The idea of the ground suddenly opening up and swallowing your house sounds like something from a nightmare, but unfortunately the phenomenon of sinkholes has recently become a reality for some people in the UK. While sinkholes are still considered to be very rare in the UK, a spate of recent cases has brought the issue into the media spotlight.
According to a report in the Guardian, a sinkhole occurs when the underground layers of soil and rock are eroded away, creating a cavity. If there is too much weight for the surface above the cavity to support – such as if a property is built there or if the surface level simply goes unsupported for too long – the area collapses. The erosion of the soil and rock can be caused by excessive rain, which has led many to suggest that the recent wet weather could have put more properties in the UK in danger.
Normally, Britain averages one sinkhole per month, but in February this year ten sinkholes were reported across the country. On February 5th a 17ft deep and 10ft wide hole appeared in the garden of a property in Barnehurst in Bexleyheath. The homeowner, Gretel Davidson, assumed that the damage would be covered by her buildings insurance policy; however, as the sinkhole only affected the garden and not the house itself, it was not included in the policy.
According to the British Geological Survey (BGS), it is difficult to predict where a sinkhole will appear, but there are some indicators. Naturally occurring sinkholes are caused by the erosion of soluble rocks such as gypsum and chalk, so areas with a great quantity of soluble rock beneath the surface are more prone to sinkholes. Sinkholes can also be caused by the collapse of old mine shafts, so areas of the country where a great deal of mineral extraction has occurred are also at a higher risk. The BGS lists the Mendips, parts of Wales, the Peak District, and the northern Pennines including the Yorkshire Dales, parts of Dorset, Hampshire, the Chilterns and Ripon as prone areas.
For those concerned about the risk of sinkholes in their area, the Council for Mortgage Lenders advises: "We would suggest to borrowers to get the best building insurance cover they can, and be sure exactly what the insurance covers."
You can also check when buying a property whether there has been any history of mining activity, while companies such as Landmark and GroundSure can provide environmental risk information and digital mapping of the area you live in.