Advice about the different types of damp that can affect your home - penetrating or rising damp. Where to get help from specialist technical contractors.
Damp can cause mould on walls and furniture and make timber window frames rot. Damp housing is unhealthy, smelly and encourages the growth of mould and mites. These can increase the risk of respiratory illness.
If you have the type of damp which causes a tidemark, it needs to be traced from the source of a leak, rain seeping through windows or rising dampness due to a defective or missing damp proof course.
Penetrating Damp
This occurs when moisture is getting into the property. This may be a roof leak, a leaking rain water pipe, an overflow that has not been properly fixed, water coming in from the gutters, water coming in from piles of rubbish lying against the wall.
Penetrating damp can affect almost any location in the home and is usually the result of a building or plumbing fault allowing water to enter into the property. A brown stain normally occurs on the affected surface, which grows in size as more water penetrates. If the fault is not rectified plaster will start to perish and in the case of ceilings could even collapse.
This will need investigation to stop the source of the water seepage. Affected areas may need re-plastering or redecoration after a drying out period.
Rising Damp
Damp patches appear lower down on the wall. Rising damp is where dampness is coming up the wall from the ground because the damp proof course is not working. In some older properties and in places below ground level there may not be a damp proof course.
The most obvious signs of rising are a brown "tidemark" on the wall and the plaster below feels cold or damp to the touch. Rising damp can affect any wall in contact with the ground and therefore can affect internal as well as external walls. It does not normally rise above about 1 metre (3ft) in height.
This will need investigation by owners or landlords and will probably need a specialist survey to be carried out, followed by remedial work to sort the problem out.
This will require a qualified contractor, who should be a member of the British Wood Preserving and Damp Proofing Association. Affected areas will need re-plastering.
