German construction contracts measure work against the allgemein anerkannte Regeln der Technik, the generally recognized rules of technology. Work counts as free of defects only if it has the agreed quality and follows these rules. A rule counts as recognized only when the great majority of technical experts hold it. It must also have proven itself in practice, not only in science: sich auch praktisch bewährt. For this reason, the standard takes up new methods late. A builder who departs from it carries the risk, because a departure is generally treated as a defect. A new building product with no recognized rule behind it needs a general approval from the German Institute for Building Technology before it may be used.
In November 2024, the federal cabinet approved a draft law for a Gebäudetyp E, a building type for simple and experimental building. Under the draft, in contracts between expert businesses, a departure from the recognized rules would no longer count as a defect under three conditions. It must be disclosed to the client before the work starts. The client must not object at once. And the building must remain safe and fit for use over time. A new government draft went to the Bundestag on 8 June 2026.