Commercial Building Inspector B2Floor ConstructionMedium
A commercial building inspector is observing the construction of a masonry bearing wall supporting a precast concrete plank floor. The plans indicate that the wall is constructed of 8-inch (203 mm) nominal concrete masonry units (CMU). What is the minimum nominal thickness of a concrete masonry bearing wall required to support a floor, according to the IBC?
- A10 inches (254 mm)
- B6 inches (152 mm)
- C8 inches (203 mm)
- D4 inches (102 mm)
Show answer & explanationAnswer & explanation
Correct answer: B. 6 inches (152 mm)
According to IBC Section 2109.2, the minimum nominal thickness of masonry bearing walls shall be 6 inches (152 mm). This applies to walls supporting floors or roofs.
Why the other options are wrong
- A. 10 inches is a common thickness for walls requiring higher strength, fire ratings, or for taller buildings, but not the minimum.
- C. 8 inches is a common and acceptable thickness for masonry bearing walls, but not the minimum.
- D. 4 inches is generally too thin for a masonry bearing wall and is typically used for non-bearing partitions.
Masonry Bearing Wall Min. Thickness
The IBC specifies minimum nominal thicknesses for masonry bearing walls to ensure adequate structural capacity and stability when supporting floors or roofs.
- Minimum 6 inches (152 mm) nominal thickness.
- Applies to walls supporting floors or roofs.
- Thicker walls may be required based on height, loads, or fire rating.
- Non-bearing walls can be thinner (e.g., 4 inches).
Memory trick: Bearing wall's strength, 6 inches in length, for floors to rest, it passes the test.