Establishing outsourcing and supply chain plans for prefabricated construction projects under uncertain productivity Pei-Yuan Hsu 1* , Marco Aurisicchio 1 , Panagiotis Angeloudis 2 1 Dyson School of Design Engineering, Imperial College London, Exhibition Road, South Kensington SW7 2AZ, London, UK 2 Department of Civil and Environmental Engineering, Imperial College London, Exhibition Road, South Kensington SW7 2AZ, London, UK p.hsu15@imperial.ac.uk Abstract. Unlike stick-built construction projects, structural components in prefabricated construction projects are produced in a factory environment. Thus, similar to manufacturing industries, the productivity of building components fluctuates, owing to human error and machine malfunction. Since the site demand must always be met, outsourcing manufacturing is employed to supplement the uncertain self-production. Furthermore, storage facility between factory and construction site becomes indispensable because these components are large in size, yielding a three-tier supply chain that is absent in the traditional construction. The objective of this research is to determine the most appropriate production plan and the optimal outsourcing quantities for multi-prefabricated components under this context. A workflow which includes a two-stage stochastic programming model and a mixed integer linear programming model is established for solving the above issues. Also, the most favourable schemes for distributing components and the variation of inventory are also disclosed. An infrastructure built through prefabrication method has been chosen as a case study for validation. 1 Introduction In conventional stick-built construction projects, raw materials are dispatched by suppliers to construction sites following the orders placed by construction contractors [32]. In this context, the supply-demand relationship appears to be straightforward, because there are only two decisions to be made: when and how many to purchase. It should be noted that all the orders are based on a predetermined construction schedule [34]. Furthermore, the raw materials on the supply end are always ready to be sent over to the site [5]. In recent years, the construction sector is undergoing a shift from stick-built to prefabricated construction method. In prefabricated construction projects, building materials are initially shipped to the manufacturing facility, where they are transformed into structural components following a rigorous production sequence [22]. The completed components are then transported to sites for assembling. Moreover, the logistics of prefabricated construction also includes aspects that distinguish it from generic supply chains [13]. For instance, prefabricated structural components are usually tailor-made and project-specific, so their total production quantity usually matches the demand from the construction site exactly. Consequently, the inventory of