How to estimate cost of extension before buying a house without builder yet)?

[chillybits]

I am overseas during the week at the moment (an in law taken ill) but need to buy a house as our house is under offer. I am home this weekend but need to be very discriminating when looking at houses.

Its SW London. Does anyone have any guidance as to how much I should estimate for a 2 storey extension, which would extend the kitchen dining area and the boxroom above by 6 foot in one direction. Apart from lighting there would be no services to extend as it would be pure floor space, no bathroom or anything involved but it looks like existing external guttering/drain would need moving by about a foot.

I don't really have time to involve builders at this stage. Its a bit of a nightmare logistically.

I'm would be guessing at £30K? You could speak to the EA that is selling the property you are interested in and as you are abroad they could get a builder to go round and look at the property and give you some idea? It is really difficult to quote anything without seeing it.

About £1500 per sqm to extend. Am in middle of all this malarkey now. It's always more than you think.