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1 October 2020

Extension costs

Ever wondered how much an extension costs? We've got the latest figures from RICS to help make it that little bit clearer
RC
Rachel Christie

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.

If you're a Which? member you can log in now to unlock RICS pricing data on varying sizes of extensions.

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Total project costs
House extensions Floor size(m) Flat roof Pitched roof
Single storey with one window 3x3
  3x5
  4x4
  4x6
Double storey with two windows 3x3
  3x5
  4x4
  4x6

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