Lean Construction is a combination of original research and practical development in design and construction with an adaption of lean manufacturing principles and practices to the end-to-end design and construction process. Unlike manufacturing, construction is a project based-production process. Lean construction is concerned with the alignment and holistic pursuit of concurrent and continuous improvements in all dimensions of the built and natural environment: design, construction, activation, maintenance, salvaging, and recycling (Abdelhamid 2007, Abdelhamid et al. 2008). This approach tries to manage and improve construction processes with minimum cost and maximum value by considering customer needs (Koskela et al. 2002[1]).
The term "Lean Construction" was coined by the International Group for Lean Construction in its first meeting in 1993 (Gleeson et al. 2007). The Construction in "Lean Construction" refers to the entire industry and not the phase during which construction takes place. Thus, Lean Construction is for owners, architects, designers, engineering, constructors, suppliers.
Historical Development
Lauri Koskela, in 1992, challenged the construction management community to consider the inadequacies of the time-cost-quality tradeoff paradigm.[2] Another paradigm-breaking anomaly was that observed by Ballard (1994[3]), Ballard and Howell (1994a[4] and 1994b), and Howell (1998). Analysis of project plan failures indicated that "normally only about 50% of the tasks on weekly work plans are completed by the end of the plan week" and that constructors could mitigate most of the problems through "active management of variability, starting with the structuring of the project (temporary production system) and continuing through its operation and improvement," (Ballard and Howell 2003[5]).
Evidence from research and observations indicated that the conceptual models of Construction Management and the tools it utilizes (work breakdown structure, critical path method, and earned value management) fail to deliver projects 'on-time, at budget, and at desired quality' (Abdelhamid 2004). With recurring negative experiences on projects, evidenced by endemic quality problems and rising litigation, it became evident that the governing principles of construction management needed revisiting. One comment published by the CMAA, in its Sixth Annual Survey of Owners (2006), pointed to concern about work methods and the cost of waste:
"While the cost of steel and cement are making headlines, the less publicized failures in the management of construction projects can be disastrous. Listen carefully to the message in this comment. We are not talking about just materials, methods, equipment, or contract documents. We are talking about how we work to deliver successful capital projects and how we manage the costs of inefficiency."[6]
[edit]A new paradigm
Koskela (2000)[7] argued that the mismatch between the conceptual models and observed reality underscored the lack of robustness in the existing constructs and signaled the need for a theory of production in construction. Koskela then used the ideal production system embodied in the Toyota Production System to develop a more overarching production management paradigm for project-based production systems where production is conceptualized in three complementary ways, namely, as a Transformation (T), as a Flow (F), and as Value generation (V).
- Transformation is the production of inputs into outputs.[7]
- Flow can be defined as "Movement that is smooth and uninterrupted, as in the 'flow of work from one crew to the next' or the flow of value at the Pull of the customer."[8]
- Value is "What the Customer is actually paying for the project to produce and install."[8]
Koskela and Howell (2002) also presented a review of existing management theory – specifically as related to the planning, execution, and control paradigms – in project-based production systems. Both conceptualizations provide a solid intellectual foundation of lean construction as evident from both research and practice (Abdelhamid 2004).
Recognizing that construction sites reflect prototypical behavior of complex and chaotic systems, especially in the flow of both material and information on and off site, Bertelsen (2003a and 2003b) suggested that construction should be modeled using chaos and complex systems theory. Bertelsen (2003b) specifically argued that construction could and should be understood in three complimentary ways:
- As a project-based production process
- As an industry that provides autonomous agents
- As a social system
[edit]What is lean construction?
Lean construction is a “way to design production systems to minimize waste of materials, time, and effort in order to generate the maximum possible amount of value," (Koskela et al. 2002[1]). Designing a production system to achieve the stated ends is only possible through the collaboration of all project participants (Owner, A/E, Constructors, Facility Managers, End-user) at early stages of the project. This goes beyond the contractual arrangement of design/build or constructability reviews where constructors, and sometime facility managers, merely react to designs instead of informing and influencing the design (Abdelhamid et al. 2008).
Lean construction recognizes that desired ends affect the means to achieve these ends, and that available means will affect realized ends (Lichtig 2004). Essentially, lean construction aims to embody the benefits of the Master Builder concept (Abdelhamid et al. 2008).
"One can think of lean construction in a way similar to mesoeconomics. Lean construction draws upon the principles of project-level management and upon the principles that govern production-level management. Lean construction recognizes that any successful project undertaking will inevitably involve the interaction between project and production management." (Abdelhamid 2007)
Lean construction supplements traditional construction management approaches with (Abdelhamid 2007): (1) two critical and necessary dimensions for successful capital project delivery by requiring the deliberate consideration of material and information flow and value generation in a production system; and (2) different project and production management (planning-execution-control) paradigms.
While lean construction is identical to lean production in spirit, it is different in how it was conceived as well how it is practiced. There is a view that "adaptation" of Lean Manufacturing/Production forms the basis of Lean Construction. The view of Lauri Koskela, Greg Howell, and Glenn Ballard is very different, with the origin of lean construction arising mainly from the need for a production theory in construction and anomalies that were observed in the reliability of weekly production planning.
Getting work to flow reliably and predictably on a construction site requires the impeccable alignment of the entire supply chain responsible for constructed facilities such that value is maximized and waste is minimized. With such a broad scope, it is fair to say that tools found in Lean Manufacturing and Lean Production, as practiced by Toyota and others, have been adapted to be used in the fulfillment of Lean construction principles. TQM, SPC, six-sigma, have all found their way into lean construction. Similarly, tools and methods found in other areas, such as in social science and business, are used where they are applicable. The tools and methods in construction management, such as CPM and work breakdown structure, etc., are also utilized in lean construction implementations. The three unique tools and methods that were specifically conceived for lean construction are the Last Planner System, Target Value Design, and the Lean Project Delivery System.
If the tool, method, and/or technique will assist in fulfilling the aims of lean construction, it is considered a part of the toolkit available for use. A sampling of these tools includes: choosing by advantages (CBA),[citation needed] BIM (Lean Design), A3, process design (Lean Design, offsite fabrication and JIT (Lean Supply), value chain mapping (Lean Assembly), visual site (Lean Assembly); 5S (Lean Assembly), daily crew huddles (Lean Assembly).
The common spirit flows from shared principles:
- Whole System Optimisation through Collaboration and systematic learning
- continual improvement/pursuit of perfection involving everyone in the system
- a focus on delivering the value desired by the owner/client/end-user
- allowing value to flow by systematically eliminating obstacles to value creation and those parts of the process that create no value
- creating pull production
The differences in detail flow from a recognition that construction is a project based production where the product is generally a prototype.[citation needed]
The priority for all construction work is to:
- Keep work flowing so that the crews are always productive installing product
- Reduce inventory of material and tools and
- Reduce costs[9]
While lean construction’s main tool for making design and construction processes more predictable is the Last Planner System (see below) and derivatives of it, other lean tools already proven in manufacturing have been adapted to the construction industry with equal success. These include: 5S, Kanban, Kaizen events, quick setup/changeover, Poka Yoke, visual control and 5 Whys (Mastroianni and Abdelhamid 2003, Salem et al. 2005[10]).
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