Why it matters
Government guidance issued on 7 September 2023, after the death of a child in Rochdale, states that damp and mould can cause respiratory illness that is serious and, in the worst cases, fatal. Babies and young children, older people, pregnant women and people with existing lung or immune conditions are at greatest risk.
Telling the three kinds apart
- Condensation appears as water on windows and as black spotted mould in corners, behind furniture, on north-facing walls and round window reveals — the coldest surfaces, and the places where air does not move. It is worst in winter.
- Penetrating damp appears as a patch that grows after rain and has an edge to it. The cause is nearly always found outside at the same spot: a blocked or broken gutter, a cracked downpipe, missing pointing, a slipped tile, failed sealant round a window. A leaking pipe inside produces the same sort of patch.
- Rising damp appears as a tide mark, usually with white salts, low on a ground-floor wall. Houses built since the late nineteenth century have a damp-proof course to stop it, and the usual fault is that the course has been bridged — by soil, paving or render raised above it — not that it has failed.
Rising damp is diagnosed far more often than it occurs. A surveyor who is independent of any firm selling treatment is the person to confirm it.
Dealing with condensation
A household puts litres of water into the air every day by breathing, cooking, washing and drying clothes. Condensation is controlled by producing less of it, removing it and keeping surfaces warm.
- Remove it at source. Extractor fans in the kitchen and bathroom are run during cooking and bathing and for a while afterwards, with the door shut.
- Keep background ventilation open. Trickle vents in window frames and airbricks are there for this purpose.
- Produce less. Lids go on pans; clothes are dried outdoors, or in a closed room with a window open or a fan running, and tumble dryers are vented to the outside.
- Heat steadily. A house kept at an even, moderate temperature has warmer walls than one heated in short bursts.
- Let air move. Furniture is kept a few centimetres off outside walls, and wardrobes are not overfilled.
Insulation raises the temperature of walls and so reduces condensation, provided ventilation is kept, as set out under insulating a home.
Removing mould
A small area of mould caused by condensation can be cleaned by the occupier. It is wiped away with a cloth and a mould-removing cleaner or soapy water, wearing gloves and with the window open, and the cloth is thrown away. Mould is not brushed off dry, which spreads the spores. Large areas, mould that returns at once, and anything caused by contaminated water are work for a professional. Paint does not cure it, as explained under preparing walls and woodwork for painting.
Cellars
A cellar is below ground and is damp by nature. Used for storage, it needs ventilation, not waterproofing. Turning one into a living room means lining it with a waterproofing system, which is specialist work covered by the Building Regulations.
Rented homes in England
Damp and mould in a rented home are the landlord's responsibility to investigate. The official guidance tells landlords not to wait for medical evidence before acting, and the Housing Ombudsman's report of 2021 on the subject was titled "It's not lifestyle", in answer to the habit of blaming tenants.
Awaab's Law is named after Awaab Ishak, who died in December 2020, aged two, after prolonged exposure to mould in his family's flat in Rochdale. Its first phase has applied to social landlords in England since 27 October 2025. It requires them:
- to make emergency hazards safe within 24 hours of a report;
- to investigate significant damp and mould within 10 working days of being notified;
- to send the tenant written findings within three working days of the inspection;
- to make the home safe within five working days; and
- to offer alternative accommodation if that cannot be done in time.
The government has said that later phases will add other hazards in 2026 and 2027, and that the law is to be extended to private landlords under the Renters' Rights Act.
A tenant reports the problem to the landlord in writing and keeps a copy, with dated photographs. If nothing is done, the environmental health department of the local council can inspect any rented home and order repairs. Social tenants can also take a complaint to the Housing Ombudsman.
Housing law in Scotland, Wales and Northern Ireland is separate.