What is a joist commonly used for?

A joist is a critical structural element used primarily to frame a building's roof or floor. It spans between walls or beams, providing support and helping to distribute loads across the structure. Joists are essential in maintaining the integrity and strength of the framework, allowing for the safe construction of floors and ceilings by bearing weight and creating a level surface for additional layers, such as flooring or roofing materials.

While lateral support is important in construction, it is typically the role of other elements such as braces or shear walls rather than joists. Supporting roofing layers is more specific to trusses or rafters that hold the roofing materials, while enhancing thermal insulation is not a function of joists, but rather the role of insulation materials specifically designed for that purpose. Thus, framing a building's roof or floor accurately captures the primary function of joists in construction.