How to Remove Mould From Walls and Stop It Coming Back
Clean small patches with detergent or a fungicidal spray, then fix the moisture source — otherwise it returns in weeks.
Short answer: For patches under about one square metre, wipe the mould away with a fungicidal spray or hot soapy water, dry the surface fully, and then fix the cause — usually condensation from poor ventilation, a leak, or cold spots on outside walls. Cleaning alone always fails; the mould returns within weeks if the moisture stays.
Mould grows where surfaces stay above roughly 70% relative humidity. In most homes that means bathrooms, behind furniture pushed against exterior walls, and around single-glazed windows in winter.
Removing it safely
- Open a window and wear gloves and an FFP2 mask; avoid brushing dry mould, which releases spores.
- Spray a fungicidal wash or use hot water with washing-up liquid; wipe with a disposable cloth.
- Rinse, then dry the surface completely with a fan or dehumidifier.
- Bag and bin the cloths rather than reusing them.
- Repaint with an anti-mould emulsion once fully dry.
Fixing the cause
| Cause | Sign | Fix |
|---|---|---|
| Condensation | Window streaming in the morning | Ventilate, extractor fan, dehumidifier |
| Cold bridging | Mould in room corners | Insulate, move furniture 5 cm off the wall |
| Plumbing leak | Localised damp patch | Repair the pipe or seal |
| Rising damp | Tidemark near the skirting | Professional survey |
When to call a professional
Get help if the affected area is larger than one square metre, if mould keeps returning after two proper cleans, if it appears on plasterboard that feels soft, or if anyone in the home has asthma or a weakened immune system.
Want to go further? Read our guide on How to Fix One Cold Room in an Otherwise Warm House or browse everything in Home.
Frequently asked questions
- Does bleach kill mould on walls?
- It removes the colour but often leaves roots in porous plaster. A fungicidal wash is more effective.
- Is black mould dangerous?
- Prolonged exposure can worsen asthma and allergies. Small patches cleaned promptly are low risk.
- Do dehumidifiers stop mould?
- They help a lot in condensation-driven cases, keeping humidity around 50%. They cannot fix a leak.
Sources & references
About the author
Elena Marsh
Senior Editor, Money & Consumer
Elena has covered personal finance and consumer rights for over a decade. She translates dense financial rules into steps readers can act on the same day.
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