BAMB´s mission is to enable the shift to a circular building sector. The current financial models support a linear use of resources, in a take, make, use, waste sequence. To enable re-use, repair and circular material flows in industrial symbiosis we need new ways to calculate and use the financial advantages of a circular building sector. Variables like ownership, transactions, former externalities and timescales could need new approaches to support the recovery and reuse of building components and Reversible Building Design.