How to Install a Shower Pan: Step-by-Step Guide

A shower pan is the waterproofed base layer beneath your tile floor. It consists of a sloped mortar bed, a waterproof membrane (the liner), a second mortar topping bed, and a clamping or bonding drain assembly. When installed correctly, the system directs any water that penetrates grout joints back through the drain rather than into the subfloor. Get it wrong and you risk mold, rot, and thousands of dollars in remediation.

This guide walks you through every phase in sequence: rough-in measurements, mortar mixing ratios, liner lapping, drain bolt torque, and the 24-hour flood test you should never skip. Whether you are a dedicated DIYer or a contractor brushing up on best practices, the steps below represent current industry standards as reflected in the Tile Council of North America (TCNA) Handbook and International Residential Code (IRC) Chapter 24.

For more on the fixtures that go above the pan, see our guide to the best flushing toilets and our bathroom exhaust fan installation guide. If you are retiling an existing shower, our accessible bathroom remodel guide covers ADA clearance requirements you should plan for before breaking ground.

What is a shower pan and how does it differ from a shower base?

The traditional site-built shower pan is the dominant method in tile shower construction because it accommodates any footprint, supports heavy natural stone, and allows the drain to be positioned anywhere in the floor plan. It is also the method required by most tile manufacturers when specifying their products for wet areas.

Prefabricated bases are faster to install (1 to 2 hours vs. 2 to 3 days for a mortar pan), but they come in fixed sizes, limit tile choices to those light enough not to crack the acrylic, and tend to flex underfoot over time. If your shower is a standard 36-inch by 36-inch or 32-inch by 32-inch configuration and you are not tiling the floor, a prefab base is a practical choice. For anything custom, plan on a mortar pan.

What tools and materials do you need to install a shower pan?

Materials checklist

• Portland cement type I/II (one 47-lb bag per 10-12 sq ft of floor area)
• Clean sand (plaster or masonry sand, washed, no organic material) at a 3:1 sand-to-cement ratio by volume
• 40-mil CPE liner (or PVC liner) sized to extend 6 inches up each wall plus the floor area plus 6-inch overlap at corners
• Two-piece clamping drain (body pre-installed before liner, clamping ring installed after liner)
• Roofing felt (15-lb) for the pre-slope base layer isolation
• Metal lath or backerboard for the curb if framed
• Foam backer rod for liner corners (optional but recommended)
• CPE liner cement / solvent for seaming sections
• Duct tape or liner clamps to hold liner in position during mortar pour
• Tile, thinset, and grout for the finish surface
• Silicone caulk (100% silicone, color-matched) for change-of-plane joints

Tools checklist

• Half-inch drill with paddle mixer attachment
• 5-gallon mortar bucket or mortar tub
• Pointed margin trowel and flat screed board or steel float
• Rubber mallet
• 4-foot level and torpedo level
• Tape measure and chalk line
• Utility knife (new blades -- CPE is thick)
• Spud wrench or adjustable wrench for drain bolts
• Hot-glue gun (to tack liner corners before folding)
• Garden hose for the flood test
• Marking pencil

How do you install a shower pan step by step?

Phase 1 -- Subfloor preparation and drain rough-in

Step 1: Verify the subfloor is solid. Walk the subfloor and mark any squeaky or springy spots. Drive 1.5-inch screws every 6 inches across the entire shower area to eliminate flex. Deflection in the subfloor is the primary cause of cracked tile and liner failure over time.

Step 2: Confirm drain location and rough-in height. The drain body (lower half of the two-piece clamping drain) should be set so the top of the drain weep holes sit approximately 1.5 inches above the finished subfloor. This accounts for the pre-slope mortar bed (3/4 to 1 inch), the liner thickness (about 1/16 inch), and the topping mortar bed (3/4 to 1.25 inches). The final clamping ring surface should end up flush with or just below your finished tile surface.

Step 3: Install the lower drain body. Thread or glue the drain body into the drain pipe. The drain body must be level in both directions. Use a small level and shim with mortar if needed. Do not permanently bond it until the pre-slope mortar is packed around it.

Step 4: Rough frame the curb. A typical shower curb is framed with three 2x4 pieces stacked horizontally, which gives a finished height of approximately 4 to 6 inches after tile. Nail or screw the curb framing to the subfloor and to the wall studs on each side. Wrap the curb framing with 15-lb roofing felt before lining to provide a smooth surface for the liner.

Phase 2 -- Pre-slope mortar bed

Step 5: Lay roofing felt. Staple a layer of 15-lb roofing felt over the entire shower floor area and up the curb. This isolates the pre-slope from the subfloor and protects the wood during the wet mortar pour.

Step 6: Mix dry-pack mortar. Combine Portland cement and clean sand at a 3:1 ratio by volume. Add just enough water so the mix clumps in your hand but releases no water when squeezed. This is the "dry-pack" consistency. One 47-lb bag of Portland and about 150 lbs of sand fills roughly 10 square feet of floor to a 1-inch depth.

