The master thesis deals with an efficient use of existing structures of the city. In addition to the potential for climate and resource protection, social and design aspects are put to the test using the case study. In the conversion design, a protection of existing structures is to be exercised that goes beyond the protection of historical monuments. Demolition should only be demonstrably socially and ecologically justified. Furthermore, the work deals with vacancy and with the decline of retail trade, which increasingly prevents German city centers from urban vibrancy, culture and economic development. The design is intended to offer approaches to solutions in the area of known problems: Redensification, Profitability and Climate Protection. Hybridity of use describes the building: at least half of the total floor space is to serve residential purposes. In addition, commercial as well as social facilities will be integrated. In particular, urban planning goals are to be observed: The combination of different types of housing is preferred. The first floor as a whole of the facade design promotes the exchange between public and private space. Through this, on the one hand, the commercial use benefits from a self-confident appearance in the urban space. Important components of the design are the immediate outdoor areas, the courtyard, the roof, the circulation areas and the square. Aim of the design: 1. a townhouse that is sustainable and corresponds to the idea of a heterogeneous urban block 2. preservation of the existing substance as much as possible, if necessary justified changes to the existing structure 3. creation of living space for different user groups 4. coherent operator concept for commercial uses 5. design concept that can be derived from all parts of the existing structure and from the location.