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20th February 2012

Subterranean Development on the Rise

The development and extension of residential property below ground level is becoming increasingly common in London and other high value locations.

The problems associated with such ‘subterranean development’ are attracting growing interest and concern, giving rise to legal challenges and proposals for policy and legislative reform.

The benefits of subterranean development to owner occupiers and developers are clear – it offers an opportunity to increase the size of a building and increases its market value. However, neighbouring residents or businesses may be concerned about the impact of such development on their own property due to the potential for disruption to foundations, soil erosion or interruption of pre-existing surface or sub-soil water flow. There is also the disruption, noise, vibration and dirt that can arise during the construction process, which has the potential to reduce rental incomes or sales values. Care must be taken to see that the construction works do not damage neighbouring properties and that a suitably designed scheme is prepared which includes dealing, for example, with common issues such as damp proofing. Defective design and construction works could result in expensive claims potentially defeating the object of the development.

It is the problems associated with subterranean development that have given rise to a number of legal challenges from disgruntled residents to planning permissions granted for basement extensions in London. The Royal Borough of Kensington and Chelsea has vowed to review its planning policies relating to subterranean development in response to a growing number of applications and at least one successful judicial review.

However, in many cases, basement extensions are permitted development, bringing them outside the scope of planning control. This has led some to call for legislative reform and a new Subterranean Development Bill has recently been introduced to Parliament. If enacted, it will introduce a new requirement on developers to submit a ‘Subterranean Development Application’ to the local planning authority, and to serve a ‘Subterranean Development Notice’ (similar to a notice under the Party Wall Act) on any adjoining owner, before starting work.

The Subterranean Development Bill is a Private Members’ Bill only and, accordingly, it is unlikely to reach the statute books. The Government has expressed the opinion that legislation is unnecessary and that appropriate safeguards are already available to regulate basement works. However, it seems that they may come under increasing pressure to reconsider this position, or at least that planning policy will become more stringent. Those considering subterranean development may want to start work sooner rather than later.

For more information, please contact Gemma Harris on gemmaharris@hewitsons.comor on 01223 532747

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