Heijunka: Leveling Work for Flow and Predictability

Heijunka, Leveling Work for Flow and Predictability

In this blog, I want to walk you through one of the most powerful concepts in Lean construction. Heijunka is leveling. It ties directly into Takt time and Takt planning, and when you truly understand it, your projects will never be the same. I am going to connect this idea directly to construction because the application is phenomenal.

What Is Heijunka?

Heijunka means leveling, and it is one of the most beautiful concepts in Lean thinking. When you pair it with Little’s Law, it becomes even more meaningful. In manufacturing, Little’s Law is slightly different, but when translated into construction it points to the need for the right batch sizes, leveled work, and finishing as you go. Everything should be leveled to create predictable flow.

Fixed Units and Flow Units

When we visited Japan with Paul Akers, we saw Heijunka everywhere. In construction, you either have a fixed unit and a flow unit or two possible flowing units where one must be fixed.

In a warehouse, either workers or product can move. You choose one to remain fixed and the other becomes the flow unit. In construction, the train of trades and the materials being installed are the flow unit. The building itself is the grow unit, which Nicholas Modig describes, because it is being formed and shaped every day.

In Toyota manufacturing, the car is the flow unit and the plant is the fixed unit. The principle is simple, no matter the environment. Identify what needs to flow and level everything around it.

Three Real Scenarios from Japan

We saw three examples that perfectly showed Heijunka in action.

Scenario one had five big machines and two humans. The machines moved faster than people, so the work was leveled by pairing two people with the machines.

Scenario two was the opposite. One human needed two machines to maintain flow. She would complete one step, move in a circle, complete the next step, place the part, and repeat. One person to two machines kept the system leveled.

Scenario three had one machine but required two humans. This was because the bottleneck was not the equipment but the human action required.

These examples show that Heijunka does not have one formula. You might need more humans than machines, more machines than humans, or different combinations altogether. What matters is that the system is leveled and flow is maintained.

How Leveling Works in Line Manufacturing

In Toyota’s line manufacturing system, cars move forward and spend about fifty seconds at each station. Everything in each station is designed to fit inside the Takt time. The work is leveled across machines, people, and work content. Some stations have two machines on each side, others require more humans, and some require only one machine because the work takes less time.

The result is perfect balance. Perfect flow.

How Heijunka Applies to Construction

In the United States, we rarely level work this intentionally. In the Takt production system, however, we absolutely do. We take a pull plan and then design how crews move from zone to zone. If one trade moves slower than another, we adjust that trade. Maybe they need two well prepared and fully kitted crews. That removes the bottleneck.

Sometimes the bottleneck is the zone. Sometimes the trade. Sometimes the work structure. The point is simple. Work must be packaged to flow. That is Heijunka.

Once the work is leveled, variation drops dramatically. You can monitor small disturbances, pull the andon, stop the line, and fix issues before they turn into massive problems.

The Human Side of Leveling

Heijunka is not only good for flow. It is good for people.

Humans thrive in even flow. It is safer. It is more visual. It reduces friction. It creates calm.

And yet, many Western superintendents resist stability. They fear looking lazy. They want adrenaline. They want to feel like firefighters. This creates the firefighter arsonist superintendent.

The Firefighter Arsonist Problem

I once set up a project in Tucson. It was organized, clean, safe, and leveled. The Last Planner System was in place. Huddles were running. Buffers were planned. The site flowed so smoothly that some people thought nothing was happening. But the work was going in fast and at high quality.

A superintendent took over after six weeks. At first things were stable. Then the systems slowly disappeared. Huddles stopped. Deliveries blocked the entrance. Trash accumulated. Work fell behind. When I asked why, he said the systems were boring.

He did not understand that boring meant stable. Stable meant productive.

He needed excitement, so he created chaos. He started fires so he could put them out. The flow collapsed.

The Key Concept Many Miss

In Lean thinking, stability is everything.

• Respect for people is first.
• Stability is second.
• One piece flow is third.
• Flowing together and takt time come after.
• Visual systems and total participation follow.
• Only then do we get continuous improvement.

Without stability, nothing works. This is the heart of Heijunka.

Flow State

Flow state occurs when the system moves without friction, bottlenecks, or interruptions. It is enjoyable. It is natural. It is predictable.

Paul Akers demonstrated this perfectly when he taught us how to get off a train in Tokyo. Move. Do not stop. Follow the signs. Have your transit card ready. Keep flowing.

Millions of people move effortlessly because the system is leveled.

Final Challenge for Construction Leaders

• What can you level tomorrow on your project?
• Where can you remove friction?
• Where can you stabilize flow?

Heijunka is one of the greatest gifts Lean gives us. When you level work, you create safety, clarity, quality, and predictability. You create morale. You create flow.

I hope you enjoyed this blog.