48" Shower Base Installation
Full installation guide for a 48-inch shower base, including mortar bed prep, drain rough-in, leveling a larger pan, and securing wall flanges.
Tools Needed
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Instructions
Check Framing & Drain Location
Confirm framed opening is the correct width (48") and depth for your specific base model. Verify the drain rough-in is within the base's acceptable tolerance — typically ±1/2".
Subfloor Preparation
A larger base is more sensitive to subfloor flatness. Use a 4-ft level to check in multiple directions. The entire footprint should be flat within 1/4". Repair any soft or uneven areas.
Dry-Fit the Base
With a helper, set the 48" base into position dry. Check level along both the long and short dimensions. The larger span means any twist or bow in the subfloor is amplified — address it now.
Mark & Install Drain
Mark drain center, remove base, and install the drain body with plumber's putty. Confirm the drain height — the top of the drain flange should be flush with the top of the mortar bed.
Apply Full Mortar Bed
Mix dry-pack mortar and spread a consistent 1.5–2" layer across the entire footprint. For a 48" base, use a screed board to ensure even distribution. Compact mortar firmly.
Set Base with Helper
A 48" base is heavy and awkward — use a helper. Lower the base straight down onto the mortar. Press and tap with a rubber mallet. Check level immediately in all directions and along both diagonals.
Fasten & Support
Screw all wall flanges into studs. For a 48" base, also check that the center of the base is supported by the mortar — press the center and confirm no flex. Add mortar under any unsupported areas.
Leak Test
Plug drain and fill with 2–3" of water. Wait 20 minutes and inspect below for leaks. The longer base has more joint surface area — check all four sides.
Silicone Caulk Perimeter
After wall installation, apply matching silicone caulk at all base-to-wall joints. Tape both sides of the joint with painter's tape, apply caulk, smooth, and remove tape immediately for a clean line.
