In solid lumber joists, rafters, and beams, notches shall not be located in the middle ___ of the span?

In the context of structural engineering and building codes, the rule regarding notches in solid lumber joists, rafters, and beams is designed to ensure the integrity and strength of the wood members. Notches weaken the structural capacity of the beams and joists by reducing the effective cross-section available to carry loads.

The two-thirds rule states that notches should not be located in the middle third of the span. This means that the area from the one-third points on each side of the span is critical for maintaining the strength of the structural member. By avoiding notching in the middle third of the span, engineers ensure that the maximum bending moment, which occurs around the center, is not compromised by reducing the effective area where tensile and compressive forces are acting.

This prevents potential structural failure due to overloading or excessive stress, which could occur if notches were made in this vulnerable area. Therefore, the requirement that notches not be in the middle third of the span aligns with best practices in construction and structural integrity maintenance.