Damp, mould and condensation

Damp occurs when a fault in the building’s structure lets in water from the outside.

Damp can originate from:

• leaking pipes, wastes, drainage and overflows 
• rain water from defective roof coverings, blocked or leaking gutters and broken pipes 
• penetrating dampness around windows, through walls and due to raised ground levels 
• rising damp due to lack of, or no effective, damp proof course.  

It can be recognised by:

• Peeling wallpaper
• Bubbling or flaking paint
• Tea discoloration patches on plaster
• Fragmented plasterwork or tide marks
• Wet patches
• Warped or stained woodwork
• Salty fluff
• Occasionally black mould, pink or green mildew.

This occurs when warm moist air reaches cold surfaces – such as walls, ceilings, windows and pipes – it turns back into water droplets (condenses) making those surfaces damp. When this type of damp sits on the surface several hours, it forms mould.

Condensation is easily recognised by the black mould it causes on cold surfaces like window frames, external walls, skirting boards, ceiling. The mould spores from these surfaces spread around the property and can form colonies of mould on furniture, clothing, bedding.

Condensation is caused by:

• Humidity/moisture held by the indoor air
• Inadequate ventilation
• Missing or incomplete insulation resulting in cold spots
• Inadequate heating resulting in lower surface temperatures.

Condensation usually happens during cold weather and appears on cold surfaces and areas where there is little movement of air. For example, in corners of rooms, on or near windows, in or behind furniture. If left untreated, mould will spread.

• Make sure your home is properly heated: try to leave the heating on a low to moderate setting for long periods. 
• Have the right balance between heating, ventilation and insulation.  
• In the short term, wipe off the condensed water from windows and sills with a fungicidal wash, every morning when condensation is occurring. Wring the cloth out in a sink rather than drying it out on a radiator. 
• 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. 
• If you use a washing machine or tumble dryer, make sure it is vented to the outside. 
• Always run an extractor fan or open a window when showering or cooking. 
• Keep trickle vents open at all times. 
• Close the bathroom and kitchen doors when these rooms are in use. You should do this even if these rooms have extractor fans. 
• Put cold water in the bath before adding hot. 
• Allow space for air to circulate in and around your furniture. 
• Leave space between the backs of wardrobes and the wall. 
• Where possible, put wardrobes against internal rather than external walls. 
• Dry clean carpets that have mildew.  

• Never dry laundry on radiators: you should make sure that if possible, you dry washing outside or put it in the bathroom with the door closed and the window open or extractor fan on. 
• Don’t leave kettles boiling. 
• Don’t use paraffin and portable flueless bottled gas heaters - these can produce a lot of moisture. 
• Never overfill wardrobes and cupboards because this restricts air circulation. 
• Don’t use your gas cooker to heat the kitchen because this appliance produces moisture when burning gas.  
• Never block permanent ventilators - for example, vents to windows, airbricks to walls and chimney breasts.