Public building law includes all legal regulations that concern the public law requirements as well as the state supervision and regulation of the structural use of land.
In order to build on your property in Germany, you usually need a building permit. In order to issue a building permit, the authority in the area of public building law must observe numerous legal regulations, in particular the admissibility of a building project under building planning law and building regulations.
Building planning law is concerned with orderly urban development in the area of public building law, cf. § 1 para. 5 BauGB. Roughly speaking, it’s about where you can build which buildings. For this purpose, the municipalities primarily issue so-called development plans (B plans), which, among other things, determine what type of buildings should be built in certain areas (e.g. purely residential areas, industrial areas, etc.). Building planning law is essentially regulated in the Building Code (in particular Sections 29-35 BauGB) and the BauNVO.
Building regulations, on the other hand, serve to avert danger in the area of public building law; roughly speaking, it is about how a building can be built and used (type and extent). In the area of public building law, this is intended to prevent dangers arising from the construction or use of structures, for example due to a lack of stability. The building permit process is also part of the building regulations, which is regulated in the respective laws of the federal states. (e.g. HBauO, BayBO)