How to Build a DIY Shower Pan

Introduction

Building your own custom shower pan may seem intimidating, but with the right materials and techniques, it can be an achievable DIY project. A shower pan is the base or floor of a shower that contains the water and slopes it towards the drain. Constructing one yourself allows you to customize the size, shape, depth, and style to perfectly fit your space. Plus, you can save on labor costs compared to hiring a professional.

This comprehensive guide will walk you through the entire process of how to build a DIY shower pan from start to finish. We’ll cover planning considerations, step-by-step build instructions, tips for waterproofing, choosing materials, common mistakes to avoid, and much more. With the help of this guide, you’ll gain the knowledge and confidence take on this satisfying DIY bathroom project. Let’s get started!

Planning Your Custom Shower Pan

Before you start building, there are some key factors to consider in your planning and design phase:

Choose a Location

Consider existing plumbing and space constraints when deciding on a location. Building around existing plumbing will save on costs.
Pick a bathroom space with adequate ventilation to prevent mold and mildew.
Ensure you have enough space for the rough opening and dimensions you want. Measure carefully!

Select a Shape and Size

Custom showers can be rectangular, neo angle (offset corner), square, or other unique shapes.
Standard sizes range from 32” x 32” to 60” x 42” but can be customized.
Factor in the rough opening size, desired interior space, and user height.

Determine the Threshold Height

Typical shower pan depth is 2” but can vary from 1 1⁄2” to 3”.
A lower threshold makes entry easier. A higher threshold contains more water.
Consider user accessibility needs and preferred look.

Choose a Drain Type and Location

Center drains provide optimal slope. Side drains give a walk-in style.
Pick a drain style: clamping, compression, or screw-down.
Ensure the drain location aligns with the existing plumbing or plan new plumbing.

Select Your materials

Mortar beds are the most robust and resistant option. Pre-slope kits are simpler for DIY.
Waterproofing options include hot mop, sheet membranes, or liquid sealants.
Choose tile, stones, or acrylic surround materials. Consult local codes.

Once you’ve answered these questions, you can start gathering the necessary materials and tools.

Materials and Tools Needed

Constructing a mortar bed shower pan has minimal requirements. Here’s an overview of the basic materials and tools needed:

Materials

Mortar mix or pre-slope shower base kit
Drain assembly with drain pipe (2″ ABS or PVC)
Waterproof liner or membrane (PEX, Chlorinated polyethylene, TPO, sheet vinyl)
Thin-set mortar
Tile, stone, or alternative surround materials
Pipe glue, silicone caulk

Tools

Tape measure
Level
Screwdriver
Pencil
Utility knife
Mixing bucket
Margin trowel
Grout float
Sponge
Tile cutter (if needed)

Specialized tools like a laser level can also be useful but are not essential. Consult local building codes for any specific material or waterproofing requirements.

How to Build the Mortar Bed

With your design plan and materials ready, it’s time to start building the mortar bed—the foundation that gives structure and slope to the shower floor.

Step 1: Construct a Wall Frame

Build 2×4 stud wall frames to the interior dimensions of your planned shower space. This encloses the area.
Ensure the framework is plumb, square, and level using a level, measuring tape, and plumb bob.

Step 2: Add Blocking for Support

Cut 2×4 blocks to fit tightly between the wall studs approximately 1″ above the floor.
Predrill and screw blocks in place on all sides to provide a base for the mortar bed to rest on.

Step 3: Establish Drain Piping

Mark the drain hole location based on your plan.
Cut a 4″ diameter hole through the subfloor for the drain.
Install drain piping per manufacturer instructions. Attach elbow joint and extend to main plumbing.

Step 4: Build the Mortar Base

Mix mortar to a firm, damp consistency in batches.
Starting at the drain, apply 1″- 2″ layer of mortar over the entire shower pan area, encasing the drain.
Slope the mortar down to the drain 1⁄4” per foot. Use a level and straight 2×4 to screed and form pitch.
Allow mortar to fully cure for 72 hours before waterproofing.

The result will be a pre-pitched mortar bed ready for the waterproof liner.

Tips for Applying Waterproof Membrane

Once your mortar bed has cured, the next step is installing a waterproof liner or membrane over the entire base. This critical layer prevents leaks and moisture damage.

