I agree, anyone who pours a slab at 4"s in my humble opinion is just asking for failure
Need to know subgrade to properly design concrete. With unknown subgrade I would use 6 as minimumWe just did permanent concrete at our ranch gate entrance a few months ago, and also did the garage area at same time. We used 4000psi strength concrete at 5.5 inches thick, with 1/2" rebar at 16" grid spacing, with 6 Guage welded wire sheets laying down on top of the rebar. All rebar was placed on 2.5" plastic risers which elevates the rebar above the water vapor ground sheet and directly into middle of the concrete slab.View attachment 682188View attachment 682189