Property disrepair including damp and mould

What’s causing the damp and mould?

Mould is caused by damp conditions. Sometimes it's easy to spot the cause of damp.

Condensation is the most common form of damp in rented properties.

It appears when excess moisture in the air comes into contact with a cold surface, such as a window or a cold wall. It can lead to mould growth and tends to be worse in winter.

It can be caused by a tenant not ventilating or heating their home properly.

It can also be caused by poor insulation or faulty heating and ventilation systems, which are the responsibility of the landlord.

Ventilation and controlling moisture

Everyday activities like cooking, showering and drying clothes create moisture in your home, which can lead to condensation.

It can help if you do the following in the bathrooms and kitchen:

  • keep the door closed while cooking/washing so that the excess moisture doesn’t spread around the whole house
  • use the extractor fan and/or open a window to let the steam escape
  • when cooking, use lids on saucepans to contain the steam
  • close the door again after using the room and leave it to ventilate for a short while
  • close the window and leave the door ajar so it can slowly warm up again without a rush of cold air flooding into the rest of the property

Around the property:

  • when condensation forms on windows, it can run down and pool on the window sill - make sure to wipe this away so it doesn’t attract mould spores
  • avoid drying wet clothes on radiators and keep the space around them clear so the warm air can circulate properly
  • make sure any room used for hanging out laundry is well ventilated
  • keep the thermostat at a minimum of 15°C in very cold weather - not only will this help reduce condensation levels in the property, but it will also protect the pipework from freezing

Information on controlling condensation and mould

What is condensation?

There is always some moisture in the air, even if you cannot see it. If air gets cold, it cannot hold all the moisture produced by everyday activities, and some of this moisture appears as tiny droplets of water, most noticeable on windows on a cold morning. This is condensation. It can also be seen on mirrors when you have a bath or shower and on cold surfaces such as tiles or cold walls. It is not always visible, especially on surfaces such as wallpaper.

Condensation occurs in cold weather, even when the weather is dry. It doesn’t leave a ‘tidemark’ around its edges on walls. If there is a ‘tidemark’, this dampness might have another cause, such as water leaking into your home from a plumbing fault, loose roof tiles or rising damp.

Look for condensation in your home. It can appear on or near windows, in corners, often behind curtains and in or behind wardrobes and cupboards. Condensation forms on cold surfaces and places where there is little movement of air.

Problems that can be caused by excessive condensation

Dampness caused by excessive condensation can lead to mould growth on walls and furniture, mildew on clothes and other fabrics and the rotting of wooden window frames. Also, damp, humid conditions provide an environment in which house dust mites can easily multiply. The presence of mould and dust mites can make existing respiratory conditions such as asthma and bronchitis worse. Condensation mould often appears as small black dots.

First steps against condensation

You will need to take proper steps to deal with condensation, but meanwhile, there are some simple things you should do straight away.

Dry your windows and window sills every morning, as well as surfaces in the kitchen or bathroom that have become wet. Wring out the cloth rather than drying it on a radiator

First steps against mould growth

First, treat the mould already in your home, then deal with the basic problem of condensation to stop mould from reappearing.

To kill and remove mould, wipe down or spray walls and window frames with a fungicidal wash that carries a Health and Safety Executive (HSE) ‘approval number’, and ensure that you follow the instructions for its safe use. These fungicidal washes are often available at local supermarkets and many DIY stores. Dry-clean mildewed clothes and shampoo carpets. Do not try to remove mould by using a brush or vacuum cleaner.

After treatment, redecorate using good-quality fungicidal paint and a fungicidal-resistant wallpaper paste to help prevent mould from recurring. The effect of fungicidal or anti-condensation paint is destroyed if covered with ordinary paint or wallpaper.

Remember: the only lasting cure for severe mould is to get rid of the dampness.

What causes condensation?

There are four main factors that cause condensation:

  • too much moisture being produced in your home
  • not enough ventilation
  • cold surfaces
  • the temperature of your home

You must look at all these factors to cure a condensation problem.

Too much moisture being produced in your home

Our everyday activities add extra moisture to the air inside our homes. Even our breathing adds some moisture (remember breathing on cold windows and mirrors to fog them up). One person asleep adds half a pint of water to the air overnight and at twice that rate when active during the day.

To give you some idea as to how much extra water this could be in a day:

  • 2 people at home for 16 hours = 3 pints
  • a bath or shower = 2 pints
  • drying clothes indoors = 9 pints
  • cooking and use of a kettle = 6 pints
  • washing dishes = 2 pints
  • bottled gas heater (8 hours use) = 4 pints

Total moisture added in one day = 26 pints or 14.8 litres.

Reduce the potential for condensation by producing less moisture
  • hang your washing outside to dry if at all possible, or hang it in the bathroom with the door closed and a window slightly open or an extractor fan on. Don’t be tempted to put it on radiators or in front of a portable electric or gas heater
  • if you use a tumble drier; make sure it is vented to the outside or that it is of the condensing type
  • always cook with pan lids on, and turn the heat down once the water has boiled. Only use the minimum amount of water for cooking vegetables
  • when filling your bath; run the cold water first, then add the hot - it will reduce the steam by 90%, which will help to prevent condensation
  • try to avoid the use of bottled gas heaters; they produce about 8 pints of moisture from an average-sized gas cylinder
  • don’t use your gas cooker to heat your kitchen as it produces moisture when burning gas. (You might notice your windows misting over)
  • if you use baby sterilizing equipment, ensure that you open a window when it is in use

Ventilation of the home

Ventilation can help to reduce condensation by removing moist air from your home and replacing it with drier air from outside.

