Install Shower Pan or Liner
Install mortar bed shower pan or PVC liner with proper slope for drainage. This critical step prevents water damage and is the foundation of your shower waterproofing system.
Quick Summary
4-8 hours
$200-$800
Medium-Hard
Level, trowel
Before You Start
Critical Pre-Installation Checklist
Choosing Your System
The two main approaches are pre-sloped foam pans and traditional PVC liner with mortar bed. Here's how to choose:
Tools and Materials
For Pre-Sloped Foam Pans
- • Pre-sloped shower pan (sized for your shower)
- • Unmodified thinset mortar
- • Notched trowel (1/4 inch square notch)
- • Level (4-foot recommended)
- • Utility knife
- • Screwdriver for drain assembly
- • Measuring tape
- • Mixing bucket and drill mixer
For PVC Liner Method
- • PVC shower liner (40-mil thickness)
- • Shower drain assembly (two-part)
- • Dry-pack mortar mix or sand/cement
- • Trowels (margin and finishing)
- • Level and slope measuring tool
- • Utility knife or scissors
- • PVC liner adhesive or staples
- • Mixing tools for mortar
Installation: Pre-Sloped Foam Pan
Prepare the Drain Opening
Your plumber should have installed the drain assembly during rough-in. Verify it's level and at the correct height for your pan system. Most foam pans require the drain to be slightly recessed below the subfloor level.
Critical measurement: The top of your drain assembly should be at the exact height specified by the pan manufacturer (typically 1/4 inch to 1/2 inch below the subfloor). Too high and the pan won't sit flat; too low and water won't drain.
Mix and Apply Thinset Mortar
Mix unmodified thinset to a thick peanut butter consistency. Apply a layer to the subfloor where the pan will sit, using a 1/4 inch square-notch trowel. Create full coverage without voids - this bonds the pan and fills any minor irregularities.
Why unmodified thinset? Foam pan manufacturers specify unmodified thinset because it doesn't contain polymers that could react with the foam. Using modified thinset can void your warranty.
Set the Pan
Carefully lower the pan into position, aligning the drain opening with the drain assembly. Press down firmly and evenly to seat the pan in the thinset. Work quickly - you have about 20-30 minutes before the thinset starts to set.
Pro tip: Have a helper guide the drain alignment while you lower the pan. It's nearly impossible to see the drain hole while setting a large pan by yourself.
Level and Secure
Place your level on top of the pan in multiple directions. The pan should be perfectly level (the slope is built into the pan itself). Press down on any high spots. If one side is low, you may need to lift and add more thinset.
- • Check level side-to-side
- • Check level front-to-back
- • Check both diagonals
- • Verify drain is centered in opening
- • Make sure pan sits flat with no wobbling
Install Drain Components
Follow your pan manufacturer's drain installation instructions exactly. Most systems use a bonding flange that sits over the pan's drain opening and integrates with the waterproofing membrane. Install according to specifications.
Each manufacturer has a specific drain system: Schluter uses Kerdi-Drain, Wedi uses Fundo drain, etc. The drain assembly creates a waterproof connection between the pan and the finished tile surface. Don't substitute components from different systems.
Allow to Cure
Let the thinset cure for 24 hours minimum before proceeding. Don't walk on the pan or install backer board during this time. The bond between pan and subfloor must be fully set before any additional weight or stress.
Installation: Traditional PVC Liner
Note: This method is more complex and typically done by professionals. If you're a DIYer, strongly consider a pre-sloped foam pan instead. These instructions are provided for understanding the process.
Create Pre-Slope Layer
Install a thin mortar bed sloped toward the drain. This pre-slope layer goes under the liner and directs any water that gets through to the weep holes in the drain. Mix dry-pack mortar (4 parts sand to 1 part cement, just enough water to hold shape when squeezed).
Install Bottom Drain Flange
Install the lower portion of the two-part drain assembly onto the drain pipe. This creates the base that the liner will clamp to. Ensure it's level and the weep holes are clear.
Cut and Position PVC Liner
Cut the PVC liner to size (must extend up walls at least 3 inches above curb height). Position over the pre-slope, starting at the drain and working outward. Fold corners carefully - don't cut them. Use the manufacturer's corner folding technique.
Corner folds are critical. The goal is waterproof corners without cuts. Search online for "PVC shower liner corner fold" video tutorials for the proper technique.
Clamp Liner to Drain
Cut an X in the liner over the drain opening. Install the top drain flange, clamping the liner between the two flanges with bolts. This creates a watertight seal. Don't over-tighten - you can crack the flange.
