The usable floor area of a residential building should be understood as the area of all rooms in the building, with respect to load bearing and non-bearing structures, (i.e. the net area of the residential building) decreased by:
- the general public area (i.e. the total area of rooms and designated parts of rooms and storeys used for general circulation),
- the area of rooms designated for installations and technical appliances,
- the area of rooms comprising separate premises located in the building (e.g. cellars, attics, storage rooms, garages).