Tile is not waterproof. Grout is not waterproof. Silicone is not waterproof for long. A tiled shower sheds most of the water that hits it and lets the rest through, and that’s fine as long as something behind the tile catches it and carries it to the drain. In most Lower Mainland homes built before the mid 2000s, nothing does. The shower worked for fifteen years on luck, and then the subfloor went soft.
This is what we find when we open a wall, and what we build in its place.
What we usually find
Three assemblies, roughly by era.
Homes from the 1950s through the 80s have a mortar-bed shower. The floor is a thick bed of sand and cement over a tar paper or vinyl liner, and the walls are tile on a cement scratch coat over metal lath, or later on cement board. The mortar bed is strong and it drains reasonably, but the liner only covers the floor and the first few inches of wall. Everything above that relies on the tile and grout. Thirty years later the grout has cracked, the water has been going into the wall, and the framing behind the shower head is dark.
Homes from the 90s and 2000s have the fast version: greenboard or plain drywall behind the wall tile, a fibreglass or acrylic pan on the floor, and a bead of caulking where the two meet. Greenboard is paper-faced gypsum that resists moisture a little better than regular drywall. It is not a waterproofing layer. When the caulk joint at the pan fails, and it always does, water runs behind the tile and the gypsum turns to paste.
Newer homes sometimes have a proper membrane. Sometimes they have a paint-on liquid used at half the required thickness, or a sheet membrane with unsealed corners. The product on the label doesn’t tell you how it was installed.
What has to be there
A shower needs a continuous waterproof layer directly behind the tile, on every surface that gets wet, connected to the drain in a way that water can’t get around. That’s the whole principle. We build it as a Schluter KERDI system because it’s what we’re certified in and because it does each part of the job well:
- Walls: a sheet membrane bonded to cement board or directly to drywall, with every seam overlapped and sealed. Water that gets through the grout hits the membrane and runs down.
- Floor: a pre-sloped foam pan or a mortar bed pitched to the drain, with the membrane bonded on top, so the water running down the walls lands on a sloped waterproof surface and heads for the drain.
- Drain: a bonded flange drain that the membrane seals directly to. This is the part that fails in most other systems. A clamping drain that relies on a rubber gasket under a mortar bed is a leak waiting for a decade to pass.
- Corners, curb, niche, bench, pipe penetrations: every one is a place where the membrane has to turn, and every one gets a preformed corner or a sealed patch. The niche is a box inside the wall that’s waterproofed like a small shower. The bench is part of the pan.
Then we plug the drain, fill the pan, and leave it. If the water level holds, the shower is waterproof before a single tile is set. If it doesn’t, we find out now instead of finding out from your downstairs neighbour.
Why the tile still matters
Once the assembly is right, the tile does its job better too. Large-format porcelain on a flat, bonded substrate has fewer joints for water to find. Grout stays intact longer when the substrate doesn’t move. Silicone at the changes of plane, where the wall meets the floor and the walls meet each other, flexes with the house instead of cracking like grout does. Mitred corners and slab walls, the custom tile work we do most, only hold their lines because the surface behind them is true. See shower tile installation for how the two halves come together.
How to tell yours is failing
You don’t need to open the wall. Look for these:
- A soft spot in the bathroom floor near the shower or the toilet.
- Grout that’s cracked or missing along the bottom course, or a caulk line that’s pulled away from the pan.
- Tile that sounds hollow when you tap it, or a wall that flexes when you push it.
- Staining on the ceiling below, or in a condo, a note from the strata.
- A musty smell that doesn’t go away with cleaning.
Any one of those means water is somewhere it shouldn’t be. Two means the assembly has failed and the question is how far it’s spread. We see it constantly in older homes in North Vancouver, where the rain makes everything worse, and in the 1990s bathrooms across Coquitlam and the rest of the suburbs.
Repair or rebuild
People ask whether the shower can be patched. Regrouting and recaulking buys time if the assembly underneath is sound and the problem really is just the surface. If water has been getting behind the tile, no amount of surface work fixes it, because the wet is already in the wall. The honest fix is to take the shower back to the framing, replace what’s soft, and rebuild it as a system. It’s more expensive than a patch and much less expensive than doing it a second time.
The question to ask any installer
“What’s your waterproofing, and do you test it before tile?” If the answer is a product name and yes, you’re in good hands. If the answer is about the tile, the grout, or a sealer, keep looking. A shower is a waterproofing project with a tile finish, and the finish is the easy part.
If your shower is showing any of the signs above, request a quote and send a photo. We’ll tell you what’s probably behind the wall before we open it.