Building planning law makes a fundamental distinction between the inner area and the outer area. The inner area is understood to be the built-up districts that actually have a consecutive, coherent development that is an expression of an organic settlement structure. Outdoor areas are areas outside of built-up areas and outside the scope of (qualified or project-related) development plans (see also "Development plan; information" under "Related topics").

Municipalities can by statute

1. define the boundaries for built-up districts (demarcation bylaws),
2. define built-up areas in the outer area as built-up districts if the areas are shown as building land in the land use plan (definition statutes),
3. incorporate individual areas outside of built-up areas into the built-up districts if the incorporated areas are characterized accordingly by the structural use of the adjacent area (incorporation statutes).

The demarcation bylaws only have a declaratory effect. It shows which plots of land still belong to the built-up areas and which already belong to the outdoor area.

With the help of a demarcation statute, the municipality can define built-up areas in the outer area as built-up districts if the area is shown as a building area in the land use plan. Such bylaws are therefore only possible if there is already a corresponding representation in the land use plan and a certain building context actually exists.

The inclusion bylaws can be used to include individual areas outside the inner area if they are already characterized accordingly by the structural use of the adjacent area. When such a character can be assumed depends on the specific situation in each individual case.

The legality of a determination or inclusion bylaw requires that it is compatible with orderly urban development, that it does not justify the permissibility of projects that are subject to an environmental impact assessment obligation and that there are no indications of impairment of the conservation objectives and protection purpose of sites of Community importance and European bird sanctuaries within the meaning of the Federal Nature Conservation Act.

The bylaws may also contain provisions that regulate the permissibility of construction projects in more detail. The determination and inclusion bylaws are drawn up in a legally regulated procedure in which both the affected public and the affected authorities and other public agencies are given the opportunity to comment within a reasonable period of time.