For which extensions and conversions do I need a building permit?

Sabine Neumann Sabine Neumann
A Modern Family Home: The Nook, Hall + Bednarczyk Architects Hall + Bednarczyk Architects Modern Living Room
Loading admin actions …

Do you want to expand your living space or renovate your home differently, but you are not sure what is permitted and to what extent with permission? We try to shed light on the matter and show you which measures do not require approval and which changes you need to obtain permission for. However, it should be said that state building regulations can vary from state to state, as can the development plans of individual communities and properties. An architect can also advise you.

Extensions and conversions for more living space

An extension, a conversion or an expansion are often chosen methods to create more living space. This may become necessary, for example, if the family grows or if you need more space for your hobby or job. Today we'll go into the legal background on one hand and the other hand you'll also get a little inspiration about what your addition, conversion or expansion could look like.

Among other things, we clarify questions such as: How big can I build without a building permit?, What can I build on my property without a permit? and “Is there a penalty for building a patio cover without a building permit?” We'll go into an extension without a building permit and inform you about the complex topic of exterior building permits.


Nobody is allowed to extend anything here in Germany just like that and at will. If you want to expand your living space with an extension, it doesn't matter whether you live in a villa with a huge plot of land in the middle of nowhere or a terraced house in a new development: expanding a residential building with an extension always requires approval.

Interior remodeling

All construction work within your own four walls does not require approval. As long as nothing is changed on the external walls, no load-bearing walls are torn down or the house is not listed as an internal monument, these renovation measures do not require approval. However, if you want to expand your attic, a building permit may be necessary, for example, if the conversion work creates your own, separate apartment.

Windows and doors

You don't need a permit for new windows and doors if you're just replacing and renewing them. However, if you want to enlarge and/or move the openings, you should first find out whether the external features of the property are subject to design regulations, which, among other things, regulate the appearance and size of windows and doors.


Whether you need a permit to build a garage depends on both the size of the planned garage and the federal state. It is therefore advisable to always contact the responsible authority in advance.

Winter garden

Adding a winter garden to the house involves a structural change. Accordingly, a building permit is required whenever there is a connection to the house. Glass buildings without such a connection, however, are considered greenhouses and may be built without permission.


If you want to expand your living space with a dormer window, you cannot simply implement this measure in most federal states. However, whether a building permit is required or a preliminary building request and thus a simplified procedure is sufficient depending on where you live.

Garden house

Whether the construction of a garden house requires approval or registration or is completely free depends on the respective development plan. The size of the planned building as well as the furnishings and location in the garden play an important role. It is therefore advisable to obtain detailed information before construction.

Whether you're renovating, remodelling, or expanding any area of your house, it is necessary to take note of structural walls. Read the article How to know if a wall is structural and can be demolished for further information.

Merging two apartments

Make 1 out of 2: If you plan to combine two apartments, you usually have to submit a building application, as this usually results in breakthroughs in load-bearing walls and these require a building application in most federal states.

Need help with your home project?
Get in touch!

Highlights from our magazine