From Lean to Lean construction

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Represented a.o. by the five generic principles offered by Womack & Jones (1996)

E. Presenting the concept as an easily understandable commodity with a catchy title;

A couple of authors, Liker (2004) and Womack & Jones (1996, 2005) present normative guidelines about how to commence the ‘Lean journey’.

F. Presenting the concept as timely, innovative and future-oriented;

Though it might have some years on its back now, the idea comprises an ongoing pursuit of perfection. No picture of perfect can be perfect (Womack & Jones, 1996).

G. Interpretive viability, i.e. leaving room for interpretation

Concepts such as waste, quality and customer value and the strategic/operational distinction definitely offer discretional space.

In the next section the diffusion of Lean into the construction industry is accounted for in order to lay the ground for the preconditions to the invention of the LPS.

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architectural, engineering and construction (AEC) sector where it has been promoted as a means to increase productivity and project performance (e.g. via the EGAN report, DETR, 1998). The promotion of Lean construction has been highly visible in countries such as USA, UK and Denmark. Lean entered construction a couple of years after it had gained momentum in western manufacturing industries. Its application to the built environment was first discussed by Koskela (1992), who investigated what he referred to as ‘the new production philosophy and its application to construction (Jørgensen & Emmitt, 2008, 387). Koskela will be returned to soon.

According to Kristiansen et al. (2005,) data from Statistics Denmark showed that the large Danish contractors (defined as having more than 500 employees) had grown at the expense of their medium-sized competitors (defined as having between 100 and 500 employees) with the result that these medium-sized contractors' share of the market almost halved between 1992 and 1999; their turnover dropped from the 24 per cent of the total turnover to 13 per cent. Their share of the total number of employees fell correspondingly from 25 per cent to 16 per cent. A review of the information at the home sites of the largest contractors showed that they had also bought installation firms, building material firms and firms in carpentry and other trades/crafts. In doing so the largest contractors had become much larger, had reduced the market competition and had acquired the means of controlling larger parts of the supply chain.

Simultaneously this development and consolidation also led to adoption of new strategies, ranging from more aggressive marketing to the adoption of management innovations such as lean construction and partnering. Extensive advertising in newspapers and television demonstrated that the large contractors had started to marketing themselves as especially customer oriented with slogans such as “Forvent lidt mere” (Expect a little more) (NCC) and Højgaard og Schultz which later merged with Monberg og Thorsen to MT Højgaard had the slogan: “Bygger på dialog”

(Building on dialogue). Today MT Højgaard emphasises the value of people, both in their corporate logo and approach to management of projects (Kristiansen et al., 2005, p. 507).

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The largest Danish owned contracting company (MTH) developed a new concept for construction management based on lean manufacturing principles. Called “TrimByg”, (trim build) it is based on the use of a process-planning tool, the LPS. TrimByg has subsequently been adopted and promoted by the Danish Technological Institute (TI) as “the” way to manage construction projects. In the following two sections the translation of Lean to Lean construction in literature is accounted for.

Thereafter the LPS, as it is textually defined is explained, and related to the Lean idea in general.

Furthermore, its status as being an MCS is accounted for.

4.2.2. Theory

The transfer of the Lean idea to construction in literature commenced with Koskela (1992), who conceptualised the ideas from the development and experiments of the Just-In-Time production system and quality control in Japan into a new production philosophy in construction. Koskela argued that there were two kinds of phenomena in all production systems: conversions and flows.

While all activities expend cost and consume time, only conversion activities add value to the material or piece of information being transformed into a product. Thus, the improvement of flow activities should primarily focus on their reduction or elimination, whereas conversion activities should be made more efficient. In the design, control and improvement of production systems, both aspects have to be considered. According to Koskela, traditional managerial principles had considered only conversions, or all activities have been treated as though they were value-adding conversions. Due to these traditional managerial principles, flow processes had not been controlled or improved in an orderly fashion. This had led to complex, uncertain and confused flow processes, the expansion of non-value-adding activities and the reduction of output value, according to Koskela (Koskela, 1992, 13).

The new conceptual model that Koskela developed is a synthesis and generalisation of different models suggested in various fields, like the JIT movement (Shingo, 1985) and the quality movement (Pall, 1987). According to Koskela (1992), the output of each conversion is usually variable, to such an extent that a share of the output does not fulfil the implicit or explicit

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specification for that conversion and has to be scrapped or reworked. Koskela (1992) used Juran (1988) to emphasise the consequences of variability in output: “about a third of what we do consists of redoing work previously done”. Besides that, the specification for each conversion is imperfect;

it only partially reflects the true requirements of the subsequent conversions and the final customer.

The impact of this issue concerns lost opportunities to fulfil customer requirements. Thus the task was to develop a model covering all important features of production that were lacking in the conversion model. The new production model was as follows:

‘Production is a flow of material and/or information from raw material to the end product. In this flow, the material is processed (converted), it is inspected, it is waiting or it is moving. These activities are inherently different. Processing represents the conversion aspect of production; inspecting, moving and waiting represent the flow aspect of production. Flow processes can be characterised by time, cost and value. Value refers to the fulfilment of customer requirements. In most cases, only processing activities are value-adding activities. For material flows, processing activities are alterations of shape or substance, assembly and disassembly’ (Koskela, 1992, 14).

Koskela summarised his thoughts of production management into what became the Transformation-Flow-Value (TFV) theory of production. The contribution consisted in the proposition that all three elements are to be managed at simultanaeously. All three views should be integrated and balanced:

The TFV theory of production (Koskela, 2000)

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Koskela’s paper contributed heavily to the subsequent development of the Lean Construction idea, and his proposition – which was that a neglect of managing flows and narrowing the focus to only conversions had led to complex, uncertain and confused flow processes, non-value-adding activities and a reduction of output value – was adopted by Howell and Ballard (1995). Howell and Ballard (1995) observed that typically only half of the tasks in a weekly plan are realised as planned on site, and the reasons for this ‘inefficient’ situation are found in Koskela’s (1992) propositions. In a series of experimental work, a new approach to production control, called the Last Planner System (LPS), was developed by Ballard (1994, 2000) with the aid of Howell (Ballard & Howell, 1998 and 2003).

The LPS was to represent Koskela’s (1992) theoretical propositions in practice through its concrete form as a practical tool.