CSLB General Building (B)Site Work, Foundations and ConcreteMedium
A continuous wall footing must support a wall load of 4,000 pounds per linear foot. The soil at the site has an allowable bearing capacity of 2,000 pounds per square foot. What minimum footing width is required?
- A1 foot
- B2 feet
- C3 feet
- D4 feet
Show answer & explanationAnswer & explanation
Correct answer: B. 2 feet
Required footing width = wall load / allowable soil bearing capacity = 4,000 lb/ft ÷ 2,000 lb/sf = 2 feet. This ensures the footing distributes the load without exceeding the soil's bearing capacity.
Why the other options are wrong
- A. 1 foot would only support 2,000 lb/ft, insufficient for the 4,000 lb/ft load.
- C. 3 feet would be oversized, wasting material beyond structural need.
- D. 4 feet would be double the necessary width for this load.
Footing Width Sizing
The minimum footing width needed is calculated by dividing the applied load per linear foot by the soil's allowable bearing capacity.
- Formula: Width = Load (lb/ft) ÷ Bearing Capacity (psf)
- Soil bearing capacity is determined by geotechnical report or code tables
- Undersized footings can cause settlement or foundation failure
Memory trick: Divide the load by what soil can hold to get width in feet, bold.