Rising damp myth

Rising damp came to prominence during the 1960’s, as a result of hard hitting campaigns by companies selling damp proofing products and is subsequently responsible for a self-perpetuated industry that has a reported turnover industry in excess of £200 million per year. To cure the problem of rising damp, many organisations have been established within the last 40 years or so, specialising in providing chemically injected damp proof courses.

The process of Rising damp does exist and is a well documented scientifically established phenomenon; it is the upward movement of water from the soil, by the process of capillary action, caused due to differences in water potential and surface tension. The moisture may draw soluble salts from the ground and those from the wall itself. If the water evaporates from the walls surface, these leave behind the salts, which crystallise to form the traditionally seen efflorescence.

This may be exacerbated if these salts are hygroscopic, whereby they may absorb moisture from the surrounding air, increasing the height at which the damp may rise.

Rising damp may occur for a number of reasons, there may have been work carried out externally which has increased the ground levels, and subsequently bridged the DPC, there may be mortar snots in the cavity, or the floor construction might be inadequate, and the Damp proof membrane might have been punctured.

Many homes were built without a Damp proof course, usually those before 1900’s e.g. Victoria terraced, and have not caused any problem for the homeowner. This raises the question, as to the impact that Rising Damp may have on a building, particularly those that have modern central heating and adequate ventilation.

Rising damp is often misdiagnosed as the primary cause of damp at low level by Chartered Surveyors, whom may be carrying out a mortgage valuation or suchlike. Many surveyors often use incorrect methods to diagnose damp levels, i.e. a moisture meter which is calibrated for timber used on masonry.

Surveyors often recommend (usually as a precaution, in response to the high risk of litigation), further investigations by specialists or salesman, even when there is negligible evidence of damp. Consequently, many Homeowners and buyers alike, often find themselves being recommended damp proofing treatment by a biased specialist whom has a vested interest to find a problem of Rising damp.

Rising damp should never be considered in isolation, as the favourable conditions, which may have led to the high moisture readings, will increase the likelihood of other issues such as Condensation, Woodworm, and Dry/Wet Rot.

It is estimated that approximately 10% of damp may be attributable to Rising damp; although it is likely the figure is much lower than this. Therefore it is imperative, that if you detect damp at low level, or are advised of such, that you seek to explore other potential causes, such as Condensation and Penetrating damp. As it is far more likely, that you have a problem with a drain, leaking gutter/ down pipe or plumbing leak, which may often be much cheaper to remedy.