IRCAD 3 is an extension project that responds to the need to enlarge the Digestive Cancer Research Institute, which trains surgeons from all over the world on new surgical techniques. The extension stands in the existing courtyard and is connected to the existing entrance to IRCAD 1. The idea is to create an extension that flows naturally from the existing facility. It is a simple rectangle on one level so that it does not obstruct the view from neighbouring buildings or prevent light from entering them. The façades use the same solid and perforated bluish-grey aluminium cladding. The living roof, treated as a fifth façade, is mainly covered with a deep layer of earth, making it possible to use tall plants. Because of the constraints of the site, and to make it possible to integrate the entire programme, two basement levels are being created. The design of the extension will highlight the level of expertise taught at this world-class institution. With this restructuring project, the IRCAD aimed to bring the different activities taking place at basement level up to current standards, and to separate circulation flows. Our aim is to integrate the new standards, to improve working conditions for staff, and to connect these spaces with the IRCAD 3 extension.