CSLB General Building (B)Site Work, Foundations and ConcreteMedium
A residential contractor is pouring a continuous footing for a single-story wood-framed addition in an area with no special frost concerns. Per the California Building Code, what is the minimum required depth of footing below the lowest adjacent undisturbed ground surface?
- A24 inches
- B12 inches
- C18 inches
- D6 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 12 inches
The CBC/CRC requires exterior footings to extend at least 12 inches below the undisturbed ground surface, primarily to reach adequate bearing soil and reduce the effects of surface moisture and erosion. Deeper depths may be required where frost depth or expansive soils dictate.
Why the other options are wrong
- A. 24 inches is not the general code minimum for standard conditions.
- C. 18 inches exceeds the minimum unless site conditions require it.
- D. 6 inches is too shallow to meet code minimum bearing depth.
Minimum Footing Depth
The minimum vertical distance a footing must be embedded below undisturbed ground surface per building code, ensuring adequate bearing and protection from surface effects.
- Code minimum is 12 inches below undisturbed grade for standard footings
- Deeper depths required for frost lines or expansive soil per soils report
- Footings must bear on undisturbed or properly compacted engineered fill
Memory trick: Twelve inches down keeps your footing sound.