Residential Building Inspector B1Floor ConstructionEasy
A contractor is installing a wood floor system for a residential addition. The plans call for 2x10 joists spanning 14 feet (4.27 m). The building code requires a minimum bearing length for joists on wood or metal supports. What is the minimum bearing length required for these joists?
- A2 inches (51 mm)
- B1 inch (25 mm)
- C1.5 inches (38 mm)
- D3 inches (76 mm)
Show answer & explanationAnswer & explanation
Correct answer: C. 1.5 inches (38 mm)
The 2021 IRC specifies a minimum bearing length of 1.5 inches (38 mm) for wood joists, rafters, and beams supported on wood or metal. This ensures adequate support and prevents crushing of the wood fibers at the bearing points.
Why the other options are wrong
- A. 2 inches is acceptable but is not the minimum requirement.
- B. 1 inch is insufficient and does not meet the minimum IRC bearing length.
- D. 3 inches is also acceptable but exceeds the minimum required bearing length.
Wood Joist Minimum Bearing Length
The IRC mandates a minimum bearing length for wood joists, rafters, and beams on their supports to ensure structural stability and prevent localized crushing.
- Minimum 1.5 inches (38 mm) on wood or metal.
- Applies to joists, rafters, and beams.
- Ensures adequate load transfer and prevents damage.
Memory trick: One and a half, a joist's sure stand.