NEIGHBOURLY feeling is a fine thing. Fancy a cuppa? Oh, do come in. Having a barbecue this evening — would you like to join us? Until one dark day the neighbours arrive at the door with architectural plans in hand and mention the “E” word. And we’re not talking Ecstasy but another touchy subject: extension.

This is an increasingly common scenario. Exorbitant stamp duty fees, rising property prices and all those TV programmes saying “don’t move, improve” mean more of us are extending our homes. In 2004-05 more than 340,000 English households applied for planning permission to extend compared with 211,000 in 1999-2000.

Extending, if done well, can make financial sense. For example, putting a £50,000 extra bedroom on a London two-bedroom Victorian terraced house could put £75,000 to £100,000 on the asking price, according to Mark Maynard, owner of the estate agent Humphreys Skitt & Co in Blackheath, southeast London. “People will pay a big premium for the ‘wow’ factor. So if, for instance, you put in a big, open-plan living area for £50,000 it is likely to sell for £100,000 more than before,” he says.

The live-in kitchen-diner, where kids can do homework while you cook dinner and dad watches TV on the sofa, is the in-thing. But what the glossy mags don’t tell you is that what you gain in space you can lose in friendships.

Jane and Andrew have just added a £130,000 kitchen-diner with office and loo to their four-bedroom Victorian terraced house. “These houses are quite big, but the kitchen, where we spent most of the time, was very cramped and narrow.”

They took plans to their neighbours. “The friendship soured immediately,” says Jane. “Before the extension the neighbours could look right into our kitchen in so much detail they were able to comment on things they saw. Our neighbours’ main concern was that the side window of their kitchen would look on to a brick wall. The wall was several metres from their house down a slope, so light was not obstructed, but the view would be less interesting.”

The couple applied for planning permission and their neighbours objected. The couple then scaled back the design, so that it could be built without planning permission. You can usually extend your house by 15 per cent of its size if it is detached or a semi, or by 10 per cent if it’s in a terrace, without planning permission under “permitted development” rules. “When the work was finished we invited the neighbours round to thank them for being accommodating, but they said: ‘This has changed our lives. We wish you had just moved’. ”

The termination of a friendship is a small price to pay on the Richter scale of house extension stories. A dream home could cost you your marriage, your sanity, or both if tension from neighbours gets out of hand.

Charlie MacKeith, of the architectural practice Research Design, says: “The first question we ask when someone comes to us is, how do you get on with your neighbours? If you don’t get off on a good footing with them, the project might fail at the planning stage or, even worse, if they are unhappy and the project does go ahead, your quality of life could be ruined by the tensions with next door.”

Even if you don’t need planning permission, you should address party wall issues and basic concerns, such as light and view. Research Design recently pebble-dashed the side of an extension at the request of a neighbour, who wanted that side to match his house, or you could use a nicer material such as reclaimed bricks to improve a neighbour’s view.

Julie and her husband, Ian, coped with possible objections from their neighbours in South London by keeping them informed. They wanted storage at the side of the house and to add light and depth to the kitchen. The couple mentioned their ideas to their neighbours, who were worried because someone in the neighbourhood had built an ugly brick extension blocking out light. Julie said: “The size meant we could extend under permitted development, but we had to make sure they would enter a party wall agreement with us so it was legal.

“I invited the neighbour around often for coffee and asked for ideas. We asked them to our house to meet the architects (Research Design), who brought 3-D drawings showing precisely how much shadow would be cast into their garden. It was important for us to communicate from the beginning and be sympathetic to their point of view. Our architects designed the extension with a stepped roof rather than a flat one to minimise the amount of shadow and we used attractive materials like wood and glass.” The couple even offered to pay for the neighbours’ windows to be cleaned and also use of the skip. “When it was finished we held a party for all the neighbours in our street to acknowledge the inconvenience and to see the end result, which everyone enjoyed.”

MacKeith says: “It is in human nature to be territorial. Many people just don’t want the status quo to change, but government policy is to increase density, so extensions are something people will have to get used to.”

Research Design Architecture, 020-8297 4101, info@researchdesign.co.uk

BOX CLEVER

How to convince the neighbours about your proposed building work:

• Broach the idea in conversation. They shouldn’t hear about it first through an architect’s plans or a lamppost notice.
• Try to establish what will be accepted under planning regulations and address your neighbour’s concerns quickly.
• If the extension is near a jointly owned wall or boundary, you must first obtain a party wall agreement from your neighbour. See www.odpm.gov.uk
• Consider paying your architects to do 3D drawings and models. Two-dimensional drawings can look too abstract.
• Give your neighbours regular updates.
• Treat with sympathy issues of light, view and trees, etc. If scaffolding marks your neighbour’s grass, returf it.
• Allow between £1,000 and £2,000 a square metre for building an extension, depending on materials and fittings.

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