The lack of adequate consideration of the underlying factors affecting the methods of building assembly often results in inefficiencies in the uses of building materials, equipment and manpower. These inefficiencies are further compounded by the nature of the construction industry, which traditionally involves complex processes that result in wastages during production. To address this problem, this study integrates the principles of Design for Manufacture and Assembly (DFMA) and Lean Construction to develop a design assessment and optimization system to assist designers in the selection of alternative building design elements and materials in a building information model. This assessment and optimization system rely on metrics derived from production data associated with the ease of assembling, ease of handling, the speed of assembling and the wastage during assembly or construction of a building element or material. This paper presents the development of BIM-OfA assessment logic and its application for assessment and optimal selection of building envelop through the extension of Building Information Modelling (BIM). The system demonstrates its adequacy as an indicator of construction and material efficiency, its integration with BIM further enhances the practicality of using production data such weight of components, number of on-site workers and number of parts, for buildability assessment to improve efficiency and reduce waste.