Method

Lean house (TPS house)

In French: Maison du Lean

The Lean house represents the Toyota Production System as a building: a foundation of stability, two pillars — just-in-time and jidoka — and a roof that carries the objectives.

What it is

The architectural metaphor serves to say one thing that lists of tools do not: these elements depend on one another. A roof does not stand without pillars, and pillars do not stand without a foundation.

The foundation is stability: 5S, standardised work, visual management, equipment reliability, load levelling. Building just-in-time on an unstable process is like putting up walls on sand — that is why so many Lean roll-outs collapse after six months, even though the tools were the right ones.

The first pillar, just-in-time: producing the right product, in the right quantity, at the right time. It rests in turn on three elements — the takt time that sets the pace, continuous flow that removes intermediate stocks, and pull flow that authorises producing only what has been consumed.

The second pillar, jidoka: quality built into the process rather than checked afterwards. It brings together error-proofing devices (poka-yoke), the andon that makes it possible to signal and stop, and the principle of never letting a non-conforming part through to the next station.

A representation, not a standard

Several versions of this house exist, and they do not put the same elements in the same places — kaizen appears sometimes in the foundation, sometimes in the centre; respect for people sometimes as a pillar, sometimes as a base. None is official.

It is a teaching diagram, not a reference framework. Discussing it as if one had to decide between the variants misses what it teaches: the order of construction, and the fact that you cannot take a tool from the middle and hope it will stand on its own.

The common mistake

Starting with the pillars. A kanban project in a workshop whose equipment breaks down and where no standard exists produces exactly the opposite of what is sought: pull flow makes disruptions immediately blocking, without the base that would make it possible to treat them. The conclusion is then that "Lean does not work here", when one has simply built in the wrong order.

On the shop floor — Pharmaceutical industry

A site suspended its pull-flow project for a quarter to first deal with the reliability of two pieces of equipment and overhaul the workstation standards. The kanban deployed afterwards held; the previous attempt, two years earlier, had been abandoned within six weeks.

The other tools illustrated by this trade: healthcare and life sciences.

Frequently asked questions

What are the two pillars of the Lean house?

Just-in-time on one side, jidoka on the other. The first settles the question of quantity and timing: produce only what is demanded, when it is demanded. The second settles that of conformity: never pass on to the next station a part known to be bad.

What does the foundation of the Lean house contain?

Everything that makes a process predictable: order and cleanliness of the workstation, written work standards, legible display of the current state, equipment that does not break down, load spread evenly. There is nothing spectacular about these elements, and they are what decides whether the rest will hold.

Is there an official version of the Lean house?

No. Several representations circulate and they do not put the same elements at the same levels, in particular continuous improvement and respect for people. None has normative status. Looking for which one would be the right one distracts from what the diagram serves to convey: an order of construction.