In preparation for the planned linear collider TESLA, DESY is designing the required buildings and facilities. The accelerator and infrastructure components have to be allocated to buildings, and their required areas for installation, operation and maintenance have to be determined. Interdisciplinary working groups specify the project from different viewpoints and need to develop a common vision as a precondition for an optimal solution. A commercial requirements database is used as a collaborative tool, enabling concurrent requirements specification by independent working groups. The requirements database ensures long term storage and availability of the emerging knowledge, and it offers a central platform for communication which is available for all project members. It is successfully operating since summer 2002 and has since then become an important tool for the design team.