Almondia – Bautipps Die Bauherrenberatung

build a granny flat

Have you decided to incorporate a separate living unit into your house, a so-called granny flat ? Congratulations! To guide you on your way to building a granny flat, we’ve broken the process down into five easy-to-follow phases. So you can relax and be perfectly prepared for the concrete planning.

the essentials in brief

  • Typically, a granny flat is built either in the basement, on the ground floor or directly under the roof of the house.
  • Construction can be divided into five phases: Construction planning, financing, construction, use and maintenance – the respective phases are explained in more detail in our article
  • In order to be able to deduct the construction of the granny flat later on from tax, separate invoices must be written for construction work on the main house and on the granny flat.
  • The construction of a granny flat results in additional costs of €30,000-60,000.
  • The homeowner is responsible for the maintenance of the granny flat. However, renovation costs are tax deductible.

1st phase: construction planning

In the basement: Ensure sufficient natural lighting! – eg by building on a slope Good soundproofing –> suitable for rental Cheapest variant with additional costs of €20,000-30,000

ground floor: Only recommended for a floor plan area of approx. 120 square meters Ground floor: handicapped accessible Ensure adequate soundproofing and thermal insulation!

In the roof: Communal stairwell, since the external staircase is expensive Make sure there is sufficient ventilation under the roof! Ensure good impact sound insulation!

There are various ways of integrating a granny flat into the residential building. The three most popular are installation in the basement , on the ground floor or under the roof.

A granny flat in the basement offers the great advantage that it has its own floor and is therefore very attractive for future tenants. Another advantage is that most basement ceilings are made of concrete and therefore provide good sound insulation. This ensures privacy for both tenants and landlords.

The biggest problem with the granny flat in the basement is the lighting conditions. Light wells alone are not enough for most tenants. It is therefore advisable to plan with a storey height of at least 2.50 m so that sufficiently large windows are possible. When building on a slope, the easiest way to ensure sufficient natural light is in the basement. Compared to a basement, the construction of a granny flat in the basement represents additional costs of around €20,000-30,000 and is therefore the cheapest option for integrating it in the house.

The granny flat on the ground floor offers the great advantage that it is handicapped accessible: It is therefore particularly suitable for multi-generational living. The biggest disadvantage is that it increases the floor plan of the entire house enormously. Therefore, a granny flat on the ground floor is only recommended from a floor plan area of approx. 120 m². It is important here that attention is paid to sufficient soundproofing and thermal insulation during construction.

The third option is the granny flat on the top floor. It is the most expensive variant because the attic apartment has to be ventilated at great expense. Because insulation and sealing alone are usually not enough to counteract the musty, musty smell that one knows from the dusty attic. The problem can best be solved architecturally with roof surfaces made of concrete slabs. These ensure that it stays warm and dry in winter and pleasantly cool in summer.

2nd phase: financing

Extended state funding from the KfW bank: Up to €50,000 possible

Some municipalities support the construction financially

Secure interest and repayment through rental income

Once the decision for a type of granny flat has been made, the second step follows: financing. Because the granny flat is a self-contained residential unit, extended state financing can be applied for through the KfW bank . The loan for the “Energy-Efficient Construction” program, for example, can be doubled to €100,000 instead of €50,000 with a granny flat.

There are also some municipalities that financially support the construction of a granny flat because this creates more living space without additional costs for the infrastructure. So it might be worth checking with the community.

3rd phase: construction

Roughly estimated additional costs of €30,000-60,000
Hardly any more construction time
Separate apartment entrance, not house entrance!
Separate gas, water and electricity meters!
Request a separate invoice from the construction company – in order to be able to deduct the granny flat from the tax!

Once a design has been drawn up and financing secured, the third phase begins: construction. Depending on the type of granny flat you have decided on, the effort and costs of the construction vary greatly. For all variants, however, the construction time is not significantly extended. The additional costs of building a granny flat also increase slightly as a percentage of the overall building. As a rough estimate, you can expect additional costs of €30,000-60,000.

The separate residential unit can be integrated into a prefabricated house as well as into a solid house . Because the demand is constantly increasing, there is now a variant with an attached granny flat for most house designs.

For the construction itself, there are still a few things to consider: The basic thing is that the apartment must not have a separate house entrance, but only a separate apartment entrance.

In addition, separate gas, water and electricity meters should be installed during construction to prevent future conflicts with tenants.

It is also important that you make sure that you have separate invoices from your construction company. This is the only way that the construction of the granny flat can later be deducted from taxes.

4th phase: Use

own use
Separate office multi-generational living
To rent
Separate gas and heating meters. Clearly defined limits. Rental income must be taxed

It is good if you have already thought about how you want to use your granny flat beforehand. There are basically two options: renting and personal use.

Depending on the location and furnishings, it is usually not difficult to find a suitable tenant. You should make sure that your landlord is sympathetic to you. Because although a granny flat guarantees privacy as a separate living unit, there will be one or two encounters between tenants and landlords. Also, make sure you have separate water and gas meters to avoid arguments.

You always have the option of asserting your own needs and using the additional apartment as an office, for example. However, the most common use of granny flats is multi-generational living.

5th phase: maintenance

Maintenance costs of 5-10 € per month
Renovation every 5-10 years
Warning: tax deductible!

In addition to the usage phase, the maintenance phase also runs at the same time. Like any useful object, the granny flat is also subject to wear and tear. It is your job as a landlord to keep the apartment in good condition. On the one hand, there are ongoing maintenance costs, which can amount to up to €5-10 per month, depending on the tenant. It is also advisable to create a reserve as a buffer for major renovations: the maintenance reserve is not mandatory, but essential. The Association of Private Builders (VPB) offers a rule of thumb as to how much should be set aside: Set aside one euro per square meter of living space every month! This means you are prepared for renovations every 5 (kitchen, bathroom) to 8 (living room) years, as well as for unexpected major repairs.

When renovating your granny flat, the following always applies: All work is tax deductible.

If you follow these five phases on the way to the granny flat, nothing can actually go wrong.

Autorin Sarah Völkl

Sarah Völkl hat Architektur studiert und ist seit Jahren das Gesicht von a better place. Mit ihren Videos ist sie bei YouTube vielen Personen schon länger bekannt. Sarah teilt Ihr Wissen jetzt auch bei den Bautipps von Almondia.

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