Concrete Shower Pan: How to Build One That Lasts a Lifetime

When you want a fully custom, tile-ready shower base in any shape or size, a concrete shower pan is the traditional, bombproof solution. Built correctly with the right slope and waterproofing, a concrete shower pan supports any tile and outlasts prefabricated acrylic bases by decades. Built wrong, it becomes a slow, hidden leak that rots the subfloor. This guide walks through the exact method to get it right.

Part of our Bathroom Remodeling & Flooring guide — explore the full guide →

What a Concrete Shower Pan Is

A concrete or mortar shower pan, sometimes called a mud pan, is a sloped bed of deck mud (a dry-pack sand and cement mixture) poured over a waterproof liner and shaped to drain toward the center. It creates a rigid, custom-sized base you then tile over. Because it’s site-built, it accommodates odd room shapes, curbless entries, and large tile that a molded pan can’t handle.

Two Building Methods

There are two accepted ways to build a mortar shower base, and choosing the right one prevents the most common failure.

• Traditional two-layer method: A pre-slope mud bed, then a PVC or CPE liner, then a second mud bed on top. Water that penetrates the tile drains down to the liner and out through weep holes in a clamping drain.
• Topical membrane method: A single mud bed sloped correctly, then a surface-applied waterproofing membrane like a sheet or liquid system, bonded to a bonding-flange drain.

The traditional method has protected showers for generations but requires a two-part clamping drain and careful weep-hole management. The topical method is faster and is the modern standard for many tile setters. Never build a single mud bed with a liner underneath and no pre-slope; water pools on the flat liner and breeds mold.

The Critical Slope Requirement

Every shower floor must slope toward the drain at a minimum of 1/4 inch per foot, per plumbing code. For a typical drain located 24 to 30 inches from the walls, that means the mud bed is about 1 inch higher at the walls than at the drain. In the two-layer method, the pre-slope under the liner must also pitch at 1/4 inch per foot so any water reaching the liner runs to the weep holes rather than sitting flat.

This is the single most important detail. A flat pre-slope traps water against the liner indefinitely, and that trapped moisture is what causes musty smells and failures years later.

Materials and Tools

Here’s what a typical mud pan build requires:

• Deck mud (sand-topping mix or a dedicated mortar mix, roughly 60 to 80 pounds per 3 sq ft at 1.5 inches)
• Shower drain assembly (clamping drain for the two-layer method, bonding-flange drain for topical)
• Waterproof liner (40-mil PVC or CPE) or a topical membrane system
• Galvanized lath or fiberglass mesh for the top bed if needed
• Wood float, margin trowel, and a level
• Pipe or wood screeds to set your slope

Deck mud should be mixed on the dry side, about the consistency of damp sand that holds a ball when squeezed but crumbles when poked. Too wet and it won’t hold a slope; too dry and it won’t pack.

Step-by-Step Build (Two-Layer Method)

1. Set the drain. Install the clamping drain’s lower flange to the waste line at the correct height for two mud beds plus tile.
2. Pack the pre-slope. Screed a mud bed from 1/4 inch thick at the drain up to the proper height at the walls, maintaining 1/4 inch per foot of slope. Let it cure overnight.
3. Install the liner. Lay the PVC liner over the cured pre-slope, running it up the walls at least 3 inches above the finished curb height. Fold, don’t cut, the corners. Fasten only above the waterline.
4. Clamp the drain. Cut the liner over the drain opening, bolt down the drain’s clamping ring, and leave the weep holes open.
5. Protect the weep holes. Place a few pieces of gravel or a weep-hole protector around the drain so mud doesn’t clog them.
6. Pack the top bed. Screed the second mud bed over the liner, matching the 1/4-inch-per-foot slope, and float it smooth. Let it cure 24 to 48 hours.
7. Tile. Set your tile with thinset once the bed is fully cured.

