Extension over existing annexe costs

Thundercat_2

Hi!

I currently live in a detached house which had an annexe/extension added in 1995/96 (we bought the house last year). It's a large extension and virtually doubles the footprint of the house.

The problem is that it makes the upstairs of the house feel small in comparison to the downstairs, so we've been toying with the idea of extending upstairs over the existing ground floor to match the footprint upstairs as well.

I realise that the first thing we would need to discover is whether the existing extension could support the weight of the additional floor(s), but as a rough guide what sort of cost per m2 would we be looking at. We live in Surrey, so I presume that would make things more expensive (it usually does!!), but it would be great to get a ball park figure so that we could work out a very rough costing.

We're also considering re-roofing the whole lot if we did the extension and putting some loft rooms in the newbuild part, so I suppose we're looking at actually adding two floors to that part of the house - don't know if that changes things?

Thanks in advance!!

System

in all honesty i don't think a finger-in-the-air, rule of thumb price per square meter will help at all in this case, you've got so many potential issues that are going to impact on the cost of that extension, it would be better to get someone (builder/architect) to visit the site and have a good gander at it!