Rising damp, penetrating damp and condensation are the three most common types of damp for residential properties.
is the most common kind of damp. It is caused by moist warm air condensing on cool walls, particularly in rooms that naturally generate a lot of air moisture, such as kitchens and bathrooms. It's mainly, but not always, a winter problem, as walls tend to be colder than the air inside.
Condensation can be exacerbated by central heating that gets very warm and then cools down again, as this creates warm, damp air that can then condense, causing condensation.
A lack of ventilation can also make the problem worse. This can be particularly apparent in old homes, which were designed to be naturally 'breathable' and allow damp air to evaporate out of the house. The removal of existing chimneys and energy-saving measures, such as fitting air-tight double glazing, can reduce ventilation in old homes, and create a condensation problem.
If left untreated, condensation can damage paint and plaster and cause window frames to decay, so when you see it form you should wipe it away with a cloth. If you'd rather use less elbow grease, some gadgets claim to be able to help with condensation and leave your windows streak-free – find out what happened when we tried out the .
If a lack of ventilation is the problem, there are systems available to help improve it – read our first look review of the positive input ventilation system to see if it could help. Dehumidifiers can also come in handy to reduce how much moisture is in the air in the first place – find out how to buy the for your home.
is caused by ground water moving up through a wall or floor. It's natural for walls and floors to allow a little water in, but it’s usually stopped from causing damage by a barrier called a damp-proof course or damp-proof membrane (see image below).
Newer houses will have both, as they are a requirement of building regulations (Part C for England and Wales). Older buildings (particularly those built before regulations came into force in 1875) may not, or they may have worn or been damaged over time. If this is the case, your walls or floor may suffer from rising damp.
Rising damp can also happen when there's a lack of drainage, or the level of the ground outside your home is higher than your damp-proof course, allowing water to get above it.
Read our guide to find out how to treat issues with rising damp, and whether you need to call in a professional to deal with it. If you do, our page will give you an idea of how much you need to spend.
is caused by water leaking through walls. This type of damp may expand across your walls or ceiling, but this will move horizontally, rather than by travelling up walls (as is the case with rising damp).
Penetrating damp is usually caused by structural problems in a building, such as faulty guttering or roofing, or cracks in the walls, which let water in when walls or roofs are soaked with water during heavy rainfall. It can also be caused by internal leaks, such as leaky pipes underneath the sink or bath.
You’re more likely to get penetrating damp if you live in an older building with solid walls, as newer cavity walls provide some protection.