jueves, 18 de septiembre de 2008

What is lean construction?

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) ”. 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.
Lean construction aims to embody the benefits of the Master Builder concept. Essentially, Lean Construction recognizes that desired ends affect the means to achieve these ends, and that available means will affect realized ends (Lichtig 2004).
Lean construction supplements traditional construction management approaches with: (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.
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.
As Sowards stated (2004) the priority for all construction work is to:1) keep work flowing so that the crews are always productive installing product;2) reduce inventory of material and tools and3) reduce costs.
While Lean Construction’s main tool for improvement in construction is the Last Planner System (see below), 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 Five Whys (Mastroianni and Abdelhamid 2003, Salem et al 2005). Other Lean tools may prove useful once tested in construction.
Cain (2004 [- a or b Clive?]) suggests lean construction be defined by six goals of construction best practice:
1. Finished building will deliver maximum functionality, which includes delighted end users.
2. End Users will benefit from the lowest optimum cost of ownership.
3. Inefficiency and waste in the use of labor and materials will be eliminated.
4. Specialist suppliers will be involved in design from the outset to achieve integration and buildability.
5. Design and construction will be through a single point of contact for the most effective co-ordination and clarity of responsibility.
6. Current performance and improvement achievements will be established by measurement.
"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)

Practical applications
(it would be good to add examples from other countries here such as Denmark, US, Chile, Brasil, Peru, Sweden, in addition to others from the UK)
In the UK, a major R&D project, Building Down Barriers, was launched in 1997 to adapt the Toyota Production System for use in the construction sector. The resulting supply chain management toolset was tested and refined on two pilot projects and the comprehensive and detailed process-based toolset was published in 2000 as the 'Building Down Barriers Handbook of Supply Chain Management-The Essentials'. The project demonstrated very clearly that lean thinking would only deliver major performance improvements if the construction sector learned from the extensive experience of other business sectors. Lean thinking must become the way that all the firms in the design and construction supply chain co-operate with each other at a strategic level that over-arches individual projects. In the aerospace sector, these long-term supply-side relationships are called a '
Virtual Company', in other business sectors they are called an 'Extended Lean Enterprise'.
The UK 'Building Down Barriers Handbook of Supply Chain Management-The Essentials' states that: 'The commercial core of supply chain management is setting up long-term relationships based on improving the value of what the supply chain delivers, improving quality and reducing underlying costs through taking out waste and inefficiency. This is the opposite of 'business as usual' in the construction sector, where people do things on project after project in the same old inefficient ways, forcing each other to give up profits and overhead recovery in order to deliver at what seems the market price. What results is a fight over who keeps any of the meagre margins that result from each project, or attempts to recoup 'negative margins' through 'claims', The last thing that receives time or energy in this desperate, project-by-project gladiatorial battle for survival is consideration of how to reduce underlying costs or improve quality'.