Which floor joist size, when exceeded, requires solid blocking?

Which floor joist size, when exceeded, requires solid blocking?

• A. 2 x 8
• B. 2 x 12
• C. 2 x 6
• D. 2 x 10

Answer: (B)

Blocking between floor joists is used to tie the joists together, preventing twisting and helping carry loads more evenly across the span. The need for solid blocking increases as the joist depth grows, because deeper joists are more prone to lateral movement and deflection under load if they’re left unblocked. In typical practice, once you’re dealing with floor joists that are as deep as a 2x12, solid blocking is required. That threshold is why this option is considered the correct one here: 2x12 represents the depth at which the blocking requirement is triggered. The smaller joists listed do not cross that depth threshold, so they’re not the trigger for mandating solid blocking in this context.

Blocking between floor joists is used to tie the joists together, preventing twisting and helping carry loads more evenly across the span. The need for solid blocking increases as the joist depth grows, because deeper joists are more prone to lateral movement and deflection under load if they’re left unblocked.

In typical practice, once you’re dealing with floor joists that are as deep as a 2x12, solid blocking is required. That threshold is why this option is considered the correct one here: 2x12 represents the depth at which the blocking requirement is triggered. The smaller joists listed do not cross that depth threshold, so they’re not the trigger for mandating solid blocking in this context.