(1) Unless this Subtitle leads to a different conclusion, the provisions of Chapter 1 of Subtitle 1 as well as of sections 650b, 650e to 650h apply accordingly to contracts for architectural and for engineering services.
(2) The rules for calculating compensation as set out in the Scale of Fees for Architects and Engineers (Honorarordnung für Architekten und Ingenieure), as amended, apply to the adjustment of remuneration in the case of orders pursuant to section 650b (2), to the extent that work to be performed or cancelled under the order falls within the scope of application of the Scale of Fees. In all other cases, the adjustment of the remuneration for the increased or reduced expenditure of time and effort based on the performance ordered may be agreed freely. Insofar as the contracting parties do not conclude an agreement, section 650c applies accordingly.