How can I work out how much for an extension

stardoman

I've got planning permission to build a 2 storey rectangular extension on the back of my house. There is a conservatory there at the minute which will need to be pulled down. The extension is 8mx3m, so I guess the square metreage is 48m. Someone said to bank on £1K for every square metre. Is this a good rule of thumb? I've been a bit concerned reading some of the threads on here where 2 storey extensions are £110K etc. as we haven't as much as that to spend.

We are waiting for building regs to come through at the moment. How detailed a spec should be do for the builder's? Is there anything online we can use as a basis for a spec?

Thanks. Mandy.

Tucker

I think the general guide is £1000 per sq metre, not foot.

That's getting a building firm to deal with the whole build for you.

lincroft1710

If an architect/planning consultant has drawn up plans for building regs appro, these should show all details necessary for builder to follow, e.g. foundation depth, floor, wall and roof construction and insulation, plumbing, drainage and stormwater requirements.

dander

I think it's generally best to take the £1k as the bare minimum it might take, you'll have to work hard to keep it down to there.