Damp and mould

Dampness can occur in homes for many reasons. It can lead to mould and mites, problems keeping your home warm and damage to the building.

Causes of damp

There are many causes of damp, including:

  • leaking pipes and overflows
  • rain water entering through holes in the roof
  • blocked or damaged guttering
  • rising damp caused by a defective or missing damp course
  • gaps in the external walls or around the windows
  • in newly built homes, water used in construction may still be drying out

These problems often leave a tide mark or coloured stains. The cause of the damp should be repaired as soon as possible. You will then need to dry the dampness out.

If you see black mould growing this is likely to be caused by condensation.


When air gets colder it holds less moisture and this makes tiny drops of water form. Condensation usually happens in cold weather on both wet and dry days. It occurs on cold surfaces and in areas with little air movement. Signs of condensation include:

  • water forming on windows
  • mould growth on window frames
  • damp and mould forming on external walls
  • mould forming in areas behind large pieces of furniture
  • mouldy clothes
  • mould growing in corners of rooms and where walls and ceilings meet

There is also a type of condensation called interstitial condensation. This happens when warm, moist air soaks into a wall, ceiling or floor before hitting a cold surface within. The air quickly cools and water is left as dampness on the surface. This can look like rising damp. Interstitial condensation can lead to rot and corrosion.

Avoiding condensation

Produce less moisture by:

  • drying washing outside – if you need to dry clothes indoors, do it this in the bathroom with the extractor fan on or a window open
  • venting non-condenser tumble dryers to the outside
  • opening the window to allow moist air to escape after a bath or shower

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

  • opening a window of the room you are using a small amount
  • using a cooker hood that vents to the outside
  • do not block or completely cover ventilation points or chimneys (fit an air brick with a louvred grill)
  • ventilate cupboards and wardrobes – either by cutting a slot in the back or leaving a gap between the furniture and the wall

Keeping your home warm will also reduce condensation. You can do this by fitting insulation and draught excluders.

Dealing with existing condensation and mould

Control mould growth – wipe surfaces with a fungicidal wash, dry clean mildewed clothes and shampoo carpets. Do not brush mould as this releases spores into the air.

Remove excess moisture from your home – wipe water off windows and surfaces as it forms or use a dehumidifier.

Keep the property warm and ventilated.

Last updated on 13/11/2020