Damp, condensation and mould

There are four types of damp that can affect your home. It is important to understand the differences so that the cause can be identified and addressed appropriately.

Rising damp

Rising damp occurs when water rises from the ground into the property. This can happen where the Damp Proof Course (DPC) is damaged or missing, or in older properties where no DPC was originally installed. A DPC is a horizontal layer of waterproof material built into the walls just above ground level to prevent moisture rising through capillary action.

Rising damp generally affects basements and ground floor rooms. It typically rises no more than 300–600mm (12–24 inches) above floor level and often leaves a visible “tide mark” on walls. White salt deposits may also appear.

It is usually present all year but becomes more noticeable in winter. If untreated, it can cause plaster to deteriorate and wallpaper to peel.

Penetrating damp

Penetrating damp is caused by water entering the property through defects in the building’s external structure, such as damaged brickwork, missing pointing, cracked render or roof issues.

It usually appears on external walls or ceilings and is often more noticeable after rainfall. It typically presents as a defined damp patch that feels wet to the touch.

Defective plumbing

Leaks from water or waste pipes are a common cause of damp, particularly in kitchens and bathrooms. These can affect both internal and external walls and are usually present regardless of the weather outside.

You should check visible pipework, seals around sinks, baths and showers, and any accessible external pipework such as guttering. If you suspect a leak, it should be reported promptly to your landlord or letting agent.

Condensation

Condensation is the most common cause of damp experienced by tenants. It occurs when warm, moist air comes into contact with cold surfaces, causing water droplets to form.

These damp areas can lead to the growth of black mould. Condensation is most common during colder months and is typically found on windows, walls and in corners of rooms.

While condensation cannot always be completely avoided, there are practical steps you can take to reduce moisture levels and limit mould growth.

Produce less moisture

Daily activities generate moisture, so reducing this can help minimise condensation.

• Dry clothes outdoors where possible. If drying indoors, use a well-ventilated room such as a bathroom and keep the window slightly open.
• Vent tumble dryers externally or use a condenser dryer.
• Cover pans when cooking and avoid leaving kettles boiling unnecessarily.
• Avoid using paraffin or bottled gas heaters, as they produce large amounts of moisture.

Remove excess moisture

Regularly remove condensation from surfaces where it collects.

• Wipe windows and sills each morning
• Pay particular attention to bedrooms, kitchens and bathrooms
• Consider using dehumidifiers in areas where moisture builds up

Ventilate to remove moisture

Good ventilation is essential to reduce condensation without significantly cooling the property.

• Open windows regularly, even slightly
• Use trickle vents where available
• Use extractor fans in kitchens and bathrooms

This helps moist air escape and allows drier air to circulate.

Heating and insulation

• Maintaining a consistent background level of heating can help prevent condensation forming.
• Short bursts of high heat followed by cooling can increase condensation, so steady heating is generally more effective.
• Adequate insulation and draught proofing can also help reduce cold surfaces and improve energy efficiency.

Black mould can grow on walls, ceilings, furnishings, clothing and other items. It should be removed carefully to prevent spores spreading.

• Wipe away mould using a damp cloth and dispose of it afterwards. Avoid brushing mould, as this releases spores into the air.
• Clean affected areas using a suitable fungicidal treatment or diluted bleach solution.
• Wear gloves and consider eye protection when using cleaning products.
• Always test cleaning solutions on a small, inconspicuous area first.

Natural treatments such as a diluted tea tree oil solution may also be used on suitable surfaces.

After cleaning, allow the area to dry fully. Where necessary, apply anti-mould paint or treatments to help prevent recurrence.

If you are struggling with energy costs, support may be available.

You can find advice and support through Ofgem’s energy advice services, and eligible households may be able to access additional assistance through schemes such as the Priority Services Register.

Priority services register

Information on cost of living support and available grants, including schemes to improve home energy efficiency, can be found on official government and energy advice websites.

Energy support