Residential Building Inspector B1Floor ConstructionEasy
A builder is installing bridging between 2x10 floor joists. What is the primary reason for installing bridging in a floor system with solid sawn lumber joists?
- ATo create a fire-blocking barrier within the floor cavity.
- BTo stiffen the floor and prevent the joists from twisting or buckling.
- CTo increase the load-carrying capacity of individual joists by transferring load.
- DTo provide a nailing surface for the ceiling finish below.
Show answer & explanationAnswer & explanation
Correct answer: B. To stiffen the floor and prevent the joists from twisting or buckling.
Bridging (either solid blocking or cross bridging) between floor joists serves to stiffen the floor and provide lateral support to the joists. This prevents them from twisting, rotating, or buckling under load, thus enhancing the overall stability and performance of the floor system.
Why the other options are wrong
- A. While solid blocking can act as fire blocking in some cases, it's not the primary purpose of all types of bridging.
- C. Bridging helps distribute concentrated loads, but its primary role is not to increase the ultimate load capacity of a single joist, but rather to stabilize the system.
- D. This is generally not the primary purpose; separate furring strips or direct attachment to joists is used.
Floor Joist Bridging
Diagonal or solid members installed between floor joists to provide lateral support, prevent twisting, and distribute concentrated loads.
- Enhances floor stiffness and stability.
- Prevents joists from buckling or rotating.
- Can be solid blocking or cross bridging.
Memory trick: Bridging Brings Better Bracing.