The issues you have here is the roof height, if it is possible to raise the ridge level we would suggest that the upper floor extension is carried out in timber, this will keep the load down.
If you have a raft foundation it would suggest the formation has a low capacity, but would not restrict you should you wish to extend.
To test whether you can extend into the loft we can undertake a feasibility report and look into planning rules and the impact your proposed extension has on the surrounding area.
We do offer a scheme design service and would be pleased to undertake this study for you, this early scheme design service will confirm whether to can or cannot extend.
Regards,
Jeremy Wedge MIstrutE CEng On Behalf of Loft Conversion UK
