What is the maximum depth ratio for notches at the ends of solid lumber members?

The maximum depth ratio for notches at the ends of solid lumber members is indeed 1/4 of the member's depth. This guideline is primarily based on structural integrity and load-bearing capacity. When notches are cut too deeply, they can significantly weaken the lumber, potentially leading to failure under load. By limiting the notch depth to 1/4 of the total depth, the structural performance of the lumber is maintained while still allowing for some alterations that may be necessary for installation, such as fitting beams into joists or other framing elements. This ratio helps ensure that the member retains a significant amount of its original strength while accommodating necessary construction modifications.

The other options represent ratios that are either too deep, which would compromise the wood's structural integrity, or do not align with accepted engineering practices for lumber notching. Understanding these limitations is crucial for ensuring safe and effective construction practices.