What is the minimum reinforcing bar requirement for a slab-on-ground with turned down footings?

In the context of poured concrete foundations, specifically for a slab-on-ground with turned down footings, the requirement for reinforcing bars is essential to ensure structural integrity and load distribution. The minimum requirement typically calls for a reinforcing bar in both the top and bottom of the footings.

Having a #4 bar positioned in both the top and bottom helps manage tensile stresses that occur in the concrete due to various loads and environmental factors. The bar at the top is crucial to resist any tension forces that might pull the concrete apart, especially when subjected to bending moments. The bar at the bottom counteracts the compressive forces and provides additional stability and reinforcement.

This configuration is vital because it provides a more robust overall structure that can handle potential cracking and shifting, particularly in regions with expansive soils or where settlement might occur. Therefore, the requirement for reinforcing bars in both positions ensures that the slab's integrity is maintained under various conditions and loads.