TY - CONF TI - Minimizing rework in offsite construction: error propagation analysis and quality control C1 - Singapore, Singapore C3 - Proceedings of the 34th Annual Conference of the International Group for Lean Construction (IGLC 34) SP - 862 EP - 874 PY - 2026 DO - 10.24928/2026/0258 AU - Ammar, Baseel Andres AU - Yu, Haitao AU - Sheikhkhoshkar, Moslem AU - Hamzeh, Farook AD - MSc Student, Civil and Environmental Engineering Department, University of Alberta, Edmonton, Canada, baseelan@ualberta.ca, orcid.org/0009-0008-3650-619X AD - Research and Development, Landmark Group of Companies Inc., Edmonton, Alberta, Canada, haitaoy@landmarkgroup.ca, orcid.org/0000-0002-7798-4867 AD - Visiting Scholar, University of Greenwich, School of Engineering, London, UK, m.sheikhkhoshkar@greenwich.ac.uk, orcid.org/0000-0001-9067-2705 AD - Professor, Civil and Environmental Engineering Department, University of Alberta, Edmonton, Canada, hamzeh@ualberta.ca, orcid.org/0000-0002-3986-9534 ED - Hamzeh, Farook ED - Poshdar, Mani ED - Garcia-Lopez,, Nelly P. AB - Offsite construction (OSC) is increasingly used to enhance productivity, quality, and schedule reliability through industrialized, standardized production processes. However, OSC systems remain susceptible to local execution errors that propagate across interconnected production stations, resulting in rework, delays, and waste. This research examines error propagation within an off-site wall manufacturing line by applying lean principles and techniques. An explanatory case study methodology integrates both qualitative and quantitative approaches. Gemba walks, and a Five Whys root cause analysis was conducted to identify recurring quality defects at stud locations where nails were missing. Subsequently, statistical analysis compared design and as-built dimensions of wall panels to quantify absolute and percentage errors originating from framing and nailing operations. The cumulative impact of these errors was assessed against allowable tolerance limits to determine the likelihood of defects at downstream stations. Findings demonstrate that minor geometric deviations introduced at upstream stations accumulate and surpass tolerance thresholds, substantially increasing defect rates as production advances. These results underscore the necessity of quality-at-the-source practices and intermediate quality checks in OSC systems. This study advances lean construction knowledge by providing empirical evidence of station-level error propagation and recommending targeted remedial actions to improve production flow stability and built-in quality. KW - Offsite construction KW - lean production KW - error analysis. PB - T2 - Proceedings of the 34th Annual Conference of the International Group for Lean Construction (IGLC 34) DA - 2026/06/22 CY - Singapore, Singapore L1 - http://iglc.net/Papers/Details/2549/pdf L2 - http://iglc.net/Papers/Details/2549 N1 - Export Date: 19 June 2026 DB - IGLC.net DP - IGLC LA - English ER -