Extensions: the facts

11 min read

PROJECT ADVICE

The ins and outs of planning an addition can seem daunting, but our expert guide will help make the process go smoothly

FEATURE ARABELLA YOUENS

The roofline echoes the gables of the house in this design by Eastabrook Architects
Extension to a London Victorian house by Oliver Leech Architects
HollandGreen brought modern glazing to this listed farmhouse
PHOTOGRAPHS (OLIVER LEECH ARCHITECTS) STÅLE ERIKSEN

1 THE FIRST STEPS TO BUILDING AN EXTENSION

A firm understanding of the ultimate intention of the extension will help to make decisions about everything from size and window positioning to materials and colours, says Chris Pask, director of architecture and interiors firm Charlton Brown. Also, contact your buildings and contents insurer to inform them about your plans to check what is and isn’t covered.

2 WHAT IS PERMITTED DEVELOPMENT?

If the project falls under permitted development rights, it’s possible to avoid the need for full planning permission. Generally, single-storey rear extensions can extend out by up to 3m from a semi-detached or terraced house and by 4m from a detached house (based on plans of the building on 1 July 1948). You can also apply for prior approval for rear extensions up to 6 or 8m in length (depending on whether the house is detached or not); these can’t exceed 4m in height.

3 LAWFUL DEVELOPMENT CERTIFICATES

When extending under permitted development, it’s still advisable to apply for a lawful development certificate to document that the project was legal at the point of construction. Once this application is validated by the council, it could take around eight weeks for a response. Unlike a normal planning application, the council can’t refuse the certificate if it complies with permitted development requirements.

4 SECURING PLANNING PERMISSION IN LONDON

If the building isn’t listed or in a conservation area (see below), it’s still a good idea to talk to the local authority to get pre-application advice, if the extension is remotely controversial in design or size. Also, talk to neighbours to sound them out (before entering into a party wall discussion). Look for a precedent in the area that could mean the project is in good standing. ‘Regular dialogue with the local planning officers and use of digital technologies is the key to our successful planning outcomes and the reason for our 100% success rate for new builds and extensions across London,’ says the team at Studio Elephant.

5 LISTED BUILDINGS

‘The single most important thing you have to do before embarking on a project for a listed house is to demonstrate that you fully understand the building,’ says Dr Simon Thurley who sits on the advisory board of RedBook, a consultancy that advises on high-value property projects. ‘Normally this is done by commissioning a conservation s

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