Different kinds of square metres/feetWhen using square metres, it is important to be clear about what they represent. In briefing, it is best to work with so called usable square metres. These concern the amount of space that will be directly available for users activities, and exclude non-usable areas such as the space required for partitions or columns. However, there are different ways of defining and measuring space and the exact definitions vary per country and per sector. Frequently used space categories are: -Gross external area (gea): the total floor area of a building, measured to the external face of the external walls on each floor level. Also known as Gross floor area (gfa).-Gross internal area (gia): the area of a building measured to the internal face of the perimeter and atrium walls.-Net internal area (nia): the usable area within a building measured to the internal face of the perimeter walls on each floor level, excluding common facilities such as circulation areas, lobbies and bathrooms. Also known as nfa (net floor area) or nla (net lettable area).-Net usable area (nua): the areas in the building that are directly targeted at the users activities. It is the same as nia but excludes primary circulation (circulation linked to major routings in the buildings and fire escapes). As said, this figure is the most useful for briefing purposes and it can be further subdivided into primary spaces, support spaces and fm spaces. GEA External structure (i.e. facade)GIA Internal structure (e.g. walls/columns)Common functions (e.g. wcs, lobbies)NIA Primairy circulation (e.g. main corridors)NUA FM spaces (e.g. storage area)Support spaces (e.g. restaurant, library)Primary spaces (e.g. workstations, meeting rooms)40