Skip to main content

Keep your home free from damp and mould

It's not uncommon to have damp and mould in a property at some point. Even in warm and well looked after properties, mould growth can occur in some parts of the home, especially in colder months. Most mould growth that people will experience is the result of condensation. However, some instances of damp and mould may be the result of rising or penetrating damp or possibly a plumbing leak.

Reports of damp increase during winter with colder temperatures. The likelihood is that the risk of properties getting mould will increase with the energy costs rising and us all looking to reduce our use of heating.

It is important to be aware that there is a difference between mould caused because of a defect in the property and the mould caused by condensation.

Causes of damp and mould

A number of things can cause damp in the home. It can come from:

  • Leaking pipes, wastes or overflows (plumbing leaks)
  • Rain seeping through the roof where a tile or slate is missing, spilling from a blocked gutter, penetrating around window frames, or leaking through a cracked pipe (rain penetration)
  • Rising damp due to a defective damp-course or because there is no damp-course - these causes often leave a 'tidemark' (rising damp)
  • Water vapour or moisture from inside the dwelling coming into contact with a colder surface, such as a window or wall (condensation)

If your home is newly built, it may be damp because the water used during its constructions (e.g. in plaster) is still drying out.

If your home is damp for any of these reasons, it may take weeks of heating and ventilation to dry it out. Hiring a dehumidifier will help.

If you don't think the damp comes from any of these causes, then it is probably condensation.

Damp

The four main types of damp are:

Water rising from the ground into the home causes rising damp.

The water gets through or round a broken damp proof course (DPC) or passes through the natural brickwork if the property was built without a DPC. A DPC is a horizontal layer of waterproof material put in the walls of a building just above ground level. It stops moisture rising through the walls by capillary action.

Rising damp only affects basements and ground floor rooms. It normally rises no more than 12 to 24 inches above ground level (300mm to 600mm). It usually leaves a 'tide mark' low down on the wall. You may also notice white salts on the affected areas.

Rising damp will be present all year round but is more noticeable in winter. If left untreated, it may cause wall plaster to crumble and paper to lift in the affected area.

Note - you will rarely see black mould where there is rising damp (and then only in the early stages). This is because rising dampness carries with it ground salts which prevent the growth of black mould.

This type of dampness will only be found on external walls or in the case of roof leaks, it will normally show as water staining on ceilings. It only appears because of a defect outside the home, such as missing pointing to the brickwork, cracked rendering or missing roof tiles. These defects then allow water to pass from the outside to the inner surfaces.

Penetrating dampness is far more noticeable following a period of rainfall and will normally appear as a well defined ‘damp-patch’ which looks and feels damp to the touch.

Note - black mould is rarely seen on areas of penetrating dampness. This is because the affected area is usually too wet and the dampness contains salts picked up when passing through the wall, which prevent the growth of black mould.

Leaks from water and waste pipes, especially in bathrooms and kitchens, are relatively common. They can affect both external and internal walls and ceilings. The affected area looks and feels damp to the touch and remains damp whatever the weather conditions outside. A quick examination of the water and waste pipes serving the kitchen and bathroom and the seals around the bath, shower and sinks; plus the external pipework, such as guttering will usually find the source of the problem.

Note - black mould will rarely be seen on this type of dampness because the area is usually too wet and the chemicals in a waste water leak will prevent mould growth.

This is by far the most common cause of dampness experienced by tenants and householders, resulting in a large number of enquiries or complaints received by the Council.

Condensation is caused by water vapour or moisture from inside the dwelling coming into contact with a colder surface, such as a window or wall. The resultant water drops (condensation) may then soak into the wallpaper or paintwork or even plasterwork. In time, the affected damp areas then attract black mould that grows on its surface.

Condensation mainly occurs during the colder months, whether it is rainy or dry outside. It is usually found in the corners of rooms, north facing walls and on or near windows. It is also found in areas of little air circulation such as behind wardrobes and beds, especially when they are pushed up against external walls.

Note - black mould is frequently seen on this type of dampness.

Condensation

There is always moisture in the air, but as air temperatures cool down, the air can’t hold as much moisture and tiny drops of water appear – this is condensation. It mainly happens during cold weather and appears on cold surfaces and places where there is little air movement such as:

  • In corners of rooms
  • Near and on windows
  • Behind cupboards and wardrobes

It is in these conditions that black mould can start to appear.

