The State Law on the Prohibition of the Misuse of Residential Space (ZwEWG) authorizes municipalities in which the adequate supply of rental housing to the population under reasonable conditions is particularly at risk to stipulate by ordinance that residential property may be used for purposes other than housing only with their approval.
A change of use occurs, in particular, if
- more than 50% of the living space is used or made available for commercial or self-employed purposes,
- is structurally altered or used in such a way that it is no longer suitable for residential purposes,
- is rented out as a vacation home or otherwise used for the purpose of accommodating guests for more than a total of twelve weeks (84 days) in a calendar year,
- stands vacant for more than six consecutive months, or
- is demolished.
It is up to the respective municipality to determine which instances of misuse it includes in its bylaws and thus makes subject to a permit requirement. The specific details of the prohibition on misuse are also set forth in the municipal bylaws.