two-by-four boards on top of the first boards.

A shower floor consists of two layers. The subfloor is made of a bed of mortar and creates a slope towards the drain. 

• Glue the two-piece drain into place if you or the plumber haven’t already. 

• Remove the top half of the drain and use a rag to block the drain opening. 

• Lay felt paper or plastic underlayment flat on the subfloor. Cut a hole in the material at the drain location to expose the drain. 

• The first mortar bed should meet the top of the lower drain piece. Calculate a 1/4-inch-per-linear-foot pitch away from the drain. 

• Mark the height of the outside edge of the mortar bed and measure the distance to the existing subfloor.

• Using scrap pieces of lumber, cut several blocks (about one per foot) and place them at the outer edges of the shower to use as screeding blocks. You’ll leave these blocks in place after pouring the bed.  

• Mix the mortar following manufacturer instructions in the 5-gallon pail. 

• Pour the mortar bed and trowel it smooth, using the screed blocks and the top of the installed drain bottom as a guide. Take care to avoid blocking the drain’s weep holes. 

• Allow the bed to cure overnight.

You can purchase a PVC shower pan membrane in almost any size you need at your local home center or hardware store. 

• Lay the membrane flat onto the mortar bed, continuing it up the walls about six inches and covering the entire shower curb.

• With roofing nails, attach only the membrane’s top edge to the wall. Leave the membrane draping over the curb.  

• Fold the corners into themselves and tuck the excess between the corner stud spaces with a plastic taping knife. Use caution not to cut the material. 

• Alternatively, use a wood chisel to create a void to tuck the liner material into at the corners. 

• Carefully cut the liner around the drain to expose it and the connecting bolts. 

• Use silicone caulk to seal the cut edge to the drain piece. 

• Remove the stuffed rag and bolt the top half of the drain to the lower part. 

• Use painter's tape to cover the drain once again.

Installing tile in a wet location requires using a proper substrate. Check your local building code for any additional requirements to the following steps. 

• Staple a plastic sheet, felt paper, or another vapor barrier over the exposed wall studs to meet code. Avoid stapling below the top of the PVC liner.

• Install cement board to code and snug against the top of the mortar subfloor. Avoid installing fasteners below the top of the liner. 

• Conceal the shower curb, fully encasing it with the cement board. You can use fasteners through the liner here. 

• Cover the exposed screw heads at the shower curb with silicone caulk.

• Caulk the gap between the cement board edges and the mortar bed with silicone caulk.

An expanded metal lathe provides extra strength to your shower base. 

• Cut a piece, or several, of expanded metal lathe and lay them over the mortar subfloor.

• Leave the drain and a 1-inch space around it uncovered. 

• The shower curb doesn’t need lathe coverage. 

• You don’t need to secure the lathe with fasteners. The next mortar bed will hold it in place.

The second mortar bed provides a finished surface for tiling. 

• With a pencil and straightedge or chalk line, create a line 1 1/2 inches above the subfloor’s height around the shower’s perimeter.  

• Adjust the drain height to create a 1-inch space between the drain’s top and the bolted-on upper part. 

• Mix another batch of bed mortar.

• Pour, screed, and trowel smooth a second mortar bed using the chalk line and the drain’s height as your guide.

• Allow the bed to cure overnight. 

Your shower base is now ready for your best shower tile ideas:

• Twist the drain left or right until it matches the tile height. You may have to insert needlenose pliers or another tool into the drain to get a grip. 

• Or, you can simply hire a bathroom tile installer near you to do the rest.