Tips - Extensions

April 27, 2007 by kotoman

Planning permission in England, Wales and Northern Ireland is required if the total extra space exceeds 70 metres cubed or 15 per cent of the original volume of the house – whichever is greater.
Planning permission is needed in Scotland if the total extra space is more than 50 metres cubed or one-fifth of the original house volume – whichever is greater.
Previous extensions can count towards these limits, so always check with your local authority.
Single- or two-storey extensions usually need building regulations approval.
Conservatories may be exempt from planning permission if they are small but they require building regulations approval when the floor area exceeds 30 square metres.

How much will it cost?

Adding to your living or kitchen space with an extension is a great idea, but a garden room or conservatory could work out cheaper. A garden room is similar to a conservatory but usually has a solid rather than glass roof.

A single-storey extension (3×3m, one window) could cost between £14,750 and £17,750; a garden room between £10,500 and £12,500 (3×3m) and conservatory (3×3m) between £10,000 and £12,000. Floors are extra.

Extensions and garden rooms can take between eight and 12 months, from planning to completion, while a conservatory can take as little as six weeks.

Insider tips

Mike Lawrence, author of the Which? Book of Home Improvements:

Structural elements such as the roof supports need to be approved by the local authority at planning stage to avoid late changes and delays.
Local authorities now frown on flat roofs for single-storey extensions, so be prepared for the expense of a pitched roof.
Using your own plumbers and plasterers can upset your builder, and needs to be handled diplomatically but firmly.
Plumbers and electricians must be fully qualified – always ask your builder whether his sub-contractors are.
On a complex project, using an architect is usually worth the cost.

Home-improvement expert Alison Cork:

Only manage a project yourself if you have the time and can visit the site regularly. Otherwise, leave it to a professional.
Keeping a spreadsheet of costs is wise, as paperwork is often a builder’s Achilles heel.
Always allow at least three months to organise any official permission (if required).
Having several things done at once, like the extension and bathroom, is a good idea and usually saves money overall.

source: Which