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There's no doubt that extensions cost a lot of money, but a lot of the time they're well worth the investment.
It's always a sensible idea to get two or three quotes before you commit, but here's a general idea of costs to get you started.
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If you're a Which? member, log in now to unlock pricing data from the Royal Institution of Chartered Surveyors (RICS) for various sizes of extensions.
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House extensions size and costs | Floor size (metres) | Flat roof | Pitched roof |
Single storey with one window | 3 x 3 | ||
3 x 5 | |||
4 x 4 | |||
4 x 6 | |||
Double storey with two windows | 3 x 3 | ||
3 x 5 | |||
4 x 4 |
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Before you take the plunge, consider these points:
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Get a quoteThe best place to start is to try and find someone who has been through the process before and get their recommendations for good local architects, structural engineers and builders.
Which? Trusted Traders has a great library of vetted and reliable traders in your local area.
Discover the key questions you should be asking your builder, and what you can expect from an architect, in Advice from a builder and architect
Ready to plough ahead with your extension? Read our guide to Building regulations and planning permission and look over our Building an extension timeline, which breaks down a standard week-by-week extension building schedule