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Condensation, damp and mould

Condensation happens in all homes when warm moist air meets a cold surface and tiny water droplets develop. The more moisture in the air, the more water is produced. 

Everyday activities such as cooking, washing clothes and bathing create moisture in the air. There is always some moisture in the air and warm air holds more moisture than cold air. You notice it when you see your breath on a cold day or when the mirror mists over when you have a bath. 

Condensation often happens because warm damp air from kitchens and bathrooms moves to cooler areas, such as bedrooms. It happens more in cold weather, even if it is raining or dry. Look for it in corners, on or near windows and in or behind wardrobes and cupboards.

How it affects you

If left unchecked and untreated, condensation can become a serious problem. Too much condensation will make your home damp. House dust mites and mould growth both occur more often in damp conditions and these are associated with allergic reactions. 

Damp conditions can also cause damage to your home, such as causing windows to rust or rot, and plaster to perish, and in serious cases can damage electrics. Your decorations can be spoilt by damp and mould growth. 

Is it condensation or a leak?

Condensation is caused by moisture produced in the home, but it’s not the only cause of damp. It can also come from building or plumbing leaks or rising damp.

A double-glazed window with water droplets building up on the bottom of the glass

Typical signs of condensation

  1. Dampness occurring in winter rather than summer.
  2. Walls, ceilings and cold surfaces, such as cold water pipes, “sweat” with moisture.
  3. Water appears on the inside of windows.
  4. Outside walls are affected rather than walls between rooms.
Spots of black mould forming around the inside of the window frame

Signs of mould because of Condensation

  1. Damp and black mould in the corners of rooms, behind furniture and in cupboards.
  2. Clothes in cupboards and drawers have a musty smell and mildew on them.
Dampness from leaks

Signs of leaks or penetrating dampness

  1. It can happen at any time of year.
  2. You can see a definite damp area with water staining.
  3. Little or no black mould appears on the damp area. If you suspect that dampness in your home is caused by a leak you should report it to us.

Preventing condensation: your responsibilities

Looking after your home
  1. Remove mould growth by using a mould and mildew cleaning product (available from most supermarkets and DIY stores). Make sure you use a product which has a Health and Safety Executive approval number and that you follow the manufacturer’s instructions.
  2. Wipe down the inside of windows if they become wet with condensation.
  3. Do not place beds and wardrobes against outside walls as mould is more likely to grow behind furniture.
  4. Don’t put too many things in wardrobes and cupboards as it stops the air circulating.
  5. If you rent a home from the Council, report any repairs to us promptly, including any problems with extractor fans and heating systems. 
  1. When you redecorate your bathroom or kitchen use a paint designed to be used in these rooms. 
  2. If you are decorating a room where mould is a problem it’s best to remove any wallpaper and instead use a good quality fungicidal paint.
  3. Treat and remove the mould before redecorating; there are various products on the market that will help, such as fungicidal products available in DIY stores.
  4. Use a stain block or sealer to help stop mould coming back.
Reducing steam and moisture 
  1. When cooking, cover pans with lids and keep the kitchen door closed to stop wet air from circulating around your flat or house. Make sure a window is open or the extractor fan is on.
  2. If you use a tumble dryer, make sure it is vented so that the air escapes to the outside. 
  3. If you have to dry clothes indoors put them in a room and close the door, leaving the window wide open or fan on. 
  4. When bathing, run cold water into the bath first and then run the hot water. This creates less steam.
Heating your home
  1. Heat all rooms even if they are not being used – radiators with thermostatic radiator valves (TRVs) will give you greater control over the heat from each individual radiator. 
  2. If you have central heating use the thermostat to set the temperature to a comfortable level (around 18°c to 21°c). Remember, turning the thermostat down by one or two degrees can save energy and save you money.
  3. Do not place furniture in front of radiators, as this will stop them from heating the room. 
  4. Do not use the heating on a high setting for short periods of time. Heating your home for a longer time at a lower temperature will keep your home warmer and cost you less.
  5. Do not use portable LPG (Calor Gas) heaters. These produce a lot of moisture and are not allowed in our homes for health and safety reasons. 

If you are struggling to heat your home and need advice on how to stay warm and save on energy bills please visit the Green Doctors website or visit the government website.

Ventilating your home
  1. It’s important to allow plenty of fresh air into your home to stop the air indoors becoming stale and humid, which is not good for your health. 
  2. Always keep a small window or an air vent open when you are at home. It’s best to keep air vents open all the time. 
  3. After you’ve had a bath or shower, open the bathroom window until the steam has cleared or use the extractor fan if you have one.
  4. When cooking, make sure the kitchen door is closed and either the extractor fan is on (if you have one) or a window is open.
Extractor fans
  1. Some of our homes are fitted with extractor fans. These can quickly remove damp air from kitchens and bathrooms, where most moisture is produced.
  2. Extractor fans should be used whenever you are cooking or bathing. After you’ve finished in the bathroom or the kitchen, leave the fan on for about 20 minutes to make sure all the steam has cleared.
  3. When using an extractor fan keep the windows in the room closed. If a window is open the fan will draw air in from outside, rather than drawing the damp air out from the room. Make sure your curtains or blinds don’t cover the fan.
  4. Some fans switch on and off automatically according to the amount of moisture in the air. Do not turn these off at the power switch as they are designed to work when they are needed. If you suspect that they are coming on more or less often than they should please report this to us.

Repairs and improvement works for tenants: our responsibilities 

In most cases if you follow the steps here you will be able to keep condensation under control. Hopefully this will avoid the need for repairs, but please let us know if condensation continues to be a problem.

Older and disabled tenants

If you are a tenant over 65 years of age or are disabled, we may be able to help you treat mould in your bathroom, toilet or kitchen. Please contact us to arrange an inspection.

We will consider carrying out work if:  

  1. There is widespread mould growth in a bedroom or living room. 
  2. You are a tenant and have followed this advice and still have very bad condensation and mould growth.
  3. You have bad condensation and mould like this in a living room or bedroom contact us to arrange an inspection – we may need to carry out works, which could range from a professional mould clean, to insulating walls or fitting extractor fans.

We will not carry out work: 

  • on small areas of mould 
  • in hallways, bathrooms, toilets or kitchens 
  • if you have small patches of mould growth, you will need to remove it yourself using cleaning products and anti-mould paints.

If you have questions about condensation or responsibilities for repairs in your home, please contact us on 0800 137 111 or email [email protected].

Housing Association and privately rented tenants

If you have questions about condensation or responsibilities for repairs in your Housing Association or privately rented home, contact your landlord as soon as possible and write (by letter, e-mail or text message) to them about the problems with the property.

Visit Shelter's website for further advice on how to report problems and for a template letter you can use and keep copies of all letters, e-mails and messages that you send.  

If you have contacted your landlord about repairs needed in your rental home and have not received a satisfactory response, the Private Sector Housing Team may be able to take action to get them to complete works. They can provide advice and where necessary, order the landlord to do the necessary repairs.

More information can be found in:

If you have any queries, you can contact the Private Sector Housing Team by calling the Environmental Healthline on 020 7361 3002 or by email at [email protected].

Last updated: 7 June 2023