Building a 3-family house: costs, floor plan, plot (2026)

Three flats under one roof: how to plan a 3-family house as a prefab house, calculate costs per residential unit, estimate the plot requirement and gauge the floor plan.

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3-family house as a prefab house: costs, floor plan and plot at a glance — 3-family house as a prefab house – costs per residential unit, plot requirement and floor plan at a glance.

Direct answer

What does a 3-family house cost and which plot does it need?

A 3-family house with around 300 m² of living space costs, at a market range of €2,400 to €3,800 per square metre, roughly €720,000 to €1,140,000 for the building portion, i.e. about €240,000 to €380,000 per residential unit. With a GRZ of around 0.4, the plot requirement is about 350 to 450 m². All apartment-building models in our database are calculated project-specifically and listed with price on request. As of 2026, guide values.

Typical plot size for a 3-family house

The plot requirement results from the permissible plot ratio and the building footprint. With a GRZ of around 0.4, 40 percent of the plot area may be built on. A 3-family house occupies about 130 to 160 m² per storey. From this follows a calculated plot requirement of roughly 350 to 450 m², when parking spaces, driveway and outdoor facilities are included.

In denser locations with a higher GRZ or more permissible storeys, the project manages with less plot area. The development plan and the state building code are decisive. Before buying, the plot check is worthwhile, to check buildability and permissible residential units.

Costs by living space and per residential unit

The total range is derived from the market range of €2,400 to €3,800 per square metre of living space, multiplied by the typical living space. The value per residential unit divides the total range by three flats. These are guide values for the building portion excluding the plot.

Living space	Market range	Total (building)	per residential unit
260 m² (compact)	€2,400 – 3,800/m²	€624,000 – 988,000	€208,000 – 329,000
300 m² (standard)	€2,400 – 3,800/m²	€720,000 – 1,140,000	€240,000 – 380,000
320 m² (generous)	€2,400 – 3,800/m²	€768,000 – 1,216,000	€256,000 – 405,000

As of 2026, guide values. Building portion excluding plot, servicing and outdoor facilities. Specific prices project-specific. More in the guide apartment building prices.

Cost blocks at a glance

Besides the pure building, the total costs are spread across several blocks. The percentage shares are usual orders of magnitude and serve as an initial orientation.

Cost block	Usual share	Note
Building / construction (turnkey)	approx. 70 – 78 %	Shell, fit-out, building services
Servicing	approx. 3 – 6 %	Water, wastewater, electricity, connections
Outdoor facilities	approx. 5 – 9 %	Parking spaces, driveway, garden
Construction incidental costs	approx. 12 – 18 %	Planning, structural engineering, permit, fees

As of 2026, guide values. Shares vary depending on the plot and fittings. Calculation with the cost calculator.

Floor-plan concept: 3-family house as a 2-unit-per-landing building with a unit in the roof

A 3-family house can be planned as a 2-unit-per-landing building with two flats on the ground and upper floors plus a third flat in the roof or setback storey (Staffelgeschoss). A central stairwell serves all units. The diagram is not to scale.

A central stairwell (yellow) serves three flats over two to three storeys. Schematic representation, Prefabricated House.

Quick yield calculation as an example

Suppose a 3-family house with 300 m² of living space costs, including the plot, around €1,050,000. At an achievable net cold rent (Kaltmiete) of €12 per square metre, rental income of around €43,200 per year results. From this follows a gross rental yield of about 4.1 percent. If management costs, maintenance and the rental-loss risk are deducted, the net yield falls accordingly.

Simplified model calculation, not investment advice. Plot and rent levels vary greatly by location. Tax effects such as declining-balance depreciation or the special depreciation under Section 7b EStG are not taken into account here. As of 2026, binding information: tax advice.

Matching prefab house models with 3 residential units

These models from our database represent a 3-family house. Because the plot, unit mix and fittings shape the price, they are calculated project-specifically and listed with price on request. The listing is alphabetical, no ranking.

Model	Provider	Residential units	Living space	Storeys	Price
3 residential units with gable roof	Haas Fertigbau	3 residential units	approx. 260 m²	2	Price on request
Apartment building Trio with gable roof	SchwörerHaus	3 residential units	approx. 320 m²	3	Price on request

Living spaces as rounded guide values of the example configuration according to the provider. All prices project-specific, therefore on request. As of 2026.

More sizes in the apartment building cluster

4-family houseFour flats, compact 4-unit-per-landing 6-family houseSix flats for investment properties 8-family houseEight flats for infill development

An overview of type, construction method and providers is offered by the page apartment building. Example layouts and units-per-landing types are shown by the apartment building floor plans.

Building a 3-family house: frequently asked questions

Answers on costs, plot, flat sizes and tax topics for the 3-family house.

How much does building a 3-family house cost?

As a guide, a market range of roughly €2,400 to €3,800 per square metre of living space applies (as of 2026). For a 3-family house with about 300 m² of living space, this gives a rough total range of around €720,000 to €1,140,000 for the pure building portion, excluding the plot. Servicing, outdoor facilities and construction incidental costs are added. Because plot, unit mix and fittings strongly shape the price, prefab house providers calculate each project separately. The models in our database are therefore listed with price on request.

How large does the plot for a 3-family house have to be?

With a plot ratio (Grundflächenzahl, GRZ) of around 0.4 and a building footprint of about 130 to 160 m² per storey, the calculated plot requirement is roughly 350 to 450 m². Parking spaces, the driveway and outdoor facilities are added. In denser locations, smaller plots are possible if the GRZ is higher or more storeys are permissible. The development plan (Bebauungsplan) and the state building code (Landesbauordnung) are decisive. The figures are guide values and do not replace a review of the specific plot.

Which flat sizes are usual in a 3-family house?

A 3-family house usually spreads three flats over two to three storeys. Common layouts range from the two-room flat with around 55 to 70 m², through the three-room flat with about 75 to 95 m², to the family-friendly four-room flat with 100 to 120 m². A mixed offer of smaller and larger units increases rentability and spreads the vacancy risk. The exact unit mix is planned project-specifically with the provider.

Is a 3-family house worthwhile as an investment?

A 3-family house spreads the risk of rental loss across three units and can at the same time be planned as a combination of owner-occupation and letting. Whether the project pays off depends on the plot price, construction costs, achievable rent and financing. Tax incentives such as the declining-balance depreciation (degressive AfA) or the special depreciation under Section 7b of the Income Tax Act (EStG) can improve the calculation. Details are always to be checked on a case-by-case basis. As of 2026, binding information is provided by tax advice.

What tax advantages are there when building a 3-family house?

For newly built rental residential buildings, there are in principle several instruments: the declining-balance depreciation, the special depreciation for new rental housing under Section 7b EStG, and subsidised loans in the KfW climate-friendly new-build programme. The conditions change regularly and are tied to energy standards and deadlines. Check specific interest rates and programme details individually. As of 2026, binding information is provided by tax advice and the KfW.

How long does building a 3-family house as a prefab house take?

The shell-construction phase on site is short with timber prefab construction, because the wall and ceiling elements are prefabricated in the factory. For a 3-family house, from the floor slab to turnkey handover, depending on the completion stage, expect about six to nine months. Lead time for planning, building permit and servicing is added. The exact schedule depends on the provider, the plot and the fittings.

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