For the topical method, you build a single sloped bed, let it cure, then apply your waterproofing membrane and bond it to the flanged drain before tiling. Fewer steps, but the membrane work must be flawless.

Testing for Leaks

Before you tile, always flood-test the pan. Plug the drain, fill the pan with water to just below the curb, mark the level, and leave it 24 hours. If the level drops, you have a leak in the liner or drain connection to fix before any tile goes down. Skipping this test is how expensive failures get sealed inside a finished shower.

Cost of a Concrete Shower Pan

Material cost is low; the value is in the labor and skill. Expect:

• DIY materials: $150 to $350 for mud, liner or membrane, and drain
• Professional mud pan install: $600 to $1,500 for the base alone
• Full custom tiled shower: $3,000 to $8,000+ including walls and glass

A mud pan costs more in labor than dropping in an acrylic base, but it’s the only way to get a truly custom size, a curbless entry, or large-format tile on the floor.

Common Mistakes That Cause Failures

The failures I get called to fix almost always trace to a few errors: no pre-slope under the liner, clogged weep holes, a mud mix that was too wet to hold slope, and skipping the flood test. Another is running the liner too low up the walls, so water wicks behind it at the curb. Take the extra day to build the pre-slope, keep the weep holes clear, and flood-test every time.

Mixing Deck Mud Correctly

The mortar mix is where a lot of DIY pans go wrong, so it’s worth getting the ratio right. Deck mud is a dry-pack mixture, typically 4 to 5 parts sand to 1 part Portland cement, with just enough water to hold together. You can buy pre-blended sand-topping mix and add a little more sand and cement, or mix from scratch. The finished consistency should feel like damp beach sand that holds a firm shape when squeezed in your fist but crumbles when you poke it.

If the mix is soupy, it won’t hold the slope and will slump toward the drain, ruining your pitch. If it’s bone dry, it won’t pack together and the bed will be weak and crumbly underfoot. Add water sparingly, a splash at a time, and mix thoroughly. Work in batches you can screed within about 30 to 45 minutes, before the cement begins to set. A properly packed deck mud bed is dense, holds a crisp slope, and cures into a rock-solid base.

Curing and Timeline

Patience during curing prevents cracks and weak spots. After packing each mud bed, keep it undisturbed and let it cure. The pre-slope should sit overnight before you lay the liner, and the top bed needs 24 to 48 hours before you tile. In dry or hot conditions, lightly misting the surface or covering it with plastic slows evaporation and produces a stronger cure, since mortar gains strength through hydration, not just drying out.

A realistic timeline for a mud pan looks like this: day one, set the drain and pack the pre-slope; day two, install and test the liner, then pack the top bed; day three or four, begin tiling once the bed is firm. Rushing any of these stages, especially tiling over a bed that’s still soft, leads to problems that only show up months later. Building the pan over a long weekend, with the flood test in between, is a comfortable pace.

Frequently Asked Questions

How thick should a concrete shower pan be? The top mud bed is typically 1.5 to 2 inches thick at the perimeter, tapering toward the drain to maintain the required slope. The pre-slope bed underneath starts around 1/4 inch at the drain. Combined, expect roughly 2 to 3.5 inches of total build.

How long before I can tile a mortar pan? Give the top mud bed 24 to 48 hours to firm up before setting tile. Tiling over a bed that’s still soft leads to shifting and cracked grout down the line.

Can I build a concrete pan directly on a wood subfloor? Yes. Over a solid, properly deflection-rated wood subfloor, you build the pre-slope, liner, and top bed right on top. Just confirm the floor framing meets the L/360 deflection standard so the rigid tile assembly doesn’t flex and crack.

Is It the Right Choice for You?

Build a concrete shower pan when you need a custom size, a curbless design, or a large-tile floor that a molded base can’t provide, and when you or your installer have the skill to nail the slope and waterproofing. It’s more work than a prefab pan, but done correctly it’s the most durable shower base you can build, easily lasting the life of the bathroom without a single leak.