What is the function of a joist in construction?

In construction, the function of a joist is primarily to support the loads of floors and ceilings. Joists are horizontal structural elements that span open spaces, distributing weight and providing the necessary framework to uphold the materials above them, such as flooring and ceiling finishes. They are essential for the structural integrity of a building, ensuring that it can safely bear the weight of occupants, furniture, and other loads while maintaining stability.

The other options do not accurately describe the primary role of a joist. Anchoring walls is typically the responsibility of the foundation and framing systems. Outer insulation serves to control thermal transfer and is not related to the function of joists. Providing plumbing space is more associated with the layout of the framing rather than the joists themselves, as plumbing often runs between or within other structural components. Thus, supporting floor and ceiling loads is the correct and definitive function of a joist in construction.