questions r.e. extensions

[Hattie11]

Hi we are in a semi-detached house, and both ours and our adjoining neighbour have single storey extensions out the back. We would both like to extend these to be double storey.
a) would this save much in costs if we had them both built by the same builders?
b) does this require planning permission?
c) does anyone have a guess at costings for this?

I do know that our foundations are secure for a second storey, and i think it'd be about 28sq/m.

I will be getting some quotes and advice from builders - but i'm impatient and know that mumsnetters are wise

I don't know how the new planning rules will change things, but as I understand it at the moment, you definitely need planning permission to go double storey. It depends on your council, but our council is quite strict about double storey extensions in semi detached houses - we're in the middle of planning at the moment and were told that we couldn't go double storey all across the back regardless of whether our attached neighbours had no objections - we've had to leave over 2m from what is the join (if you see what I mean) as single storey, double storey for part way across the back, but that might be different if you can submit applications at the same time referring to each other's plans.

I'm guessing that it would probably be cost effective - don't really know but anticipate it must be easier to do a roof across the two houses etc than separate ones etc and the builder may give you a better price / discount because its a bigger job for him.

Also not sure about costings, but would guess at £25,000 to £30,000k??

Thanks for that mandy. That's exactly what I guessed for costings. Fingers crossed we do get permission!

I would be wary of sharing a contract with your neighbours. What if they have problems on their side that you don't, or you are happy with different specs, etc etc. I would get a builder to quote for them as 2 separate but concurrent jobs - it will still be easier/potentially cheaper for him (but probably not a huge amount cheaper), but your contract will be clearly for your property only.

(a) I would endorse the sugestion by RationalBrain

(b) Here is the official guidance for extensions

(c) Over the past year I have received tenders for several 2-storey domestic extensions ranging from £1,300 to £2,100 per sq m. The higher ones were 'all in' prices i.e. including fully fited kitchen and bedroom units and all interior finishes

That's a very good point rationalpoint and cheers for the link pendeen I shall have a look.