Exploring Critical Risk Factors in Volumetric Modular Construction: Fault Tree Analysis with Stakeholders' Perspectives on Probability and Impact

Numerous benefits are delivered by the utilization of volumetric modular construction (VMC); however, it carries unique risks at different project stages, which is one of the significant reasons for its low adoption. To date, scant research has adequately examined VMC's risks during projects. This study aims to address this knowledge gap by identifying and assessing critical risk factors (CRFs) within VMC from different stakeholder group perspectives in Australia and New Zealand (NZ). A survey of 110 VMC professionals from Australia and NZ, which examined 31 specific CRFs, was established via a literature review. The CRFs were divided into their associated VMC project stage: (1) design and planning (DP); (2) off-site manufacturing (OM); (3) transport and logistics (TL); and (4) on-site assembly (OA). Fault tree analysis (FTA) was then used to analyze the CRFs. The results indicate that the DP stage risks are the most significant since they could affect VMC's downstream stages. Essential CRFs at each stage were design freeze or change order issues, module geometry conflicts, size and weight restrictions, and dimensional and geometrical variabilities. To the best of the authors' knowledge, this study represents a first attempt at analyzing VMC CRFs in the Australian and NZ construction industry. Overall, this study could contribute to enhancing VMC practices and furthering VMC's adoption as a sustainable and circular construction practice.