Updated
Black Mould On A Painted Ceiling
Black or grey speckling has spread across a painted ceiling or the top of a wall, usually in a bathroom or bedroom.
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What's happening?
Speckled black growth on a painted ceiling is surface mould feeding on condensation. Warm moist air rises, meets the coldest surface in the room — normally the ceiling, an external corner or the reveal around a window — and condenses there. Paint gives it a surface to colonise. It concentrates in bathrooms and above beds because those rooms produce the most moisture and are often the least ventilated. The government's joint guidance with UKHSA is direct about this: damp and mould are not a lifestyle choice, and the underlying cause — a structural defect or inadequate ventilation — must be found and fixed. Wiping the mould off and repainting treats the symptom, and it returns in the same pattern within months.
What usually causes it?
- An extract fan that is missing, blocked, ducted into a loft space or too weak for the room
- A cold ceiling or cold spot where warm room air condenses, often from missing or compressed loft insulation
- Drying washing indoors, or a tumble dryer venting into the room
- Doors and trickle vents kept closed, so moist air stays in the room after a shower or bath
- Furniture or storage tight against a cold external wall, killing air movement behind it
- A cold bridge at a lintel, a wall tie or a poorly insulated reveal, showing as a hard-edged line of growth
- Paint with no mould inhibitor used in a room that produces constant moisture
Is it dangerous?
Mould in the home carries real health risk. Government guidance sets out that damp and mould can significantly affect physical and mental health, and that children, older adults and people with existing respiratory conditions are at greater risk of severe effects. It also states landlords must identify and address the underlying cause rather than treating it as tenant behaviour. Do not dry-brush mould, which puts spores into the air; wipe it with a suitable fungicidal wash.
Can I fix it myself?
Treat the growth with a fungicidal wash, following the product's contact time rather than wiping straight off, and ventilate while you work. Then attack the cause: run the extract fan during and for at least fifteen minutes after every shower, open a window or trickle vent, keep furniture a hand's width off cold walls, and stop drying washing in that room. If the fan barely holds a sheet of paper against its grille, it is not moving enough air and needs looking at.
When should you call a painter and decorator?
Call a painter and decorator once the ventilation is sorted, to strip, treat and recoat in a system with a mould inhibitor that will hold in that room. Call an electrician or ventilation installer first where the extract fan is missing, failed or discharging into a loft — Approved Document F sets the extract requirement for wet rooms, and no decoration survives without it.
What will the painter and decorator actually do?
- Establish whether the pattern is condensation mould, a cold bridge or a leak, from where the growth sits
- Wash the affected area with a fungicidal treatment and allow the specified contact time
- Strip and make good any paint that has lifted or is heavily colonised
- Recoat with a moisture-resistant, mould-inhibited system suited to a bathroom or kitchen ceiling
- Flag where the real cause is ventilation or insulation, so the trade that can fix it is brought in
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