What is Gross Building Area (GBA)?

Gross Building Area (GBA) is a measurement used to define the total constructed area of a building, measured to the external face of the exterior walls. It includes all enclosed floors—both above and below ground—such as basements, mezzanines, plant rooms, service areas, lift cores, stairwells, and internal walls.

Unlike Gross Floor Area (GFA), which is often tied to planning rules and may exclude certain spaces, GBA captures the entire built footprint, regardless of whether the space is usable or leasable. It’s commonly used for construction costing, valuation, insurance assessments, and comparing building efficiency across different developments. In short, GBA tells you the full size of the building as it has been constructed, wall-to-wall.