Do you want to convert, renovate or modernise a building? Depending on the scope and type of construction work, you may also require authorisation for this. If you are planning to remodel a building, you should therefore enquire with your building authority at an early stage about what needs to be taken into account.

Modernisation refers to structural measures that

• sustainably increase the utility value of the living space or the residential building,
• improve the general living conditions in the long term or
• bring about lasting savings in energy or water.

You must also comply with public law regulations (e.g. fire protection regulations and clearance areas) when converting, renovating or modernising.

Energy performance certificate

The energy performance certificate for existing buildings helps tenants and buyers to obtain comparable information on the energy quality of buildings.

Renewable energies

The Federal Building Energy Act (GEG) and the Renewable Heat Act (EWärmeG) in Baden-Württemberg were passed with the aim of reducing the emission of climate-damaging greenhouse gases and conserving limited energy resources (oil, gas and coal).

The regulations of the State Heating Act for existing residential buildings have been in force since 1 January 2010. 15 percent of the energy required for heating and hot water must be covered by the use of renewable energies (biomass, solar energy, geothermal energy, bio-oil and biogas) if the heating system is replaced. The law was last amended on 7 February 2023. The following applies to the relationship between Baden-Württemberg's EWärmeG and the federal GEG: In municipalities that have already drawn up a municipal heating plan, a separate resolution is required that gives the heating plan external effect and legal force and thus makes the obligation under Section 71 (1) GEG to use 65% renewable heat when replacing heating in existing buildings and in new buildings in the already built-up area binding. As long as a separate resolution has not yet been passed, the EWärmeG will continue to apply to existing buildings (until 1 July 2026 at the latest in municipalities with more than 100,000 inhabitants and 1 July 2028 in municipalities with less than 100,000 inhabitants, when the GEG will also apply to existing buildings).

There are only exceptions to the fulfilment of the requirements of the EWärmeG if

• these are exceptions to the scope of application listed in Section 2 (2) EWärmeG,
• all fulfilment options conflict with public law regulations,
• it is not technically possible to implement all options,
• the obligation to utilise represents an unreasonable hardship for the homeowner (e.g. if the homeowner does not have sufficient financial resources).

The installation of heating systems that utilise renewable energies is also financially subsidised.

Irrespective of this, the obligation to use 65% renewable heat in new-build areas applies from 1 January 2024.

Change of use

A change of use is basically the same as the construction of a building: for example, you may need planning permission if you use a flat as an office or a warehouse as living space. A change of use may, for example, mean that you have to provide more parking spaces.

In certain cases, a change of use does not require planning permission. However, you may have to carry out a planning permission procedure (simplified or comprehensive planning permission procedure) or a notification procedure.

Subdivision of a residential building - creation of condominium ownership

If you would like to sell the flats in your apartment building individually or transfer a flat to your child, you will need, among other things, a certificate of separate ownership and a partition plan. You will need these when you declare to the land registry that ownership of the property is to be divided up and condominium ownership established for the individual flats. The division only becomes effective with the creation of the so-called "residential property registers".