What is the minimum strip footing width for a 2-story building?

• A. 350 mm
• B. 250 mm
• C. 300 mm
• D. 400 mm

Answer: (A)

The key idea is that footing width is chosen to spread the wall loads over a safe area of soil. For a two-story building, the loads transmitted to the foundation are higher than for a single-story, so the strip footing must be wider to keep the bearing pressure within what the soil can safely support. A minimum width of 350 mm provides enough bearing area to handle typical residential loads on common soils, while keeping excavation practical and ensuring there’s adequate concrete around the wall to carry the load and resist edge cracking or differential settlement. If the soil is weaker or loads are higher, the footing would be widened further, but 350 mm is the smallest width used in standard practice for two-story homes. The other options would either be too narrow to meet the required bearing capacity or wider than necessary for a minimum specification.