Floor area (GFA) is a building

Building

In architecture, construction, engineering, real estate development and technology the word building may refer to one of the following:...

, architecture

Architecture

Architecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...

 and real estate

Real estate

In general use, esp. North American, 'real estate' is taken to mean "Property consisting of land and the buildings on it, along with its natural resources such as crops, minerals, or water; immovable property of this nature; an interest vested in this; an item of real property; buildings or...

term referring to the amount of area (measured as square feet or square metres) taken up by a building or part of it. The ways of defining "floor area" depend on what factors of the building should or should not be included, such as external walls, internal walls, corridors, lift shafts, stairs, etc. Generally there are 3 major differences in measuring floor area.

• Gross floor area GFA - The total floor area contained within the building measured to the external face of the external walls.
• Gross internal area GIA - The floor area contained within the building measured to the internal face of the external walls.
• Net internal area NIA (or usable floor area UFA)The NIA is the GIA less the floor areas taken up by lobbies, enclosed machinery rooms on the roof, stairs and escalators, mechanical and electrical services, lifts, columns, toilet areas (other than in domestic property), ducts and risers.

External links

http://www3.imperial.ac.uk/propertymanagement/space/faqs
Imperial College London, Department of Property Management.