Lean in construction

The term ‘Lean Construction’ was coined by the International Group for Lean Construction at its first meeting in 1993 (Howell, 1999) and refers to the application of the Lean concepts originating in manufacturing, to construction processes. Koskela (1992), served as a catalyst for research on applying the Lean concepts to construction by first introducing the idea of understanding construction as a production system (Salem et al., 2005). Koskelas (1992) report first considered the idea of applying the new production philosophy based on the concepts of the Toyota Production System (TPS) to construction. Since the 1990’s, the literature reveals many examples of applying the Lean principles to construction using different tools such as the Last Planner System (Ballard, 2000), visualisation (Moser & dos Santos 2003), daily huddle meetings (Mastroianni & Abdelhamid 2003), first run studies (Ballard & Howell 1997) and poke-yoke (Milberg & Tommelein, 2003). The Last Planner System appears to be the most widely used system based on the Lean concepts in construction (Salem et al., 2005). Despite an increasing focus on the adaptation and application of Lean tools to construction since the 1990’s, reports in the UK appear to suggest that the construction industry has generally been slow in taking up these ideas (Johansen et al., 2002).

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The following section discusses the benefits and highlights the challenges of Lean Construction.

2.8.1

Benefits of Lean Construction

Lean Construction has the goal of better meeting customer needs while using less of everything. This is achieved by placing an emphasis on the flow and value generation view of processes in addition to the conversion view of conventional engineering and production. The flow view is crucial in production for focusing on waste elimination and in engineering the value view is highly significant (Koskela & Huovila, 1997). Four main benefits of applying Lean to construction can be established from the literature review: 1) to identify and remove waste (Koskela & Huovila, 1998; Howell & Ballard, 1994) 2) to minimise variation (Howell et al., 2001) 3) to embrace uncertainty (Howell, 1999) and 4) to promote team work (Howell, 1999).

2.8.1.1 Identify and remove waste

An important focus of Lean application is to reduce waste. Waste in construction stems from the same “activity-based” thinking (Section 2.5.4) as in mass production. This activity based thinking makes it difficult to identify waste and to see the interdependencies between these activities, making it difficult to manage dependence and variation. The seven areas of waste identified by Toyota (Section 2.2.1), can also be found in construction processes. Koskela (2004) identifies a further area of waste in construction: making-do. Making-do as a waste refers to a situation where a task is started without all its standard inputs, or the execution of a task is continued although the availability of at least one standard input has ceased. The term input refers not only to materials, but to all other inputs such as machinery, tools, personnel, external conditions, instructions (Koskela, 2004). The consequences of making-do are classified as technical and behavioral (Grosfeld-Nir & Ronan, 1998). From a technical perspective, making-do leads to an increase in processing time and variability. Increased variability leads to more work in process or longer lead times. The increased processing time leads to a decline in productivity and to more operating expenses. Increased work-in-process

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necessitates increase in complexity of controls. A further consequence of making do is poor quality and more rework (Koskela, 2004).

2.8.1.2 Minimises variation

Another benefit of applying the lean concepts to construction is to assure that variation in work flow is minimised and to decouple what cannot be controlled. Lean works to isolate the crew from variation in supply by providing an adequate backlog or tries to maintain excess capacity in the crew so they can speed up or slow as conditions dictate (Howell et al., 2001).

2.8.1.3 Embraces uncertainty

Lean construction embraces uncertainty in supply and employs production planning to make the release of work to the next crew more predictable. Collaboration between work crews is improved as is an understanding of the causes of variation.

2.8.1.4 Promotes team work

Lean supports the development of team work and a willingness to shift burdens along supply chains. Partnering relationships coupled with lean thinking make rapid implementation possible. Where Partnering is about building trust, Lean is about building reliability (Howell et al., 2001).

The literature also reveals some challenges that are experienced when applying the Lean concepts to construction projects which are concerned with 1) the unique circumstances of construction (Howell, 1999; Koskela, 2000; Ballard & Howell, 1998) 2) the complexity of construction projects (Williams, 1997; Bertelsen, 2003; Salem, et al., 2006) 3) activity-based approach (Miller, et al., 2003) and 4) difficulty in justifying research and training (Banik, 1999). A more detailed discussion on the challenges faced when applying the Lean concepts to construction and overcoming these challenges can be found in Appendix A.4.

As mentioned in Section 2.8, the Last Planner System is the most widely used system for production planning and control of construction projects, based on the Lean concepts. The LPS was developed by Ballard (2000) to broaden the view of the construction process by

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providing a better link between planning and execution and a way to cope with the critical situation of production control. The idea behind the Last Planner System, is to focus on the “last planner” on the hierarchical chain of planners at the interface to execution, so that feasible work assignments are pulled into the system rather than pushed. Tasks can only enter into the execution phase if they have met all prerequisites and it is not assumed that tasks are ready from the start of authorisation as is the case in traditional project management. The Last Planner System combines central elements of task management and flow management to address the deficiencies of traditional Project Management (Koskela, 1999).

The following section takes a closer look at the Last Planner System and identifies challenges experienced during implementation.