To remove mould from a wall, put on gloves, goggles and a mask, shut the door, open the window, and wipe the patch with a mould and mildew cleaner. Government guidance prefers these products to bleach. Let the wall dry completely. Mould will come back unless the moisture causing it is found and fixed. Large areas need a professional, and in a rented home that is the landlord's job.
Is black mould on walls dangerous?
It can be. The government's 2023 guidance, Understanding and addressing the health risks of damp and mould in the home, last updated in April 2026, says damp and mould mainly affect the airways and lungs, and can also affect the eyes and skin. It lists cough, wheeze and shortness of breath, a higher risk of airway infections, and the development or worsening of conditions such as asthma and allergic rhinitis.
The guidance says everyone is vulnerable, but some people are at greater risk, including:
- people with asthma, COPD, allergies or other lung or heart conditions
- people with weakened immune systems
- babies, children and older people
- pregnant women
- people with mental health conditions
The NHS lists mould among the things that can trigger asthma symptoms, and notes that aspergillosis, an illness caused by aspergillus mould, can come from damp buildings, though it is rare in healthy people.
This guide is not medical advice. If you are worried about symptoms, speak to your GP or a pharmacist, and if someone in the house is in a higher-risk group, treat the mould as urgent.
How to remove mould on walls safely, step by step
The steps below follow the government guidance for small areas on hard, painted surfaces.
- Photograph it first. The guidance suggests photographing the mould and, if you can, drawing round it. That record helps whoever looks for the cause.
- Protect yourself. Wear a mask, gloves and goggles, whatever the size of the patch.
- Shut the door and open the window, so spores are not carried round the house but the room stays ventilated during and after cleaning.
- Wipe, don't brush. Use a cloth and a mould and mildew cleaner, following the product's instructions. Dry brushing or vacuuming mould tends to spread spores, so decorators avoid it.
- Let it dry completely.
- Bag and bin the cloth, or wash it, along with any protective clothing.
Mould on soft or absorbent materials is harder. The guidance notes that mouldy carpets, soft furnishings and ceiling tiles may have to be thrown away because the mould may be impossible to remove completely. The same goes for badly affected wallpaper, which the Centre for Sustainable Energy says should be removed if it is too far gone for treatment to work.
Bleach or mould remover?
The advice here genuinely conflicts. Many guides, including the Centre for Sustainable Energy, tell you to spray mould with a bleach-based product and treat an area about a metre wider than the visible patch. The government guidance says mould and mildew products should be used in preference to bleach, for health and safety reasons. We follow the government guidance. Whatever you use, read the label and never mix cleaning products.
When it's too big to clean yourself
The government guidance says most people can reasonably deal with condensation and very small amounts of mould, but larger areas should only be tackled by qualified professionals. If mould covers a large part of a wall or ceiling, keeps returning within weeks, is behind furniture across a whole wall, or the plaster underneath is soft, crumbling or blown, stop and get the cause assessed.
Why mould keeps coming back: find the moisture first
Cleaning removes the mould. It does not remove the reason it grew. The guidance says simply removing surface mould will not stop it reappearing. It describes four types of damp:
| Type | What it is | Typical signs |
|---|---|---|
| Condensation | Moisture from inside the home settling on cold surfaces. The most common type. | Mould in corners, round windows, low on walls behind wardrobes and sofas |
| Penetrating | Water getting in from outside through walls, roofs, windows or floors | Patches that grow after rain, often near gutters or a cracked wall |
| Rising | Ground moisture rising through walls and floors, usually in older properties | Tide marks low on ground-floor walls; often misdiagnosed |
| Traumatic | Leaks from pipes, baths, sinks or tanks, or flooding | A spreading stain, often under a bathroom or near pipework |
The guidance warns that rising damp is often misdiagnosed and that chemical testing is the most reliable way to confirm it. It also lists useful checks: blocked or damaged gutters and downpipes, broken window seals, cracked render, a bridged damp proof course, peeling wallpaper, defective plaster, extractor fans that are broken or switched off, and low insulation.
For condensation, the everyday fixes are familiar: extractor fans running in the kitchen and bathroom, lids on pans, internal doors shut when cooking or showering, laundry dried outside where possible, and a gap between furniture and outside walls. The Centre for Sustainable Energy recommends keeping indoor relative humidity between 40% and 60%, with mould risk rising above 60%. A cheap hygrometer shows which rooms need more ventilation.
Who can find the cause?
If the source is not obvious, the government guidance points to building surveyors, damp surveyors (it lists qualifications such as CSRT and CSSW), ventilation specialists and council environmental health officers. A leak needs a plumber or roofer. A decorator comes in once the cause is fixed and the wall has dried out.
Does anti-mould paint work?
It helps, as the last step rather than the first. Fungicidal paints contain an additive that slows mould growth on the painted surface. Dulux Trade Mouldshield Fungicidal Matt, for example, contains a fungicide that inhibits mould and fungi on interior walls and ceilings and is tested to BS 3900 Part G6. Dulux Trade recommends its eggshell version where heavy condensation or frequent splashing is likely, as in some kitchens and bathrooms, and advises brush or roller only, as spraying fungicidal paints is not recommended.
