basement conversion london

Basement Renovation in London – Your ten step Guide

April 7, 2015

basement project 2


This 10-point guide by planning consultants Alistair Grills Associates and luxury interior designers Callender Howorth sets out what homeowners and developers need to do to get their planning permission for basement construction in London.

With the number of basement constructions increasing exponentially in London Borough of Kensington and Chelsea (RBKC), the Council has moved to limit the area of new or extended basements and reduce their impact on neighbours.

1. Where to Start?

The starting point for anyone contemplating a basement extension must be the RBKC Planning website, and particularly the new Basements Planning Policy document adopted in January 2015. It is essential to understand from the outset what is, and is not, possible to achieve with your property.

For instance, is your property listed on Historic England’s register? Does it lie within a Conservation Area? Is the site within an area at risk of flood, or where there are difficult ground conditions? Are there any trees close by? If the answer to any of these questions is “Yes”, then certain restrictions apply which will dictate the final form of your extension. RBKC’s latest policies prevent the creation of new or extended basements below listed buildings; allow only one storey basements; and, if extending into the garden, allow only 50% of the garden area to be developed.

Basement project 12. Consult a Professional

Speaking to a planning professional at an early time will allow you to avoid costly pitfalls. Particularly within Kensington & Chelsea, planning applications involve the preparation of numerous drawings & reports and it is sensible to get a feel as to whether your ideas are achievable “in principle” before you set out too far down the road. Also, be realistic when putting together your wish list – accept that certain items, such as excavating below listed buildings, is not likely to be achievable within the Borough, whereas extending below the garden may be.

3. Prepare Sketch Plans

Armed with your planning advice, work with a designer, architect or specialist basement company to draw up sketch plans of your proposal. If your property is not listed, but is located within a Conservation Area, RBKC will be particularly interested in the visible skylights, light wells, ailings, grilles and other paraphernalia required to allow daylight within the hidden basement.

4. At what Cost?

43Ask your architect, designer or basement company to obtain a ball park costing of your proposals at an early time. The consultants should also be able to advise on the costs of preparing and submitting the necessary planning application.

5.Submit a Pre-Application Advice Request to the Council

RBKC no longer allows negotiation of planning application content once a planning application as been submitted. Discussion of proposals now takes place at the pre-application stage with the formal submission of a Pre-Application Advice Request to the Council, incorporating sketch designs, existing & proposed floor area tables and as much other relevant information as is available. The more information that can be submitted, the more accurate the Council’s response will be. Officers will meet you on site to discuss the proposal and issue a formal advice letter. Be aware, however, that planning officers are not bound by their pre-app advice as a planning approval is a political decision made by elected members (or one they agree to delegate to officers). Officers will advise on any changes that may have to be made to basement designs to conform to RBKC planning policy.

6.Think about how your basement will be constructed

Screen Shot 2015-04-07 at 5.47.30 PMAnother important consideration is how easy it will be for a contractor to construct your basement. For instance, is your site landlocked or to the rear of your house? Will the surrounding road network accommodate large construction vehicles? Can a skip to be placed outside the house? Put quite simply, the easier the basement construction is, the lower the build cost is likely to be. Moreover, the Council will need to assured that the basement is buildable without an unacceptable level of inconvenience or disturbance to neighbours.

7.Consult your Neighbours

36Face the fact that basement construction is not likely to be popular with neighbours, unless they are thinking of doing one themselves. Put yourself in their position and do everything you can to minimise the disruption to their lives. Following the Council’s detailed policies will help keep you on the right side of the law. Once you have your formal Pre-Application Advice letter arrange to meet your immediate neighbours and possibly the Chair of the local amenity group to take them through the plans. Don’t expect an enthusiastic reception, but emphasise what you will do to alleviate their concerns.

8. Prepare your Planning Application

Depending on the particular circumstances affecting your property, and the scale of the proposals, the formal planning application may require the preparation & submission of some, or all, of the following documents:

– Existing & Proposed Drawings

– Planning, Design & Access Statement Statement (including RBKC’s Pre-Application Advice Letter)

– Heritage Impact Assessment (if a listed building and/or a Conservation Area is affected)

– Engineering Design and Construction Statement (EDCS)

– Demolition and Construction Management Plan (DCMP)

– Construction Traffic Management Plan (CTMP)

– BREEAM for Domestic Refurbishment Assessment

– Flood Risk Assessment

– Demonstration of effective Sustainable Urban Drainage

– Pre-application consultation report onfirmation that neighbours have been provided with copies of the EDCS (see above) and notified of the provisions of the Party Wall process.

Where relevant:

– Site Waste Management Plan (for very large basements)

– Arboricultural Report (where trees are affected)

9. From Submission to Determination

Post-submission, RBKC will check if all of the necessary documentation has been submitted and will then validate the application. The Council will consult internally and externally with; inter alia, statutory consultees, residents and amenity bodies. A straightforward application should take 8 weeks to determine; perhaps slighter longer if it has to be decided by the Planning Committee. However, most planning applications can be determined by the Executive Director using his delegated powers. An application has to go before the Planning Committee if:

– there have been three or more objections and the Executive Director for Planning and Borough Development is recommending that planning permission should be granted

– an elected Member has requested that the application be considered by Committee

– the Executive Director for Planning and Borough Development has decided that the application should be considered by the Committee

– an application is contrary to the Council’s planning policies and the Executive Director’s recommendation is to grant permission.

10. Approval!

25Once approved, RBKC will issue a formal decision notice which is likely to set out a number of planning conditions, some of which may request additional details before you can start on site. However, you’re over the worst and can look forward to the basement construction process!

Contact Callender Howorth Interior Designers, London for advice on planning and designing your basement project. Our in-house architects and project managers have a wealth of experience in creating bespoke projects incorporating kitchens, media rooms and even wine cellars.


Alistair Grills