Density of built use

The density of built use can be determined by stipulations relating to

• the site occupancy index or the size of land on which structures can be built,
• the floor-space index or the size of the floor area, the cubic index, or the cubic capacity,
• the number of entire storeys,
• the height of built structures.

The Land Use Ordinance regulates the upper built density level for each type of building area.

The site occupancy index (GRZ) states how many square meters of built space are permissible per square meters of land. If for a plot of land measuring 1,000 sq. m. the site occupancy index is 0.5 it means 500 sq. m. can be built on.

The floor-space index (GFZ) states how many square meters of floor per square meter of land are permissible. A floor space index of 1.2 means that for a plot of land measuring 1,000 sq. m., there can be a maximum of 1,200 sq. m. floor space.

The cubic index (BMZ) regulates how many cubic meters of building mass are permissible per square meter of land in commercial and industrial areas.

The term “entire story” is defined in the Hessen Building Code (HBO). It stipulates from when an entire story is deemed to exist. The number of permissible entire storeys can be stipulated as a maximum number or as a mandatory figure.

The height of built structures states how high a built structure can be in relation to a point of reference (for example the surface of the road).
 
Together with the building authority the City Planning Department has compiled a site occupancy index and floor-space index work aid, which provides an overview in text and diagram form for determining built density on the basis of the various versions of the Land Use Ordinance.