Hi,
Just looking at a house, but I’d want a double storey side extension put on and I’m trying to gauge whether it’s worth it.
Normal stuff; lower floor will be an integral garage and utility (maybe a toilet if there’s space).
Upper floor will be making an existing bathroom bigger and adding in another bedroom.
Any help with likely costs would be appreciated.

Many many variables there

Will depend on where you are in the country, what’s there at the moment (do you need services moved), what the ground is like (depth of extensions) any trees nearby, what finishes you want, etc.

£1000 per sq m is a place to start. Possible to spend less if you really scrimp or do some yourself. Easy to spend more especially if you have a problem site or want a high spec finish.

Think of a number, double it and then add £20k.

Building sheriff extension calculator

£1200 SQ for finished but diy decor

£30k is a typical figure.
Add or subtract depending on the fit-out – cheap or quality etc.

£1200 SQ for finished but diy decor

1st and second floors?
I would like the the roof to be pitched, no flat.
I can get a friend to do the flooring and another for the plumbing. Happy to paint it myself.

I don’t think it will add enough value to your property to cover the costs but it will make your house a better place to live.

If you’re planning on staying around then it is worth it IMHO.

There is probably lots you can do yourself – it’s not all difficult – lots of labour costs doing donkey work.

Best of luck….and we’ll need pics when you get started!

I don’t think it will add enough value to your property to cover the costs but it will make your house a better place to live.

Depends how much you pay for the house surely?

We built a similar sounding extension for £28k including the fit out in 2007. So that was garage on the ground floor, bathroom and dressing room above. Decent quality fit out,sogood quality electric garage door, good bathroom equipment etc. It has a pitched roof etc and included putting new drains in for the toilet/shower etc.

Think it was approx 3m x 8 m,so 24 sq metres .

If your house has a value of X and the extension costs Y – I am suggesting the value of the finished property will be less than X + Y.

What you paid for the house doesn’t affect this theory but does influence whether you feel spending money on an extension is money well spent.

I am hypothesizing – you have the figures so I suppose I should shut up now! 😉

I love these questions. They make for the most entertaining reading.
Basically, you ask a ridiculous question, get a load of conflicting answers and go off on many tangents, add more information, people re-comment with revised advice.
You end up non the wiser??

True, but you can often end up being aware of things to consider that you were previously ignorant of.

True, but you can often end up being aware of things to consider that you were previously ignorant of.

+1

Yes, and you’ll be aware of a lot more things that have no relevance to your needs because answers here are based primarily on speculation with no knowledge of your site or real needs.
How are you going to know which answers here have any real meaning for you?
That’s why consulting a professional who can do a site visit and understand your needs will actually provide proper worthwhile advice.

Fees will be +£5k, groundwork and build.

Contingency of whatever your first number was 🙂

£1000-1200/sqm is very low. We always work on £1500-2000/sqm, depending on level of finish. Once you have your figure, add 10% for contingency.