Here are some tips for clean, seamless waterproofing:

Thoroughly clean and dry the surface first. Vacuum up any loose material or dirt.
Apply thin-set mortar to the shower pan and 4″ up the walls. This gives the membrane adhesion.
Cut the membrane to the appropriate size. Make relief cuts at corners to allow folding.
Fold it into the drain to create a seal. Apply 100% silicone caulk around drains.
Roll or press the membrane firmly into the thin-set to bond. Avoid creases or bubbles.
Overlap seams by 6 inches and seal with seam tape.
Extend the membrane 4-6 inches up the framing walls and seal edges.

Take care to properly seal all seams, corners, drains, and edges for a watertight liner.

Install Tile or Alternative Surround Materials

Once your shower pan and waterproofing membrane are installed, you’re ready for the final step—adding tile or other decorative surround materials. Here are some tips:

Let thin-set mortar cure fully before applying tile. This prevents sagging.
Mix tile adhesives to a paste-like consistency. Use a notched trowel to evenly spread on the walls.
Cut tile pieces to fit against walls and around niches or shelves using a snap tile cutter.
Apply tiles from the bottom up, pressing firmly into the thin-set. Use spacers between tiles.
Seal all joints between tiles with grout. Smooth with a float for consistent grout lines.
Allow grout to fully cure, then seal tiles with a water-resistant sealer.
If using alternative surrounds like acrylic or fiberglass, carefully measure the area then cut panels to size with a utility knife. Attach with adhesives.
Finally, caulk all seams and joints with a flexible, waterproof silicone.

8 Mistakes to Avoid with DIY Shower Pans

Constructing your own shower pan offers many advantages, but there are also some pitfalls to be aware of. Here are 8 common mistakes to avoid on your DIY shower pan project:

Not adequately sloping to the drain – Failure to slope the mortar bed at least 1⁄4” per foot can lead to standing water.
Uneven or wavy bed – Use screed boards and levels to ensure an even plane with no dips or high spots.
Not fully curing mortar – Allowing the thin-set bed to fully cure over 72 hours prevents cracks or instability.
Poor membrane seals – Ensure all seams, edges, corners, and drains are fully sealed without gaps or bubbles.
Insufficient membrane overlap – Seams should overlap by at least 6 inches and be taped properly.
Applying tile too soon – Let thin-set mortar cure fully over 24-48 hours before applying tile.
Using improper grout – Ensure grout is suitable for wet areas and apply per manufacturer specifications.
Inadequate tile spacing – Use spacers between tiles and don’t force tiles tightly together. Allow minimum 1/8” spacing.

FAQs About Constructing DIY Shower Pans

What is the optimal slope for a shower pan?

The International Residential Code requires a minimum 1⁄4” per foot slope. For optimal drainage, a 1⁄2” slope per foot is recommended.

What thinset mortar should I use?

Use unmodified thinset rated for wet areas. Latex-modified thinset offers stronger adhesion and some waterproofing.

What is the best drain configuration?
Center drains promote the most efficient drainage from all sides. Linear or perimeter drains work well for narrow shower pans.

Can I build a shower pan on a wood subfloor?
Absolutely, you just need to properly waterproof and isolate it from the subfloor with a vapor barrier.

What precautions should I take for an upstairs shower pan?
Ensure a solid floor structure without flex. Add blocking/brackets between joists for stability. Waterproof diligently.

Can I install radiant floor heating under a mortar bed?
Yes, you can embed heating coils in the thinset layer beneath the mortar bed. Keep at least 1” above coils.

Should I use a pre-slope shower base?
Pre-slope kits are easier for beginners. But poured mortar beds are stronger and can be fully customized.

How do I create a curbless shower pan?
Omit the side curbs and extend the waterproofing membrane over the threshold onto the bathroom floor. Slope the entire area to the drain.

Conclusion

Building a custom shower pan requires careful planning, solid construction methods, and attention to detail – especially for waterproofing. But with the right process, tools and patience it can be an achievable and fulfilling DIY bathroom project. Just be sure to follow building codes and safety practices. We hope this comprehensive guide provides all the tips and step-by-step instructions you need to successfully construct your own DIY shower pan. Happy building!