Ask a foreman which plan he works from and you usually hear one of two answers. He prints the master schedule and ignores half of it, or he keeps his own list in a notebook nobody in the office has seen. Both cost you days.
The master schedule tells you whether the job will finish on time. The lookahead tells you whether next Tuesday will work. Your crew works from the lookahead. You manage the promise with the master.
What the master schedule is for
The master schedule covers the whole job, from start to handover. It holds the phases, the milestones, the dates in the contract and the logic that ties them together.
It should stay coarse. A bar that says "rough framing, 15 days" is the right level. Load every room and every pour into it and nobody keeps it updated. Many contractors refresh the master on a fixed cycle, often monthly, and at each change order or big slip.
What the lookahead is for
A lookahead is a rolling window cut from the master, usually three to six weeks long. It trades the long view for detail. That 15 day framing bar becomes walls on grid lines 4 to 7 on Monday and Tuesday and the next run on Wednesday.
The real job of the lookahead is to find what stops each task from starting and to clear it before the week arrives. The Lean Construction Institute workbook puts the typical window at five to six weeks, because many constraints take longer than a week to clear. Shops doing short service or install jobs often run three weeks, which is the setup in our 3-week lookahead guide.
Which one the crew should work from
The crew works from the lookahead, and from the weekly plan pulled out of it. The master is too coarse to tell a crew lead what to do on Thursday.
The office keeps one eye on the master. Every week, compare what the lookahead says will happen against the milestone dates. If the lookahead keeps sliding past a milestone, that is your early warning, weeks before the owner notices.
The mistake that creates two sets of dates
The most common failure is a lookahead built on its own, in a separate spreadsheet, with dates that no longer match the master. Soon the office quotes one date and the field works to another.
Keep one rule: the lookahead is always drawn from the master, never created beside it. When the field finds that a task needs more time, the change flows back up to the master the same week. If the change touches a linked chain of work, check the critical path before you promise a new finish date.
A weekly routine that keeps both honest
Pick one fixed slot, such as Monday morning, and run four steps.
- Roll the window forward one week and pull the next tasks in from the master.
- Walk each task in the window and list what blocks it. Give every blocker an owner and a date.
- Commit the coming week only to tasks with no open blockers, with a named person on each.
- Push any slip or new duration back into the master before the meeting ends.
Then measure. Count how many of last week's committed tasks were finished. That ratio is Percent Plan Complete, and our Percent Plan Complete guide shows how a small crew can track it in a few minutes a week.
Running both from one plan
The cleanest setup is one schedule with two zoom levels. Keep the full job on a Gantt chart with milestones for the dates you promised. Link tasks with dependencies so a slip in one trade pushes the work that follows. Filter the timeline to the next few weeks for the lookahead meeting, assign each task with a priority, and let the crew open the same plan on their phones.
Zace gives you Gantt charts, milestones, timeline and dependency views and task assignment, on web, Android and iOS. The master and the lookahead stay the same data, so there is no second set of dates.
Frequently asked questions
What is the difference between a master schedule and a lookahead schedule?
The master schedule covers the whole job with phases, milestones and contract dates. The lookahead is a rolling three to six week window cut from the master, broken into detailed tasks so the crew can see what is ready to start.
How far ahead should a lookahead schedule look?
Three to six weeks covers most jobs. Use a longer window when constraints such as approvals or material deliveries take more than a few weeks to clear, and a shorter one for quick service or install work.
How often should each plan be updated?
Update the lookahead every week in a fixed meeting. Update the master on a regular cycle, often monthly, and whenever a change order or a slip moves a milestone.
Give the master the promise and the lookahead the week, draw one from the other, and your crew will always know which plan to trust.
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