According to code, what fraction of the depth of a joist is the maximum allowed for notches in the top or bottom?

The correct answer is based on building codes that provide guidelines for the structural integrity of joists. For notches made in the top or bottom of a joist, the maximum allowed depth for these notches is typically one-sixth of the joist's depth. This limitation is established to ensure that the joist maintains its load-bearing capacity and structural strength.

Making a notch that exceeds this fraction can compromise the joist's ability to support loads properly, potentially leading to structural failures, especially in load-bearing situations. Building codes are designed to promote safety and stability in construction, and adhering to these guidelines is crucial for avoiding issues related to joist performance.

The other options indicate greater fractions of the joist depth, which would not align with safety protocols set forth by building codes, thereby increasing the risk of structural inadequacies when notches are introduced into the joist design.