House Extension Prices

How much will an extension to your house cost?

An extension to your house can be a easier option to moving for gaining more living space, but how much will it cost for types of extension of different sizes?

The table below gives examples of the range of prices we have had submitted. As a rough idea you can typically say that it will cost at least £1000 per m2 or  93 per ft2 including basic plumbing and electrician work. This price is per unit area of internal floor space and so a 5x4m single floor extension will have a total floor area of 20m2 and a double storey will have 40m2.

Here are some prices from Whatprice users and personal research. The amount of information submitted varies and what you see is what we get! If you have any of your own feedback then please fill out the form at the bottom of the table and help this project.

House Extension Prices: Disclaimer
Category Average Cost Price Range Units Last Updated
£25500 £9500-34000 per house 2014-09-22
£5800 £3600-8000 per item/job 2015-01-04
£10010 £30-15000 per m2 2014-12-17
Double storey £42875 £49-94000 per house 2015-01-02
Double storey £47052 £10000-148000 per item/job 2014-07-10
Double storey £16275 £500-145000 per m2 2015-07-02
Planning costs £5290 £1000-27000 per item/job 2014-09-09
Single storey £23381 £800-100000 per item/job 2015-06-28
Single storey £3295 £500-24000 per m2 2015-07-05

Typically, a single storey extension will cost more per metre squared than a double storey. In theory a triple storey would cost less still. In practise the difference in cost may be small though. The price per square metre also depends on the size of the property. There are basic costs that don't increase too much with size and hence the cost per square metre will decrease as the floor area increases.

The price for a home extension depends on several factors

As an example the final cost of the project could comprise of

The fixtures and fittings aren't just electrical and plumbing work but all the plastering and floor work. The shell build includes the windows and external doors plus roof.

A general process for getting an extension built might be

  1. Sketch out some plans/ideas yourself
  2. Approach an architect and get some detailed drawings made
  3. Apply for planning permission
  4. Get some quotes in (can be done before planning permission if not sure on budget I guess)
  5. Agree contract with builder. A useful suggestion that some people have done is to break down the payment into different sections based upon completion of job.

This is just a simplified overview, you will also need to get building regulations approval and permission (at least no dispute) from your neighbours as well.

Please try our new (added 2011) extension calculator which will estimate the cost of your extension based on external dimensions, roof type and number of storeys.

This is NOT a form for requesting quotes. Please use this instead if you desire a quote for work

Please tell us your own prices

"Great site for gaining the basic knowwledge to begin planning the costs"


"I spent ages trying to work out how to extend my home and by how much, there are some really useful firms such as home extension studio who can help you through the initial stages of your project"


"Siskel and Ebert give it two massive thumbs up"

Mr. Siskel

"Found the page very useful as it would help when getting quotes from the builders and know what to expect. Many Thanks."


"thanks, really useful to start thinking about the extension project."

Dr Siva

"I found the page very useful"


"thank you, a very useful guide, we will very likely extend now rather than move!"


"very helpfull plain and simple. "

r white

"This was really useful. It is usually so difficult to get 'rough ideas' from trades people when you are at the initial stages of a new plan - so thank you very much!"

A Colville

"thank you,found the page very very good "


"extremely useful, just needed ball-park figures, thanks a lot"


"This has answered all the main questions I had about planning an extension. Great."


"This is such a great web site. We are thinking of an extension and this gave us the exact (How to go about it)!"

J. Arya

"i have just moved back from spain where i had a building firm. the prices there are very differant to the uk . i found your page very helpfull many thanks mark mccall"

mark mccall

"is vat on top of the quoted price per m2? ie another 17.5%"


"can't definitely say for those submitted by users but its extremely unlikely someone would quote the price they paid before VAT. In general all prices on the site include VAT (where required) as they are what consumers have been billed"


"Do the guide prices per sq ft include VAT?"

Steve Smith