Almost every construction schedule is built the same way: define the sequence of activities, assign a duration to each one, and calculate the completion date by working backward from the end. On paper, it's flawless. In practice, almost no project meets that schedule.
The problem isn't the planning itself, but its starting point: it assumes each task will begin as soon as the previous one ends, that materials will arrive on time, that the next trade will be available, and that there will be no last-minute changes. On a real site, none of those conditions always hold.
The shift in approach: planning backward
The Last Planner System (LPS), developed within the Lean Construction methodology, reverses the usual logic. Instead of pushing the plan from the start, it works backward from the final milestone through pull planning: each party involved — site manager, subcontractors, suppliers — sits down to define what the previous team needs to have finished so they can start their own task without delay.
The result is a plan built by the people who will actually execute it, not imposed from a technical office. That changes the level of commitment: teams aren't following someone else's instructions, they're meeting their own commitments.
The metric that actually matters: PPC
LPS measures the Percent Plan Complete (PPC): of all the tasks committed for the week, how many were actually completed. It doesn't measure whether the project is moving forward — it measures whether we did what we said we would do.
When PPC is low, the answer isn't to push the team harder. The root cause of each missed commitment is analyzed — lack of material, labor, information, weather conditions — and corrected in the following weekly cycle. Over time, that discipline of analysis raises PPC consistently, and with it, the reliability of the overall schedule.
What this means for the developer
For whoever is funding the project, LPS translates into one very concrete thing: predictability. A schedule that gets met isn't down to luck or pressure, but to a planning system designed to catch problems before they delay the project, not after.
At Mellado PM we apply Last Planner System and Pull Planning on every project we manage. It's not theory: it's the difference between an office schedule and a deadline that actually gets met on site.
Before the delays pile up
Weeks behind, and nobody can explain why?
There is usually a specific reason, and it is rarely the one given in the weekly meeting. Tell me how the programme is being run and I will show you where the time is going and how much of it can still be recovered.
Fifteen minutes on the phone clears up more than a report.