Black mould on walls is one of the most common problems in UK homes, and one of the most frustrating, because it tends to come back. That’s because the mould itself is a symptom. Clean it off without dealing with the moisture that fed it, and it returns within weeks. This guide covers both halves: getting rid of the mould safely, and fixing why it grew.
Why black mould grows
Mould needs three things: moisture, a surface to grow on, and time. In most homes the moisture comes from condensation — warm, moist air from cooking, bathing, breathing and drying clothes meeting a cold surface and turning back into water. That’s why mould appears in the same places: cold external walls, corners, behind wardrobes, around window reveals, and in bathrooms.
Less often, mould is fed by water coming from the building itself: rain getting through a wall, a leak from a pipe, or damp rising at low level. That kind of mould won’t go away with better ventilation, so it’s worth telling the difference. Our damp checker helps you work out which you’re likely dealing with.
How to remove black mould safely
- Protect yourself. Wear rubber gloves, and ideally goggles and a mask. Open a window.
- Don’t dry-brush or vacuum it with a normal vacuum. That releases spores into the air.
- Use a fungicidal mould wash suitable for the surface, following the instructions. Wipe the mould away with a cloth, then dispose of the cloth.
- Treat the surrounding area, not just the visible spots.
- Let the surface dry fully.
- Only then redecorate, with an anti-mould paint if you like — but only once the moisture problem is under control, or it will grow straight back.
- Soft furnishings and clothing with mould on them should be washed or professionally cleaned; heavily affected items may need throwing away.
For large areas, or where someone in the home has a respiratory condition or a weakened immune system, get help rather than tackling it yourself.
How to stop black mould coming back
This is the part that actually works:
- Ventilate at source. Use extractor fans in the kitchen and bathroom, and check they genuinely extract (a sheet of paper should be held against the grille). Keep them running for a while after cooking or showering.
- Keep trickle vents open on windows, and open windows briefly each day.
- Dry washing outside or in a vented or condensing dryer. Drying a load of washing indoors releases litres of water into the air.
- Put lids on pans and close the kitchen door when cooking.
- Heat more evenly. Low, steady background heat keeps walls warmer than short bursts, and warm walls don’t attract condensation.
- Leave a gap behind furniture on external walls so air can circulate.
- Don’t block air bricks or vents.
When mould points to a building problem
If mould keeps returning to one wall or one corner despite good ventilation and heating, look for a defect:
- a cold bridge — a lintel, a concrete beam or a gap in insulation that makes one spot colder;
- missing or slumped insulation in the loft or walls;
- rain getting in through failed pointing, cracked render, a leaking gutter or defective window seals;
- a leak from plumbing, often behind a bath or shower;
- in older solid-walled houses, modern finishes trapping moisture in walls built to breathe.
These need finding and fixing rather than repeated cleaning. Our guides to treating damp walls and telling condensation, penetrating and rising damp apart go further.
Is black mould dangerous?
Government guidance developed with the UK Health Security Agency is clear that damp and mould can affect health, particularly for children, older people and people with respiratory conditions such as asthma. The answer isn’t panic; it’s dealing with the cause promptly.
If you rent
If you rent your home, damp and mould is your landlord’s responsibility to investigate and put right. Government guidance for landlords, published after the death of two-year-old Awaab Ishak in 2020, is explicit that damp and mould should not be blamed on tenants’ “lifestyle”, and that landlords must identify and address the underlying cause. Report it in writing, with photographs and dates.
If you’re buying
Mould on a viewing is a clue, not a verdict. A freshly painted wall in an otherwise tired house can be hiding it. A Home Survey Level 2 or Level 3 will look for damp and mould and point to likely causes; where there’s a specific concern, an independent damp and timber survey finds the actual source. We sell no treatment, so the advice is only about what the building needs. Get in touch.
Sources and further reading
- Damp and mould: understanding and addressing the health risks — government guidance for rented housing providers (GOV.UK)
- Damp in historic buildings — Historic England
- Homeowner advice: damp and mould — Property Care Association