A Systematic Review and Stage-Based Taxonomy of Lean-Sustainability Integration in Modular Off-Site Construction

Question: What are the current research topics, patterns, and trends concerning Lean–sustainability integration in modular off-site construction? What are the critical research gaps, challenges, and opportunities for advancing Lean-enabled sustainability in MOC across manufacturing and on-site assembly/construction stages? Purpose: To synthesize and structure the state of knowledge on Lean–sustainability integration in MOC, with a stage-based focus on barriers, opportunities, and the role of digital enablers. Research Method: Systematic Literature Review of 71 peer-reviewed journal articles (2004–2024), combining bibliometric mapping with qualitative thematic coding across off-site manufacturing and on-site assembly stages. Findings: Research emphasizes economic outcomes, shows moderate attention to environmental outcomes, and gives limited treatment to social sustainability. Barriers are stage-dependent: manufacturing challenges relate to standardization and production system design, while on-site assembly emerges as a key bottleneck due to variability, coordination complexity, and workforce constraints. Digital tools (e.g., BIM, analytics, simulation, and integrated delivery approaches) are frequently positioned as enablers but are rarely connected explicitly to sustainability outcomes in a unified framework. Limitations: The review is limited to journal articles and does not empirically validate findings through case studies or field interventions; coding outcomes depend on available reporting detail in the literature. Implications: Advancing sustainable modular construction requires stage-specific Lean strategies and clearer linking of Lean practices and digital enablers to Triple Bottom Line outcomes, especially social sustainability in both factory and site contexts. Value for authors: Provides a stage-based taxonomy that helps practitioners anticipate where Lean implementation typically breaks down (especially during assembly), and where digital practices can be prioritized to reduce variability, improve coordination, and strengthen sustainability performance.