Damp and mould

Damp and mould solutions 

There is always some moisture in the air, even if you cannot see it.  If the air cools it cannot hold all the moisture and tiny drops of water appear as condensation.  Condensation is not the only cause of damp.  There are some initial steps you can take against condensation and mould, but you will eventually need to take long-term steps to deal with the causes of condensation.  We have also listed a few points to remember in an effort to reduce condensation in the home.


What is condensation?

There is always some moisture in the air and when air cools it cannot hold all the moisture and tiny drops of water appear.  This is condensation. Condensation is most likely to become a problem during cold weather but it can occur all year round, whether it is raining or dry.  It does not leave a ‘tidemark’ in the same way that rising and penetrating damp frequently does.  It appears on cold surfaces and in places where there is little movement of air.  It can be found in corners, on or near windows or on walls behind furniture.  In bad cases it can also occur inside cupboards and wardrobes.  The problem can be worst on north-facing walls and on walls exposed to the prevailing wind (because these are typically colder).  Black mould often starts to form if there is a persistent problem.


What are the other causes of damp apart from condensation?

Damp can also be caused by:


  • Leaking pipes, wastes or overflows.

  • Rain seeping through the roof where a tile or 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 or because there is no 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 (e.g. in plaster) is still drying out.  If your home is damp for any of these reasons it may take weeks of heating and ventilating 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.  Condensation problems are often characterised by mildew and by areas of black mould, particularly in colder areas of the building and behind furniture.


What initial steps can I take to reduce condensation?

You will need to take proper steps to deal with the causes of condensation but meanwhile; you can take action right away to reduce the problem.


  • Start with wiping down the windows and sills every morning and then wring out the cloth rather than drying it on a radiator.

  • Ensure that steam from the bathroom and kitchen doesn’t spread round the house.

  • Close the doors and open windows to let the steam out.


(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).


What initial steps can I take to deal with the problem of mould?

Treat the mould already in your home.  (If you then deal with the basic causes of condensation, mould should not re-appear).


To kill and remove mould:


  • Wipe down walls and window frames with a fungicidal wash, which carries a Health and Safety Executive ‘approval number’ (available from most DIY shops).

  • 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 future mould growth.  Note that this paint is not effective if overlaid with ordinary paints or wallpaper.


The only lasting way of avoiding problematic or severe mould is to eliminate the dampness caused by condensation.


What long-term steps do I need to take to avoid condensation?

There are four steps to take that will help you reduce the condensation in your home.


1. Produce less moisture

Some ordinary daily activities produce a lot of moisture very quickly.

  • Cooking

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

  • Paraffin and portable flue less 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).  DIY 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 that is being produced all the time, much of which comes 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 windows 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 as 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 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.  Leave space between the back of the wardrobe and the wall.  Put floor-mounted furniture on blocks to allow air underneath.  Where possible, position wardrobes and furniture against internal walls (walls which have a room on both sides) rather than against outside walls.


If you replace your window units at any time, make sure that the new frames incorporate trickle ventilators.  You should also ensure that some openable part of each window is at the top so as to avoid ‘dead spaces’ that will not get adequate ventilation.


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 ventilators.

  • 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 (e.g. a gas fire) or cooker.

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


If you live in a house or bungalow, insulating your loft is a cost-effective way of cutting heating 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 insulation, 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 sufficient ventilation.  Locking all moisture inside a building, how matter how warm it is, will cause high humidity and potential problems.


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 not one at home.  This is very important in flats and bungalows and other dwellings where the bedrooms are not above a warm living room.  If possible install a small heater with a thermostat in each bedroom (but do not use a paraffin or flueless bottle 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.


What are the points to remember when trying to reduce condensation in my home?


Produce less moisture

  • Cover pans.

  • Dry clothes outdoors.

  •  Vent your tumble dryer to the outside.

  • Avoid using paraffin or flue less bottled gas heaters.


Ventilate to remove moisture

  • Ventilate whenever someone is at home.

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

  • Ventilate cupboards, wardrobes and blocked chimneys.


Insulate and draught proof

  • Insulate the loft.

  • Draught proof 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.  You could contact the Energy Savings Trust on 0800 512012, or alternatively contact Housing Advice using the link below.


Related information:

Damp and mould guidance leaflet


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