CSLB General Building (B)Site Work, Foundations and ConcreteHard
A footing is being poured in direct contact with earth (no formwork on the bottom). According to standard concrete reinforcement practice, what is the minimum required concrete cover over rebar for this condition?
- A1.5 inches
- B3 inches
- C3/4 inch
- D2 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 3 inches
For concrete cast against and permanently exposed to earth, the standard minimum cover requirement is 3 inches, providing extra protection against moisture, soil chemicals, and corrosion since no formwork barrier is present.
Why the other options are wrong
- A. 1.5 inches applies to formed concrete exposed to weather (e.g., #5 bars and smaller).
- C. 3/4 inch cover applies to concrete not exposed to weather or earth, such as interior slabs.
- D. 2 inches is generally used for larger formed exterior elements, not earth-formed footings.
Concrete Cover for Earth-Formed Elements
Concrete cast directly against and permanently exposed to earth requires greater minimum rebar cover than formed concrete.
- 3 inches minimum cover for concrete cast against earth
- 1.5 inches typical for formed concrete exposed to weather
- 3/4 inch typical for interior, unexposed concrete
Memory trick: Dirt-formed footings need the thickest skin — 3 inches to protect within.