TY - CONF TI - Schedule delay in construction delivery methods under extreme uncertainty C1 - Singapore, Singapore C3 - Proceedings of the 34th Annual Conference of the International Group for Lean Construction (IGLC 34) SP - 655 EP - 667 PY - 2026 DO - 10.24928/2026/0315 AU - Song, Junting AU - Jaramillo, Daniel Esmeral AU - Lu, Yu-Peng AU - Eskew, David AU - Abandoh, Christopher AU - Nguyen, Tran AU - Pishdad, Pardis AU - Zeng, Qinghao AD - School of Building Construction College of Design, Georgia Institute of Technology, Atlanta, Georgia, jsong600@gatech.edu AD - School of Building Construction College of Design, Georgia Institute of Technology, Atlanta, Georgia, djaramillo30@gatech.edu AD - School of Building Construction College of Design, Georgia Institute of Technology, Atlanta, Georgia, ylu793@gatech.edu AD - School of Building Construction College of Design, Georgia Institute of Technology, Atlanta, Georgia, deskew3@gatech.edu AD - School of Building Construction College of Design, Georgia Institute of Technology, Atlanta, Georgia, jcabandoh3@gatech.edu AD - Part-time Lecturer, School of Building Construction, College of Design, Georgia Institute of Technology, Atlanta, Georgia, dnguyen458@gatech.edu AD - Professor, Graduate Program Director; Director, Smart Built Environment Eco-System (Smart Bees) Laboratory, School of Building Construction, College of Design, Georgia Institute of Technology, Atlanta, Georgia, pardis.pishdad@design.gatech.edu AD - School of Building Construction, College of Design, Georgia Institute of Technology, Atlanta, Georgia, qzeng41@gatech.edu ED - Hamzeh, Farook ED - Poshdar, Mani ED - Garcia-Lopez,, Nelly P. AB - Increasing global disruptions, such as pandemics, trade policy shifts, and supply chain shocks, have intensified uncertainty in construction project delivery. Yet much prior research has examined how project delivery method selection influences project outcomes under conventional conditions, with limited attention to performance under extreme uncertainty. This exploratory comparative study examines schedule delay performance across four delivery methods, Design–Bid–Build (DBB), Design–Build (DB), Construction Manager-at-Risk (CMAR), and Integrated Project Delivery (IPD), with the COVID-19 period (2020–2022) serving as an empirical case of extreme uncertainty. Using publicly verifiable multi-source project documentation, including Federal Emergency Management Agency (FEMA) disruption records, Engineering News-Record (ENR) reports, and project documentation, this study compiled a dataset of 17 non-residential construction projects using a self-defined, normalized Uncertainty Schedule Delay Index (USDI). Descriptively, within this dataset, more collaborative delivery methods, such as IPD and CMAR, tended to show lower schedule delays than DBB and DB. To contextualize these findings, practitioner insights were collected through interviews highlighting early engagement, proactive procurement, and effective team communication. Together, these findings contribute exploratory comparative evidence on delivery method performance and offer practical insights for schedule risk management under extreme uncertainty. KW - Collaboration KW - integration KW - schedule delay KW - uncertainty KW - Integrated Project Delivery (IPD). 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/2590/pdf L2 - http://iglc.net/Papers/Details/2590 N1 - Export Date: 19 June 2026 DB - IGLC.net DP - IGLC LA - English ER -