A matter of (damp-proof) course

Chartered Surveyor and Company Director Kate Farrar takes a look at damp-proof courses, what they do and how to look after them.


Damp-proof courses form a barrier against moisture entering a wall. They are most commonly found installed horizontally at the base of a wall but in modern buildings you will also find them installed vertically, around window openings for example.

Although this method of excluding water from a building has been known since Roman times, surprisingly damp-proof courses have only been mandatory in UK construction since 1877. Historically, impervious stone or low-absorption brick, pitch, lead, slate, or asphalt have been used. Most modern damp-proof courses will be polyethylene.

To avoid any risk of a damp-proof course being bridged and damp entering a building as a result, it is important to maintain a height of at least 150mm (6”) between a damp-proof course and the outside ground.

Unfortunately, we frequently find damp-proof courses are bridged, e.g., by an external render, flower beds, paving or timber decking. Even if a hard surface such as decking, or paving is not physically bridging the damp-proof course they can still lead to a problem with damp inside the house as rain hitting the hard surface can splash-back onto the wall above the damp-proof course.

If you are concerned about damp in your property, contact Woodward Chartered Surveyors in Herts, Middlesex and London to arrange for an inspection.

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