What anti-mould paint cannot do is cope with a wall that is constantly wet. Painted over an unresolved leak or a cold, damp corner, it will eventually fail like any other paint. Decorators generally redecorate mould-affected areas in this order:
- Cause found and fixed, and the wall allowed to dry out.
- Mould cleaned off and the surface left to dry.
- Any loose paint or blown plaster removed and made good.
- Stains sealed with a stain-blocking primer such as Zinsser, so marks do not bleed through.
- Two coats of a fungicidal or washable finish suited to the room.
A landlord who had us deal with mould in a rental bathroom described the job in a Houzz review:
To remove bad mould from a bathroom ceiling and wall tops in our rental property. After removal, seal with mould sealer and re-decorate affected areas.
An excellent job, done at extremely short notice, still perfect after 18 months.
Outside, the principle is similar. On a Cambridge house exterior affected by mould and flaking paint, we jet-washed with an anti-fungal wash before repainting. Our exterior painting page explains how we prepare walls.
Renting? It's usually your landlord's job
If you rent, damp and mould is normally the landlord's responsibility to fix. The government guidance says that, whatever the type of damp, landlords are legally responsible for addressing damp and mould, should not blame it on tenants' normal activities such as cooking and drying laundry, and should not wait for medical evidence before acting. It also advises landlords to inspect again at least 6 weeks after remedial work to check the problem has not returned.
For social housing tenants in England, Awaab's Law now sets fixed deadlines. Under the government's guidance for tenants, social landlords must:
- deal with emergency hazards, such as very serious damp or mould, by investigating and making the home safe within 24 hours
- investigate significant damp and mould hazards within 10 working days of a report
- make the home safe within 5 working days of the investigation finishing
- give you a written summary within 3 working days of the investigation
- start any further work within 5 working days, and in all cases within 12 weeks
Private tenants are protected by other legislation, such as the Housing Act 2004, which local councils enforce. If your landlord does not act, the government guidance points tenants to their council and to Shelter for advice.
For landlords, the order of work matters. We can redecorate once the cause has been dealt with, but painting over active damp before a tenant moves in usually just postpones the problem.
How we'd approach it
A small patch of condensation mould on a window reveal is a DIY job: clean it, dry it, improve the ventilation and keep an eye on it. Call a professional if the mould is widespread, keeps returning, comes with damp plaster or staining, or anyone in the home is in a higher-risk group.
We are decorators, not damp surveyors, and we will say so if we think you need one. Where we come in is the making good: removing damaged paint or paper, sealing stains, getting our plasterers to repair blown plaster, and repainting with a finish suited to the room. If that is where you are, our interior decorating page explains how we work, and Graham will visit, look at the wall and put the work in a written quotation; you can arrange a free visit here. You can also read what customers say about us on our reviews page.
Questions people also ask
Can I just paint over mould?
No. Paint over live mould will usually fail and the mould will grow back through it. Clean it off, fix the moisture, let the wall dry, seal any stain and then repaint.
Why does mould come back after I clean it?
Because the moisture is still there. The government guidance says removing surface mould alone will not stop it reappearing. Condensation is the most common cause; leaks, penetrating damp and rising damp need a different fix.
Is anti-mould paint worth it?
As a finishing coat in bathrooms, kitchens and cold rooms, yes. Fungicidal paints such as Dulux Trade Mouldshield inhibit growth on the surface. They do not fix a leak or a constantly wet wall.
Who pays to fix mould in a rented home?
Usually the landlord. Government guidance says landlords are legally responsible for addressing damp and mould whatever the type of damp. Social landlords in England must also meet the Awaab's Law timescales.
How soon can I redecorate after treating mould?
Once the cause is fixed and the wall is fully dry. If you are not sure the cause has been dealt with, waiting a few weeks to see whether the mould returns is sensible before spending money on decorating.
Talk to Graham about your interior decorating
Graham visits free of charge, looks at the job with you and sends a detailed written quotation. You don't pay until you're happy with the finished work. We work across Cambridge and the towns and villages around it: find your area.
Sources
- Understanding and addressing the health risks of damp and mould in the home, GOV.UK (MHCLG, DHSC and UK Health Security Agency) (checked 23 October 2026)
- Awaab's Law: guidance for tenants in social housing, GOV.UK (MHCLG) (checked 23 October 2026)
- Asthma, NHS (checked 23 October 2026)
- Aspergillosis, NHS (checked 23 October 2026)
- Condensation, damp and mould, Centre for Sustainable Energy (checked 23 October 2026)
- Dulux Trade Mouldshield Fungicidal Matt, Dulux Trade (AkzoNobel) (checked 23 October 2026)
Written by Graham Halpenny Decorators. Third-party prices, product data and regulations are credited to their source with the date we checked them; they are not our prices. Spotted something out of date? Let us know.
