Core TradesQuestion 122 of 700
What is the MINIMUM concrete cover required to protect reinforcing steel in concrete that is cast against and permanently exposed to earth?
a.3/4 inch
b.1-1/2 inches
c.2 inches
d.3 inches
Explanation
Concrete cast directly against earth requires 3 inches of cover because the rough soil interface offers the least protection against moisture and corrosion. 1-1/2 inches applies to formed surfaces exposed to weather (smaller bars), 2 inches to larger formed bars exposed to weather, and 3/4 inch to interior surfaces not exposed to weather or ground.
Law Reference: 2025 CA Building Code, Chapter 19 (per ACI 318 §20.5.1)Practice all 700 questions free — no signup required.
Related questions on this topic
- CALCULATION: A ceiling requires R-49 insulation. If a certain blown insulation provides R-3.5 per inch, what minimum installed thickness is needed?
- A kickout (diverter) flashing is installed where a roof edge meets a vertical wall at the bottom of a roof-wall intersection. Omitting it commonly causes:
- Under normal ambient conditions, what is the MINIMUM period that standard structural concrete should be kept continuously moist to develop adequate strength and durability?
- A rectangular slab measures 30 ft by 40 ft and is 4 inches thick. How many cubic yards of concrete are needed (before any waste allowance)?
- Assuming proper placement and curing, which change to a concrete mix will produce the GREATEST increase in compressive strength?
- For a one-story wood-frame dwelling on stable soil with no deeper frost-line requirement, what is the MINIMUM depth below the undisturbed ground surface to the bottom of an exterior footing?
Last reviewed: · editorial process
PrepPass Editorial Team · Verified against California CSLB General Building (B) Trade Examination · How we review