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Damp and mould advice

Penetrating Damp Identification

Damp patches high up on walls or ceiling

Contributing Factors

  • Leaking gutters/concrete gutters
  • Blocked guttering
  • Leaking down pipes/leaking plumbing/blocked toilet
  • Slipped tiles or slates on roofs/ damaged facia
  • Running overflows
  • Blocked gullies
  • Perished brickwork or pointing
  • Cracked render
  • Defective concrete flaunching around chimneys
  • Defective flashing around chimneys/flues/soil and vent pipes and at abutments of roofs to vertical walls
  • External wall cavities bridged by patios, high ground levels or prolonged accumulation of rubbish

Rising Damp Identification

Dampness staining and mould growth (the mould growth will be due to condensation) along lower areas of walls; typically a meter above floor/ground level

Contributing Factors

  • Missing or bridged damp proof course (bridged would typically be evidenced by rising damp in isolated areas)
  • For note : Properties constructed pre 1900 often have slate damp proofing which is more susceptible to movement and can fracture

If you know the above is not contributing to the dampness in your property, then the most likely cause is condensation.

Condensation Identification

Presence of black/green mould on ceilings, walls, doors, windows, furniture and clothing.

Water droplets on walls and windows

Contributing Factors

  • Cold external wall, floor and ceiling surfaces due to lack of insulation or poor design
  • Inadequate or uneconomic heating (condensation form under heating will appear on the coldest surfaces first e.g. single glazed windows and in poorly ventilated properties behind furniture)
  • Lack of controllable ventilation (windows, mechanical extraction fans)
  • Excess moisture from household activities (lifestyle)

What is condensation?

The air around us holds a certain amount of moisture; when warm air comes into contact with a cold surface the temperature of the air falls. When the air gets colder, it cannot hold all the moisture and tiny drops of water appear. Examples of this are when the mirror mists over when you have a bath or a shower and when you can see your breath on a cold day.

What causes condensation?

Condensation occurs mainly in cold weather, whether it is raining or dry. Condensation forms on cold surfaces and in places where there is little air, for example:

  • On windows
  • In corners of rooms
  • Behind or inside wardrobes or furniture where they are positioned close to the wall.

It often forms on north facing walls. If you have humid air and cold surfaces in your home, you are likely to have condensation.

The lifestyle contributing factors of condensation are:

  • Not ventilating sufficiently, especially when cooking or bathing
  • Not heating the home sufficiently
  • Drying clothes indoors
  • Excessive storage of personal items/furniture
  • Overcrowding

Immediate steps to deal with condensation can be seen below:

  • Wipe down affected windows and sills daily
  • Condensation channels and sponge strips can be bought at DIY stores. These collect the condensation water.
  • A dehumidifier can also help with warm moist conditions as it collects moisture from the air.

How to prevent dampness and condensation

These are the main things you can do to help reduce condensation.

Reduce the moisture in your home:

Everyday activities in your home produce a lot of moisture, for example having a bath. The following suggestions cost nothing and require little effort:

  • Cover pans when cooking and do not leave the kettle boiling.
  • Open a window or use an extraction fan when cooking or bathing.
  • Close kitchen and bathroom doors when in use, even if using an extractor fan.
  • Avoid using portable, flue-less bottled gas heaters. These heathers put a lot of moisture into the air.
  • Dry your washing outdoors or in the bathroom with the door closed, window open or extractor fan on. Resist the temptation to hang it over your radiators or storage heaters.
  • Vent your tumble dryer outside, unless it’s the self-condensing type. DIY kits are available to do this.

Ventilate your home

It is important to ventilate each room to ensure a constant supply of fresh air especially in the kitchen and bathroom, to assist with this you can

  • Install extractor fans or a humidistat- controlled electric fan, in your kitchen and bathroom. These come on automatically when the air becomes humid and are not expensive to run.
  • Keep trickle ventilators open at all times or a window, slightly open when someone is in the room. Trickle vents can be fitted to existing windows.
  • Ventilate cupboards and wardrobes by cutting a ventilation slot in shelving and making ‘breather holes’ in doors and back wardrobes. Try to leave a space between the furniture and the external wall or if possible position your furniture against internal walls.

Insulate and heat your home effectively:

Insulating and draught proofing your home will reduce fuel bills and help to reduce condensation by keeping your home warm. The following are suggestions of how to heat and insulate your home well:

  • Insulate your loft and draught proof the loft hatch. Do not block the opening under the eaves.
  • Install cavity wall insulation.
  • Secondary and double glazing of windows will reduce heat loss but you must ensure there is some ventilation.
  • In cold weather, keep a low heat on all day even when no one is home.
  • Upgrade your heating system.  A central heating system with individual thermostatically controlled radiators can provide a low constant heat to all rooms. Where this is not possible oil filled electric radiators are a good alternative.

If you draught proof your home, DO NOT:

  • Block permanent ventilators.
  • Completely block chimneys. You should leave a hole, roughly the size of two bricks and fit a louvered grille over it.
  • Draught proof a room where there is a cooker  
  • Draught proof windows in the kitchen or bathroom.

Single glazed windows also provide a cold surface for warm, moist air to condense onto, particularly if they have a metal frame.  

How your home has been built can increase the likelihood of condensation occurring.

Properties with solid walls tend to suffer with condensation as they provide a cold surface for warm moist air to condense onto. This encourages dampness and mould growth. If your home was built prior to 1932 it is very likely you have solid walls. Most recent pre-cast concrete construction is also likely to suffer from condensation.

The problem with solid walls can be improved with a combination of measures. These include external insulating, cladding, double glazed unit with trickle vents and an effective heating system.

Cavity walls offer better insulation, keeping heat in, therefore reducing the likelihood of condensation occurring. If your house was built after 1932 and the outside walls are thicker than 30cm, it is likely that you do have cavity walls. To measure the thickness of the outside wall, open your front or back door, or window and measure from the outside face of the wall to the inside face of the wall. The measurement will only be a rough figure; there will be layers of internal plaster and external render to take into account.

Treating mould

You can treat any mould growth you have in your home but you need to tackle the causes of condensation to prevent the mould coming back.

To kill and remove moulds remove any wallpaper in the affected rooms. Moulds thrive on the wallpaper paste and the spores cannot be removed from the paper. Wipe down walls and window frames with an approved fungicidal wash. Follow the manufacturer’s instructions carefully.  Dry-clean mildewed clothes and shampoo carpets. Disturbing mould by brushing or vacuum cleaning can increase the risk of respiratory problems. After treatment, you can redecorate using a good quality fungicidal paint to help prevent mould recurring. Note that this paint is not effective if overlaid with ordinary paints or wallpaper.

Useful Information

The information provided is only a guide. If you are in doubt, please contact the Private Sector Housing Team on tel: 01702 318050 or Email:

For independent, expert advice on saving energy in your home, contact the Energy Saving Advice Service on tel: 0300 123 1234, email: or via their website in the Related Content section.