Rough extension cost estimate

[CaptainSlow]

I'm after some advice from any builders or anyone in the know on the cost of an extension.

Brief will be to build a single storey rear extension I guess 8' * 15'. There is currently a patio there so that will need to be broken up aswell. I require it to be finished to a standard where all I need to do is put some paint on the walls. I would prefer pitched roof depending on cost. Any rough cost estimates?

[dave_s13]

£1500 per square metre - to be on the safe side.

[CaptainSlow]

Ok thanks, does that include footings, brickwork, roof, plastering etc? Plus VAT I'd guess?

eta

Also we have french doors at the moment, could these be reused on the extension?

Edited by CaptainSlow on Monday 18th October 12:39

[dave_s13]

No that that should be everything.

Groundworks, footings, building fabric, services, internal finish and VAT.

Providing it's straightforward of course.

I'm not in the trade or anything though just part way through removing the back of my house and making it bigger.....fvckin nightmare!

Bear in mind 8 feet is only 2.4ish metres. You can go back 3m without needing planning - providing there is adequate distance to back of garden. Check planning portal for info on permitted development stuff.

Also pray your ground conditions are good and you don't need to spend 5 grand on piling/ring beams etc.

[Spudler]

dave_s13 said:

£1500 per square metre - to be on the safe side.

Based on?.

OP, you need to supply more info, brick/stone? concrete/clay/slate roof covering?
Even better, put a pic up of where you want to build.

[Busamav]

Whenever I have the info to hand and reverse price the actual cost of an extension to the m2 price it ends up around £1650 / m2. That is in Thames valley area.

Smaller jobs obviously can work out far more than that per / m2

[dave_s13]

Spudler said:

dave_s13 said:

£1500 per square metre - to be on the safe side.

Based on?.

OP, you need to supply more info, brick/stone? concrete/clay/slate roof covering?
Even better, put a pic up of where you want to build.

Based on when i asked a similar question and also the cost my extension would roughly have been had it been straightforward.

Obviously a very rough rule of thumb but gives the op an idea.

I spent 10 grand before laying any bricks by the way. It's been a rude awakening that's only getting worse, we have to move out at whe weekend. For 6 bloody weeks!

[CaptainSlow]

Thanks for advice so far, rough picture attached.

I'm in the Thames Valley area. What I'm considering is a brink built extension.

I have a detached house with double garage attached. The room on the side of the house the garaged is attached to is a full lenth lounge with curently double french doors onto the patio. I would like to remove these doors and have a new room off the back that also runs partially behind the garage. Currently the garage has a personnel door onto the garden that I wouls like to open into the extension. The garage also has a window which would need blocking in.

I would like the french doors to be moved into side of the extension. I am thinking of a flat roof on the extension and probably refelting the garage at the same time.

[Busamav]

Firstly I would be trying to talk you out of the flat roof , unless the main house has that feature

I suspect you will be doing well to get that for much under 25k .

[Boshly]

Extensions approx £100-£150/sqft (£1100-1600/sqm). Will naturally depend very much on finish and specification. Yours sounds pretty basic (as in no kitchen no bathroom no decorations etc) so lower end. Budget lower end but bear in mind any variation (footings key here) will send you up the scale very quickly indeed.

New build houses £125-£250/sqft (I'm sure you can work it out multiply by 10.76)

New build at £250/sqft will include very high quality finish, basement and swimming pool.