DIAGONISING THE PROBLEM

Few things are as off-putting when you walk into a property as being greeted by a pervasive smell of damp. The psychological effect on prospective house buyers has yet to be scientifically quantified, but as estate agents know better than most, dubious aromas have a distinct tendency to discourage offers. So for anyone carrying out renovation work, discovering that there’s a damp problem can seriously affect the project’s bottom line. Unlike most other worrisome wafts however, when it comes to damp, the risk of offending peoples’ olfactory senses is likely to be the least of your worries. At worst it can be a symptom of structural defects linked to dry rot, wet rot or beetle infestation. However, damp doesn’t always advertise its presence, and can happily wreak long-term damage in hidden voids far beyond the reach of the average human nose. Which is why surveyors routinely occupy themselves by prodding internal surfaces with hand-held damp meters.

It’s hardly surprising that in a rainy country like Britain the subject of water ingress has such a firm grip on the national psyche, even spawning whole industries dedicated to battling disconcerting damp patches. Unless carefully managed, water has significant potential to damage and disrupt. As well as instigating decay in timber structures, over time water can erode solid masonry because it expands around 8% in volume when it freezes, exerting a pressure equivalent to two tons per square centimetre. However these sorts of headline grabbing risks are extreme examples, and normally only arise in cases of long-term neglect.

The way moisture affects old buildings has only recently started to be fully appreciated, and the automatic reaction of many mortgage lenders to the slightest sniff of damp has long been to insist on ‘essential repairs’ often resulting in sales-driven timber and damp contractors unnecessarily injecting chemical damp

CAUSES AND SOLUTIONS

A well maintained building shouldn’t need special treatments to manage damp. Most problems can be remedied with common-sense maintenance. Your first task should always be to identify the true cause. Then, once this has been resolved, keep the house hea ted and allow sufficient time for the walls to dry out.

Most ‘damp problems’ are initially spotted as distinctive brown staining that appears on internal plasterwork, sometimes accompanied by a smattering of white salts.the location of this staining within the property can provide a useful clue to the underlying causes you’ll want to look for, so in this article we’ve described what to look for in different parts of a building.

‘ ‘ Given half a chance rain will find its way indoors through even the tiniest gaps and cracks

proof courses (DPCS) into the affected areas. In truth, the occasional spot of damp isn’t necessarily a problem and is not an unusual occurrence in many older properties. Damp patches are often a relatively harmless symptom of a minor fault that can be attended to during routine maintenance. The main concern in such cases is normally whether there’s any risk of long term exposure causing rot to structural components such as suspended timber floors.

DAMP AT HIGHER LEVELS

Roofs and stacks are normally the most exposed part of a building and given half a chance rain will find its way indoors through even the tiniest gaps and cracks in these building elements. It’s therefore not surprising that evidence of water staining on upstairs ceilings, chimney breasts and upper walls can usually be traced back to defects in roofs. Surveyors pay particular attention to weak points such as the junctions where chimney stacks protrude through roof slopes and where roofs meet parapet walls. These intersections should be firmly sealed with watertight lead flashings. Another common type of weak point is found where two adjoining roof slopes meet to form a valley. But these aren’t the worst offenders.

Top of the list of suspects is our old friend the flat roof.these are particularly prone to developing leaks because they are