One of the main items of a building survey and one of the most commonly asked areas of investigation by clients is around damp. 

There are principally two types of damp, penetrating damp and rising damp.  Some building surveyors may consider condensation as the third area of dampness, albeit this is not considered dampness on a technical point.  This is because condensation, both main and interstitial, is internally introduced.  When talking about dampness, we generally consider damp coming from the outside of a structure to the inside of a structure.   

An example of penetrating dampness is say a guttering leak or flashing leak, which introduces rainwater into a building from a defect in the weather tightness of the structure. These are fully investigated during a building survey.  

Rising damp is generally harder to define and generally operates in tandem with penetrating dampness.  A lay explanation of rising damp is dampness which wicks, or through osmosis, works its way up a wall.

In most cases, the classic definition would be dampness that is introduced from groundwater, such as where a render may be in contact with the external ground levels, there may be a high water table, such as in a basement and this penetrates and rises through plasterwork for example.  This contact with the elevations means that the water rises through the elevations, through the depth of the elevations and internally on plasterwork through hydroscopic salts, which means the moisture tracks up the elevations. 

It is generally held that rising damp can be measured up to 1 metre from its source, generally meaning 1 metre measured to the internal elevation. 

This pattern of tracking up through internal plasterwork and tide marking generally differentiates rising damp from penetrating damp.  It should be noted however that the definition of rising damp must penetrate the walls and therefore there is always a penetrating element to rising dampness; salt tests can differentiate ground water from rainwater; our building surveyors can undertake such tests.

This post covers the definitions, or the lay definitions, of rising and penetrating damp. Further posts will concentrate on the causes and remedies of rising dampness and condensation. 

Our surveyors are on hand to assist in both defect diagnosis and building surveys.