Step 7: Establish slope guide marks. Mark the wall at 1/4 inch per foot rise from the drain. For a 36-inch-deep shower, the back wall high point of the pre-slope should be 3/4 inch (3 feet x 1/4 inch/foot) above the drain surface. Snap chalk lines on each wall to guide your screed.

Step 8: Pack and screed the pre-slope. Pack mortar firmly from the drain outward, mounding it slightly higher than the guide marks. Use a straight 2x4 or metal screed rod to drag across the surface, working toward the drain to establish the slope. The pre-slope should be compact with no voids. Let cure 24 to 48 hours before liner installation.

Phase 3 -- Liner installation and drain clamping

Step 9: Cut the CPE liner to size. Measure the floor area and add 6 inches of run-up on each wall. For a 36x36 shower: 36 inches + 6 inches (back) + 6 inches (front past curb) = 48 inches. Add 12 inches for the two side walls. If the shower is larger than standard liner sheet width (typically 60 inches), you will need to seam two pieces using CPE solvent cement -- overlap a minimum of 3 inches and allow the seam to bond for 30 minutes before handling.

Step 10: Form liner corners. Cut a diagonal relief slit from the inside corner up to where the liner begins its wall run. Fold the resulting flaps into a neat corner pleat and bond with CPE cement. Press firmly and hold for 60 seconds. Optionally, use a foam backer rod behind the corner to create a coved profile that eliminates the 90-degree stress point.

Step 11: Set the liner over the pre-slope. Lower the liner into position, working it into each corner without stretching. The liner must sit flat on the pre-slope -- no bridging across the drain area. Center the liner over the drain body hole.

Step 12: Make the drain cutout. Mark the drain bolt circle on the liner by pressing down from above to feel the bolt hole positions. Use a utility knife to cut an X or circular hole exactly at the drain pipe opening -- cut only the pipe opening, not the bolt ring area. The liner must cover the entire clamping flange.

Step 13: Install the clamping ring. Thread the bolts up through the clamping ring from below (or follow your specific drain manufacturer's sequence). Set the clamping ring on top of the liner, aligning bolts with the holes in the drain body. Tighten bolts in a star pattern (like lug nuts) to compress the liner evenly between the two metal surfaces. Tighten to snug -- do not over-torque or you will deform the liner. Most manufacturers spec 20 to 30 in-lbs.

Step 14: Fasten liner to walls. Use roofing nails or staples to tack the liner to the wall studs, staying above the finished flood line. The bottom 2 inches of the liner must be free and unattached to allow expansion. Do not nail through the liner below the curb height.

Phase 4 -- Flood test

Step 15: Plug the drain and fill. Insert a test plug (an expandable rubber stopper) into the drain opening above the clamping ring. Fill the shower floor with water to a depth of 2 inches -- just below the top of the curb. Mark the water level with a pencil or painter's tape.

Step 16: Wait 24 hours and inspect. Check the water level after 24 hours. Any drop of more than 1/8 inch indicates a leak. Also inspect the ceiling below the shower (if applicable) and the surrounding subfloor for moisture. A small amount of evaporation is normal; actual water loss is not.

Step 17: Find and fix leaks before continuing. Common leak points are the drain clamping ring (re-tighten or re-seat), liner corner seams (re-bond with CPE cement), and staple holes above the curb that are below water level (seal with CPE patch and cement). Re-test after any repair.

Phase 5 -- Topping mortar bed

Step 18: Install the drain strainer or extension. Once the flood test passes, remove the test plug. If your drain has a weep hole guard (a perforated cover that sits over the weep holes to keep mortar out while allowing water drainage), install it now. Some systems use gravel or pea stone around the weep holes instead.

Step 19: Pack the topping mortar. Mix a fresh batch of 3:1 dry-pack mortar. Pack it over the liner at the same 1/4-inch-per-foot slope as the pre-slope, working from the walls toward the drain. The topping bed should be a minimum of 3/4 inch thick at the drain and thinner walls are acceptable but not less than 1/2 inch. Screed firmly so the mortar contacts the liner uniformly.

Step 20: Let cure before tiling. Allow the topping mortar to cure a minimum of 24 hours (48 hours preferred) before setting tile. The surface should be hard and sound when tapped. Walking on uncured mortar can shift the slope.

Phase 6 -- Tile installation

Step 21: Apply thinset and set tile. Use a floor-rated thinset mortar (ANSI A118.4 or A118.11 for large-format tile). Use a notched trowel sized for your tile (typically 1/4 x 3/8 inch for 4x4 to 12x12 tile; 1/2 x 1/2 inch for large format). Back-butter large tiles for full coverage. Work outward from the drain.

Step 22: Maintain slope and grout joints. Tile spacers are critical at the drain -- many clamping drains include adjustable height strainer plates. Set the strainer ring height to be flush with or 1/16 inch below finished tile surface. Use wedge leveling clips if setting large-format tile to prevent lippage.

