Removing Bathroom Mould
Bathroom mould is one of the most common household problems in Ontario homes, driven by the province's humidity cycling through humid summers and sealed, heated winters. The bathrooms in Ontario's housing stock — particularly older homes with inadequate exhaust ventilation — are prime environments for mould growth on grout, caulking, and ceilings.
Before You Start: Safety First
For surface mould on tile, grout, or caulking — black specks that wipe off — basic household precautions apply: ventilate the space, wear rubber gloves, and avoid inhaling spray mist. For mould that covers more than roughly 1 square metre, or mould behind walls or under flooring, stop and call a professional mould remediation company. Large infestations require containment and professional equipment.
Surface Grout and Tile Mould
- Apply undiluted white vinegar to the mouldy grout — let sit 15–20 minutes. Vinegar kills approximately 82% of mould species and is safe for tile and grout
- Scrub with a stiff grout brush
- Rinse and dry thoroughly
- For severe discolouration: a paste of baking soda and hydrogen peroxide (3% solution), applied, left 10 minutes, scrubbed, then rinsed
- Bleach solution (1 tablespoon per cup of water) works on white grout but can discolour coloured grout and should be rinsed completely
Caulking
Mouldy caulking is almost always better replaced than cleaned. The mould grows into the silicone matrix and cannot be fully eliminated from inside the material. Remove the old caulk with a caulk remover tool, clean the joint thoroughly, let dry 24 hours, and re-caulk with a mould-resistant silicone caulk (available at any Ontario hardware store).
Ceiling Mould
A ceiling with mould specks from condensation (common in Ontario bathrooms with inadequate exhaust) can be treated with a diluted bleach solution applied with a cloth. Address the root cause — improve exhaust ventilation — or the mould will return within weeks.