What is the primary intended function of a joist in construction?

The primary intended function of a joist in construction is to support floor and ceiling loads. Joists are horizontal structural members typically made of wood or steel, and they are crucial in distributing the weight of the floors and ceilings above them to the vertical supports, such as beams or walls.

When a load is applied to a floor or ceiling, the joists bear that load and help maintain the structural integrity of the building. They are commonly spaced at specific intervals to ensure that they can effectively support the load without sagging or failing. This load-bearing capability is essential for creating safe and functional spaces within residential and commercial buildings.

In regard to other options, while joists can contribute to the overall support for parts of a roof by working in conjunction with rafters, their primary designation is focused on floors and ceilings. Supporting walls is a responsibility more characteristic of beams and load-bearing walls rather than joists. Finally, providing insulation is not a function of joists; insulation can be placed between them, but joists themselves do not provide this thermal barrier. Thus, the emphasis on their role in supporting floors and ceilings is what makes that option correct.