Any masonry structure, unprotected by a properly installed rising damp treatment (damp proof) course, is susceptible to natural rising damp. Damp will rise by capillary action through the pores of the masonry, seeking a means of evaporation which is generally the warm internal wall finishes.
The moisture will continue to rise until it reaches a height where, unless no evaporation is possible, gravity takes over and pulls it down again. This height is seldom more than 1.20m, although deposits of ‘salts’ may be found higher in the wall, often driven there by the use of non-breathing plasters, renders, ‘tanking’, paints or vinyl wall papers.
The telltale signs of rising damp include a “tide-mark” on the wall above skirting boards of up to 1 meter however, it is important to remember that there are many forms of damp that can affect a property.
Rising Damp can lead to timber decay to bearing end timbers.
How to treat rising damp
This is generally achieved by installing a chemical damp-proof-course.
A damp proof course is a waterproof barrier that spans the width and length of your wall. It stops water from the ground rising up through the wall through capillary action. The DPC needs to be installed at least six inches / 150mm above ground level according to British Standard 6576 and Building Regulations also state it should be at this height. DPC’s come in a variety of different forms, from sheet materials such as plastic through to chemical formulations.
Any salt damaged plaster will also need to be removed / replaced with a salt retardant render.