Dampness and mould growth

Page last updated at 07 July 2015 at 09:10

Dampness & Mould Growth

Wet surfaces encourage the growth of mould.

This can aggravate chest related illness including asthma.

Dampness will also damage the building and make it more difficult to keep your home warm.

Dampness occurs in properties for a number of reasons:-

Rising Damp
Caused by the absence, breakdown or bypassing of a damp proof course or membrane.  It is characterised by wet patches to ground floors and walls with sometimes a white powdery 'tidemark' deposit.

Penetrating Damp
Caused by such things as old brickwork that becomes porous, leaking roofs and gutters and rotted windows and doors.  It is characterised by discolouration to internal decoration, peeling wallpaper and sagging ceilings.

Condensation occurs when there is too much water vapour in the air.  the lower the temperature of the air the less water vapour it can carry.  Water droplets form when warm, moist air is rapidly cooled.  You will be aware of condensation from your own breath on a cold day or on windows and mirrors when taking a bath.

Condensation is a particular problem on cold days when it causes water droplets to form on cold surfaces where there is little air movement to dry it, such as in corners, behind furniture and inside wardrobes.  The lack of air movement combined with the dampness allows mould to grow on any absorbent surface such as wallpaper, plasterwork but also clothing and bedding.  It is characterised by uniform areas of mould that is often black.

How can I avoid condensation?
There are three basic ways to avoid or reduce condensation and its effects:-

Boilingpot1.  Produce Less Moisture

  • Cover steaming pots and pans and do not leave kettles boiling
  • Avoid using portable gas heaters because they produce a lot of water vapour
  • Do not dry washing indoors except in a room with the window open and the door closed
  • Always vent tumble dryers to the outside air

Open Window2.  Ventilate the Property to remove moist air

  • Use mechanical extraction in the bathroom and kitchen and keep the doors to these rooms closed whilst in use and for a period afterwards
  • Keep windows slightly open to aid air movement
  • Leave wardrobe and cupboard doors ajar or cut breather holes to aid air movement.  Do not overstock shelves and, if possible, place them against the warmer inside walls.

Loftinsulation3.  Insulation and Heating

  • Insulate your loft, including the loft hatch to prevent heat loss
  • Cavity wall insulation will prevent heat loss and keep your walls warmer
  • Double-glazing will prevent, heat loss and keep the glass warmer but you must ensure that trickle vents are provided to allow some air movement
  • In cold weather keep a low level of background heating on



  • Block permanent ventilators
  • Block chimneys.  Install a ventilation grille instead
  • Draught-proof kitchens and bathrooms or rooms containing a gas heating appliance

How to treat mould

  • Regularly wipe down affected surfaces with a household detergent
  • Dry clean mildewed clothes
  • Decorate using good quality fungicidal topcoat paint

See our Condensation Advice Leaflet for further information.

If the property you are privately renting is suffering from dampness and/or mould growth and you would like to speak to a member of Private Sector Housing, please call 023 8068 8329.