If joists are lapped over the girder, the minimum amount of lap is 3 inches and the maximum overhang is ___ inches.

If joists are lapped over the girder, the minimum amount of lap is 3 inches and the maximum overhang is ___ inches.

• A. 12
• B. 6
• C. 9
• D. 3

Answer: (A)

When joists lap over a girder, you’re balancing a secure load transfer with keeping the end of the joist properly supported. The lap length of at least 3 inches gives enough surface on the girder for fasteners to bite through both joists, creating a solid connection that shares load across the girder. The overhang at the outer end should not be too long, because a longer cantilever increases the bending moment at the girder and can lead to excessive deflection, loosening of nails, or inadequate bearing for the joist end. Keeping the overhang to a maximum of 12 inches provides a safe, practical limit that maintains structural integrity while allowing the joist to overhang for bearing or alignment needs.

When joists lap over a girder, you’re balancing a secure load transfer with keeping the end of the joist properly supported. The lap length of at least 3 inches gives enough surface on the girder for fasteners to bite through both joists, creating a solid connection that shares load across the girder. The overhang at the outer end should not be too long, because a longer cantilever increases the bending moment at the girder and can lead to excessive deflection, loosening of nails, or inadequate bearing for the joist end. Keeping the overhang to a maximum of 12 inches provides a safe, practical limit that maintains structural integrity while allowing the joist to overhang for bearing or alignment needs.