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A programme says what should happen. On a busy site, what actually happens depends on whether each crew can start: are the drawings approved, is the material here, is the work before theirs finished? The Last Planner System is a lean planning method built on that question. The people who direct the work, the "last planners", plan it together and commit only to tasks that are ready.
The programme shows ceilings in level 2 zone A next week, so the site manager puts it in the weekly plan. On Monday the drylining crew arrives to find two ducts still clashing with the grid, and a sprinkler drop waiting for an approved drawing. The crew stands around for half a day, then moves to work that wasn't planned. The ductwork team, which didn't know the ceiling was coming, carries on elsewhere.
In the look-ahead meeting two weeks earlier, the BIM coordinator opens zone A in the model with the foremen. The two open clashes and the missing sprinkler drawing are logged as constraints, each with an owner and a date. One clash is fixed that week; the other isn't, so the foreman commits only to the part of the zone that is clear. The promise is kept.
The four levels of planning
Lean construction applies ideas from lean manufacturing to building: make work flow, remove waste (waiting, rework, moving material twice) and make handoffs between crews reliable. The Last Planner System, developed by Glenn Ballard and Greg Howell, is its best-known planning method.
| Level | Horizon | Who | What comes out |
|---|---|---|---|
| Master schedule | Whole project | Planner, project leaders | Milestones |
| Phase (pull) plan | One phase, to a milestone | All trades in the phase | Agreed handoffs, worked back from the milestone |
| Look-ahead | About six weeks | Foremen, coordinator | Tasks screened for constraints, constraints removed |
| Weekly work plan | Next week | Foremen | Commitments to ready tasks only |
Each week, the team checks which commitments were kept. PPC (percent plan complete) is commitments kept divided by commitments made. A missed commitment gets a reason (drawing late, material not delivered, previous work not finished), and the reasons are tracked to fix the causes.
Building a pull plan
Pull planning starts at the milestone and works backwards. Each trade puts its tasks on the board, saying what it needs from the trade before it to start. The handoffs are agreed between the people who will make them.
The milestone is "roof watertight, zone B". Put the tasks in the order the trades would agree them.
Pull-plan the roof
Milestone: roof watertight, zone B. Put the tasks in the order the trades would agree them.
- 1Roof slab poured
- 2Level 2 frame complete
- 3Roof watertight
- 4Membrane laid
- 5Upstands and outlets formed
- 6Slab cured and handed over
Then decide which of these is a constraint for the roofing crew: "Roof slab in zone B not yet poured", "Membrane delivered to site", "Crane booked for the day".
Key takeaways
- Pull planning works back from a milestone; each trade says what it needs from the one before.
- A task is ready only when its constraints are gone: information, materials, access, the work before it.
- PPC (percent plan complete) measures kept promises, not progress against the programme.
- Use the model to show a zone's sequence in pull planning and to find missing information in the look-ahead.
Your notes
Related tool
Play your programme (P6 or MS Project) on the IFC model: see it built day by day, find late work and sequence errors.
Open 4D Simulator →