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Scheduling

A constraints log: clearing what blocks next week's work

By Review.LivePublished 3 min readHow we write

Tuesday morning, the tile crew arrives on level 2 and cannot start. The shower pans have not been flood-tested, and the tile is still at the supplier. Both problems were known two weeks ago, one buried in an email and the other in a foreman's head.

Seen from above, rows of pipe sections, manhole rings and precast blocks laid out on a graded site, waiting to be installed.
Photo: Iain on Unsplash

A constraint is anything that will stop a task from starting or finishing as planned and is not simply the previous task in the sequence: a missing approval, material, answer, inspection, permit or access. Lean planning calls clearing them "making ready"; a constraints log keeps that work on track by naming one person who promises to clear each constraint by an agreed date. Without the log, constraints are known but not owned, and they surface on the morning the crew arrives.

  1. Screen the look-ahead one week at a time: next week's tasks first, then the week after, out to the end of the window.
  2. Check the same things for every task: information and answers, approved submittals, material on site, crew, equipment, access, permits, and the inspection before it.
  3. Log each constraint on one line: the task, what is missing, who will clear it, the date the task needs it and the date promised.
  4. Name a person, not a company. "The owner" or "mechanical" cannot promise anything; a named coordinator or foreman can.
  5. Review the log at the weekly meeting, top to bottom: cleared, at risk, overdue. Mark cleared items as resolved instead of deleting them.
  6. Release only constraint-free tasks into next week's plan. A task with an open constraint stays in the look-ahead until it is clear.
  7. Record why promised work was missed, using a short, fixed list of reasons, and add a screening check for any reason that repeats.

Common mistakes

  • Naming a company, or "TBD", as the owner of a constraint.
  • Keeping constraints in email threads instead of one list.
  • Deleting cleared items, so the history is lost.
  • Letting the log become a list of complaints with no dates.

Checklist

Screening one task

  • Information and answers in hand
  • Submittals approved
  • Material on site or confirmed
  • Crew and equipment booked
  • Access and space clear
  • Previous inspection passed
  • Each open item logged with a name and a date

Check your understanding

A task on the look-ahead cannot start until the previous trade finishes. Does that belong in the constraints log?

Show the answer
Usually not. Lean planning defines a constraint as something the look-ahead does not already show, so a handoff from the previous trade is handled by the sequence itself. Log it only when that previous work is at risk for its own reason, such as a missing inspection or material, and then log that reason.

Sources

  1. Last Planner System Standard Work (LookAhead Planning; Constraint Log; Reasons for Variance)Lean Construction Institute · accessed
  2. Glossary (Constraint; Constraint Log; Make Ready Process)Lean Construction Institute · accessed

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