Shower Waterproofing Inspection Checklist: The Twelve Things to See and Photograph Before a Single Tile Goes On

When to show up

Ask the setter, before the job starts, to call you when the waterproofing is done and the flood test is in. Put it in the contract if you have to. The pan and walls are normally done in a day and tested overnight, so you are looking at the morning of day two. Tell him you are coming to take pictures, not to argue; a good setter likes this, because the photographs protect him too. A setter who does not want you there before the tile goes on has told you something.

The twelve things

1. The backer. Cement board, glass-mat gypsum, or foam board (Kerdi-Board, Wedi). Not green board, not purple board, not drywall of any colour. If it is drywall, stop here; this page explains why. Photograph: a wall with the product name visible.
2. The pan slope. 1/4 in. per foot to the drain, in every direction from the walls. On a 36×60 that is 3/4 in. of drop from the long wall and 3/8 in. from the short. Put a level on it; the bubble should sit off-centre toward the drain. A flat spot in a corner is a puddle for life. Photograph: the level on the pan, two directions.
3. The drain. A bonded-flange drain with the membrane lapped onto the flange and no wrinkles, or a clamping-ring drain with the liner clamped and the weep holes clear of mortar. The drain body should be the right height for the tile thickness; a drain set for 3/8 in. tile under a 1/4 in. mosaic sits proud and holds water. Photograph: straight down into the drain.
4. The membrane, everywhere. Continuous over the whole floor, up every wall to at least above the shower head, and across the ceiling if it is a steam shower. No bare backer showing through. Sheet seams overlapped 2 in. and set in thinset, or banded; liquid membrane two full coats with no thin spots where the backer colour shows. Photograph: each wall, full height.
5. The corners. Every inside corner on the floor and every wall-to-wall corner has a preformed corner piece or fabric embedded in liquid. Three planes meeting is where pinholes live. Photograph: each floor corner, close.
6. The curb. Membrane wraps up the inside, over the top and down the outside. No screws through the top. The top slopes toward the shower; set the level on it. A curb that was framed with wood and board must be wrapped completely; a foam curb is already waterproof but its joints are banded. Photograph: along the top of the curb.
7. The niche. Wrapped on all five faces with the band or sheet carried out onto the wall around it, or a preformed niche set in thinset and banded at its perimeter. The sill is sloped out. Photograph: inside the niche.
8. Penetrations. The valve and the shower arm have pipe seals or are collared with membrane; the handheld and the tub spout the same. Grab-bar screws and glass anchors have not happened yet and should go into wall tile with sealant, not the curb. Photograph: the valve.
9. Fasteners. On a foam board system, every screw has a sealing washer and is covered with sealant or a patch. On cement board under liquid, every screw head is coated. Count them on one wall; if half are bare, the wall is a colander. Photograph: a run of screws.
10. The flood test. Water in the pan, drain plugged, level marked with tape, left 24 hours. You want to see the water still at the tape, or arrive while it is in and photograph the tape and the water with your phone’s timestamp, then again the next day. No test, no tile. If the setter says his system does not need one, he is right about the system and wrong about his seams. How the test works.
11. Blocking. Not waterproofing, but your last chance: solid wood behind the backer where the grab bars go, where the glass panel clips to the wall, and where a future bench or shelf might. Ask; if it was done at framing, the setter will know where. Photograph: whatever he points at.
12. The valve depth and the slope outside. The valve’s rough-in has a depth range marked on the plaster guard; the finished tile face must fall within it or the trim will not fit. The bathroom floor just outside the curb should be flat or slope away, not toward. For a curbless shower, the floor outside slopes toward the drain for several feet and that is its own inspection.

What a bad one looks like

Grey cement board with nothing on it and a bucket of thinset ready to go, because “cement board is waterproof”. A pan of mortar with no visible membrane and a two-piece drain with the bolts loose. Liquid membrane the colour of the board in streaks where the roller ran dry. A curb with the backer screwed down through the top, four screws, right where the water runs. Poly stapled behind the board and nothing in front of it, which was the standard in 1988 and is a sponge today. A niche cut into the wall after the membrane went on, with raw board inside. Any one of these is a conversation before the tile, not after.

If something is missing

Say so, that day, in writing, with the photographs. Most of this is fixable in an hour while the walls are open: a corner piece, a band over a seam, a second coat, a sealed screw. The curb and the pan slope are not an hour; they are a redo, and it is cheaper to redo a $900 pan than a $3,800 shower, which is cheaper than a $15,000 bathroom. You are not inspecting against your own taste; you are asking the setter to meet the instructions printed on the pail or the roll he used, and he cannot argue with those. If he does, the contract checklist covers the holdback that keeps the last payment in your hands until the work is right.

Keep the photographs with the house papers. When you sell, a buyer’s inspector can see only tile; your pictures are the only proof that there is a shower under it. On the $3,800 shower, the waterproofing is about $1,300 of the price, and these twelve photographs are the receipt.

Questions people ask

Sources and further reading

• Tile Council of North America: the TCNA Handbook methods for tile over wood, concrete and in showers, and the ANSI lippage and grout standards a tile setter is held to.
• Schluter Systems Canada: the Kerdi shower system and Ditra uncoupling membrane installation handbooks, with the drain, curb and flood-test details.
• Ontario’s Building Code: the official page with the current regulation; stair dimensions, bathroom finishes and floor framing are in Part 9.