usable floor area
The enclosed interior floor area of a built object, excluding the space occupied by fixed walls, columns, and other structural elements.
Usable floor area is the total of all enclosed area within a building or built object which is not occupied by fixed structural elements (such as columns or walls). It includes common areas, rental areas, and areas devoted to building operations.
An area is only comparable alongside the standard it was measured to. National measuring codes differ over balconies, atrium voids and shafts, so two published figures for one building can both be correct.
A figure that covers a complex rather than a single building is a different measurement again. Where a tower shares a podium, the record has to say whether the podium is inside the figure.