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 illness.
Some damp is caused by condensation. This page explains how condensation forms and how you can keep it to a minimum, so reducing the risk of dampness and mould growth.
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 on 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 or cupboards. It often forms on north-facing walls.
Condensation is not the only form of damp. It can also come from:
- leaking pipes, wastes and overflows
- rain seeping through the roof where a tile of slate is missing, spilling from a blocked gutter, penetrating around window frames, or leaking through a cracked pipe
- rising damp due to a defective damp course
These causes of damp often leave a tidemark.
If your home is newly built it may be damp because the water used during its construction (for example in plaster) is still drying out.
If your home is damp for any of these reasons it may take weeks of heating and ventilation to dry it out. Hiring a dehumidifier will help.
If you do not think the damp comes from any of these causes then it is probably condensation.
How to avoid condensation
These three stages will help you reduce the condensation in your home:
1. Produce less moisture
Some ordinary daily activities produce a lot of moisture very quickly
- dry washing outdoors on the line, or put it into the bathroom with the door closed and the window open or the fan on
- cover pans and do not leave kettles boiling
- vent any tumble dryer on the outside unless it is a self-condensing type. DIY kits are available for this
- avoid using paraffin and portable flueless bottled gas heaters as they put a lot of moisture into the air
2. Ventilate to remove moisture
You can ventilate your home without making drafts
- 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 window wide. 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 it will help prevent the 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 in the back of wardrobes and leave space between the back of the wardrobe and the wall. Wherever possible position wardrobes and furniture against internal walls rather than external.
3. Insulate, draught proof 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 draught-proof the loft hatch but do not block the opening under the eves
- consider cavity wall insulation. Before deciding though, talk to your local building inspector as you will need building regulations approval
- consider secondary or double glazing
- of widows to reduce heat loss and draughts but make sure there is some ventilation
- in cold weather, keep low background heating on all day, even when there is no one at home.
Some words of warning
Don’t:
- block permanent ventilators
- completely block chimneys. Instead leave a hole about two bricks in size and fit a louvered grille over it
- draught-proof rooms where the is condensation or mould
- draught-proof a room where there is a cooker or a fuel burning heater, for example a gas fire
- draught-proof windows in the bathroom and kitchen.
First steps against mould
- treat any mould you may already have in your home. If you then deal with the basic problem of condensation, mould should not reappear
- to kill and remove mould, wipe down walls and window frames with a fungicidal wash that carries a Health and Safety Executive approval number. Follow the manufacturer’s 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 quality fungicidal paint to help prevent mould recurring. Note that this paint is not effective if overlaid with ordinary paints or wallpaper.
The only lasting way to avoid severe mould is to eliminate dampness.