Some of the most common words on a bathroom tear-out are "well, there it is". Behind a tiled tub surround or shower that has been leaking slowly for years, we often find dark staining on the drywall, soft or crumbling board, swollen framing and mould. The tile on the outside can look almost fine.
Why it happens
Grout and tile are not waterproof. Water gets through them every day. In a well-built shower, a continuous waterproof layer behind the tile stops that water and sends it to the drain. In many older bathrooms that layer was never there, or it was regular drywall behind the tile, or a thin product that has failed at the corners, the niche or around the valve.
Add a fan that is too small or never run long enough, a long heating season with a closed-up house, and a few cracked grout lines, and you have warm, wet material in the dark, which is exactly what mould needs.
What we look for
Before your project, we look for signs: loose or hollow-sounding tile, cracked or missing grout, staining or peeling paint on the wall behind the shower, a musty smell, soft spots around the tub, and water stains on the ceiling below. If your home was built before 1990, we also sample the drywall joint compound in that wall for asbestos before we open it. Mould and asbestos can be in the same wall, and the asbestos result decides how the tear-out has to be done.
How we remove it
Health guidance in Alberta and BC sorts mould clean-ups by size:
- Small areas (under about 1 square metre, roughly 10 square feet) can be handled with basic protection: an N95 respirator or better, gloves and eye protection, with the area misted and bagged.
- Larger areas need a trained crew, containment that keeps spores out of the rest of the house, and more protective gear.
- Very large areas (over about 10 square metres) call for professional remediation and an air clearance.
On our jobs that means we close the bathroom off, mist and bag the mouldy material instead of breaking it dry, HEPA-vacuum, and remove everything that is soft or stained, not just the visible spots. Framing that is sound is cleaned and dried; framing that is not is replaced. Then we find and fix the source, because mould comes back if the water does.
How we rebuild: our waterproofing standard
This is where we refuse to cut corners. In every bathroom we build, at every budget:
- Cement board goes behind the tile in the wet areas, never regular drywall.
- A bonded sheet membrane goes over the cement board as the waterproof layer, with the system's matched corners, seams and drain connections, so the waterproofing is continuous from the drain to the top of the shower.
- Liquid membrane is used only for small spot repairs, never as the main waterproofing.
- Shower floors are built to slope to the drain, and the system is flood-tested before any tile goes on.
- The exhaust fan is sized for the room and ducted outside.
Done this way, the water that gets through the grout every day has nowhere to go but the drain.
Found during testing, priced before we start
Because we look and test right after you sign, a suspected problem behind the shower is something we plan for, not a surprise. If we cannot see inside the wall before demolition, we tell you what we might find and how it would be handled, so any extra work is priced and agreed in writing before it happens.
Planning a bathroom renovation in Edmonton or Prince George? Ask us about our waterproofing standard and how we test before we build at your design consultation.
