Solid blocking is required for floor joists that exceed what nominal size?

Solid blocking is required for floor joists to ensure proper load distribution and structural integrity, particularly as the size of the joists increases. This is crucial in preventing issues such as excessive deflection or wobbling and ensuring that the floor can handle expected loads safely.

In this context, the requirement for solid blocking typically begins with joists that are nominally 2 x 12 inches in size. When joists are larger, such as 2 x 12 and above, they are more prone to movement and deflection under load. Solid blocking helps to stabilize these larger joists, creating a stronger floor system.

Therefore, the correct answer is that solid blocking is required for floor joists that exceed the nominal size of 2 x 12. This size threshold recognizes the increased span and load characteristics of larger joists, necessitating the additional support provided by blocking to maintain structural performance.