What is the minimum size and location of rebar in a footing supporting a slab?

The correct answer highlights the requirement of placing two #4 bars within the middle third of the footing depth for adequate reinforcement. This configuration is essential as it effectively enhances the tensile strength and overall stability of the footing, which is particularly important when considering the loads that will be exerted on the slab above.

Placing the rebar in the middle third of the depth of the footing allows for better load distribution and minimizes the risk of cracking or failure during the footing's use. In concrete construction, the positioning and quantity of reinforcement bars can significantly impact structural integrity. Specifically, the middle third is crucial because it is where the maximum moment occurs in a typical bending scenario, ensuring that the structure can withstand the forces imposed on it.

In contrast, other options may not meet the structural requirements as effectively or may not adhere to standard building codes and engineering practices. For instance, one #6 bar may not provide sufficient reinforcement for larger footings, while one #4 bar at the top does not align with the best practices for load-bearing applications. The option of using two #5 bars near the base does not place the rebar where it will be most effective for resisting bending moments.

Understanding these critical aspects helps ensure that the foundation of a structure is designed to