What part of a joist may not be notched?

In the context of joist construction, notching affects the structural integrity of the joists, which are critical components in supporting the weight of a building's floors and ceilings. Notching is typically restricted in specific areas of a joist to preserve its strength and load-bearing capacity.

Notching the middle third of a joist is particularly problematic. This area is where most of the tension and stress concentrate when the joist is loaded. If a joist is notched in this section, it can significantly compromise its structural strength, leading to potential failure under load. Building codes often discourage or completely prohibit notching in this area to ensure the safety and stability of the overall structure.

The other parts of a joist can be notched under certain guidelines or limitations; for instance, the ends can be notched to allow for connection and placement within load-bearing walls, while the bottom may also be notched as long as it does not exceed prescribed limits. However, notching the middle third is generally avoided due to the high risk of weakening the joist and jeopardizing structural integrity.