Extension - how much does it really cost?

[3littlebears]

That's it! Would anyone who's actually had an extension divulge how much it actually cost please? I read wildly different figures - I know the quality of the fitting out makes a big difference but hear figures of £30-£250k and am fairly clueless. Am thinking of a single storey extension 8m x 4m (ish) but would also like to rebuild garage and build over that too. Is £100k enough? £150k? I really don't know and would appreciate any advice. In the southeast...

Mmm, we're having an extension done right now but also decorating the whole house (replaster, rewire a 3 bed semi) so my figures my or may not be of help!

3 x 5m extension
3 roof velux windows, patio doors etc...
Putting up 2 new internal walls to create snug and hallway
New lintels over 2 windows
Extension makes one big open plan kitchen/diner of 5x6 so several steels in
Create small cloakroom
Put in downstairs loo
Move boiler downstairs
Plaster and 1 coat of paint

This cost approx £24k (not inc vat)

But of course this is just bare walls so we're spending a further £8k on kitchen, £1k on bathroom (not inc tiling, floors...).... Wood burner...
we also have to decorate upstairs
In total, we estimate it will cost us around £45k to do everything, that's inc carpets, tiles, costs for getting the plans for building regs done etc...

I'm in Manchester :)

Have fun - I'm really excited about getting ours done!

Do extensions usually come with a warranty?
What happens if the builder argue if a fault actually exists?
Or if they are no longer trading and a fault develops?

Some recent domestic extension projects I designed have cost between £800 sq m to £3,600 sq m.

The cheapest was a simple kitchen extension - a flat felted roof, cavity wall 'box' on a 1960's 'estate' house and the client did their own kitchen fitting, flooring and decorating.

The most expensive was extending the kitchen, dining room and hall of a C17 stone farmhouse - slate roof, stone and blockwork cavity walls, purpose made hardwood windows, 'Kutchenhaus' fitted kitchen, silica-polished slate floors and so on!

These were all completed within the last 2 years and West Cornwall prices, exclusive of my (very reasonable ) fees and Building Regulations / planing / listed building charges. If you live in England's south east, add another 30 - 50 percent!

South East here, I normally suggest a budget of £1200 - £1500/sqm for a fairly standard build. Start getting fancy and putting in high end fittings/ fixtures/audio visual then you're heading up towards £2,000.

These are always guidelines though because every builder charges differently and every client wants something a bit different.

I'd say £1400 a square metre all in
steels add to the cost but also to the value of the finished product
daylight in every room is worth the effort