A computer-implemented automated building mechanical systems design and modeling is described. The system provides a central source for all of the design and construction information for systems in a construction project in a coordinated two-dimensional and three-dimensional spatial database that is accessible as a means to produce automatically coordinated design development and construction document information of the mechanical systems. The system acquires and stores all of the appropriate design, engineering, and construction expertise information available for any building type for use in automatically assembling and coordinating the design, cost-estimating, and scheduling for the mechanical systems of the construction project. The system output model enables automatic generation of drawings and cost, manufacturing and scheduling information.