Floor area

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The floor area (abbreviation: GF) is a term from building and planning law . In Germany, it is defined by Section 20 (3) of the Building Use Ordinance (GF). This is to be distinguished from the concept of gross floor area (GFA) according to DIN 277 , in Austria according to ÖNORM B 1800 (determination of areas and volume of buildings).

In the Federal Republic of Germany, the floor area is included in the level of structural use , which, in development plans, is composed of the base area number (GRZ), the floor area number (GFZ) and the building mass number (BMZ), which defines the degree of structural use of the property. The floor area number indicates how high the ratio of the total floor area of ​​all full floors of the planned development on a property to the area of ​​the building plot may be.

The floor area is determined according to the external dimensions of the building on all full floors . Contrary to the reduction of areas under sloping ceilings described in many sources, the Federal Administrative Court clarified with its decision of June 7, 2006 that this does not conform to the legal text of the Building Use Ordinance and is therefore inadmissible. In the development plan, however, it can be stipulated that these areas - and possibly other areas such as stairwells - should also be included or, in exceptional cases, not included. Normally, balconies , loggias and terraces are not taken into account when calculating the floor area. The prerequisite for this, however, is that these so-called ancillary systems are permitted in the spacing areas according to the respective state building regulations .


The term gross floor area is often incorrectly used instead of the gross floor area (GFA) . However, this term is not defined in any standard or regulation, but persists. The floor area is determined by definition from the external dimensions of all full floors of a building. The gross floor area, on the other hand, is determined according to the external dimensions of all floors, including the non-full floors such as basements, attics, staggered floors, etc., but with the exception of floor areas of unusable roof areas, air spaces over atria and structural cavities, e.g. B. in ventilated roofs or over suspended ceilings.

The floor area number (GFZ) can be calculated based on the floor area. It describes the ratio of the floor area to the property area.

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