Damp & Condensation


What is it?

Winter time and the cold weather can result in signs of condensation inside your house. This is
quite common, even in new property. The first signs are usually the appearance of black mould
spots and a musty smell in the coldest parts of the house – usually the bedrooms and

If your property has been free from these signs in the warm summer months, then it is unlikely
to be a damp problem created by defects in the property – condensation is the most likely cause.

What is condensation? Condensation is a process where moisture (steam) in the air inside
your house is condensing out into water droplets on cold surfaces. This is most noticeable on
hard surfaces like glass or tiles, where pools of water may appear on window sills. With soft
surfaces like wallpaper, carpets, bedding and clothes you will not notice the water, but it will be absorbed into these items making them cold, damp and over time resulting in mould.


What causes it?

There are three main causes of condensation in a house:

  1. Rooms that are too cold and inadequately heated, creating lots of cold surfaces.
  2. The production of too much steam from cooking, washing, showering, clothes drying, etc all result in moisture laden warm air which will rise to the highest and usually the coldest part of the house where condensation takes place.
  3. Inadequate ventilation of the steam produced at source, which keeps it all in the sealed envelope of the house.


How can it be prevented?

You can do a lot to prevent condensation in your home:

  1. Maintain a minimum temperature in all your rooms especially bedrooms and bathrooms – temperatures should not be allowed to fall below about 18c. If you are out all day leave some heating on to keep the house warm – it costs less to maintain the temperature than to warm-up from cold and it’s much more comfortable.
  2. Minimise the amount of steam you produce when cooking and washing and always vent this to the outside – for example, by opening a window or using the cooker extractor fan. Always confine steam to the room it is produced in by keeping internal doors closed.
  3. Avoid drying wet clothes on radiators and try to keep them out by leaving them in a porch, utility or garage. Make sure clothes dryers have an external vent.


Measures such as these will cure most problems with condensation and mould. However, if the
property has become very cold and damp over a long period it may take some time to dry
everything out thoroughly with good heating so that surfaces are no longer cold and damp.