Damp and mould

There are four main types of dampness that could affect your home:

  • Rising damp;
  • Penetrating damp;
  • Damp from faulty plumbing; and
  • Condensation.

It is important to understand the difference between the different types so that the problem can be treated effectively.

What is rising damp?

Rising damp is caused by water rising from the ground into the home. The water gets through or around a broken damp-proof course (DPC) or passes through the natural brickwork if the property was built without a DPC. (A DPC is a layer of waterproof material put in the walls of a building just above ground level. It stops moisture rising up through the walls.)

Rising damp will only affect cellars and ground floor rooms. It will normally rise no more than 12 to 24 inches (300mm to 600mm) above ground level, and 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 plaster to crumble and paper to lift in the affected area.

Note: Black mould rarely appears where there is rising damp. This is because rising damp carries salts from the ground, which prevent the growth of black mould.

What is penetrating damp?

This type of dampness only appears on the outer walls (external walls) of a property or, in the case of leaking roofs, on ceilings. It only appears because of a fault outside the home, such as missing pointing to the brickwork, cracked rendering or missing roof tiles. Water can pass through these faults.

Penetrating damp is far more noticeable after it has rained and will normally appear as a well-defined ‘damp patch’ which feels damp to the touch.

Note: Black mould rarely appears on areas of penetrating damp. This is because the affected area is usually too wet. Also, the water contains salts picked up when passing through the wall, which prevent the growth of black mould.

Damp from faulty plumbing

Water and waste pipes, especially in bathrooms and kitchens, can leak from time to time. They can affect ceilings and both external and internal walls. The affected area looks and feels damp to the touch and stays damp whatever the weather conditions.

A quick examination of water and waste pipes inside the property, the seals around the bath, shower and sinks, and any external pipework, such as guttering, will usually find the source of the problem.

Note: Black mould rarely appears with this type of dampness because the area is usually too wet. Also, the chemicals in waste water will prevent mould from growing.

If you think you have rising damp, penetrating damp or faulty plumbing, please ring our repairs hotline on 01226 787878.


What is condensation?

Condensation is by far the most common cause of dampness, resulting in a large number of enquiries or complaints from our tenants and residents.

Condensation is caused by water vapour or moisture inside the home coming into contact with a colder surface, such as a window or wall.

The water drops (condensation) then soak into the wallpaper, paintwork or plaster. In time, black mould grows on the surface of the damp areas.

Condensation arises mainly during the colder months, whether it is rainy or dry outside. It is usually found in the corners of rooms, on walls that face north, and on or near windows.

It is also found in areas where there is little ventilation and 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.

What causes condensation and mould growth?

Most homes will be affected by condensation at some time. However, certain activities can increase the problem. Cooking, washing and drying clothes all produce water vapour that can only be seen when tiny droplets of water (condensation) appear on colder surfaces such as walls, windows, ceilings or mirrors.

Condensation – The amount of condensation in a home depends on three things:

  • the amount of water vapour produced in the home;
  • how cold or warm the home is; and
  • the amount of ventilation there is.

Simply turning the heating up will not solve the problem – it may only reduce condensation temporarily. You need to tackle all three issues to reduce the problem.

The first sign of a problem is ‘misting’ and water droplets on windows and other cold surfaces taking a long time to disappear. This makes the surfaces become damp (this may not always be noticeable if you have double-glazed windows). The second indication is patches of black mould growing on the walls and ceilings.

Black mould – Mould spores are too small to be seen but are always present in the atmosphere, both inside and outside homes. They only become noticeable when they land on a surface and grow. This mainly happens in the cold winter months.

Mould needs pure water to grow, and condensation is pure water (unlike rising damp and penetrating damp which picks up minerals, salts and soil when it passes through a wall or floor).

People often find it difficult to believe that severe mould can be caused by condensation and think there is fault that needs to be repaired. This is often not the case.

For mould to thrive and survive it needs:

  • moisture (from condensation);
  • food (such as wallpaper or emulsion paint);
  • a suitable temperature; and
  • oxygen.

By dealing with the causes of condensation, you will automatically deal with the problem of mould.

What can I do to reduce condensation and mould growth in my home?

The below six simple steps can help reduce the amount of condensation and black mould in your home:

1.Produce less moisture – Dry clothes outside. Avoid drying clothes indoors whenever possible. If you have to, use a clothes airer in the bathroom with the door closed and an extractor fan on or a window open. Vent tumble driers to the outside (never into the home) or use a condensing drier. Cover pans when cooking and do not leave kettles boiling. Doing this could also help you save on your energy bills.

Do not use paraffin or bottled-gas heaters.

They produce large amounts of water vapour and are very expensive to run!

Do not leave the bath, sink or basin full when you have finished washing. The water will begin to evaporate and will cause condensation.

2. Remove excess moisture – Wipe the windows and windowsills of your home every morning to remove condensation. This is especially important in the bedroom, bathroom and kitchen. Just opening the window is not enough.

3.Ventilate rooms to remove moisture – It is important to remove condensation and excess moisture by ventilating rooms. You can ventilate a room without making draughts or causing it to become cold. To do this, you may only need to open the window slightly or use the ‘trickle vent’ often found on new uPVC windows. This allows warm (but moist) air to escape to the outside and let in cool (but dry) air.

If a room feels stuffy, heavy or smells musty, it is likely that there are high levels of condensation in that room.

  • Always open a window or use an extractor fan when using the kitchen or the bathroom, and close the doors to prevent moisture in the air from spreading to other parts of the home. Continue to ventilate these rooms for a short time after a shower, a bath or cooking, and keep the door closed!
  • Open bedroom windows for up to an hour as soon as you get up and throw back the sheets or duvets to air the bed and bedding.
  • Clear windowsills of clutter that will obstruct the opening of the window or restrict the flow of air.
  • Leave a space between the back of furniture and cold walls.
  • Ventilate cupboards and wardrobes, and avoid overfilling them as this prevents air circulating.
  • Do not block chimneys, flues and air vents.
  • Open the window in the room when you are ironing or drying your hair.

4. Heat your home a little more – In cold weather, the best way to keep rooms warm and avoid condensation is to have a low background heat all day rather than heating rooms in short bursts of high heat when you are at home. Good heating controls on your radiators, room thermostats and a timer will help control the heating throughout your home and manage costs.

5.Insulate and draught-proof – This will help keep your home warm and save money on your heating bills. Most Berneslai Homes properties already have adequate loft and cavity-wall insulation.

6.Dealing with mould – Black mould can grow on walls, ceilings, silicone sealant around windows, bedding, carpets, clothes, leather goods and toys. This can be upsetting. It can also be expensive to replace items.

How can I remove mould?

Carefully remove excess mould with a damp cloth or sponge. Throw the cloth or sponge away after using it.

Clean the item with a fungicidal wash that carries a Health and Safety Executive (HSE) approval number. Make sure you follow the instructions for using it safely. You can buy fungicidal wash from many supermarkets, DIY stores or painting and decorating shops.

Clothes affected by mould should be dry cleaned.

You should shampoo any affected carpets.

After treating surfaces to remove mould, redecorate using a good-quality fungicidal paint. If you are wallpapering, add a fungicidal additive to the paste.

Please note: the fungicidal paint or wallpaper paste will not be effective if you cover it with ordinary paint or paper over it with ordinary paste.