Broadly speaking the whole enclosed area of a building within the external walls taking each floor into account and excluding the thickness of the external walls. GIA will include: ... columns, piers, whether free standing or projecting inwards from an external wall, chimney breasts, lift wells, stairwells etc.

Are stairs included in floor area?

The floor area ratio accounts for the entire floor area of a building, not simply the building's footprint. Excluded from the square footage calculation are unoccupied areas such as basements, parking garages, stairs, and elevator shafts.

Does gross internal floor area include stairs?

Gross Internal Floor Area is the area of a building measured to the internal face of the perimeter walls at each floor level, which includes: Areas occupied by internal walls and partitions. Columns, piers chimney breasts, stairwells, lift-wells, other internal projections, vertical ducts, and the like.