Extension costs- latest rates?

[monagt]

1000 to 2000 per m2

option1 to option 2
1000/M2 to raise roof using existing timber/tiles where possible and no get full floor space due to roof coming down?

 

[lowCO2design]

planning, demolition, removal, beam for new ope, door , skirting, strengthening joists, flooring, electrics, blocks, plastering, roof timbers, plasterboard, vapour barrier, insulation, felt & battens, scaffolding, preliminaries, insurance

 

[monagt]

planning, demolition, removal, beam for new ope, door , skirting, strengthening joists, flooring, electrics, blocks, plastering, roof timbers, plasterboard, vapour barrier, insulation, felt & battens, scaffolding, preliminaries, insurance

I was thinking, pop of the roof, add 2 rows blocks and do a Mansard style roof to get the extra space, maybe getting 250+ extra out of the 400. A bit simplistic, I know.

Thx for the response lowCO2, much appreciated.