Exploitation and destruction of the environment call for an inevitable paradigm shift as regards our resource consumption: "innovative" building will have to break away from the dogma of new build. We need to reconsider the existing building stock as a wealth of resources and ideas, just as we should understand recycling and upcycling building stock as architectonic potential. New approaches in architecture reveal a trend towards concepts of the frequently used but theoretically and historically rarely defined term upcycling. In that context, one often forgets that the history of building has also always been a history of, firstly, recycled and upcycled building materials and components, and secondly, of building knowledge and building styles. Comprehending buildings as a part of a social change process poses a challenge to our current habits and modern concept of unambiguity, seclusion and authorship of architecture. This publication explores the potential of historical concepts of upcycling - the qualitative recycling of buildings and building components - and confronts them with new developments in architectural and building practice. Importantly, the authors look into the question of whether and how new solutions could be found for future architecture. "Recycling and upcycling" should not be a matter of idealism, but rather present an argument for economy and the quality of structure and design. (éditeur).