Rigid building assembly that divides space horizontally into stories.
It forms the bottom of a room. It may consist of joist-supported wood planks or panels, decking or panels supported by wood or steel beams, a slab of stone or concrete on the ground, or a reinforced-concrete slab carried by concrete beams and columns. The floor assembly must support its own dead load plus the live load of occupants, activities, and furnishings. The horizontal supports beneath its top surface
and the vertical supports into which they frame
must be sufficiently large and spaced closely enough to prevent sagging of the assembly.