Attach Liner to Walls
Secure liner to wall studs using PVC liner adhesive or staples (above the 3-inch mark - staples below this will be submerged). The liner must extend up the wall continuously. No gaps or holes in the liner below the curb height.
Pour Final Mortar Bed
Mix dry-pack mortar and build the final sloped surface on top of the liner. Start from the drain and work outward, creating a consistent 1/4 inch per foot slope. Use a level and slope gauge to verify. This layer should be 1.5 to 2 inches thick at the drain area.
Slope calculation: For a 36-inch shower, you need 3/4 inch of drop (36 ÷ 12 × 0.25 = 0.75). Measure from the drain to the edge in all directions and verify this slope.
Cure Completely
Allow the mortar bed to cure for 24-48 hours before any further work. Keep it damp during curing by misting with water and covering with plastic. Don't walk on it during this time.
Common Mistakes to Avoid
Insufficient slope
Less than 1/4 inch per foot causes water pooling. Measure carefully in all directions. Pre-sloped pans eliminate this problem - another reason they're preferred for DIY.
Using modified thinset with foam pans
Always use unmodified thinset as specified. Modified thinset can damage foam and void warranties. The bag must say "unmodified" or "non-polymer modified."
Cutting corners on PVC liner
Never cut corners on a PVC liner - they'll leak. Learn the proper folding technique or use pre-formed corner pieces. Every cut is a potential leak point.
Skipping the flood test
Always flood test before tiling. Finding leaks after tile installation means demolition. This 24-hour test can save you thousands of dollars and weeks of work.
Mixing drain system components
Don't mix components from different systems. Use the drain, pan, and membrane from the same manufacturer. They're designed to work together. Mixing brands voids warranties.
Frequently Asked Questions
Should I use a pre-sloped foam pan or traditional mortar bed?
For most DIYers, pre-sloped foam pans (Schluter Kerdi, Wedi Fundo, or similar) are the better choice. They're faster to install, virtually foolproof for achieving proper slope, and integrate seamlessly with modern waterproofing systems. Traditional mortar beds cost less ($50-150 vs $200-400 for foam) but require significant skill to create consistent slope and take 2-3 days to cure. If you're hiring a professional, either works. For DIY, spend the extra on a foam pan.
What slope does a shower pan need?
Shower pans must slope 1/4 inch per foot (approximately 2% grade) toward the drain. This means a 3-foot wide shower needs 3/4 inch of drop from the edge to the center drain. Insufficient slope causes water pooling and soap scum buildup. Too much slope makes the floor feel uneven. Pre-sloped foam pans have this engineered in. For mortar beds, use a level and calculate: distance in feet × 0.25 inches = required drop.
Can I install a shower pan directly on a wooden subfloor?
Never install a shower pan directly on wood. You need a proper substrate. For pre-sloped foam pans, set them in a bed of thinset mortar over cement board or directly over properly prepared subfloor per manufacturer specs. For PVC liners, install over a sloped mortar bed that sits on cement board. Some systems allow installation over plywood, but most require cement board or a mud bed first. Check your pan system's installation manual for specific requirements.
How do I know if my shower pan is installed correctly?
A correctly installed shower pan: 1) Has consistent 1/4 inch per foot slope from all directions toward the drain (check with a level), 2) Sits flat with no wobbling or hollow spots, 3) Has all seams and connections properly sealed, 4) Extends up the walls at least 3 inches above the curb height (for liners), 5) Has the drain assembly properly clamped and sealed. Most importantly, it must pass a flood test - fill with 2-3 inches of water and wait 24-48 hours with no leaks.
What's the difference between a shower pan and a shower liner?
A shower liner (PVC membrane) is a waterproof layer installed under a mortar bed - you then tile over the mortar. A shower pan is the finished sloped surface ready for tile installation. Pre-sloped foam pans combine both functions - they're structural and waterproof. Traditional methods use a PVC liner with mortar bed on top. Modern foam pans are easier, faster, and just as reliable. Choose based on budget (liner + mortar = $50-150, foam pan = $200-400) and skill level (foam is much easier).
What's Next?
After your shower pan is installed and cured, the next critical step is applying the waterproof membrane to all wet areas. This membrane ties into your pan system and creates a complete waterproof envelope for your shower.
Don't skip ahead - proper waterproofing is the most important part of a bathroom renovation. Water damage from failed waterproofing costs thousands to repair and requires complete demolition.