- Primary space: All areas available for direct office use (offices and warehouses).
- Secondary space: All corridors, stairwells, restrooms, kitchenette as well as other surfaces that do not represent the actual usage purpose.
- The norm of the German Institute for Normalisation (DIN), the DIN277.
- The standards for the calculation of rental space for office space (MF-B) of the GIF (Society of Property Researchers eV).