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Home & garden.

Updated: 2 Nov 2021

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
Extension plans_jul19 483003

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 for various sizes of extensions.

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Total project costs of house extensions

House extensions size and costsFloor size (metres)Flat roofPitched roof
Single storey with one window3x3
 3x5
 4x4
 4x6
Double storey with two windows3x3
 3x5
 4x4
Home finances and extension costs

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Extension planning

  1. Extension costs
  2. Extension planning
  3. Building regulations and planning permission
  4. Building an extension timeline
  5. Advice from a builder and architect

Extension planning

  1. Extension costs
  2. Extension planning
  3. Building regulations and planning permission
  4. Building an extension timeline
  5. Advice from a builder and architect

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