How do I install a shower pan?

There are three common builds, and the one you pick decides most of the work.

• Prefabricated base. A one-piece base, such as Kohler's enameled cast iron model. It arrives with the slope already built in, so you set it on a level subfloor, connect the drain and seal the edges. Kohler's guide for its cast iron base says to "Construct a level subfloor that will adequately support the shower base." It also says "Do not support the shower base by the rim." Cast iron bases are heavy, and the same guide says to get help lifting.
• Mortar bed with a liner. The traditional tile shower. Oatey describes five layers in a typical build: "the subfloor; the slope base or first mortar bed; the shower pan liner; the final mortar bed; and shower tiling or floor." It is the most flexible build and the easiest to get wrong.
• Pre-sloped pan system. Some manufacturers sell a pre-sloped pan with an integrated drain and a sheet or liquid waterproofing layer on top. Oatey's QuickDrain line and Schluter's shower system are examples. The slope is built in, so there is no mortar to pitch by eye.

Oatey's own troubleshooting article points at the difference. Aside from age and skipped flood tests, it says "most shower failures today are traditional mortar bed installations" and that "newer pre-sloped pans eliminate common human errors in accomplishing the proper 2% pitch." That's a manufacturer that sells both, saying the mortar route has more room for error.

Size matters too. Before you buy anything, check our page on the minimum shower size under code so the pan you pick is legal for the space.

This is the overview for a traditional liner pan, following Oatey's project guide. A prefab base skips the slope and liner steps. Always follow the instructions that come with your specific product, because drain and liner details differ.

1. 1Set the drain base. Fasten the drain flange to the subfloor at the right height for your floor build-up. The drain must match your pipe material, so an ABS drain goes on ABS pipe and a PVC drain on PVC pipe. Use the right solvent cement.
2. 2Build the slope. Pour mortar at a slope of 1/4 inch per foot, falling from the wall framing toward the drain. Oatey's guide puts it as "¼ inch per foot sloped inward from the wall framing to the top of (but not over) the drain base." The slope goes under the liner, so any water that gets past the tile has a path to the drain. This is the layer people rush.
3. 3Cut and fold the liner. Measure the mortar bed, the curb and the height up the wall, then pre-fold the corners instead of cutting them. Oatey warns against felt paper with the liner: "since the petroleum in the felt paper can react with the liner, causing it to crack or become brittle, which can lead to leaks."
4. 4Clamp the liner to the drain. Set the liner over the drain base, cut out the bolt holes, apply a modest bead of silicone, and tighten the clamping ring. Keep the weep holes clear. Oatey says "Take care not to apply mortar or thinset to weep holes in your shower system." Weep holes let water that gets under the tile drain out. Block them and the sub-layers stay soaked.
5. 5Wrap the curb and corners. Use dam corners where the curb meets the wall. Staple only along the top edge of the liner. Oatey suggests staples "only to the top half inch of liner." Any hole lower down is a leak path.
6. 6Flood test. Covered below. Do it before the final mortar bed, backer board and tile.
7. 7Finish. Final mortar bed, waterproof wall board, tile and grout, in the manufacturer's order.

One detail worth knowing: when you attach cement board to the walls and curb, Oatey says not to "use nails or screws lower than four inches above the flood rim or the top of your curb." That keeps fasteners out of the liner's working zone.

A flood test is simple. Plug the drain, fill the pan with water to the curb height or just below it (your product's instructions say which), mark the water line, and wait. If the level drops or the ceiling below gets wet, you have a leak. Fix it and test again.

The waiting time varies by product, and the manufacturers disagree, which is worth knowing. Oatey's project guide says to "let the water sit for at least two hours." Its troubleshooting article says "Oatey recommends a minimum testing time of four hours." Schluter, for its bonded system, says the water is left "for a specified amount of time (24 hours is typical)." The takeaway: longer is safer, and your product's instructions set the minimum.

Two more points. Schluter recommends waiting a minimum of 24 hours after setting its membrane to begin water testing, so the thin-set can set. And Oatey adds "Check with local code jurisdiction for appropriate testing requirements," because your inspector may want a specific test and may want to witness it.

Do this test before tile, not after. Once tile is down, a failed test means tearing out finished work.

Codes vary by city and by edition. The UPC-based text on UpCodes gives you the general shape, and our page on shower pan liner code compares the UPC and IPC side by side. In that text:

• Site-built shower receptors must be watertight and have a flanged drain that makes a watertight joint on the floor.
• The lining runs up the sides not less than 3 inches above the top of the finished dam or threshold.
• Lining materials are "pitched 1/4 inch per foot (20.8 mm/m) to weep holes in the subdrain."
• The same UpCodes text says the receptor is tested for watertightness by "filling with water to the level of the rough threshold."

The exact heights and wording differ between the UPC and the IPC, and your city's adopted edition and amendments are what count. That is one more reason to ask the building department before you start, not after.

Here is the honest sort.

Reasonable DIY: setting a prefab base over a drain that is already in the right place, on a level subfloor, with the rough plumbing done. Careful, patient work, and the flood test is easy.

Think hard before DIY: a mortar and liner pan. Slope, liner folds, clamp ring and weep holes all have to be right, and a mistake stays hidden until it fails. Oatey rates its own liner project as "advanced," at two days or more.

Call a licensed plumber: any time the drain moves, the pipe under the pan needs replacing, the drain has to be cut into a slab, or you are converting a tub to a shower. Phoenix's Work Exempt from Permit sheet says a permit is required "for the relocation of any valves, pipes or fixtures." A new pan over a new drain position is that kind of job. Our page on tub-to-shower conversion plumbing walks through what changes, and what plumbing work needs a permit in Phoenix covers the rest.

If a plumber does the drain and you do the finishing, that's a sensible split. The drain and the test are the parts that inspectors care about, and the tile is the part you can redo.

HQ Plumbing & Air is licensed and insured, and we give upfront pricing and free estimates. If your shower pan job involves a moved drain or a permit, call us before the floor is torn up.