Holly Grundon and Alistair Watson, both in the planning and environment team at international law firm Taylor Wessing, discuss the latest trend for basement developments in the high-end property market.

Holly Grundon and Alistair Watson, both in the planning and environment team at international law firm Taylor Wessing, discuss the latest trend for basement developments in the high-end property market.

The proliferation of planning applications for subterranean development in prime Central London is well documented and it is with increasing regularity that the national press embarks upon yet another story on the latest proposals for the next “super basement”. This trend is reflected by the increase in work of this nature coming across our desks. With habitable space in London at a premium and significant restriction on homeowners’ ability to extend their properties vertically or laterally, subterranean development may provide valuable space that could not otherwise be achieved.

The extent to which a property can be enhanced is determined by the policies adopted by each local planning authority. Planning policies are primarily concerned with the use and appearance of land - considerations that have little meaningful effect when applied to proposals for subterranean development.  Therefore, unless there is a specific policy in place that addresses the issues raised by subterranean development, there is very little that local authorities can do to stop it. 

In addition, the most contentious aspects of basement development, for example construction noise and traffic; the structural stability of adjacent buildings; flood risk; and the removal of trees, are issues controlled by separate statutory regimes.  While the local authority will work to ensure that the impact on local amenity is limited as far as possible, it is only through strict policy requirements and the imposition of conditions that they are able to do this. 

Faced with an unprecedented rise in planning applications for subterranean development between 2003 and 2008, in 2009 the Royal Borough of Kensington and Chelsea adopted the “Subterranean Development: Supplementary Planning Document” (SPD).  The Borough is currently undertaking a review of its subterranean policy in response to calls for greater controls over basement development and in an attempt to introduce proportionality to proposals.  Significantly, it is proposed that no more than one basement storey will be permitted, that excavation will be limited to no more than 50 per cent of the garden, and that excavation under listed buildings and the gardens of listed buildings will be banned (subject to an exception for large sites). These changes, scheduled for adoption before the end of the year, will spell the end of mega-basements in the Borough.

Until then, planning applications will continue to be determined by reference to the policies of the Core Strategy and SPD. Planning applications will need to be submitted promptly in order to take advantage of less stringent controls over what is/is not permitted.

So what are the key issues that wealth managers and their clients should be aware of, when considering going “underground”?

If you are considering submitting a planning application for basement development, you will be required to demonstrate, through good design and supporting documents, how your proposal will address impacts on the structural stability on the property and surrounding properties, flood risk, sustainability, trees and landscaping, and construction nuisance. If the property is listed, or in a conservation area, attention must also be paid to the impact on the property’s historic environment and setting.

Key steps to achieve a successful application

1.    Engage an expert team of consultants

Subterranean development can raise many complex legal and political issues, so therefore it is essential that the applicant engages an expert team of consultants, with relevant experience.  This will ensure that the issues raised by the proposed development are dealt with quickly, comprehensively and to the satisfaction of the planning authority.  In addition to an architect, the applicant should consider engaging:

·        A structural engineer to produce a construction management plan based on the results of site-specific investigation, including bore hole and trial pit analysis.

·        A project manager to advise on construction and traffic management, and the programme of works.

·        A planning consultant to advise on policy and to engage with the planning authority and coordinate the application process.

·        A lawyer to advise on the sufficiency of the application documents in light of the adopted planning policy. 

·        An arboriculturalist for advice on tree removal and protection.

·        A sustainability consultant, since the proposals will be required to achieve a high level of sustainability.

·        A mechanical and electrical engineer to design the services within the building.

·        An acoustician to advise on ambient noise levels at the property.

·        A heritage consultant to assess the impact of the proposals on the heritage asset and surrounding conservation area (if applicable).

Each consultant will each produce a supporting document that addresses the issues raised by the proposed development in accordance with planning policy.

2.    Engage with the Local Planning Authority

Most local planning authorities offer a pre-application advice service to prospective applicants.  That advice is often subject to the payment of a fee, depending on the level of advice sought.  It is recommended that as a minimum, a site visit and following-up meeting with officers is arranged.  Taking advice on the acceptability of proposals will improve the chances of planning permission being granted as any potential issues which would otherwise result in refusal, will be resolved early on in the process.  Taking a proactive approach is likely to result in significant savings down the line in terms of both time and money. 

3.    The Construction Traffic and Management Plan

Frequently imposed as a condition on the grant of planning permission, the requirement to produce a CTMP is increasingly required upfront prior to the grant of planning permission.  The CTMP will address the most contentious issues arising from the development, such as the construction programme, conduct on site, construction noise and vehicle routing. A CTMP that comprehensively addresses those issues will close off several grounds of objection and a reason upon which the planning authority might otherwise refuse planning permission. 

4.    Notify and consult with your neighbours

Whilst there is no obligation on applicants to consult with their neighbours, it is nevertheless considered good practice to do so in respect of any major works.  It will be impossible to satisfy every objection, but in some cases consultation could lead to modifications acceptable to the applicant while mitigating problems for neighbours.  By offering to meet and explain your proposals with neighbours, there is less likely to be friction over any problems that arise subsequently, saving time and money in the long run. 

5. Costs

Where a full team of consultants are engaged, the costs of making the planning application can be in the region of £100,000 ($155,000).   However, by taking a thorough approach from the outset, the applicant will avoid spending time and money when planning permission is delayed or refused.   Depending on the area of additional floorspace, the applicant may also be liable to pay Community Infrastructure Levy and contribute to affordable housing provision.