Last week a ‘sink hole’ opened up in the drive way of a residential property in High Wycombe and the car parked in the driveway disappeared into it.
Since then I have been asked on a number of occasions whether a Home Buyers Survey can address this new (perceived) threat.
This is an understandable concern as the pictures in the news were certainly very dramatic and anyone, particularly the residents of High Wycombe, would be right to be concerned.
In 2012 a sink hole opened up near a school in Flintshire that was nearly 40 feet across.
So it appears that sink holes are no longer a phenomenon restricted to the geology of Florida.
How do sink holes form?
Water percolating through the ground can become acidic and dissolve soluble rock such as chalk or limestone (this being the prevalent rock in High Wycombe) leaving a subterranean hole or cavity.
Cavities can then sit dormant for years until there is a change in the weight bearing down upon them, leading to sudden collapse.
Recent heavy rains and flooding and resulting raised water table have almost certainly played a part in the Buckinghamshire sink hole where waterlogged clay formed the upper layers.
Mining and sink holes
Local mining, such as clay, coal, tin etc (although not in this case) can also be the culprit. Underground tunnels are similar to the cavities formed by dissolved rock.
Sink holes and home surveys
There have been no reports of visible cracks or indentations preceding the appearance of the recent sink holes.
The RICS Level 2 Survey or RICS Level 3 Survey cannot carry out subterranean investigations, save for certain aspects of drainage. (It is of course possible to build a hypothesis about the under soil and land upon which the house is built where there is evidence of movement or subsidence.)
However the searches carried out buy your conveyancing solicitor during the conveyancing phase should identify, sometimes with the help of the surveyors recommendations regarding local soil types, risks relating to mining, flood plains and other local factors.
The following article has useful local factors information about High Wycombe.
These searches will help build a risk profile of the property before you commit to the purchase.
It is worth pointing out however, that although dramatic, sink holes are extremely rare.