Making Prefabrication Lean

Glenn Ballard1 & Roberto Arbulu2

1Research Director for the Center for Innovation in Project and Production Management ( dba Lean Construction Institute), Adjunct Associate Professor at the University of California at Berkeley, and partner in Strategic Project Solutions, ballard@leanconstruction.org
2Strategic Project Solutions Inc., rarbulu@strategicprojectsolutions.net

Abstract

Construction is not manufacturing. However, manufacturing provides the elements from which buildings, bridges, highways, houses and factories are constructed. Many of these elements are made-to-stock, but some key elements are made-to-order; e.g., HV AC ductwork, custom piping, pipe supports, precast concrete, electrical switchgear, reinforcing steel, structural steel and building envelope facades. These made-to-order products are produced by fabrication shops, which sit squarely at the intersection of manufacturing and construction. Application of lean concepts and techniques to fabrication shops promises substantial benefits to the construction industry they serve. Perhaps chief among these benefits is reducing the lead time required for placing orders in advance of needed delivery. Long lead times can extend project durations, promote premature design decision making or otherwise avoidable design redundancy, and cause excess inventories and double handling of materials. A "long" lead time is determined relative to the ability of the customer (the construction site) to accurately forecast future states of the building process on site, and thus the ability to determine when a component will be required for installation. Lead times that exceed a site's window of reliability increase the probability of untimely delivery. On time-driven projects, such lead times also increase the risk of premature design decisions and/or building slack into designed capacities and strengths. Switching perspectives, demand variability is arguably the biggest headache for fabricators. Late receipt of design information, frequent design changes and changes in installation timing and sequence disrupt production schedules and cause fabricators to risk the loss of capacity. In this paper, we explore the interplay between demand variability and fabrication lead times and present a plan to study and understand their interdependencies.

Keywords

Assembly, demand variability, fabrication, fabrication shop, lead time, made-to-order products, preassembly, prefabrication

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Reference

Ballard, G. & Arbulu, R. 2004, 'Making Prefabrication Lean' In:, Bertelsen, S. & Formoso, C.T., 12th Annual Conference of the International Group for Lean Construction. Helsingør, Denmark, 3-5 Aug 2004.

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