What is the minimum load rating for soil under a footing?

What is the minimum load rating for soil under a footing?

• A. 75 kPa
• B. 50 kPa
• C. 100 kPa
• D. 25 kPa

Answer: (A)

The key idea is bearing capacity—the soil’s ability to support the load from the footing without excessive settlement or failure. The footing transfers the structure’s weight into the ground, so the soil must have an allowable bearing capacity that can carry that pressure safely. For typical residential footings, a practical minimum allowable bearing capacity is about 75 kPa. This level translates to roughly 1,500 psf, which is enough to support standard house loads with acceptable settlement. If the soil’s capacity were lower than this, you’d risk excessive settlement or failure and would need design changes such as larger or deeper footings, soil improvement, or piles. The other values would either be below what’s generally considered safe for ordinary homes or exceed the minimum threshold, but 75 kPa is the commonly used minimum reference point for this scenario.

The key idea is bearing capacity—the soil’s ability to support the load from the footing without excessive settlement or failure. The footing transfers the structure’s weight into the ground, so the soil must have an allowable bearing capacity that can carry that pressure safely. For typical residential footings, a practical minimum allowable bearing capacity is about 75 kPa. This level translates to roughly 1,500 psf, which is enough to support standard house loads with acceptable settlement. If the soil’s capacity were lower than this, you’d risk excessive settlement or failure and would need design changes such as larger or deeper footings, soil improvement, or piles. The other values would either be below what’s generally considered safe for ordinary homes or exceed the minimum threshold, but 75 kPa is the commonly used minimum reference point for this scenario.