What is the gross building area?

The gross building area of a building is calculated by adding up the areas measured at floor level of all parts (storeys) of the building (basement, semi-basement, ground floor, storeys, attic), determined according to the external dimensions of the perimeter walls including cladding.

The gross building area does not include the area of the following parts of the building:

• an external lift added to an existing building
• thermal insulation improving the energy performance of the building installed on an existing building
• storeys, or parts of storeys, with a clear height of less than 2.0 m
• galleries within a functional unit of the building
• open parts of the building (covered and uncovered terraces, canopies, loggias, balconies, eaves of cornices and other projections, external staircases, external entrance ramps, sun protection structures, skylight, smoke and ventilation domes, etc.).