This project has been about taking a first step towards developing a radically innovative circular building system, with the double goal of vastly reducing climatic impact of building construction, as well as strongly reducing costs to aid the current housing crisis. The first step in this project has been research into the reusability of building elements. As part of this process a factor based rating method was developed that can be used to evaluate how well specific building elements score on reusability. After this, both a building system -including the most rudamentary building elements - and two different building designs in strongly differing contexts were developed. These different building designs were used to test the universal usability of the building elements, whereas the developed rating method was used to test the reusability of the designed building elements. The end result suggests that a similar system has great potential to reduce both the climatic impact and economic costs of the building industry. The system was effectively integrated in both a relatively normal or standard design and a more extravagant and architecturally interesting design. The project ends with a suggestion of improvement that could be made towards a fully circular building future.