The usable area of a property is understood as the proportion of the floor area that is used according to the purpose of the building.
The usable area (NUF for short) is regulated in Germany by DIN 277 and defines it as a sub-area of the net room area (NRF). The usable area does not include traffic areas (VF) such as entrance areas, stairwells, elevators and corridors, technical areas (TF) (heating room, machine rooms, technical operating rooms) and of course also not the construction areas (KGF) of the building such as walls and columns.
An alternative term for usable area is usable area, which according to DIN 277 has not been used since 2016.
