Existing buildings are always both a challenge and an opportunity, and the transformation of existing buildings and districts has always been part of planning and building culture. Not only due to increasingly scarce resources, it has recently become the focus of current building discussions. Transformation in planning is closely linked to political and social goals, such as space and resource-saving construction, the establishment of circular economies, the use of gray energy and adaptation to climate change. These goals are not only achieved with the actual construction project, but the course is often set much earlier in planning phases.