  • help to reduce condensation that has built up overnight by ‘cross-ventilating’ your home - opening to the first notch a small window downstairs and a small one upstairs. (They should be on opposite sides of the house or diagonally opposite if you live in a flat). At the same time, open the interior room doors. This will allow drier air to circulate throughout your home. Cross-ventilation should be carried out for about 30 minutes each day
  • ventilate your kitchen when cooking, washing up or washing by hand. A window slightly open is as good as one wide open. If you have one, use your cooker extractor hood or extractor fan
  • keep kitchen and bathroom doors closed to prevent moisture from escaping into the rest of the house
  • ventilate your kitchen and bathroom for about 20 minutes after use by opening a small top window. Use an extractor fan if possible - they are cheap to run and very effective
  • ventilate your bedroom by leaving a window slightly open at night (but remember your security) and ensure the trickle vents on your windows are open permanently (if fitted)
  • to reduce the risk of mildew on clothes and other stored items, allow air to circulate around them by removing ‘false’ wardrobe backs or drilling breather holes in them. You can place furniture on blocks to allow air to circulate underneath. Keep a small gap between large pieces of furniture and the walls, and where possible, place wardrobes and furniture against internal walls. Pull shelves away from the backs of wardrobes and cupboards. Never overfill wardrobes and cupboards, as it restricts air circulation

Cold surfaces in your home

Condensation forms more easily on cold surfaces in the home, for example, walls and ceilings. In many cases, those surfaces can be made warmer by improving the insulation and draughtproofing. Insulation and draughtproofing will also help keep the whole house warmer and will cut your fuel bills. When the whole house is warmer, condensation becomes less likely.

Loft and cavity wall insulation are the most effective forms of insulation. If you install any draughtproofing, observe the following guidance:

  • do not draughtproof rooms with a condensation problem or where there is a heater or cooker that burns gas or solid fuel
  • do not block permanent ventilators or airbricks installed for heating or heating appliances
  • do not draughtproof bathroom or kitchen windows

If you are a tenant and have reason to believe that your home could benefit from an improvement to its loft or wall insulation, please contact your landlord to enquire about the possibility of such an improvement.

The temperature of your home

Warm air holds more moisture than cooler air which is more likely to deposit droplets of condensation around your home. Air is like a sponge; the warmer it is, the more moisture it will hold. Heating one room to a high level and leaving other rooms cold makes condensation worse in the unheated rooms. A short burst of high-level heating only warms up the room’s air temperature. Low or medium-level heating over a longer period will heat the air temperature and the fabric of the house, such as the walls. Once heated, the fabric will retain some of the added warmth, which in turn will reduce the time and amount of heat needed to warm the room up the next time.

Heating controls, such as thermostats and timers etc, can be used to ensure you have adequate levels of heating in the right places at the right times. This can also help reduce heating bills. Keeping the heating on low all day in cold weather will help to control condensation, but keep a check on your meters to check how much it is costing you.

  • if you don’t have heating in every room, you could keep the doors of unheated rooms open to allow some heat into them
  • to add extra heat to rooms without any form of installed heating, it is better to use electric heaters, for example, oil-filled radiators or panel heaters, on a low setting. Remember, you should not use portable bottled gas heaters in homes suffering from condensation as they give out a lot of moisture whilst in use. Contrary to popular belief, it is actually cheaper to heat a room with on-peak electricity than by using bottled gas heaters
  • if you have a freezer or other electrical equipment such as a computer or Freeview box, it is a good idea to put it in a space suffering from condensation, as the heat will help to keep condensation at bay
  • be careful not to ‘over-ventilate’ your home when it is cold, as it will cause the temperature inside to drop and make condensation more likely. It will also increase your heating costs

If you think that the heating or heaters installed in your home are insufficient to give enough heat to combat condensation, it may be worth considering improving your heating and or insulation.

If you require extra warmth or insulation, you might wish to contact us to enquire about grants and discount schemes.

Key points to remember

  • reduce the amount of moisture you produce
  • improve the ventilation
  • reduce the number of cold surfaces in your home
  • to improve the energy efficiency of your home, ring the Energy Saving Trust on 0800 444 202
  • maintain an adequate temperature
  • there may be grants and discounts available to help you insulate and heat your home. For further information, visit Help with the cost of living

Complaining about property conditions

If you live in a privately rented property that isn’t being kept in a safe condition, then you should contact your landlord or agent first and make them aware of this issue. If your landlord fails to carry out repairs, then the Housing Environmental Health team can assist with this. The team inspect your property to assess potential risks to health and safety and, where necessary, require landlords to make any repairs/improvements.

Examples of problems the team deals with include: fire safety, damp and mould, electrical safety and defective gas boilers.

You can check if your rented property has a licence by looking at the public register, which has a list of the properties that the council has licensed.

If you think that your property needs a licence or it isn’t in good repair and fails to meet the necessary standards and conditions, please get in contact with us so we can investigate this. The GLA has a rogue landlord checker that you can access.

The team's contact details are 020 3045 3456 or