What are the three main types of damp in UK homes?

The three main types are: condensation damp (caused by excess humidity from everyday activities — cooking, showering, drying clothes indoors); penetrating damp (water entering through damaged walls, roof, windows or pipes — usually leaves a defined damp patch); and rising damp (ground water drawn up through brickwork by capillary action — rare in modern homes, more common in period properties without a damp-proof course).

How do I know what type of damp I have?

Condensation: damp appears on walls and windows when the weather is cold and humid, especially in bathrooms and kitchens — it often clears when you improve ventilation. Penetrating damp: a damp patch appears on a wall or ceiling after rain, or near a pipe or window — it grows in wet weather. Rising damp: a damp patch on ground-floor walls that reaches up to about 1 metre from the floor, often with a characteristic tide mark on the plaster.

Can I treat damp and mould myself?

Condensation damp can almost always be treated yourself by improving ventilation and reducing humidity. Use extractor fans, open windows and run a dehumidifier. Penetrating damp and rising damp require professional diagnosis and repair, because the source of water entry or ground moisture must be physically stopped.

Does mould mean my house has serious damp?

Not necessarily. Mould caused by condensation is common in well-built UK homes and does not mean the structure is damaged. It means the humidity in the room is too high. Fix the ventilation and humidity and the mould stops. Damp patches that appear after rain, affect solid walls on lower floors, or keep returning after treatment should be professionally assessed.

What kills mould on walls permanently?

Nothing kills mould permanently — mould spores are present in every home and will regrow if conditions are right. The goal is to make conditions hostile to mould by keeping humidity below 60%. Treat surface mould with Zinsser Mould Killer or a diluted bleach solution, then fix the ventilation to stop it returning.

UK damp treatment guide

How to treat damp and mould in your home — UK guide

Damp and mould in UK homes is most commonly caused by condensation — and it is almost always treatable without expensive professional work. Here is how to diagnose what you have, treat it, and stop it returning.

Damp checklist Size a dehumidifier

Identifying the type of damp in your home

UK guide

First identify the type of damp you have

The treatment is different for each type. Getting the diagnosis right means you tackle the actual cause — not just the symptom.

Important: Condensation damp is treatable yourself. Penetrating damp and rising damp require a professional to stop the source of water — treating the surface alone will not fix it. If you are unsure which type you have, get a damp survey before spending money on treatments.

Step 1 — Identify what type of damp you have

The three main types have distinct causes, appearances and treatments. Check which one matches your situation:

Condensation damp

Cause: Excess humidity from everyday activities — showering, cooking, drying clothes indoors, even breathing. The moisture in the air condenses on cold surfaces (windows, walls, mirrors).

Where it appears: Bathrooms, kitchens, bedrooms, single-glazed windows. Often worse in winter when windows are kept closed and walls are cold.

Signs: Water droplets on windows in the morning. Black mould patches on walls, especially in corners and behind furniture. Condensation on cold pipes or metal surfaces.

Treatment: DIY. Improve ventilation, use extractor fans, open windows daily, run a dehumidifier. Condensation clears when humidity drops.

Penetrating damp

Cause: Water entering the property through damaged walls, roof, window frames, or leaking pipes. Rainwater finds a path through cracks, faulty guttering or porous brickwork.

Where it appears: On walls or ceilings, usually on an external wall. Often below a roof line, around windows, or near a pipe entry point.

Signs: A damp patch that grows during or after rainy weather. Tide marks or staining. Plaster that feels damp to touch. Often on one specific area rather than across a whole room.

Treatment: Professional. The water entry point must be identified and repaired. A damp-proofer or roofer is usually needed.

Rising damp

Cause: Ground water drawn up through brickwork by capillary action. Most common in older properties without a damp-proof course (DPC) or where the DPC has been bridged by soil or debris.

Where it appears: Ground-floor walls, typically up to about 1 metre from the floor. Often leaves a distinctive tide mark on plaster.

Signs: Damp at the base of walls on the ground floor. Tide marks or salt deposits on plaster. Skirting boards or floorboards showing rot at the bottom. A musty smell at ground-floor level.

