mezzanine
A floor level above ground which does not fill the entire space within the building's perimeter.
A mezzanine is an occupiable above-ground floor level, which would be a regular floor except that it does not fill its entire plane within the building's perimeter. This means that it leaves a high open space adjacent to it, and open to the next regular floor below it. Mezzanines may or may not be counted in a building's floor numbering system, but for purposes of ascertaining the standard floor count they count as full floors.
Mezzanines must leave a sufficient space at least 2 meters in height above and below them for regular human occupancy; otherwise the limited space thus formed would count as a crawl space. Underground mezzanines count as regular basement floors.
The intermediate platform must leave at least 2 meters of usable height both above and below it. Its omission from a building's numbering does not omit it from the standard physical floor count.