building costs per sq metre

[overboard]

I'm considering putting a 15 sq metre extension on my bungalow in Devon and would welcome any guides to construction costs per sq metre, covering building, electrical, plumbing and general finishing. Also any thoughts on cost of building in stone. Thanks in anticipation.

[buildersmate]

The trouble with trying to guestimate this sort of project is that the nature of the variables are too large.
Whilst for estimating purposes one might be able to use a figure for a complete house of say �1000 to �1200 psm, this is meaningless on a small project where the requirement to tightly manage the resources and the cordiantion between them drives the overall efficiency of the build (and hence the cost). Also remember that builders' cost is not a good indicator of quoted price - the difference being the margin the individual is willing to accept - which can vary according to economic climate, fit with other jobs.
Which is a long-winded way of saying the best way of assure value is via three competitive quotes - making sure you structure things so everyone is wotking off the same baselines. Competition drives value.
Can't comment on cost of building in stone, sorry.

[overboard]

Thanks for your reply buildersmate - it gives me something to go on.