Treatment: Professional. Requires a damp-proofing specialist to install or repair a damp-proof course and replaster affected areas.

Step 2 — Treat condensation damp (DIY)

If you have confirmed your damp is condensation, you can treat it yourself. The treatment has two parts: treating the surface mould, and fixing the humidity that caused it.

Part A — Kill the mould

Prepare the room. Open windows. Wear an FFP2 mask, rubber gloves and eye protection. Lay dust sheets.
Apply mould treatment. Spray Zinsser Mould Killer, Ronseal 3-in-1 Mould Remover, or a diluted bleach solution (1:4 bleach to water) onto the affected area. Leave for 15–30 minutes — check product instructions.
Scrub gently. Use a stiff brush in small circular motions. Do not scrub aggressively — this releases spores.
Rinse and dry. Wipe with a clean, damp cloth. Allow to fully dry. Run a dehumidifier in the room to speed this up.
Apply mould-resistant primer or paint (optional but recommended for walls and ceilings).

Part B — Fix the humidity source

Treating mould without fixing humidity is pointless — it will return. Fix the moisture source first:

Ventilation: Open windows for at least 10 minutes every day. Use extractor fans every time you cook or shower, and leave them running for 15 minutes after.
Dehumidifier: Run a dehumidifier in the affected room. Set it to maintain humidity below 60%. A dehumidifier is the most effective single action for persistent condensation problems.
Heating: Cold walls create condensation. Keeping a consistent background temperature (16–18°C) reduces cold surfaces where moisture condenses.
Move furniture: Push furniture 5–10cm away from external walls to allow air circulation behind and above.

Step 3 — Treat penetrating or rising damp (professional required)

If your damp is not condensation, surface treatment will not fix it. You need a qualified damp surveyor or damp-proofing specialist to:

Identify and repair the water entry point (wall cracks, roof damage, faulty guttering, pipe leaks)
Install or repair a damp-proof course for rising damp
Replaster affected areas with specialist damp-resistant plaster

What to look for in a damp specialist: Look for membership of the Property Care Association (PCA) or the British Damp Proofing Association (BPDCA). Ask for a written survey report and a guarantee. Avoid companies that quote without a proper inspection or that use high-pressure sales tactics.

Step 4 — When to get professional help (even for condensation)

Mould or damp covers more than 1 square metre
Mould keeps returning within weeks after treatment
You can see damp patches on walls or ceilings that are not on the surface
There is a musty smell that does not go away when you ventilate the room
Anyone in the household has unexplained respiratory symptoms, asthma or allergies that worsen at home
You rent and the landlord is not addressing damp — contact your local council's housing team, as landlords have a legal duty to address damp and mould under the Housing Health and Safety Rating System (HHSRS)

Step 5 — Prevent damp and mould returning

The prevention steps are the same as the treatment steps for condensation — just maintained as habits rather than a one-off effort:

☐ Open windows for at least 10 minutes every day — even in winter
☐ Use extractor fans every time you cook or shower, and for 15 minutes after
☐ Run a dehumidifier in rooms where condensation has been a problem
☐ Keep indoor humidity below 60% — use a hygrometer to check
☐ Keep background heat on (16–18°C) rather than heating in short bursts
☐ Close kitchen and bathroom doors when cooking or showering to prevent humidity spreading
☐ Dry clothes outdoors or vent your tumble dryer to the outside, not into the kitchen
☐ Check and clean extractor fans regularly to ensure they are working effectively
☐ Move furniture slightly away from external walls to allow air circulation

How to treat damp and mould in your home — UK guide

First identify the type of damp you have

Step 1 — Identify what type of damp you have

Condensation damp

Penetrating damp

Rising damp

Step 2 — Treat condensation damp (DIY)

Part A — Kill the mould

Part B — Fix the humidity source

Step 3 — Treat penetrating or rising damp (professional required)

Step 4 — When to get professional help (even for condensation)

Step 5 — Prevent damp and mould returning

Tools that help

Dehumidifier size calculator

Running cost calculator

Mould removal guide