For, like bathroom sponges, buildings shrink and swell during temperature changes and such minor blemishes are usually perfectly harmless. This is the time you should call in a structural surveyor to find out if your home is being hit by something more threatening, such as structural distortion or subsidence. Though a flurry of flooding and storm damage claims in recent years have been keeping insurance companies on red alert, subsidence has also continued to bedevil properties in areas with soft clay soils and shaky foundations.An Association of British Insurers survey shows that more than £1bn was paid out for domestic storm damage, flooding and subsidence in 2000. Last year, although less costly, the number of claims increased. And anyone who has woken to find part of their house sinking knows the nightmare it all entails.

It may mean major structural work involving many thousands of pounds – as well as the first £1,000 of any buildings insurance policy.”Such calamities can happen even after a structural survey has been carried out, for the ties holding the inner and outer skins of the walls may rot, the building bulge and the owner end up with some very costly remedial work,” says Miren O’Brien of HJP, the Surrey-based financial services company. So, unless you have spotted your dream home together with oak-beamed ceilings, Corinthian pillars and alluring inglenooks, O’Brien tells buyers to steer clear of properties that have any hint of subsidence or distortion.So how does today’s buyer guard against future subsidence? Many IFAs and mortgage brokers advise clients to adopt the insurance cover of the previous owner when buying a home. “This means the insurers will know the home’s history and be more likely to pay out if there is a claim. Otherwise, if the house reveals any hint of a problem during your initial survey, trying to find an insurer later could be exceedingly difficult,” she says.Most of the UK’s subsidence hot-spots lie south of an invisible line stretching from Hull on the East coast to Bristol in the South-west – in the Thames basin area of London and the Home Counties alone one in 50 properties has been affected in the past 25 years.

Much of the region is built on soft clay soils that shrink and swell due to moisture or lack of it and are particularly troublesome to housing foundations during very dry spells. By contrast, areas of north Scotland that are built on solid granite are completely subsidence-free.Another housing hazard is vegetation. Roots of trees and shrubs planted near developments stretch out in search of water during long dry spells and cause the soil to shrink, while removing trees near a new development can cause previously dry soil to swell up with moisture and “heave” the foundations. If you are planning to extend your garden, think carefully before choosing which trees to plant. Oak, elm, willow, poplar or ash trees are notoriously thirsty and if planted too close to the house could put your foundations at risk. If you do decide to plant near your home, use shrubs in containers or make sure any new trees are the same distance from the house as their fully grown height This will prevent their roots snaking under the foundations. And one in five subsidence claims stem from damaged drains that leak into sandy soil and cause erosion.For the past 20 years, the main cure for problem properties was underpinning.