Building Control for new roof on old outbuildings

I'm thinking of connecting 2 little outbuildings to the house, and putting on a new insulated roof.
What will Building Control think, will they want new foundations?
One is victorian stone, one is 70's blocks.
Should I dig some kind of exploratory holes?
They've been roofed for decades with no cracking so should be OK, do I have to have some kind of expensive surveyors?
George
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