Residential Building Inspector B1Footings and FoundationsEasy
A residential building inspector is reviewing the plans for a new single-family dwelling. The plans indicate that the foundation walls are constructed of masonry and are 7 feet (2134 mm) in height. What is the minimum nominal thickness required for these masonry foundation walls, according to the 2021 IRC?
- A6 inches (152 mm)
- B10 inches (254 mm)
- C8 inches (203 mm)
- D12 inches (305 mm)
Show answer & explanationAnswer & explanation
Correct answer: C. 8 inches (203 mm)
For masonry foundation walls supporting light-frame construction and not exceeding 8 feet in height, the 2021 IRC requires a minimum nominal thickness of 8 inches.
Why the other options are wrong
- A. This thickness is typically insufficient for masonry foundation walls of this height.
- B. While acceptable, this is greater than the minimum required thickness.
- D. This thickness is not the minimum requirement and is typically used for taller or more heavily loaded walls.
Masonry Foundation Wall Thickness
The minimum nominal thickness required for masonry foundation walls, based on height and supported load.
- IRC R404.1.1 (1) specifies minimum thickness.
- For masonry walls up to 8 ft high supporting light-frame, 8 inches is minimum.
- Thickness can vary with soil conditions and design loads.
Memory trick: Masonry walls, check height, then thickness; don't guess, use the code's witness.