Degree of structural use
The degree of structural use , as an indication of the intensity of property utilization and evaluation criterion in the Federal Republic of Germany, is part of public building law , especially building planning law , and represents an important urban development control instrument of the BauGB . It serves to ensure orderly urban development use. Usually there is a limitation of the building density. In addition to the " type of structural use ", it is the most important criterion for assessing the admissibility of a building project within the scope of a development plan (B-Plan) or within a district with built-up areas . The legal definitions and guide values can be found in §§ 16 ff. Building Use Ordinance (BauNVO).
The degree of structural use is determined by the base area number (abbreviated to FMO ), the floor area number ( JRC ) and the Cubic index ( BMZ (z. B. ground floor level), as well as by the number of storeys or the height eaves height , ridge height ) determines the physical structure . The permissible level of structural use results either from the stipulations of a development plan or within a built-up part of the town according to the nature of the surrounding area ( insertion requirement ).
As a rule, maximum dimensions for structural use are specified in a development plan. These may be undercut by the specific building project, but not exceeded. In certain cases, minimum dimensions or mandatory dimensions (for full floors or building heights) can be set. It is possible to apply for exceptions or exemptions from the specified dimensions as part of the building permit procedure .
Base area number (GRZ)
The base area number ( § 19 BauNVO) indicates the area portion of a building plot that may be built over; it is given with one or two decimal places , for example:
- GRZ 0.3 = 30% of the property area may be built over
Sample calculation: Floor area of the building structure (140 m²): Area of the property (500 m²) = 0.28 (thus falling below the GRZ of 0.3)
When determining the GRZ according to § 19 BauNVO, starting with the version from 1990, the base areas of all structures, such as buildings, ancillary systems and paved areas are fully taken into account. As a rule, the permissible floor space may be exceeded by up to 50% by the ancillary systems (but only up to GRZ 0.8). The BauNVO corresponding to the development plan decree is to be selected for the determination. In earlier BauNVOs, the driveways are neglected, for example, which allows a much higher level of sealing of the property area.
Floor area number (GFZ)
The floor area number ( § 20 BauNVO), abbreviated GFZ , indicates the ratio of the total floor area of all full floors of the building facilities on a property to the area of the building plot. The GFZ is a dimensionless quantity and is given with one or two decimal places. The floor area is to be determined according to the external dimensions of the building on all full floors. In the development plan, it can be stipulated that the areas of common rooms on other floors, including the stairwells belonging to them and including their enclosing walls, are to be included in full or in part or, in exceptional cases, not to be included.
Example calculation: All floor areas together (400 m²): Area of the property (500 m²) = 0.8
Example: A plot of land has an area of 500 m² and a GFZ of 1.0. The total of the floor area in all buildings located on the property may therefore also amount to 500 m². For example, you could build a four-storey building with 125 m² of floor space per floor (4 × 125 m² = 500 m²). If the same property had a GFZ of 0.5, the maximum permitted total of the floor space would be 250 m² (500 m² × 0.5 = 250 m²). With a GFZ of 1.2, a maximum floor area of 600 m² should be built (500 m² × 1.2 = 600 m²).
GFZ practice in urban development
| place | start of building | GFZ | Net density |
|---|---|---|---|
| Karlsruhe - Waldstadt | 1957 | 0.55 | 141 E / ha |
| Mannheim-Vogelstang | 1964 | 0.67 | 222 E / ha |
| Frankfurt-Northwest City | 1963 | 0.85 | 330 E / ha |
| Munich - Neuperlach | 1967 | 0.96 | 320 E / ha |
| Hamburg-Steilshoop | 1970 | 1.12 | 404 E / ha |
| Berlin-Gropiusstadt | 1962 | 1.28 | 340 E / ha |
| Heidelberg-Emmertsgrund | 1969 | 1.35 | 424 E / ha |
The GFZ changed urban planning considerably in the 20th century. After the tenement districts of the early years with their inner-city block development (e.g. Meyers Hof ), very high floor space figures of just under 4.0 were achieved. The Charter of Athens tried mid-1920s, according to the principle "this type of construction by reducing the GFZ light, air and sun to change." When the building use ordinance was drawn up after the war, this value fell to around 0.5 as a result of the row construction and later leveled off at around 1.0. The net residential density relates to the local area that was newly built as part of the major project.
Building mass number (BMZ)
The building mass number ( § 21 BauNVO), abbreviated BMZ , indicates how many cubic meters of building mass per square meter of area of a building plot are permitted or available. Building mass means everything from the floor of the lowest full storey to the ceiling of the top full storey. This standard is practically only used in commercial and industrial areas for the assessment of large warehouses and production halls.
In Austria , the gross volume over terrain is the building mass (definition ÖNORM B 1800). The outer edges of the structure are decisive here.
The use of the term “ mass ” for a volume is common in the German construction industry, but contradicts the definitions of these quantities.
See also
Individual evidence
- ↑ Fourth ordinance amending the Land Use Ordinance of January 23, 1990 , Bundesanzeiger Verlag, January 26, 1990, accessed: May 25, 2020
- ^ Dietmar Reinborn: Urban planning in the 19th and 20th centuries . 1996, p. 240
- ↑ 06.09 Urban planning density (2012 edition), ( MS Word ; 152 kB) Senate Department for Urban Development and Environment Berlin
