An approach for sustainable, cost-effective and optimised material design for the prefabricated non-structural components of residential buildings

Offsite prefabrication of the non-structural components of residential and commercial low- and high-rise buildings is becoming increasingly popular due to its sustainability, fast on-site execution, safety and costeffectiveness. The benefits of offsite prefabrication can be further enhanced if it is coupled with the principles of Design for Manufacturing and Assembly (DfMA), which is based on materials, labours and cost optimisation. Although DfMA has been widely used in automotive and other industries, it is not well-established in the offsite prefabricated construction industry. Moreover, there are no guidelines exist for applying DfMA in prefabricated construction. In this paper, DfMA principles are applied to the most common non-structural members i.e., timber frame wall and the plumbing drainage system of a local residential building in Melbourne, Australia. Site and factory observations for the manufacturing of these components were carried out to collect actual assembly times. Then, using the collected data, the design efficiencies of onsite-, offsite- and DfMA-based prefabrication were computed by developing a user-friendly tool through advanced MATLAB programming. Moreover, from a cost-benefit analysis, DfMA-based prefabrication was found to be better than conventional factory prefabrication of selected non-structural components. Furthermore, based on the results, a pragmatic framework for DfMA based design and execution in a real prefabricated construction project is proposed. The findings of this paper are significant as they can contribute to developing guidelines for DfMA based design of prefabricated non-structural components of residential buildings.