Commercial Building Inspector B2Footings and FoundationsEasy
A commercial building inspector is reviewing the design for a new five-story office building. The structural drawings indicate that the foundation system consists of concrete spread footings. According to the 2021 IBC, what is the minimum required compressive strength (f'c) at 28 days for concrete used in footings and foundation walls?
- A3500 psi
- B2500 psi
- C2000 psi
- D3000 psi
Show answer & explanationAnswer & explanation
Correct answer: B. 2500 psi
IBC Section 1904.2 specifies the minimum specified compressive strength of concrete for various applications. For footings and foundation walls, the minimum f'c at 28 days is 2500 psi.
Why the other options are wrong
- A. 3500 psi is a higher strength concrete, often used for more demanding structural elements, but not the minimum for footings.
- C. 2000 psi is generally not acceptable for structural concrete in footings and foundation walls under the IBC.
- D. 3000 psi is a common strength for structural concrete but is not the minimum required for footings and foundation walls.
Minimum Concrete Strength (Footings)
The lowest acceptable compressive strength for concrete used in footings and foundation walls, achieved after 28 days.
- IBC specifies minimums to ensure structural integrity.
- Strength is measured in pounds per square inch (psi).
- Higher strength concrete offers greater durability and load-bearing capacity.
Memory trick: Strong foundations start with specific concrete strengths.