The surface area of a building at each story level that is intended for occupancy or use is calculated from the exterior dimensions of the building or from the centerlines of walls separating buildings. Specifically excluded from this measurement are elements such as exterior walls, columns, pipe shafts, stairs, elevators, service shafts, and equipment rooms. An example would be a rectangular building measuring 50 feet by 100 feet; its surface dimension intended for occupancy is 5,000 square feet per floor.
Accurate calculation of this dimension is crucial for various reasons, including compliance with zoning regulations, determination of property taxes, and assessment of building value. Historically, this metric has served as a key indicator for urban planning and density management. Understanding it aids in project budgeting, feasibility studies, and the projection of potential rental income.