According to the website Subsidence Report an estimated 20% of homes in England Wales are subject to the risk of damage to their foundations as the ground on which they built shrinks when it dries out and swells when it gets wet. Each year, subsidence is responsible for as much damage as that caused by flooding and in the past 10 years has cost the economy some £3 billion – subsidence therefore being the most biggest and most damaging geological peril in the country.
What is it?
Subsidence is in fact a very simple concept – it refers to the foundations of a building moving downwards because the ground on which the foundations are dug no longer supports their weight.
That failure in the ground’s ability to support the weight of the building may be caused by it shrinking as it dries out, or, paradoxically perhaps, by it becoming too wet.
What causes it?
Reasons for the ground either becoming too wet or drying out and shrinking is largely due to changes in the weather.
Probably the greatest danger comes during periods of especially dry weather – and recent weather conditions may be ringing a few alarm bells as far as subsidence is concerned. Writing on the BBC website, for example, weatherman Paul Hudson has commented that after record high average temperatures during June and July of 2014, September appears to have been one of the driest on record.
During such dry periods clay soils in particular are prone to shrink and this effect may be exacerbated by tree roots spreading in search of water and causing a further collapse of load bearing soil. According to Subsidence Support, nearly two-thirds of all subsidence insurance claims arise from the effect of trees growing close to an affected building.
What are the signs and what can you do about it?
Although the most common signs of subsidence are cracks in the walls of a property and a possible disturbance in the floor levels, these same symptoms may be evident in a number of other problems too.
Your response to the problem may depend on the area in which you live and the incidence of previous subsidence in the region – clay soils, the growth of trees and shrubs close to the property or past mining and other extraction industries may all contribute to an increased risk.
One of your primary defences may lie in insuring against the risk of subsidence. By no means all home insurance policies include this peril, so you might want to consult a specialist in non-standard cover – such as that provided by us at GSI Insurance – in order to ensure that your are adequately protected.
Mitigating the risks
Even with the relevant insurance in place, you may still be expected to play your part in mitigating the risks of subsidence.
One of the principal ways in which you may be able to make a positive contribution in this regard is to take particular care of trees or shrubs growing in close proximity to your property.
Although the roots are almost certain to be a major cause of subsidence, expert opinion is generally against the complete removal of such trees and shrubs – since this may leave a hole in the ground which itself causes further potential for subsidence. The preferred course of action, therefore, is to limit further growth of the roots by lopping and pruning the branches above ground and, by reducing the foliage also reducing the root system’s demand for water. We recommend you seek expert advice if you are concerned about trees and shrubs affecting your property.