The headquarters of the Institution of Structural Engineers provides a public conference centre, members’ facilities and library, as well as flexible workspace for the Institution’s 55 permanent staff. The entrance foyer showcases the four principal building materials for creating structure: timber, glass, steel and concrete. A finely detailed, horizontal-cantilevered staircase in pre-cast concrete and steel, is a contemporary reinterpretation of the traditional cantilevered stone stair that characterised the Institution’s former headquarters. The ground level includes a 104-seat auditorium and meeting rooms. Moving up the building the spaces become increasingly private, with the members' facilities on the first floor and the upper levels reserved for staff offices. The project was designed with sustainability as a focus, reusing existing fabric wherever possible, maximising natural ventilation and enhancing thermal performance.