On the Quai aux Pierres de Taille, in the heart of Brussels, stood a former office building constructed in the 1960s. The building has been completely renovated and transformed into a mixed-use property housing offices and apartments. On the same construction site, a small residential building was also erected. Several complex issues make this conversion a particularly interesting project. For the construction of the underground parking, specialized expertise was required due to the presence of surrounding buildings, contaminated soil, and high groundwater levels. In addition to the addition of three extra floors on top of the existing building, the inclusion of balconies and winter gardens, as well as the upgrading to current standards, particularly in terms of acoustics, had a significant impact on the structural loads. In order to develop an appropriate strengthening strategy for the structure (including foundation adaptation, the replacement of load-bearing elevator and technical shafts, among others), a detailed study of the quality and nature of the existing concrete structure was carried out. The building had to be updated to meet current requirements, and the open-plan layout of the existing concrete structure allowed the new program to fit seamlessly within the existing framework. The balcony structure became exceptionally light, almost ethereal, defining the character of the building. At first glance, this structure seems to contradict fire safety requirements. However, it was connected to the main building through hybrid hinges that, in the event of a fire, when different load and bending requirements apply, transform into rigid, fixed connections, thereby stabilizing the entire structure.