Dampness and mould inside the home can cause health problems such  as allergies and asthma. When sufficient moisture is available, hundreds of species of bacteria and fungi – particularly mould – pollute indoor air.  Preventing (or minimising) persistent dampness and microbial growth on interior surfaces and building structures is important in avoiding harmful effects on health.

Moisture form on surfaces where there are warm and wet conditions, such as in bathrooms without adequate ventilation; or on surfaces separating areas with very different temperatures, such as a single glazed window during winter.. If the moisture is not wiped away it can lead to mould growth.

What is condensation?

There is always some moisture in the air even if you cannot see it. The warmer the air the more moisture it will carry, however, if the air gets cooler, it cannot hold all the moisture and tiny drops of water form. This is condensation, it is often found in corners, on and around windows, behind cupboards and wherever there is poor air flow.

Condensation occurs mainly during cold weather, regardless of whether its raining . It does not cause a ‘tidemark’ on your wall. This is caused by rising or penetrating damp.

How can I avoid condensation?

Produce less moisture

• cover pans and do not leave kettles boiling
• avoid using paraffin and portable flueless bottled gas heaters as these heaters put a lot of moisture into the air
• dry washing outdoors on a line instead of on a radiator, or put it in the bathroom with door closed and the window open or the fan on
• vent tumble dryers to the outside, unless it is a self-condensing type. DIY kits are available for this
• if you notice condensation on your windows or walls then wipe it away with a dry cloth
• do not block air vents or airbricks
• do not completely block chimneys. Instead, leave a hole about two bricks in size and fit a louvered grille over it
• do not draughtproof a room in which a cooker or a fuel burning heater (e.g.  a gas fire) is fitted
• do not draughtproof windows in the bathroom and kitchen

The key points to avoiding condensation are to ventilate and heat.

Provide adequate ventilation

You can ventilate your home without making draughts

• Keep a small window ajar or a trickle ventilator open when someone is in the room
• Ventilate kitchens and bathrooms when in use by opening the windows wider. Or better still, use a humidistat controlled electric fan. These come on automatically when the air becomes humid, and are cheap to run.
• Close the kitchen and bathroom doors when these rooms are in use, even if your kitchen or bathroom has an extractor fan. A door closer is advisable, as this will help prevent moisture reaching other rooms, especially bedrooms, which are often colder and more likely to get condensation.
• Ventilate cupboards and wardrobes. Avoid putting too many things in them as this stops the air circulating. Cut a ventilation slot in the back of each shelf or use slatted shelves. Cut ‘breather’ holes in doors and at the back of wardrobes, and leave space between the back of the wardrobe and the wall. Where possible, position wardrobes and furniture against internal walls.
• If you replace your window units at any time, make sure that the new frames incorporate trickle ventilators.
• Dehumidifiers remove moisture in the air and can be used in rooms where there is warm moisture such as kitchens and bathrooms. They should not be used in cold damp rooms.

Insulate draughtproof and heat your home

Insulation and draught-proofing will help keep your home warm and will also cut fuel bills. When the whole home is warmer, condensation is less likely.

• Insulate your loft. Remember to draughtproof the loft hatch but do not block the opening under the eaves.
• Consider cavity wall insulation. Building regulations approval maybe  required unless your cavity wall insulation provider is signed up to the competent person scheme Therefore, before deciding ahead, talk to your local building inspector for advice.
• Consider secondary and double glazing of windows as a means of reducing heat loss and draughts.  You must insure that there is adequate ventilation though.
• In cold weather, if possible, keep low level background heating on all day, even when no one is at home.

There are grants available to help with the cost of insulating your home.

How can I get rid of mould?

First steps

• First treat any mould you may already have in your home. If you then deal with the basic problem of dampness, mould should not reappear.
• To kill and remove mould, wipe down walls and window frames with a fungicidal wash, which carries a Health and Safety Executive’s ‘approval number’. Follow the manufacturer’s instructions precisely.
• Dry-clean mildewed clothes and shampoo carpets. Disturbing mould by brushing or vacuum cleaning throws mould spores in the air and can increase the risk of respiratory problems.
• After treatment, 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.
• If you notice any condensation after the mould has been removed then wipe away immediately with a dry cloth.

Is it condensation or damp?


Damp in a property can be caused by factors others than condensation.

• leaking pipes, wastes, overflows or cracked pipes
• water coming through the roof where a tile or slate is missing or spilling from a blocked gutter
• rising damp due to a defective or missing damp course

These causes of damp leave a tidemark. If you do not think the damp comes from any of these causes and there is no ‘tidemark’, it is probably condensation.

Persistent mould or damp that does not disappear after repeated treatments could be a sign of rising damp.

If you require any information or advice on treating mould or condensation please contact Environmental Health on 01784 446251 or e-mail environmental.health.domestic@spelthorne.gov.uk

Other information

Damp and mould leaflet (Pdf 1mb)