According to § 650a of the German Civil Code (BGB), a construction contract is a contract for the construction, restoration, removal or conversion of a building, an outdoor facility or a part thereof.
In this context, "production" means the initial production of a building and, in the case of an outdoor facility, the initial processing with the aim of erecting a structural facility. It is therefore always a question of the creation of something that did not previously exist.
A "restoration" is the de facto new construction (repeated or renewed construction). As a rule, damage is removed (work on existing structures).
In the case of "removal", structures or outdoor facilities are removed in whole or in part.
And a "conversion" is ultimately any intervention in a building that substantially shapes and changes it. In contrast to section 650a subsection 2 BGB ("maintenance measures"), conversion must be of a significantly higher intensity than pure maintenance work. Reference can also be made to Section 2 (5) HOAI, according to which conversions are redesigns of an existing object with substantial interventions in the construction and existing building.