According to joist notching guidelines, notches at the ends of joists should not exceed what fraction of the joist depth?

Notches at the ends of joists are critical to the structural integrity and performance of a building. The guidelines outlined in codes typically specify that notches should not exceed one-quarter of the joist depth. This limit ensures that the joist retains adequate strength and stiffness, minimizing the risk of structural failure.

When a notch is cut into the end of a joist, it removes material from a section that is under tension or bending stress. Allowing too deep of a notch could compromise the joist's ability to carry the load it was designed for, potentially leading to bending and cracking. Therefore, adhering to the one-quarter depth limit helps maintain the safety and reliability of the joists in light of these stresses.

It's essential for builders and designers to follow these guidelines closely as they impact the overall structural design and performance of floor systems.