Developing a Plot with an Apartment Building: GFZ, Parking Spaces, Profitability
Whether a plot is suitable for an apartment building is decided jointly by building law and profitability. This guide shows with a transparent worked example how GRZ and GFZ determine the possible floor area, explains when an apartment building pays off instead of a detached or semi-detached house, sheds light on the perspective of owners and heirs of a plot and provides a feasibility checklist from development plan via development and parking spaces to the neighbourhood. As of 2026.
Short answer: Whether a plot is suitable for an apartment building (Mehrfamilienhaus) is determined jointly by building law and economic viability. The site occupancy index (Grundflächenzahl, GRZ) and the floor space index (Geschossflächenzahl, GFZ) from the development plan (Bebauungsplan) define how much may be built. On an 800-square-metre plot with a GRZ of 0.4 and a GFZ of 1.2, roughly 320 square metres are buildable and around 960 square metres of floor space are permitted, as a rough estimate. The building authority has the final say. As of 2026.
GRZ and GFZ: a transparent calculation example
The permitted development of a plot is essentially determined by two key figures from the development plan. The site occupancy index (GRZ) indicates what proportion of the plot area may be built on. The floor space index (GFZ) sets the permitted floor space in relation to the plot area. The following example is approximate and serves only as guidance. The development plan and the information provided by the building supervisory authority are binding.
Rough GRZ/GFZ calculation example for an 800 m² plot (as of 2026). Guidance only, not binding.
| Variable | Value / assumption | Result (approximate) |
|---|---|---|
| Plot area | 800 m² | starting value |
| GRZ | 0.4 | up to 320 m² buildable |
| GFZ | 1.2 | around 960 m² of floor space |
| Distribution | e.g. 3 full storeys | floor space per storey around 320 m² |
| Residential units | depends on the layout | to be planned per project |
The development plan is binding
GRZ and GFZ only provide rough guidance. How many full storeys are permitted, which building height applies and how setback areas (Abstandsflächen) take effect are governed in detail by the development plan. An early preliminary building enquiry (Bauvoranfrage) creates legal certainty about the possible volume. The basics are explored in the guide on GRZ, GFZ and the building envelope.
When is an apartment building worthwhile instead of a detached house?
An apartment building is worthwhile above all where building law and plot size allow several residential units and the location suggests stable letting. If the development plan permits a higher floor space index, an apartment building makes more economical use of the plot than a detached or semi-detached house, because plot and site-development costs are spread across several units. Arguments against an apartment building include restrictive building law, a tight parking-space requirement, or a location with low rental demand.
Apartment building vs. single property on the same plot – neutral classification (as of 2026). No ranking.
| Criterion | Apartment building | Detached / semi-detached house |
|---|---|---|
| GFZ utilisation | high with permitted density | lower |
| Costs per residential unit | fall through distribution | higher |
| Parking-space requirement | higher, per residential unit | lower |
| Management | commercial operation | minimal |
| Target group | investors, owners, heirs | owner-occupiers |
Owner and heir perspective: densifying a plot
Larger, already-developed plots in family ownership are often especially suitable for infill densification. An inherited plot can, for example, be used more efficiently by replacing an old building with an apartment building or by adding a new build at the rear. It is important to clarify ownership and inheritance relationships in advance, along with existing rights such as rights of way or utility easements, and the condition of the site development. Tax questions should be examined early on with professional advice. How to build on an inherited plot is explored in a dedicated guide.
Enquire about an apartment-building project – free & non-binding
From plot to permit: request a project-specific assessment and check what volume building law and economic viability allow.
Parking spaces and other building-law levers
The number of required parking spaces is set by the municipality via a parking bylaw or the state building code (Landesbauordnung), usually as a ratio per residential unit. The values differ by federal state and municipality and can be lower in well-connected inner-city locations than on the outskirts. The parking-space ratio has a noticeable effect on economic viability, because underground garages or parking areas tie up space and costs. We do not quote blanket values, because they are regulated at municipal level. The information provided by the local building supervisory authority is binding.
Feasibility checklist before purchase
Before buying or developing a plot, a systematic review is recommended. It helps to weed out unsuitable plots early, before planning costs arise.
- Evaluate the development plan with GRZ, GFZ and the permitted number of storeys.
- Clarify site development and connections for water, wastewater, electricity and roads.
- Ask the municipality about the parking-space ratio and plan for the space required.
- Estimate setback areas and possible shading of the neighbourhood.
- Have ground conditions and possible contaminated sites checked.
- Submit a preliminary building enquiry to clarify the permitted volume with legal certainty.
Use the plot check
A plot check bundles the most important points and provides an initial assessment of whether a plot is suitable for an apartment building. The assessment only becomes reliable with the development plan and official information for the specific plot.
Suitable layouts for later planning are shown by the apartment-building floor plans, while the page on the apartment building as a prefabricated house classifies the property type. The cost side of a property is explored in the guide on apartment-building prices. Which programmes support the construction of new rental housing is covered in the guide on apartment-building funding. All routes are bundled in the overview on the apartment building.
Check a plot for apartment-building suitability
One data set, several assessments: have building law, volume and economic viability checked on a project basis before you plan or buy.
What does your dream house really cost?
Request suitable quotes from vetted manufacturers for free and compare the prices per square metre for your construction project.
Compare house prices nowImportant questions briefly explained
The most common price questions around Developing a Plot with an Apartment Building – answered concisely by the Prefabricated House editorial team (as of 2026).