Step 23: Grout and seal change-of-plane joints. After thinset cures (24 hours minimum), grout field joints. At every change of plane -- floor to wall, wall corners, tile to curb top -- leave a 1/8-inch joint and fill with 100% silicone caulk color-matched to grout. Do not grout these movement joints. This is required by TCNA EJ171 and prevents cracking as the structure moves seasonally.

Step 24: Seal grout (if using sanded or cement grout). Apply a penetrating grout sealer 72 hours after grouting. Reseal annually in high-use showers.

How long does it take to install a shower pan?

Realistic timeline breakdown

Foam pan systems (Schluter Kerdi-Shower, Wedi) compress the timeline to 2 to 3 days by eliminating the dual mortar bed requirement and the mandatory 24-hour cure between layers. However, these systems have a higher material cost and require compatible waterproofing membranes and tile thinset that bond to foam substrates.

What are the most common shower pan installation mistakes?

Detailed mistake analysis

Skipping or rushing the pre-slope: This is by far the most common failure point. Without a pre-slope, water sits under the topping mortar on a flat liner surface. The water eventually wicks into the mortar bed and breeds mold or rots the subfloor. The symptoms -- a musty smell or springy floor -- typically appear 3 to 7 years after installation, at which point full demolition and rebuild is required.

Using 20-mil liner instead of 40-mil: Twenty-mil CPE liner is available at some tile supply houses but is not rated for shower pan applications under most liner manufacturers' specs. Forty-mil is the minimum; 60-mil is preferred under heavy natural stone or in commercial applications.

Nailing through the liner below flood line: Staples and roofing nails used to tack the liner to studs must stay above the finished water line (above the top of the curb). A single nail through the liner below water level creates a slow leak that bypasses the drain entirely.

Grout at all wall-floor joints: Sanded grout at inside corners cracks when the structure moves even slightly. The crack admits water behind the tile. TCNA EJ171 requires a soft joint (silicone caulk) at all changes of plane in wet areas.

Installing tile before flood test passes: Once tile and thinset are in place, you cannot inspect or repair the liner without full demolition. The flood test before tile is a mandatory hold point, not an optional step.

Which drain brands and systems work best for shower pan installation?

For a traditional CPE liner pan, any two-piece PVC or ABS clamping drain rated for the pipe size at your rough-in location will work. The critical specs to verify are: clamping flange diameter (must be larger than your liner hole cutout), bolt circle diameter (must match the drain body), and weep hole count (minimum 3, with 1/8-inch openings).

Foam system drains use a different bonding method -- the foam pan substrate is glued to a bonding flange and sealed with the same sheet or liquid membrane used on the floor and walls. These systems are faster but require strict brand compatibility. Mixing a Schluter drain body with a Wedi substrate, for example, can void both warranties and create adhesion failures at the joint.

If you are also planning to update the toilet or other bathroom fixtures during this project, brands like TOTO, Kohler, American Standard, Woodbridge, Swiss Madison, and Gerber all offer drain accessories and complementary bathroom hardware. TOTO's Tornado Flush technology and American Standard's VorMax are worth considering for the toilet portion of a full bathroom renovation.

For more on choosing bathroom fixtures, see our bathroom fixture buying guide and our comparison of American Standard vs Kohler reliability.

Permits, code requirements, and inspections

Most jurisdictions require a building permit for shower pan installation, particularly if the drain pipe is being moved or the project involves structural modifications to the floor or walls. IRC Section 417.5 governs shower liner and pan requirements and mandates the flood test before any tile or mortar is installed over the liner.

Pull the permit if required in your jurisdiction. Permit fees typically run $50 to $150. The benefit is that a rough inspection confirms the drain rough-in is at the right height and the liner is properly installed before you tile -- errors caught at rough inspection cost an afternoon to fix; errors found years later cost thousands.

If your shower adjoins a bedroom wall in an older home, verify the vapor barrier requirements in your local code. Some jurisdictions require a vapor barrier behind the cement board on the shower walls in addition to the liner on the floor. EPA WaterSense considerations also apply if you are selecting a new showerhead as part of the project -- WaterSense-certified showerheads use no more than 2.0 GPM vs. the 2.5 GPM national standard, saving roughly 2,900 gallons per year per household according to EPA data.

• EPA WaterSense, epa.gov/watersense
• MaP flush testing, map-testing.com
• Tile Council of North America (TCNA) Handbook, tcnatile.com -- Method B414, EJ171
• International Residential Code (IRC) Chapter 24 -- Section 417.5, tile shower liners
• Oatey Co., product installation guides, oatey.com
• Schluter Systems, KERDI-SHOWER installation guide, schluter.com
• Manufacturer published specifications

Related guides

• Accessible bathroom remodel: ADA requirements and design tips
• How to install a bathroom exhaust fan
• Best bathroom floor materials: tile, vinyl, and stone compared
• ADA compliant toilet guide
• Best flushing toilets: MaP-tested rankings for 2026