How much for 5m2 extension?

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We are thinking of doing an kitchen extension on the side of a house we want to buy. The kitchen is at the end of the house, and next to it as an outside space down the side which is part of the garden. We we'd fill in that space, making the kitchen wider, so it meets the fence and the back wall when the dining room is.

This would be around 5m2, single story.

Any idea how much that would cost please?

5m2 single storey extension with 4.5m of foundations using an existing opening to a plastered finish with basic electrics and single radiator if your soil is good and no trees nearby flat roof with felt could be around 15k if you live in the North East.
5m2 with piled foundations and goal post steels including chimney demolition, fancy kitchen, under floor heating, pitched roof, reclaimed bricks and tiles in central London zone 1 could be 150k.

I think it'd be worth getting a few quotes but it'll be quite pricey as some of the costs will be pretty fixed and not much less than if you were getting a much larger extension. So I can see how it could be 15k even in a cheaper part of the country.

Thanks both.

We can't get quotes as we've got to decide tomorrow if we make an offer or not.

John the house is in outer London. The £15k that you describe for the North East. How much do you reckon that would be for outer London? We don't need it to be fancy, just functional.

I reckon you could add another 5k for outer London.

PS it will also depend on things like access or off street parking for a skip and builer's stuff etc.

How much could you afford to spend?

Its not going to cost 150k for 5m2 single storey extension!

Im a QS for a Construction Main Contractor in London, a basic build to include excavation, foundations (i very much doubt you will need piles), blockwork, flat roof, internal decs, heating, elecs, ground surveys etc. Allow £1,500-£2,000 per m2.

Your price will go up dependent on the kitchen fit out, Velux windows, full re-wire if applicable, where is the current boiler located, does it need to be moved etc etc. That will push your price up, but the basic build you will get for the rates above

That's really useful, thanks.

We'll have £20k but that's for everything including some redecoration.

I'm really reassured by what you said @dizzy. Thanks for the info. Luckily the boiler is upstairs, so that's one less cost.

Ok this is a crude calculation but it will give you a rough idea. I am building across a London Borough numerous single storey rear extensions with disabled adptations i.e wet rooms etc. 30m2 extension with new kitchen, wetroom, internal reconfiguration etc for crica £70k = £2,333 m2. Allow for unforseen items, stuff below ground etc. Choose the right builder and at £20k you will have money to spare

20k for a simple add on extension, but then more if you want to knock down the supporting walls between the existing house and the new extension. And then more to put in a new kitchen and refloor the entire new space etc

Are you sure you mean 5m squared? That would be an extension that is just 1metre (wide) by 5metres (long). Is that worth the hassle?

A few other points:
If you multiply by a basic £ rate per square metre you have to count not only the new square metres but also make an allowance for the areas of the existing house that require refurbishing (e.g. anywhere that will need new kitchen units etc, flooring, plumbing, decoration). So even if you are only planning a new build area of 5m2, you would need to multiply your basic £/m rate by more than 5.

If you want velux roof lights and a sizeable kitchen with stone work tops, in London, you should probably expect no less than £2000 per square metre - especially if you don't have any contacts or prior experience with renovations)

Don't forget that when people quote basic £/m2 rates, you would typically need to add VAT and fees to that (e.g. fees for drawings, and potentially planning permission, party wall fees, and an engineer's calculations).

^^ what Fred said. Do you mean 5m by 5m? In that case you’re looking at a 25m2 extension

Thanks all.

Yes definitely only 5m2. Just the infill between the kitchen and the garden fence. This would make a very small kitchen into an acceptable kitchen. The kitchen is just unworkable as it is. We're happy with 5m2 as it wouldn't encroach on the main part of the garden.