Lean Construction: From Theory to Implementation O. Salem, M.ASCE 1 ; J. Solomon 2 ; A. Genaidy 3 ; and I. Minkarah, M.ASCE 4 Abstract: This article compares the techniques developed for lean construction with those developed for lean manufacturing. Lean manufacturing and lean construction techniques share many common elements despite the obvious differences in their assembly envi- ronments and processes. Manufacturing plants and construction sites are different in many ways that might explain why lean production theories and practices do not fully fit the construction industry. Though many lean construction tools and elements are still in an embryonic state, lean construction techniques are gaining popularity because they can affect the bottom line of projects. Additionally, this paper presents a study of a construction project in which specific lean construction elements were tested. Each technique was evaluated in terms of its impact on the performance of the project. Based on the findings of the study, a new “lean assessment tool” is proposed to quantify the results of lean implementations. The assessment tool evaluates six lean construction elements: last planner, increased visualization, huddle meetings, first-run studies, five S’s, and fail safe for quality. This paper provides a simple and comprehensive approach that is transferable to any construction project. DOI: 10.1061/ASCE0742-597X200622:4168 CE Database subject headings: Construction management; Lean construction; Theories. Introduction Construction and manufacturing differ significantly in the physi- cal features of the end product. In manufacturing, finished goods generally can be moved as a whole to retailers or end customers. Construction, on the other hand, deals with larger units that can- not be transported. Additionally, the construction industry has three other features that distinguish it from manufacturing: On- site production, one-of-a-kind projects, and complexity i.e., tem- porary multi-organization and regulatory interventionKoskela 2002. On-site production: Construction is site-position manufactur- ing, as opposed to fixed-position manufacturing, which applies to ship and airplane manufacturing and in which the product can be moved after assembly Schemenner 1993. In construction, instal- lation and erection are the activities that most increase the value of the product. The contractor must ensure that all components assembled on site meet high-quality standards that are greatly influenced by specific site conditions. One-of-a-kind production: Normally manufacturing takes ad- vantage of specialized equipment to make standardized units, allowing only a limited level of customization by retailers. In construction, customers play a key role throughout the project cycle. Under guidance from the designer, customers define their product explicitly through the bid package or contract. The owner or the owner’s representative can modify the requirements and details of the contract by addenda before bids are opened or change orders once the bid is closed. Complexity: In manufacturing, many components from differ- ent subassemblies can be easily managed because suppliers are selected early in the design phase. Specialized facilities with suit- able technology and layout ensure the reliable flow of the product. With repetition, this supply network eventually becomes manage- able and optimized. In contrast, in construction, the completion of activities is highly interrelated and complicated. Construction projects are characteristically complex, unique, dynamic systems that must rely on an initial design that involves a number of subassemblies with variable specifications Bertelsen 2003. Being an on-site production, the installation of those subassem- blies is constrained by the interacting and overlapping activities of different contractors, making it more difficult to meet a fixed schedule. The combined effect of on-site, one-of-a-kind, and complex production is uncertainty. The manufacturing process makes it possible to reduce uncertainty by increasing control over the pro- cess itself. A steady state is desirable in order to increase effi- ciency through repetition. In construction projects, significant uncertainty exists throughout the project. Weather conditions, soil conditions, owner changes, and the interaction between multiple operations can produce unique circumstances, which could be as critical as the planned activities and have a significant impact on project cost. 1 Associate Professor, Construction Engineering and Management Program, Dept. of Civil and Environmental Engineering, Univ. of Cincinnati, P.O. Box 210071, Cincinnati, OH 45221-0071. E-mail: osalem@uc.edu 2 Graduate Student, Construction Engineering and Management Program, Dept. of Civil and Environmental Engineering, Univ. of Cincinnati, Cincinnati, OH 45221-0071. 3 Associate Professor, Industrial and Manufacturing Engineering Program, Dept. of Mechanical, Industrial and Nuclear Engineering, 633 Rhodes, Univ. of Cincinnati, Cincinnati, OH 45221-0072. 4 Professor Emeritus, Construction Engineering and Management Program, Dept. of Civil and Environmental Engineering, Univ. of Cincinnati, P.O. Box 210071, Cincinnati, OH 45221-0071. Note. Discussion open until March 1, 2007. Separate discussions must be submitted for individual papers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and possible publication on June 23, 2005; approved on December 16, 2005. This paper is part of the Journal of Management in Engineering, Vol. 22, No. 4, October 1, 2006. ©ASCE, ISSN 0742-597X/2006/4-168–175/$25.00. 168 / JOURNAL OF MANAGEMENT IN ENGINEERING © ASCE / OCTOBER 2006