How to Remove Mould from Bathroom Ceiling
Black mould on bathroom ceilings is one of the most common issues in Toronto homes and apartments — particularly in older buildings with limited ventilation, single-pane windows that cause condensation, and bathrooms without proper exhaust fans. This guide covers surface mould removal on painted ceilings. For structural mould (behind drywall, in insulation, or covering more than 10 square feet), professional remediation is recommended.
Safety Precautions
- Wear rubber gloves, eye protection, and a N95 mask when cleaning mould — mould spores become airborne when disturbed
- Ensure the bathroom is well-ventilated — open windows if possible
- Protect surrounding surfaces and your clothes
Cleaning Method: Bleach Solution (Most Effective for Bathroom Mould)
Bleach kills mould on hard, non-porous surfaces like painted ceilings effectively. The key is proper dilution and dwell time:
- Mix 1 cup of household bleach (5–8% sodium hypochlorite) with 1 gallon of water in a bucket
- Apply to the mouldy ceiling surface using a sponge, cloth, or spray bottle — work in sections of about 1 square foot at a time
- Allow the solution to sit on the surface for 10–15 minutes without scrubbing — the dwell time is essential for killing the mould at the root
- Scrub with a stiff-bristled brush or scrub pad
- Rinse with clean water
- Allow to dry completely — keep the bathroom ventilated
- Inspect after 24 hours — if any black spots remain, repeat the treatment
Alternative: Hydrogen Peroxide (3%)
- Spray 3% hydrogen peroxide directly on the mouldy area
- Allow 10 minutes
- Scrub and wipe
- Less effective than bleach on severe mould but non-toxic and no fumes — suitable when the bathroom has limited ventilation for bleach use
After Cleaning: Prevent Regrowth
Mould regrows rapidly if the conditions that caused it aren't addressed:
- Exhaust fan: Run the bathroom fan during every shower and for 20–30 minutes after. If there's no fan, install one — this is the single most effective prevention measure.
- Open window: If no fan, open the bathroom window for 20 minutes after showering to allow moisture to escape
- Squeegee surfaces: Squeegeeing the shower walls and floor after every use removes standing water
- Moisture-resistant paint: Repaint the ceiling with a bathroom-specific paint that contains mould inhibitors
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