It is not unusual for property buyers in the UK to find a reference to ground instability in the report on title prepared by their solicitor. Clay-rich soils, on which many UK cities and towns are founded, are prone to shrinking and swelling with changes in moisture content. This may cause significant structural damage to buildings and costs insurers hundreds of millions of pounds a year. Property owners are advised not to allow the ground to become too dry or too wet and not to plant or remove trees in the vicinity of their properties.
However, not many property buyers, solicitors and even developers are aware of another ground instability risk, which may not be flagged by an environmental search, but which can have disastrous consequences. This sinister risk is historic mining.
Conveyancers dealing with properties in areas of historic tin and coal mining in Cornwall or Yorkshire would obviously order a mining search; conveyancers buying or selling a property in London would not always think it necessary. Yet many areas of London are built over sites of mineral extraction (e.g. brick clay, sandstone) and mines, now derelict and backfilled. An entire 19th century chalk mine is built over in Lewisham. Over time these may collapse causing subsidence and creating sinkholes.
Properties new and old, modest and grand, have suffered recently from historic mining-related ground movement. To mention just two widely publicised examples:
- several new built houses on Bayfield Estate in North Tyneside, were sold for around £200,000 each in late 2015, only to be demolished in 2016 following discovery of subsidence due to historic mining; and
- Wentworth Woodhouse, one of the greatest private houses in Great Britain, now in a state of deterioration due to subsidence caused by the exploitation of deep coal seams under the landscaped park in the 18th and 19th century.
A prudent solicitor may recommend a mining search to his client, even if the area is not presently known to have been the site of mining activities. Providers like Terrafirma Mine Searches offer a basic search for as little as £12, which seems a small price to pay for identifying the risk of damage to the property and displacement of its occupiers.