The Last Planner® System and PPC: making the schedule happen

A CPM schedule says what should happen and when. It cannot tell whether the drawings, materials, permits, access and the crew will all be ready on the day. The Last Planner® System, developed by the Lean Construction Institute, plans the work week by week with the people who direct the crews, releases only work that is ready, and measures how reliably the promises are kept. Percent Plan Complete (PPC) is that measure.

Why schedules slip at the work face

Most slippage does not start with a bad duration. It starts with a task that could not begin: the scaffold was not erected, the isolation was not signed, the parts were still in receiving, the previous trade had not finished the area. Each looks small on the day. Repeated across crews and weeks, they become the delay the schedule update reports a month later. The method's premise is that reliable work comes from screening work for readiness before anyone commits to it.

Should, can, will, did

• Should: what the master and phase schedules call for.
• Can: what is actually ready, because its constraints (information, materials, equipment, permits, access, prior work, people) have been removed.
• Will: what a crew's foreman or supervisor commits to doing next week, chosen only from work that can be done.
• Did: what was completed as promised, and why the rest was not.

The "last planner" is the person who makes the final assignment of work to a crew. The system gives that person a voice in the plan and holds the plan to what they commit to.

The planning conversations

• Pull planning for a phase: start from a milestone and work backward, each trade stating what it needs handed over by whom. Hand-offs become explicit and buffers are placed deliberately.
• The lookahead, typically three to six weeks: break the schedule's upcoming activities into crew-sized tasks, list each task's constraints, give every constraint an owner and a date, and "make ready" so the work is clear by the time it arrives.
• The weekly work plan: each crew commits to a quantity of ready work for the week. Saying no to work that is not ready is part of the discipline.
• The daily huddle: a few minutes against the week's commitments, to raise problems while they can still be solved.
• Learning: at the end of the week, count what was kept, record a reason for each miss, and act on the most frequent reasons.

Percent Plan Complete (PPC)

PPC = commitments completed as promised ÷ commitments made, for the week. A task half finished counts as not kept: the measure is about the reliability of promises, not the amount of progress. Example: a crew commits to 12 tasks and completes 9 of them as stated, so PPC is 9 ÷ 12 = 75%.

Low PPC means the crews are committing to work that is not ready, and the downstream trades are planning against hand-offs that will not arrive. Teams new to the method often start well below 70%; steady teams commonly run at 80% or better. The trend and the reasons for variance matter more than any single week. A rising share of misses for "materials" or "prior work" points to a make-ready problem upstream of the crews.

How it fits with the CPM schedule

The two are layers, not rivals. The CPM schedule sets the logic, the critical path, the milestones and the earned value baseline. The weekly plan is how the field delivers it. Tying lookahead tasks to schedule activities keeps the layers connected: constraints show up against the activities they threaten, and the PPC of the crews on critical work becomes an early signal for the schedule's forecast, weeks before the dates move.

In DeltaSys

The DeltaSys Planner's Field Plan window follows the Last Planner® System on each project. Crews, lookahead tasks and their constraints hang off the schedule's activities. The window has a pull plan, a weekly work plan that admits only ready tasks, a daily board and a learning view with PPC and the reasons for variance. The project dashboard shows last week's PPC and the open constraints, and its two-week look-ahead flags activities whose tasks still have one.

Related: scheduling software and CPM · earned value management · the risk register.

Primavera and P6 are trademarks of Oracle Corporation; Microsoft Project is a trademark of Microsoft Corporation; PMBOK is a trademark of the Project Management Institute; AACE is a trademark of AACE International; Last Planner is a registered trademark of the Lean Construction Institute. DeltaSys is not affiliated with or endorsed by them. Standards are described in our own words; see the publications themselves for their text.