First, it is important to understand the cause of the problem

Damp is a common problem in many homes today, even in new homes with modern efficient central heating systems. It can often lead to mould forming on walls and in wardrobes, windows dripping with condensation, and for people suffering from Asthma, poor air quality can be a particular problem.

Understanding the reasons for dampness, condensation and mould are essential if the problem is to be solved and an effective remedy put in place. Misdiagnosis of the reasons for dampness in homes can lead to expensive and ineffective remedial work.

These days, virtually all damp problems in properties are caused by water on the inside trying to get out, not water on the outside seeping in.

How can this be? Read on…

Water, in its gaseous form, is called water vapour. It is invisible and suspended in the air all around us, all of the time. The warmer the air, the more water vapour it can suspend. As temperatures drop sharply on autumnal evenings, what happens to the water vapour already held in the air? Well, if the temperature of air reduces then the amount of water vapour it can hold will also reduce. This results in an excess amount of water vapour in the air, a state known as saturation (or 100% relative humidity).

Once air becomes saturated, water vapour must be lost from the ever-cooling air and condenses to form small, hovering water droplets. We know this as mist or fog.

However, before this happens we often see condensation as dew, coating grass, cars and windows in water. These solid surfaces will have cooled overnight faster than the air; condensation always seeks out the coldest surfaces first.

When showering, boiling the kettle or simply breathing, it is the minute water droplets that you see in the air when steam or water vapour hits cooler air and condenses. 

Go outside on a cold day and you can see the water droplets forming in the air as you breathe. Even indoors you are still breathing this water vapour into the air. Imagine how much you expel into your bedroom at night. This is why you wake to find condensation on your windows.

Fortunately, because windows and their frames are solid surfaces, the water stays on the surface and is easy to wipe off. However, condensation also occurs on the cold wall surfaces, around windows and in corners of rooms. These surfaces are porous and the water will be absorbed into the wallpaper and plaster. Like a sponge these areas absorb moisture quickly but take a long time to dry out; they are perfect growing mediums for mould.

To help prevent this, it is essential to do two things:

1. Ventilate rooms so the air is replaced every so often.

2. Heat the house so that the air temperature stays higher for longer. This has two effects - it will help prevent the walls getting too cold and the higher air temperature will allow more water vapour to be held before needing to condense out to a cold surface.

Yes, this costs slightly more in heating bills but repairing mould damaged walls can result in an even higher cost. 

There is also the cost to your health. Damp conditions inside a house with mould spores being breathed in is very harmful. You become more susceptible to catching colds and flu and seasonal asthma is a typical symptom. 

The health of your family and the property can all be improved by thinking about heating and ventilation.

Three homes, all with the same combination of factors - cold walls, insufficient ventilation, and high levels of humidity produced by everyday living.

Here are some interesting articles and leaflets written by experts in property damp

How does your home feel to a visitor?

Preventing condensation - written by Derwentside Homes (pdf download)

Brief Guide to Damp - written by The Letting Centre (pdf download)

Damp and Mould Information - written by The Landlord Zone (pdf download)