What is Lean?
The best analogy we have come up with is to compare Lean with a construction company's safety program. We don't define it as fall protection training, or taking an OSHA class, or a safety glasses policy, it is all those things but more than that, it is a mindset, a culture, a way to work.
When describing Lean it's not defined as pull planning, continuous improvement or eliminating waste because these are the processes or results of Lean but not the definition of it. At its core, Lean Construction is a mindset that in all aspects works to promote predictability on a project. That means Lean methods are geared toward removing assumptions (risk). The way to go about a project or a job to become predictable and remove risk is defined by the five principles.
The Five Principles of Lean Construction
1. Define Value from the customer's perspective
2. Organize just the work necessary to produce customer value
3. Make work flow uninterrupted along value stream
4. Build to the pull of the customer
5. Continuous improvement
History of Lean Construction
To create some clarity in the description above, let's go back to the beginning.
The term Lean Construction was coined in 1993 when two consultants, Glenn Ballard and Greg Howell, on a large oil refinery build-out, started asking the foremen on the project: Of all the things you plan to do this week, what actually gets done? The answer after extensive study was that about 50% of what was planned actually got done. (Note that all workers were still busy, working full-time).
Ballard and Howell came up with a system, named the Last Planner System, consisting of Pull Planning, Constraint Logs, Weekly Work Plans, and Percentage Plan Complete-tools on how to manage the schedule and the project to encourage the foremen to become better planners, and increase the percentage of what actually gets done. The idea being that if everyone on a project does what they say they will do, when they say they will do it- the project is successful. It increases the predictability of the project and if what happens in the future is more predictable than the speed of production can increase, costs will decrease etc. The mindset and/ or culture started developing from these tools.
The term Lean- originated from Toyota's Lean manufacturing process (a system based on principles of how Toyota builds their cars). Ballard and Howell did not pick the term but they gladly adopted the term and applied it to construction industry because of what Lean manufacturing represented. It rapidly caught on. (I once asked Howell how he felt about the term Lean after Toyota had serious quality issues with stuck gas pedals in their cars. Howell stated that they thought about changing the name but it was too ingrained in the industry to change, and also noted that despite the same name, the original ideas came from completely different thoughts, in manufacturing the idea was to eliminate inventory and in construction the idea was to create predictability). Many ideas do work very well across and are shared in both industries such as Waste Elimination and Continuous Improvement.
So to conclude, Lean Construction is a mindset based on working through the five principles of Lean. It is similar to safety in that it is an all encompassing idea, not just a method for a specific task.