Dampness is a major problem to many houses and flats. Dampness can cause mould on walls and furniture and make timber window frames, floors and skirting boards rot. It also encourages the growth of house dust mites and can increase the risk of respiratory illness. It can also damage wall plaster and may also give rise to dry rot.
What is the cause of my dampness?
The first thing you need to do is to establish the cause of the damp.
It is important to be able to tell the difference between damp caused by condensation and damp caused by other factors, such as rising damp, rainwater coming in, defective plumbing or poor drainage.
- Condensation tends to get worse in cold weather. The other types of damp (apart from plumbing leaks) tend to get worse in wet weather.
- Condensation tends to form patches of mould with blurred, soft edges rather than a stain mark.
- Condensation occurs when the air and/or surfaces are cold and when the moisture content of the air is high.
- Condensation occurs where there is little movement of air and can be found in corners, on or near windows, in or behind cupboards or wardrobes and often forms on north facing walls.
Watch this video from Energy Savings Trust (external link).
Penetrating dampness (repair problems):
Have you got a leak in the roof or gutter, rain water pipes or even the mains water supply? Defects of this sort should be relatively straight forward to repair once they have been tracked down, although the dampness may then take some time to dry out. It is important to ensure that you carry out regular maintenance to your property to keep it in good order. Regular checking and planned repairs are the best approach before the defects become a serious problem.
Rising dampness can affect ground floor rooms and is caused by water from the ground getting into the walls and floors, often because a damp proof course (DPC) or damp proof membrane (DPM) has failed or (in the case of many older buildings) because the property was built without such damp proofing. If you have damp, check for the following problems:
- Rubbish or soil piled up against the house above the level of the DPC.
- Missing or slipped roof tiles or slates. Damaged flat roof coverings.
- Damage or cracking to brickwork or external rendering.
- Rotten or leaking window sills. Broken or blocked guttering or rainwater down pipes.
- Blocked or missing air bricks
- Crumbling brickwork or rendering to chimney stacks.
What is condensation?
There is always some moisture in the air; even if you can not 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 or shower. House activities such as bathing, washing, cooking, drying clothes and people breathing are all things that put water into the air inside a house. Other major causes of moisture can be from flue less paraffin or bottle gas heaters, as well as unvented tumble dryers. An average family makes about 20 pints of water vapour in one day. This vapour stays in the air in warm rooms, but condenses back into water when it touches cold surfaces like windows or bathroom walls. You can not see the water droplets on absorbent surfaces but they can be clearly seen on non-absorbent glossy surfaces such as tiles and panes of glass.
Why is condensation a problem?
The water formed by condensation can be damaging to your home and your health. Moisture encourages rot in wooden objects like doors and window frames and spoil decorations and furnishings. It can provide ideal conditions for mould especially mildew which causes black patches on walls and fabric. Severe mould growth can make asthma and other respiratory illness’ worse due to the inhalation of the mould spores.
How can I reduce condensation to a minimum?
Condensation can be reduced as much as possible by following some simple tips:
- In the bathroom, always keep the door shut during use. After use keep the door shut and open the window to let the steam out.
- When you are doing something that puts water in the air, think about ventilation.
- In most cases, you can get rid of damp air by simply opening the windows. In the kitchen try using saucepan lids to cut down on steam escaping into the air. Cook with the door closed and the window open or (if you have one), the extract fan or hob extract system on.
- Dry clothes outside if possible. If clothes are being dried inside, a confined space with maximum ventilation should be used. Tumble dryers should be vented to the outside
- Using a paraffin or calor gas heater to dry clothes is not a good idea, as this can be dangerous and give off fumes and they give off a lot of water as they heat.
- Make sure that air bricks and double glazing trickle vents are clear and open.
- Make sure that your roof space is properly ventilated and insulated.
- If you are blocking up a fire place, fit an air vent to the flue of the chimney.
- Fit extractor fans to the bathroom and kitchen.
- If your home has cavity walls, consider installing cavity wall insulation.
- You can discourage condensation on the walls by insulating them. Think about the external walls first, they are always colder. Insulating plasterboard and insulation rolls are both effective.
- Heat the whole house rather than just one or two rooms and keep low background heating on all day, even when there is no one at home.
- Allow adequate air circulation around large pieces of furniture.
Remember, when the house is warmer, condensation is less likely.
How do I get rid of the mould?
First treat any mould you may already have in your home. If you deal with the basic problems of condensation, mould should not reappear. A solution of water and vinegar will remove light mould staining on hard surfaces (such as painted surfaces). To kill and remove mould, wipe down the walls and window frames with a fungicidal wash. Follow the manufacturer’s instructions carefully. Dry clean mildewed clothes and shampoo carpets. Disturbing mould by brushing or vacuum cleaning may increase the risk of respiratory problems. After treatment, redecorate using a good quality fungicidal paint to help prevent mould recurring. Please note that this paint is not effective if overlaid with ordinary paints or wallpaper. The only lasting way of avoiding severe mould growth is to eliminate the source of the dampness.