Are you planning to construct the building off the slab or will the walls have their own footing?
150mm stone and 100mm slab with light reinforcement is what I would do. But if you want to build off the slab I would normally recommend an edge thickening (and probably required if it's masonry).
As mentioned, an outbuilding over 30m^2 is when you need to get approval.
150mm stone and 100mm slab with light reinforcement is what I would do. But if you want to build off the slab I would normally recommend an edge thickening (and probably required if it's masonry).
As mentioned, an outbuilding over 30m^2 is when you need to get approval.