Laurenz Mefferdatis introduced a structural innovation at Aachen and left his mark in this free city at the beginning of the 18th century. Mefferdatis found a structure of the city, which was ruined by the major fire in 1656. The reconstruction was slow and only partial, due to the the city's lack of economic power. To avoid another such disaster, the new buildings were no longer built from wood, but from brick with "Werksteingewänden". The floor plans and the elevation followed the traditional method of construction. In the early 18th century, the early industrialisation with the new system of the "Verlagswesen" and the flourishing warm water sources provided a solid economic basis for extensive construction work. Beneath the functional buildings and churches, construction activities were driven by the wish of representation through impressive architecture, gave the construction industry a fresh impetus . The sources on which the present thesis is based was extremely difficult, both for written as well as architectural sources. That is why the thesis contains a catalogue part with an extensive compilation and description of Mefferdatis? buildings, based on information retrieved from archives as well as from existing buildings. After the catalogue, the analysis takes up the main characteristics of the Mefferdatis architectural style. In particular, the different types of floor and elevation plans for the facades with their pronounced "Fenstergewände" are worth mentioning Mefferdatis worked as master architect for the city of Aachen, whilst at the same time undertaking numerous private commissions. In the first half of the 18th century he became the preferred architect of the Council, the church, rich patricians and businessmen. His various activities included expert reports for litigations, cost and material estimates, small reparations, conversions and extensions of existing buildings, for city houses as well as for larger buildings. For newly built city houses, his drawings were mostly broad sided or square ...