Berlin Metropolitan School was founded in 2004 and is the oldest international school in Berlin-Mitte. In order to implement their advanced educational concept and accommodate their recently established senior classes, the school required additional floor space. BMS is housed in a pair of existing prefabricated structures from the GDR era that were erected in 1987, using the then widely available building types of ‘Schulbaureihe 80’. Three building wings are clustered to create a generous and protected school yard. The project comprises roof top extensions to three of the existing structures, as well as a lateral annex that continues all the way down to ground level. The new spaces provide additional classrooms, music rooms, a library with access to a roof garden, administration offices as well as a large auditorium where the main events of the school year are hosted.The construction work needed to be executed during school hours and was realized in stages according to the gradually increasing demand for additional area. Therefore the extension was designed as a prefabricated timber system that ensured speedy erection with minimal disturbance. On account of its low self weight, the timber construction required neither additional foundations nor alterations to the supporting structure of the existing fabric.Variation in room size and quality results in spaces that are fit for community and as well as for retreat-for individual learning as well as for team-based work. The sustainable building material timber is clad in copper, but it has been left visible on the inside, creating healthy, pleasant workplaces for students and teachers alike. Seen from the outside, the copper cladding matches the warm tone of the brick slips of the existing prefabricated modules, and at the same time distinguishes the new intervention from the existing building.