The cost of extending your home

Ellie Green
Authored by Ellie Green
Posted Monday, September 19, 2022 - 6:45pm

It’s a really good idea to be aware of the cost of an extension if you’re thinking about adding to your home rather than moving to a new house altogether.

The costs of extending is made up of many parts including the size of the addition, whether it’s on one or three storeys, and whether it can be achieved under permitted development or requires planning permission. 

Other areas that influence the final cost when you extend to your  house include the interiors, the design of the extension, the materials used, and which professionals you work with.

To help you get an idea of what you might pay, we’ve put together a guide to all the costs of extending and included advice on how you can make your money go further, whatever house extension you have in mind.


Building work costs depend not only on where you live and the people you've hired and the results, you're after.

Expect to pay around £1,450 to £1,700 per square metre for an extension of basic quality, £1,800 to £2,700 per square metre will give a good quality finish and £2,700 to £3,000 per square metre will allow you to achieve exceptional build.

For an extension of 4m x 5m, the build cost would be around £35,000 for an entry level build and £42,000 for a good quality build and it will cost you from £50,000 for an extension with an excellent finish. 

These costs do not include professional fees (more on this below), which can cost around 10 to 15 per cent plus VAT. With these extra costs added.

Find a Builder: How to Find the Right Builder for Your Build

How do you find a builder with the right experience and skills, and that you can trust? Here's our top advice to use on your search for a build team

6 top tips for how to find a good builder in your area

  1. Ask friends and family for recommendations
  2. Ask other tradespeople for recommendations
  3. Search online reviews and ratings
  4. Create a shortlist and interview your favourites
  5. Use a trade association like National Association of Building Contractors who have fully vetted builders.

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