Mould, damp and condensation


Types of dampness

Condensation and mould growth 

Types of dampness

Rising damp

  • Caused by water rising from the ground into the home. The water gets through a broken damp proof course or through the natural brickwork if the property was built without one;
  • Rising damp will only affect basements and ground floor rooms;
  • Usually leaves a 'tidemark' low down on the wall;
  • More noticeable in the winter;
  • If left untreated it may cause wall plaster to crumble and paper to lift in the affected area.

Penetrating dampness

  • Will only be found on external walls or in the case of roof leaks, on ceiling;
  • Only appears because of a defect outside the home, such as missing pointing to the brickwork, cracked rendering or missing roof tiles;
  • Will normally appear as a well defined 'damp-patch' and feels damp to the touch.

Defective plumbing

  • Caused by leaks from water waste and pipes; 
  • Affected area looks and feels damp to the touch.

Note: Black mould will rarely be seen in the above situations. 


  • By far the most common cause of dampness;
  • Caused by water vapour or moisture from inside the dwelling coming into contact with a colder surface, such as a window or wall;
  • Affected damp areas then attract black mould over time that grows on its surface;
  • Mainly occurs during the colder months;
  • 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. 

Condensation & mould growth

Condensation causes black mould growth.

Our everyday activities add extra moisture to the air inside our homes. 

The table below gives you some idea of how much water you could be adding to the air every day:

Activity Amount
2 people active for 1 day 3 pints
Cooking and boiling a kettle 6 pints
Having a bath or shower 2 pints
Washing clothes 1 pint
Drying clothes 9 pints
Paraffin or portable gas heater 3 pint
Total amount of moisture produced for 1 day 24 pints

The amount of condensation in a home depends upon 3 factors:

  • How much water vapour is produced by the occupier
  • The temperature of the property
  • How much air circulation (ventilation) there is

All three factors may need to be looked at to reduce the problem.

Black mould

For mould to thrive and survive it requires five elements:

  • Moisture - obtained from condensation
  • Food - such as wallpaper or emulsion paint
  • Suitable temperature - courtesy of the householder
  • Oxygen - courtesy of mother nature
  • Airborne Bacteria - courtesy of germs in the atmosphere

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

Reducing condensation & black mould

Four steps to reducing condensation and black mould growth

Produce less moisture

  • Dry clothes outdoors wherever possible. If you do not have an outdoor drying area, dry them on a clothes airer in the bathroom with the door closed and either an extractor fan on or a window open.
  • Vent your tumble driers outside including the condensing type.
  • Cover pans when cooking and do not leave a kettle boiling unnecessarily. 

Remove excess moisture

Wipe the windows and window sills 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. 

Open the windows

  • Open windows slightly to allow warm (but moist) air to escape and let in cool (but dry) air. Dry, cool air is actually cheaper to heat than warm moist air!
  • Always open a window when using the kitchen or bathroom and close the doors to stop moisture in the air from spreading to other parts of the house. Keep the window open for a short time after you have left the room. 
  • Open bedroom windows for up to one hour after your wake.
  • Leave space between the back of furniture and cold / external walls.
  • Do not completely block chimneys and flues.

Heat your home a little more

In cold weather the best way to keep rooms warm and avoid condensation is to keep low background heat on all day rather than short bursts of high heat when you are in the house. 

If you have heating controls on your radiators, room thermostats and a timer, please use them to regulate the heating throughout your home, as this will help in managing costs. 

Your responsibilities

  • Carefully remove excess mould with a damp cloth and dispose. Do not brush mould as this releases spores into the air.
  • Wipe down affected areas using a good quality mould and mildew spray.
  • After treatment redecorate using a specialist bathroom or kitchen paint, and if wallpapering the area make sure to use a good quality paste with an anti-fungicidal additive. 
  • Where possible do not use wallpaper in bathrooms and kitchens.
  • We recommend that you regularly check under divan bed drawers, behind wardrobes, bedside cabinets, bedheads and clothing stored in cupboards, you will then need to wipe down or wash clothing immediately. 

Last Updated on Wednesday, May 8, 2024