Preventing Mould in Ontario Bathrooms
Bathroom mould is one of the most common home maintenance issues in Ontario — the combination of water, warmth, and limited ventilation that defines most Ontario bathrooms is precisely the environment mould thrives in. Prevention is far easier than remediation.
Ventilation: The Primary Defence
Run your bathroom exhaust fan during every shower and for 20 minutes after you finish. The fan's job is to remove moisture-laden air before it condenses on cool surfaces and provides the water mould needs to grow. If your Ontario home was built before the 1980s, the exhaust fan may be inadequate by current standards — a modern bathroom exhaust fan should be rated at 50+ CFM for a standard bathroom, and running continuously during and after showering. If you notice condensation on the mirror or ceiling more than 10 minutes after you've finished showering, your ventilation is insufficient.
Grout and Caulk: The Entry Points
Mould enters grout and caulk through microscopic pores and cracks. Sealed grout is significantly more resistant to mould than unsealed grout — seal new grout after 28 days and re-seal annually. The silicone caulk at the tub or shower surround should be replaced when it shows any pink, grey, or black discolouration — discoloured caulk cannot be fully cleaned, only replaced.
After Showering
Running a squeegee across shower walls and glass doors after every shower removes most of the standing water that feeds mould. A 30-second post-shower squeegee dramatically extends the time between bathroom deep cleans.
When Mould Appears
Small mould spots on grout: oxygen bleach (sodium percarbonate) solution applied with a grout brush, left 10 minutes, scrubbed and rinsed. For mould on painted walls: diluted bleach on a cloth, wipe, rinse — repaint if mould has penetrated the paint surface. For mould on drywall behind tile or on structural surfaces: this requires professional remediation, not cleaning.