Have received planning to build an additional bedroom and bathroom on top of existing kitchen/flat roof. I have dug down to expose the existing foundation, and the concrete foundation is roughly about 7 - 8 inch thick, the ground below this is mainly bedrock and large stone.
The building inspector came today and asked me to expose more of the foundation so he could inspect further, I assured him that the thickness of the concrete was as above but he wants to return once i have dug further.
The extension above is only 3m x 6m with the (wall-plate) wall only about 6 courses high. I don't want the building inspector to return and inform me that i have to underpin the the foundation in order to build above, surely 7 - 8 inch of concrete on the mainly bedrock/large stone is ample to proceed.
If i have to underpin would timber-frame be an option or is there other ways please reply !