Bathroom Mould Prevention in Ontario Homes
Bathroom mould is a perennial challenge in Ontario homes — the province's climate, combined with the warm, humid conditions of daily bathroom use, creates conditions where mould can establish itself rapidly if the right habits aren't in place. Mould in the bathroom is both an aesthetic and health concern: certain mould species trigger respiratory issues and exacerbate asthma, which is particularly relevant during Ontario's winter months when indoor air circulation is limited.
The Four Conditions Mould Needs
- Moisture: The primary driver — steam from showers, splashing around sinks, condensation on cold walls
- Warmth: Mould thrives above 15°C — bathrooms are consistently warm
- Organic material: Grout, soap residue, skin cells — all available in bathrooms
- Poor airflow: Without ventilation, moisture persists after shower
Prevention Habits
Run the exhaust fan during and for 15 minutes after every shower — this is the single most effective mould prevention habit. If the fan is inadequate (check: does condensation persist on the mirror 10 minutes after a shower?), upgrade it. An exhaust fan sized correctly for the bathroom volume eliminates the moisture that mould needs.
Squeegee shower walls after each use — removing standing water from tiles dramatically reduces moisture retention in grout.
Weekly tile and grout cleaning — don't let soap scum build up; it's an organic substrate that feeds mould.
Check and reseal grout — cracked or missing grout allows moisture infiltration behind tiles, which creates hidden mould reservoirs.
If Mould Is Already Present
Surface mould on tiles and grout: hydrogen peroxide (3%) or a commercial mould remover applied directly, left for 10 minutes, and scrubbed with a stiff grout brush. For recurrent mould despite good ventilation habits, the grout may need to be sealed or replaced. For mould behind tiles or on drywall (visible as staining through the wall), professional remediation is appropriate.