How to Remove Mould from a Bathroom Ceiling
Bathroom ceiling mould is one of the most common household issues in Toronto homes — especially in older semis and detached homes with poor bathroom ventilation, and in condo units where bathroom exhaust fans vent into the ceiling cavity instead of outside. The black or grey spots that appear in corners and along edges are almost always caused by condensation from hot showers collecting on cold ceiling surfaces.
Safety First
For small areas (less than 1 square foot): you can safely treat it yourself. For larger affected areas, spreading mould, or mould that returns repeatedly within weeks of cleaning: consult a professional mould remediation company — it may indicate a ventilation or structural issue. Always wear rubber gloves and avoid inhaling mould spores during cleaning.
Step-by-Step: Removing Bathroom Ceiling Mould
- Ventilate the room — open the window and turn on the bathroom fan before starting. If neither is available, leave the door open and open a nearby window.
- Mix a cleaning solution — the most effective DIY solution for bathroom mould: 1 part bleach to 10 parts water in a spray bottle. This concentration is enough to kill mould without damaging most painted ceilings. Alternatively, a commercial mould cleaner like Concrobium Mold Control is very effective and less harsh than bleach.
- Apply the solution — spray directly onto the mould spots. Let it sit for 10–15 minutes without wiping — the dwell time is what kills the mould spores. Spraying and immediately wiping just moves mould rather than killing it.
- Scrub gently — use a soft brush or old toothbrush to scrub the treated areas. For smooth painted ceilings, a damp sponge works. Avoid abrasive scrubbers that damage ceiling paint.
- Wipe and rinse — wipe with a clean damp cloth. If you used bleach, rinse the area with a cloth dampened with clean water to remove bleach residue.
- Dry completely — this is critical. Use a clean dry towel and then run the bathroom fan or open the window until the ceiling is completely dry. Mould requires moisture — leaving the ceiling damp after cleaning virtually guarantees it returns.
Preventing Bathroom Ceiling Mould
- Run the exhaust fan during and after every shower — the fan should run while showering plus 20–30 minutes after to remove residual humidity. Many people turn it off when they leave the bathroom, trapping humid air inside.
- Check that the fan actually vents outside — older Toronto homes often have fans that vent into the attic or ceiling cavity, which causes moisture to accumulate above and eventually penetrate the ceiling. Check by holding a tissue at the fan: if the fan is working, the tissue is pulled toward it.
- Leave the bathroom door open after showering — allows moisture to dissipate into the larger home where it can disperse
- Wipe down shower walls and ceiling after use — a 30-second squeegee or towel wipe dramatically reduces the humidity introduced into the room
- Consider a dehumidifier — for chronically humid bathrooms without adequate ventilation, a small bathroom dehumidifier ($60–$150) is effective
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