Which of the following items is NOT considered incidental space?

Incidental space refers to areas that are not directly involved in the primary function of a building but serve supportive roles. These spaces typically include elements that help to define or enhance the use of the main areas.

Open areas do not fit the definition of incidental space, as they often serve an essential function in terms of circulation, gathering, or providing flexibility in a layout. Open areas usually encompass spaces designated for specific activities or interactions, rather than just supporting the primary spaces. Consequently, they are often integral to the overall design and usability of a floor plan, thus distinguishing them from incidental or merely supportive spaces.

In contrast, walls, closets, and structural columns serve as secondary elements that help define the functionality of a space, making them incidental spaces. Walls can delineate areas, closets provide storage without being primary activity zones, and structural columns support the building while not being part of the main functional areas. These elements support the overall design without being the focus of space utilization.