36"×36" Shower Base Installation
Step-by-step installation of a 36×36 inch square shower base, covering mortar bed prep, drain alignment, leveling, and wall flange fastening.
Tools Needed
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Instructions
Verify Framed Opening
Confirm your framed opening measures exactly 36"×36" and is square (measure both diagonals — they should be equal). Verify drain rough-in position matches the base's drain hole.
Prep the Subfloor
Clean the subfloor thoroughly. Check for level and flatness — use a long straightedge to find any high or low spots. Fill low spots with floor leveling compound and sand down high spots.
Dry-Fit & Mark Drain
Set the base in the opening without mortar. Mark the drain center. Check level in all directions and note which corner (if any) needs shimming via mortar depth adjustment.
Install Drain Body
Apply plumber's putty under the drain flange. Insert the drain body through the subfloor. Hand-tighten the drain nut from below, then snug with pliers. Do not fully tighten until the base is set — you may need minor alignment.
Apply Mortar Bed
Spread a 1.5" layer of dry-pack mortar across the base footprint. Build up slightly lower areas to help level the base. Keep mortar away from the drain opening.
Set & Level the Base
Lower the base onto the mortar and press firmly. Use a rubber mallet to tap down any high corners. Check level on all four sides and both diagonals. Work quickly before the mortar begins to set.
Fasten Wall Flanges
Screw or nail the perimeter flanges into studs. This locks the base in position and provides a nailing surface for backer board. Use corrosion-resistant screws.
Test Drain Connection
Plug the drain and fill the base with 2" of water. Wait 15 minutes and check beneath the floor for any leaks. Confirm water holds before proceeding to wall installation.
Cure & Caulk
Let mortar cure 24 hours minimum. After walls are tiled, fill the base-to-wall joint with 100% silicone caulk. This joint must always be caulk, never grout.