Signs of condensation include:

  • Water forming on windows
  • Mould growth on window frames
  • Damp and mould forming on internal and external walls
  • Mould forming in areas behind large pieces of furniture including wardrobes or cupboards
  • Mouldy clothes
  • Rotting leather goods, caused by high humidity
  • Mould growth in corners of rooms and in the junction between ceiling and walls

Preventing condensation

Condensation happens when the amount of heating, ventilation and moisture production in a home are not balanced. Here are three steps to help reduce condensation in your home.

Some every day activities produce a lot of moisture very quickly. You should:

  • Cover pans and do not leave kettles boiling
  • Avoid using portable flueless bottled gas heaters as these heaters put a lot of moisture into the air
  • Avoid drying your washing indoors or put it in the bathroom with the door closed and the window open or fan on
  • Vent any tumble dryer to the outside, unless it is the self-condensing type. DIY kits are available for this. Alternatively consider using a local laundrette.

It is very important to ventilate your home. You can do this without causing draughts:

  • Keep a small window ajar or a trickle ventilator open when someone is in the room
  • Ventilate kitchens and bathrooms when in use by opening the windows wider
  • Close the kitchen and bathroom doors when these rooms are in use, even if your kitchen or bathroom has an extractor fan
  • Ventilate cupboards and wardrobes. Avoid putting too many things in them as this stops the air circulating.
  • Ventilate cupboards / wardrobes - cut a ventilation slot in the back of each shelf or use slatted shelves. Cut 'breather' holes in doors and in the back of wardrobes and leave space between the back of the wardrobe and the wall
  • Where possible, position wardrobes and furniture against internal walls
  • Ensure extractor fans are fitted in your kitchen and bathroom; ideally extractor fans should have an integral humidity sensor and a 20 minute over-run

Insulation and draughtproofing helps keep your home warm and cuts fuel bills. When the whole home is warmer, condensation is less likely.

  • Warm homes suffer less from condensation. If possible keep your heating on a low setting all day as this is more effective than short bursts of heat.
  • Check your loft has at least 270mm of insulation, ensure the loft hatch is insulated too*
  • Consider cavity wall insulation. Before deciding though, you should talk to your local building inspector as building regulations approval may be required*
  • Consider secondary and double glazing of windows to reduce heat loss and draughts but you must make sure that there is some ventilation.
  • Keep low background heating on all day in cold weather, even when there is no one at home. It is cheaper than warming your home up from cold each day.

*Funding may be available to assist with these improvements. View our Local Energy Advice Partnership page or contact your fuel provider (Eon, EDF Energy etc) for further information

It is important that you do not:

  • Block permanent ventilators
  • Completely block chimneys. Instead, leave a hole about two bricks in size and fit a grille
  • Draughtproof rooms where there is already condensation or mould
  • Draughtproof a room where there is a cooker or a fuel burning heater, for example, a gas fire
  • Draughtproof windows in the bathroom and kitchen

Mould

How to treat mould

Black mould has a very distinctive appearance:

  • When active and germinating it is usually dark green or black and slimy
  • In its inactive state it will appear dry and powdery. 

Black mould is the common name given to a specific type of mould. It’s a common household problem that is generally caused by condensation or moisture in the air.

First treat any mould you may already have in your home. If you then deal with the basic problem of condensation, mould should not reappear.

  • Treat existing mould by wiping down walls and window frames with a mixture of white vinegar, water and baking soda or a mould spray remover
  • Dry-clean mildewed clothes, and shampoo carpets
  • After treatment, redecorate using a good quality fungicidal paint to stop the mould from coming back. Note that this paint is not effective if you go over it with ordinary paints or wallpaper
  • Deal with the basic problem of condensation to stop the mould from coming back

Disturbing mould by brushing or vacuum cleaning can increase the risk of respiratory problem.

Damp and mould leaflet

We have provided the leaflet below for you to print.

Damp and mould leaflet686KBpdf
Size: 686KBFile format: pdf

Energy efficiency of privately rented homes

Privately rented homes in the UK should have an energy efficiency rating of Band E. Find an energy certificate for a property on the EPC register on the GOV.UK website.

Getting your landlord to improve the energy efficiency of your home will help reduce damp and mould and could reduce your heating bills.

If the EPC rating of your rented property is F or G, please report this to us by emailing Housing.Standards@peterborough.gov.uk. We will work with your landlord to see what improvements they can make to your home.