Dampness in a house is caused by a build-up of excess moisture in the property. When houses are built, we use products such as mortar, concrete and plaster, all of which contain moisture which will be allowed to dry out during the build process. There is also a good deal of moisture in the air and the ground which surrounds our houses and soaks up moisture when it rains. It is therefore important that we control the amount of moisture in our homes, otherwise we may have problems with damp.

The main causes of damp in properties are, Condensation, Penetrating damp, Rising damp, all of them caused by different problems, but all are avoidable or treatable if present in a property.

Condensation

This is the most common kind of damp. It is caused by moist, warm air condensing onto cooler walls or windows, particularly in rooms that create a good deal of moisture, such as shower rooms, bathrooms, kitchens or laundry rooms. Not only is condensation the most common kind of dampness, it is also the easiest to cure and may on occasions be cured by simply opening windows. It tends to be more prevalent in older houses as many of the ways they were designed to ‘breath’, such as chimneys, vents and old sash windows, caused draughts which allowed air to circulate.  As time has passed, many chimneys have now been removed, insulation and double glazing installed along with other measures to insulate older houses, without introducing other methods to allow air to circulate. Modern houses are built with ventilation bricks in the outer walls and soffits to allow a flow of air and most double glazed windows will have sliding vents along the top of them to encourage air flow and ventilation.

Condensation can also be made worse by having central heating set at a high temperature during the day and allowing it to cool down by switching it off at night, causing wide variations in temperature. By doing this it will allow moisture trapped in the warm daytime air to condense out of the cooler night-time air and form on walls and windows. It may be better to try to keep the temperature of your rooms at a more even temperature, thus discouraging extra condensation.

 Condensation is visible from the formation of water droplets on windows or walls and over time, the appearance of dark mould, particularly on glass or around windows. If condensation is allowed to remain unchecked, it can eventually cause ‘mildew’ to form on fabrics and clothing, accompanied by an unpleasant mouldy smell.

Rising damp

This is caused by moisture rising up from the ground through a wall or floor, which is a natural occurrence. This is usually stopped from causing damage by a barrier called a damp-proof course or damp-proof membrane which is a horizontal waterproof membrane, usually made of plastic or bitumen felt.  In modern houses this is built into the walls of the property at a height of at least 15cm above ground level and will line the sub-floor area in accordance with Part C of Building Regulations in England & Wales.

Rising damp can occur if an older property does not have a damp-proof course or in a more modern property if the damp-proof course has been damaged in some way. There is also a danger that if you are altering the height of the ground adjacent to your property, possibly to form a raised flower bed or to lay a new drive at the side of the house, you may inadvertently cover the damp-proof course and possibly the ventilation brick built in to the lower part of the wall.

Rising damp can be identified by the appearance of white, salt like, tide marks or dark patches on your internal walls. You may also notice staining on wallpaper, which may also show signs of peeling and paint work may show signs of blistering. Plaster may also show signs of discolouration and flaking. If the problem is associated with a solid or concrete floor, floor coverings may be affected and may show signs of lifting.

 Penetrating damp

This is normally caused by structural problems within a property. Faulty guttering or roofing or cracks in the walls can be the main culprits. These allow water to leak in when walls or roofs are subjected to significant or heavy rainfall. With guttering and walls, the evidence of penetrating damp can often be seen on interior walls or ceilings close to the source of the leak, so if you see evidence of staining or a damp patch on an internal surface, start by looking at the corresponding area of the building on the exterior walls. Loose or missing pointing or mortar joints on exterior walls can be a common cause of penetrating damp and are easily rectified. The formation of black or green staining on exterior walls can often be a sign of leaky guttering or down pipes.

Roofs on the other hand, tend not to display internal damp patches or discoloration in the same area as the external leak. The water leaking into an attic, for instance, will want to fall as gravity demands and will seek the route of least resistance as it looks for a way out and may materialise in another area. This is made worse by the fact that many attic spaces now a days are lined with insulation and the inside of roof timbers may not be easily accessible or visible.

Penetrating damp can also be caused by internal leaks, such as leaky pipes underneath the sink, bath or shower tray. These can also be easy to identify as they may well be visible and are often easily rectified with a basic knowledge of plumbing.

If a surveyor has any inkling that a property may have a problem with dampness, particularly rising damp, they may ask you to have a specialist report done, which would highlight any problem areas and recommend the required remedial work..

If you are considering buying or selling a home, you may find some of these services useful: