A collaborative building design environment has been proposed to integrate, together both the heterogeneous applications and the dispersed project particípants. Based on the functional requirements identified, the conventional building product models have been extended to incorporate high-level concepts such as activity and organisation. which are essential for coordination, and a generic humanhuman interaction model has been developed, which could not only make the building domain models interaction-aware, but also serve as a base model for developing general interaction utilities. Collaborative desion environment prototypin- has been desoribed.. covering the common project workspace, general interaction utilities and multiuser interfaces. Three distribution schernes for implementing the common project workspace within a distributed environment have also been discussed.