When do I find out the cost of an extension?

[fastliving]

I'm sorry I've been hitting this section with lots of questions lately, thanks for all the help so far!

I am aiming to get a single storey extension, back and side I think about 32msq.
Additionally I am getting my garage extended & remodelled. Plus all the hard landscaping (2 patio areas & 1 path) redone.

Due to circumstances out of my control I must re-mortgage by end of Jan.
However I can't re-mortgage unless I know how much the build will cost...

I've had a couple of architects round, haven't chosen one yet, but they are vague about costs (oresumably because the plans aren't done yet and I haven't engaged them).
A friend has recommended a builder, am I best to try and get them round to give me a rough quote based on my own drawings and measurements, (even though I won't be engaging them til after planning has gone through) or rush through choosing an architect and get them to get a move on with the plans? (Then I can get a better quote from builders)
(Added complication, will need planning, but as I'm only just outside permitted building and my neighbour is hoping to extend next year hopefully that will be ok).
Any ideas?

Ask your potential re-mortgage company what they'll need, and do it quickly!

I can get enough mortgage to pay for the build (& use savings) but want to keep the cost/term of the mortgage as low as possible (I don't want to say why as it might be outting - but there's a really good reason for this) eg I want to borrow as little as possible from the re-mortgage.

I want to know which the best way to price the job within 6 weeks is? Is this possible? How?

Thanks!

Do you need planning permission?

As a quick guide .... per square metre, allow £1200-£1500 outside London. £2000psm if you are in London, this is the extension only. Gives a tough idea. X

Yes miss
Does that include architect fees, planning/building regs flooring, painting etc @Shouldbeworkingnotreadingtalk ?
Or is it just the basic shell without the extras?
Does this include VAT?
Thanks!

We have been by architects in Cambridgeshire to budget £2250 plus VAT for builders. That would be for a plastered shell including plumbing and electrics, but not flooring, decoration, any bathrooms or kitchens. It also doesn’t include architects and planning fees.

@2catsand2kids figures are spot on, unless you're having something out of the ordinary or really small.

Factor in approx. £1500 for architects fees, £700 for planning, £800-1400 for Building Control, £700 for Build Over Agreement (if required) and a possible £2500 for handling the party wall matters.

Don't forget to add in flooring, decs and kitchen etc also, as noted above.

A good architect should be able to advise on rough cost also.

I was just giving a build cost, to "first fix stage" so doesn't include fittings etc other than the best basic white plastic light switches / big standard builders fittings. Not bathrooms or kitchens.
From your replies OP I'd say you are trying to get "an exact" amount. Trust me, WHATEVER you budget, it will go over. Things happen, unforeseen problems crop up.... prices of materials may rise due to Brexit, or there may be wages increases for tradesmen. We don't know. . your'll going to need £70k minimum by the end of it, so just double check that you're putting £70K value on the house, or that you're planning to stay there for long enough to reap the rewards yourself in the enjoyment of it. Good luck!

Costs/m2 such as quoted by Shouldbeworkingnotreadingtalk are hardly ever being met by builders round here (SE.) I would say 2cats2kids is in the right ball park. It depends on the shape - a square extension with a small perimeter:area ratio will cost less than an L-shape with a high perimeter:area ratio

Ours was roughly £2k per square metre in the NW, plus VAT to basic shell.

On another thread I’ve just been told off for suggesting £1500 p m2 was normal. The poster got quotes for way under that in the Midlands. I think extras could be huge but a £20,000 job was priced at £12,000 by 3 builders I was told! So I guess you never know but most projects over spend!

I did one about five years ago and it was around £1500/m2 for the build inc heating and installing an en suite. Flooring I had already.

I let contracts in London and prices can be £3500/m2, further out the norm is £2200.

There's massive regional variations but also gulfs between builders prices.

Always get three quotes, do your homework on references and don't ever accept an 'estimate'.