What size of footing is required for a 2-story building with a load bearing value of 1,500 psf?

• A. 12 inches
• B. 15 inches
• C. 18 inches
• D. 24 inches

Answer: (B)

Footings are sized to spread the building’s load over the soil so the pressure on the soil does not exceed what it can safely bear. With a soil allowable bearing value of 1,500 psf, the footing must provide enough area per unit length so that the load transmitted per foot divided by that area stays at or below 1,500 psf. A two‑story building increases the load compared to a lighter structure, so the footing must be wider than the minimum to keep the soil pressure within the limit. Among the typical options given, the width that just meets the 1,500 psf limit without being unnecessarily large is the middle-sized one. Smaller widths would exceed the soil’s capacity, while larger widths are more than needed.