We are building a masonry two-car garage on a slope, with a storage room on the lower level and garage/parking space on the upper level. Now the floor/slab is to be poured, and I am wondering if the builder is reinforcing correctly and sizing adequately. The concrete slab will be 20 cm, and he is using 12mm rebar, with a thinner dimension in mesh above. How tightly should the thicker bars be spaced? As mentioned, it is a future two-car garage, and there is no load-bearing divider/post underneath.
What is the span length of the slab? 12s at the bottom feels good, and a 200 mm slab is quite thick. I would probably (without having calculated it) say 12s with 200 mm spacing in both directions as bottom reinforcement, and the mesh is more for crack limitation.