Condensation is caused by moist air hanging in warm still air that is not being circulated around the dwelling and making contact with colder surfaces, ie. window glass/solid brick walls or being trapped in corners by excessive furniture such as a bedroom with wardrobes etc close to corners.

The visual effect of condensation is water droplets running down the windows (usually single glazed) and wetting the wall beneath. Black mould growth spores appearing on walls/ceilings and concrete lintels above windows, especially in corners and around window reveals.

The way to reduce the likelihood of condensation forming is to carry out the following preventative measures :-

1. Warm the rooms during cold weather with central heating or similar.
2. Ventilate by leaving a fanlight window trickle venting in order to create air change ventilation. By opening a fanlight does not loose heat in most cases but actually circulates the heating around the rooms more efficiently.
3. Wipe off any mould spores with an approved fungucide or even a weak household bleach solution to stop the spores growing which attracts the moist air to it making it worse.
4. Insulate the cold walls when decorating with polystyrene or similar material sold in wallpaper retailers.
5. Use a fungucidal paste with the wallpaper.
6. Open windows when bathing/cooking involving steam of any kind.
7. Do not totally block up open disused fire places or airbricks etc or make rooms totally draft proof by sealing around windows and doors etc.
8. Do not use portable gas heaters without adequate ventilation as these can create approx 2 pints of moisture per hour into the room atmosphere at times.

The above is a general guide on preventing or reducing condensation but there are situations where the age and type of construction can make it very difficult to stop altogether.

In this case you will need to report this to your area surveyor who will give either further advice or arrange to carry out more involved preventative works.