Difference in cost between single and double storey extension?

[nikos]

We're looking at a house to buy which would need the kitchen extended. Since we would be doing that anyway, would it be much more expensive to go to 2 stories? Also does anyone know of any good websites that give good pictures of what extensions will look like?

dont quote me but when I asked a builder the same question, its all down to square footage in total, they reckon about £1000 per square metre for an extension. so if your downstairs is the same size as your upstairs then it will be double the price iyswim.
you'll probably need planning permission and an architect, but the architect will be able to draw it out for you.

I'm a building control officer and we estimate cost on £1k per sqm of floor area created.

Go for it!! in for a penny in for a pound. We are in the middle of our double storey extension . As everyone else has said, yes it goes by square metreage. If you are goign to the hassle of sourcing a builder, gaining planning, getting the mortage to pay for it you may as well (obviously, if its not stretching you too much, financially). You'll be kicking yourself you didn't put the other storey on once its finished if you don't. Good luck!