What is lean construction?

Project and site management

Have you ever heard this edict? “A butterfly flapping its wings in New Mexico causes a hurricane in China?”
It’s called the butterfly effect.

In truth, this butterfly example is a bit of an exaggeration, but the underlying principle is not; small changes can have large consequences. And those large consequences become impossible to predict the longer time runs on. Now map this concept to construction projects and our traditional waterfall planning method.

What researchers have noticed is that performing 100% of the design & planning effort before we break ground falls short.
Because of the size and length of construction projects, we get caught by the butterfly effect time and time again.

Defensive design

In 2004, Patrick MacLeamy produced a set of curves that would firmly solidify the problems of our traditional design-build approach. It’s called the MacLeamy curve.
The MacLeamy curve draws our attention to the fact that much of the design of a typical construction project occurs at a time when changes to design are costly. On this graph, this is where red and blue lines intersect.
MacLeamy explains in the video below that designers are doing what he calls “defensive design”:

A new approach was needed to move shift the design work (and the curve) back toward the early stages of the project when changes are not so costly and the ability to impact the project outcomes is high as well. This is where Lean Construction comes in!

Lean construction

It has been around since the late 1990’s but maybe you’ve never heard of Lean Construction. Perhaps inspired by the trend in software development toward designing and coding software in bursts incrementally, the developers of Lean Construction came up with a method to produce a predictable workflow on construction project, taking ideas from Toyota’s Production Line System.

Lean Construction is new approach to building that is iterative. Planning, design and building are done in smaller chunks one at time with a detailed approach called “the Last Planner Method.”

Rather than perform all of the planning & design up front, then move on to building (what we call the Waterfall Method of project management), in Lean, work is planned, designed and scheduled in a weekly fashion, incrementally.

Lean planning in construction is based on the commitment to deliver a certain element of work and element of time per day starting from the end and moving back to the beginning Lean Construction is all about collaboration. It’s a real wake-up call from the traditional approach in construction where Owners lay out the requirements and Contractors go out and build, only discussing when there are issues or setbacks.

Instead we invite all parties to the table to plan, design, estimate, budget and optimize. All stakeholders collaborate and plan together; owner, contractor, sub-contractors, designers, engineers, schedulers, cost engineers, etc.

The team will often prototype a design, rather than forge ahead and build. Prototyping provides us with a visual and functional model that we test and evaluate. Today’s advanced BIM software tools are allowing us to quickly prototype designs and walk through them virtually.

Rather than pricing a design, the team designs to the allotted budget. Cost and work optimization is one of the biggest benefits of Lean Construction. Studies suggest adopting Lean Construction can save up to 30% of the project cost.

Collectively the team will come up with opportunities, suggestions, debate with the owner, build scaled models, mockups, and be involved with end-users & clients to gather feedback.

Lean construction focuses on reducing waste

A big focus of Lean Construction and Lean Planning is to reduce waste in Construction. Research estimates that only 40% of all budget on a typical construction project is spent on value-added activities, while the remaining 60% of budget is non-value adding actions, such as:

  • Waiting time (materials, sign-off, previous work, etc.
  • Inventory stockpiling
  • Correction of defects
  • Overproduction (activities not on Critical Path)
  • Inefficient transportation
  • Poor planning

The collaborative nature of Lean Construction makes maximizing value and eliminating waste much easier.
One of the principles of Lean Construction is called “the Value Stream”: the team aims to adopt the most effective process, achieved by the minimum number of value added steps.

What does a Lean Construction Schedule look like?

In a Lean Construction project, we often build a straightforward milestone schedule for the chunk of work we’re focused on. This is different that traditional CPM schedules.

A lot of the planning and scheduling in Lean Construction is termed “pull-planning.” In pull-planning, we plan backwards, starting with the end in mind and defining the backward steps incrementally.

In pull-planning, key milestones are broken down into 3 or 6 week lookahead schedules keeping the focus on the work in front of the team at the moment.
We ask:

  • What do we need to be ready?
  • What decisions need to be made?
  • What materials to allow the work to happen?

The 6-week schedule is planned out by the individuals who will perform the work – the contractors and tradespeople.
In scheduling, team members answer either:

  • Yes I can do that
  • No I cannot do that, because….. then this because becomes a new constraint.

Then the team works on how to remove that constraint.


How do you go about implementing Lean Construction? There are lots of ways. But get ready for to turn your familiar construction build routine upside down. Once you adopt it, Lean Construction is not just how you work, but how you live. Start by getting involved in Communities of Practice. Plan a visit to a Lean Construction project site, attend presentations or a bootcamp. Some even offer simulations on approaching a lego build with the Lean methodology.

However you decide to get your feet wet with Lean Construction, make sure you approach it with an open mind. As inventor/engineer Charles Kettering said: “There exist limitless opportunities in every industry. Where there is an open mind, there will always be a frontier.“

About the author: Michael Lepage, PMP is the founder of Plan Academy, an online training platform built for project controls professionals with on-demand courses on Project Controls, Planning & Scheduling software, Delay Analysis and project management for heavy industries. Try our flagship Primavera P6 course.

The circle of productivity

Discover how to improve productivity on your construction site.

Powered by

Easy-to-use construction software for streamlining processes, collaboration and connecting field with office

Provivienda uses LetsBuild to build 5x faster

Further reading