How many inches must joists overlap when they are not running continuously?

Joists that do not run continuously must overlap by a minimum of three inches to ensure proper load distribution and structural integrity. This overlap helps to maintain strength at the joint and prevents potential failure at the connection point, which is critical for the overall stability of the framing system.

Using a three-inch overlap also aligns with building codes and best practices that prioritize safety and performance in construction. An overlap that is too small, like two inches, may not provide sufficient support, while larger overlaps, like four or five inches, may be unnecessary and can lead to wasted materials and increased labor without significantly enhancing structural strength. Therefore, adhering to the three-inch overlap standard is both efficient and effective.