Damp and condensation

The following information answers frequently asked questions about damp and mould.

What is condensation?

There is always some moisture in the air, even if you cannot see it. If the air gets colder it cannot hold all the moisture and tiny drops of water appear. This is condensation. You notice it when you see your breath on a cold day, or when the mirror mists over when you have a bath.

Condensation occurs mainly during cold weather, whether it is raining or dry. It does not leave a `tidemark'. It appears in cold surfaces and in places where there is little movement of air. Look for it in corners, on or near windows, in or behind wardrobes and cupboards. It often forms on north-facing walls.

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How to avoid condensation

These four steps will help you reduce the condensation in your home.

1. Produce less moisture

Some ordinary daily activities produce a lot of moisture quickly.

Cooking:To reduce the amount of moisture, cover pans and do not leave kettles boiling

Paraffin and portable flueless bottled gas heaters: These heaters put a lot of moisture into the air - one gallon of gas or paraffin produces about a gallon of water vapour. If you have a problem with condensation, try to find an alternative means of heating.

Washing clothes: Put washing outdoors to dry if you can. Or put it in the bathroom with the door closed and the window open or fan on. If you have a tumble dryer make sure you vent it to the outside (unless it is the self-condensing type). DIT kits are available for this.

2. Ventilate to remove the moisture

You can ventilate your home without making draughts.

Some ventilation is needed to get rid of moisture being produced all the time, including that from people's breath. Keep a small window ajar or a trickle ventilator open when someone is in the room.

You need much more ventilation in the kitchen and bathroom when cooking, washing up, bathing and drying clothes. This means opening the window wider. 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. Doing this will help stop the moisture reaching other rooms, especially bedrooms, which are often colder and more likely to suffer condensation.

Ventilate cupboards and wardrobes. Avoid putting too many things in them, as that stops the air circulating. Cut a ventilation slot in the back of each shelf or use slatted shelves. Cut `breather' holes in doors and in the back of the wardrobe. Leave space between the back of the wardrobe and the wall. Put floor-mounted furniture against internal walls (walls which have a room on both sides) rather than against outside walls.

If you replace your window units at anytime, make sure that the new frames incorporate trickle ventilators.

3. Insulate and draught proof

Insulation in the loft, cavity wall insulation and draught proofing of windows and outside doors will help keep your home warm and you will have lower fuel bills as well. When the whole home is warmer, condensation is less likely.

When draught proofing:

  • Do not block permanent ventilation.

  • Do not completely block chimneys (leave a hole about two bricks in size and fit a louvered grille over it).

  • Do not draught proof rooms where there is condensation or mould.

  • Do not draught proof a room where there is a fuel-burning heater (for example, a gas fire) or cooker.

  • Do not draught proof windows in the bathroom or kitchen.

If you live in a house, insulating your loft is a cost-effective way of cutting costs. Remember to draught proof the loft hatch but do not block the opening under the eaves.

Cavity wall insulation is also an effective way of cutting heating costs. Before deciding on this method of insulating, however, you should talk to your local building inspector as building regulations approval is required.

Secondary and double glazing of windows reduces heat-loss and draughts but you must ensure that there is some ventilation.

4. Heat your home a little more

In cold weather, the best way to keep rooms warm enough to avoid condensation is to keep low background heating on all day, even when there is no one at home. This is very important in flats and bungalows and other dwellings where the bedrooms are not above a warm living room. So if possible, install a very small heater with a thermostat in each bedroom (but do not use a paraffin or flueless bottled gas heater for this purpose). The thermostat will help control heating and costs.

Dehumidifiers will help dry out damp in newly built houses. They can also help reduce condensation in warm rooms with a lot of moisture, but they are of little use in cold damp rooms.

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Points to remember

Produce less moisture:

  • cover pans

  • dry clothes outdoors

  • vent your tumble dryer to the outside

  • avoid using paraffin or flueless bottled gas heaters.

Ventilate to remove moisture:

  • ventilate when someone is in

  • increase ventilation of the kitchen and bathroom when in use and shut the door

  • ventilate cupboards, wardrobes and blocked chimneys.

Insulate and draughtproofing:

  • insulate the loft

  • draughtproof windows and external doors

  • consider cavity insulation

  • consider secondary glazing

  • find out if you are eligible for a grant or other help.

Heat your home a little more:

  • if possible, keep low background heat on all day

  • find out about benefits, rebates and help with fuel bills.

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Is your home damp?

Damp can cause mould on walls and furniture and make timber window frames rot. Damp housing encourages the growth of mould and mites, and can increase the risk of respiratory illnesses. Some damp is caused by condensation.

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First steps against condensation

You will need to take proper steps to deal with the condensation, but meanwhile there are some simple measures you can take right away.

Wipe down the windows and sills every morning. Wring out the cloth rather than drying it out on the radiator.

Condensation channels and sponge strips can be bought at DIY shops. They are fitted to windows to collect the condensation and thus help prevent window frames from rotting and avoid damp forming under sills. Care must be taken to fit these devices properly.

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First steps against mould

First treat the mould in your home. If you deal with the basis problem of condensation, 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 `approval number'. Follow the instructions precisely. Dry-clean mildewed clothes, and shampoo carpets. Disturbing mould by brushing or vacuum cleaning can increase the risk of respiratory problems.

After treatment, redecorate using a good fungicidal paint to help prevent mould. Note that this paint is not effective if overlaid with ordinary paint or wallpaper.

The only lasting way of avoiding severe mould is to eliminate dampness.

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Is it condensation?

Condensation is not the only cause of damp. It can also come from:

  • leaking pipes, wastes or overflows

  • rain seeping through the roof where a tile or slate us missing, spilling from a blocked gutter, penetrating around window frames, or leaking through a cracked pipe

  • rising damp due to defective damp-course or because there is no damp-course.

These cause of damp often leave a `tidemark'.

If your home is damp for any of these reasons it may take weeks of heating and ventilation to dry out. Hiring a dehumidifier will help.

If you do not think the damp comes from any of these causes, it is probably condensation.

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Contact us

If you have any queries about damp and mould, please contact Woking Repair Service at:

Monument Way East
Unit 14a
Woking
Surrey
GU21 5LY

Tel: 0800 521555

E-mail repairs@woking.gov.uk