A constraint is anything that will stop a crew from doing the work you're asking them to do. The stud material sitting on a truck in Fontana. The RFI on the header detail that's been "with the architect" for nine days. The elevator inspection nobody scheduled. Traditional scheduling treats these as bad luck. Last Planner treats them as the whole job. The difference between a superintendent who hits his weekly plan and one who's always explaining variances is almost never talent or effort — it's whether he screened the work for constraints before he put a crew on it.
Good software helps, but only if you understand what the software is supposed to be doing for you. So before we talk about tools, let's be clear about the actual practice, because the tool is just a place to store and surface it.
Make-Ready Is the Real Job
In the Last Planner System, work moves through a funnel. The master schedule tells you roughly when things should happen. The lookahead — usually a rolling six weeks — is where you take those chunks and ask, "What has to be true before a crew can actually start this?" That screening is called make-ready. Anything that isn't true yet is a constraint, and your job for the next several weeks is to knock those constraints down so that by the time the activity reaches your weekly work plan, it's genuinely ready — not "should be ready," genuinely ready.
Here's the rule that matters most: only ready work goes into the weekly plan. If you commit a crew to an activity that still has an open constraint, you haven't made a plan, you've made a wish. The whole system is built to keep wishes out of the weekly commitment. Everything else — the tracking, the assignments, the alerts — exists to serve that one discipline.
Most teams that "try Last Planner" and give up were doing the ritual (sticky notes, a Friday meeting) without doing the screening. They pulled work forward, wrote it on the wall, and were surprised when half of it didn't happen. The screening is the work. The meeting is just where you report on it.
The Seven Constraint Categories — and How to Screen for Them
When you pull an activity into the lookahead, walk it against a standing checklist. I've watched superintendents run this from memory and miss the same category every time, so put it in your lookahead software as a template and force yourself through all seven:
- Materials — Is it ordered? Confirmed ship date? Where does it stage, and can the crew actually reach it on the day? Material on site but buried behind three other trades' deliveries is still a constraint.
- Information — Are the drawings clean for this scope? Any open RFI or unapproved submittal touching it? An activity waiting on an RFI is not ready no matter how badly you want the crew working.
- Predecessors — Is the prior work actually done, or scheduled to be done? Framing has to be complete and inspected before you close a wall, not just "mostly framed."
- Labor — Right crew, right size, right skill, actually available that week? Specialty labor — waterproofing, a specific welder, controls tech — often needs weeks of notice.
- Equipment — Lift, crane pick, pump, scaffold. Shared equipment across areas or projects is where schedules quietly collide.
- Space — Can this crew own that area that day, or is another trade in it? Overhead conflicts (duct vs. sprinkler vs. cable tray in a tight plenum) are the classic space constraint people forget until two foremen are standing under the same ceiling.
- Permits & inspections — What sign-off has to happen first, and is it scheduled? A rough-in inspection you forgot to call is a self-inflicted delay.
Screen every new activity against all seven. The ones you skip are exactly the ones that bite you Thursday afternoon.
Every Constraint Gets a Name, an Action, and a Date
A constraint with no owner does not get resolved. Ever. "Someone needs to follow up on the storefront glass" is not a constraint, it's a complaint. Make it real by forcing three fields on every single one:
- Who — a person, not a company. "Mike at the glazing sub," not "the glazier." Roles don't return phone calls; people do.
- What — the specific action. "Confirm the fabrication release and get a firm delivery date," not "handle the glass."
- By when — the need-by date, backed off from when the crew is scheduled to start. This is the number that drives escalation.
This is where scheduling software earns its keep. When you log a constraint against an activity in a tool like LookAheadWall, it rides with that activity across every weekly review, it's assigned to a named person, and it shows a due date the whole team can see. The point isn't the software being clever — it's that the constraint can't quietly disappear the way it does off a legal pad in someone's truck.
Tracking, Escalation, and the "Truck List"
Once constraints are logged and owned, you're managing a list, not fighting fires. Status stays simple: Open, In Progress, Resolved, Blocked. Update it at least weekly in the planning session, and more often for anything critical. The one status that should make your neck hairs stand up is Blocked — that's a constraint whose owner can't resolve it alone and needs you or the PM to break something loose.
Set a hard rule for escalation: any constraint that passes its need-by date without resolution goes up the chain automatically. Good software will flag overdue items and surface them on the PM's dashboard so leadership sees the stuck ones without you having to build a report. But the mechanism matters less than the discipline — an overdue constraint that nobody escalated is going to become a missed activity, full stop.
The practical rhythm I've seen work: a short daily huddle where the foremen run their open constraints — the "truck list" of things they're chasing — and a longer weekly planning session where you screen new work entering the lookahead and formally verify what's ready to commit. Daily is for chasing. Weekly is for committing.
Verify Ready — Don't Take the Optimist's Word
The single most valuable habit in the whole system is refusing to take "it'll be fine" as a resolution. When the constraint owner says the material's arriving Monday, that's a claim, not a fact. Verify it — tracking number, confirmed release, an actual inspection date on the calendar. I've lost more Mondays to "the truck's on its way" than to any other single phrase on a jobsite.
So before an activity crosses from the lookahead into the weekly work plan, close the loop: the owner confirms resolution, the planning lead sanity-checks that it's real, and the resolution gets recorded. Only then does the work become a commitment. This is the gate that protects your Percent Plan Complete, and it's the gate everyone is tempted to skip when they're behind and desperate to show progress. Skip it and you're just moving the failure from the constraint log to the weekly variance report.
Handling the Categories Differently
Not every constraint behaves the same way, and treating them identically is a rookie mistake.
Long-Lead Materials
Switchgear, elevators, structural steel, custom storefront, big AHUs — these live outside the six-week lookahead. You track them on a separate long-lead log with need-by dates driven off the master schedule, sometimes months out. If a piece of gear has a 22-week lead and you first notice it in your six-week window, you're already 16 weeks late. The lookahead catches the ordinary stuff; a discipline of long-lead tracking catches the killers.
Information Constraints
Tie these straight to your RFI and submittal logs. An RFI that's open is an information constraint by definition, and its answer date drives whether the dependent activity can proceed. Watch for the reverse, too: a design change or a late-approved submittal can spawn brand-new constraints on work you thought was clean. Re-screen affected activities whenever a change lands.
Predecessor Constraints and Buffers
This is where sequence discipline pays off. Don't schedule the following trade nose-to-tail with the one ahead of it. Frame-to-rough-in usually wants a day or two of buffer for cleanup, punch, and the inspection. Rough-in to cover (drywall, pour, backfill) always wants the inspection signed off first — closing a wall over un-inspected work is how you end up cutting it back open. Little discipline things save the big rework: megger the runs before you close the wall, pressure-test the pipe before the drywall crew shows, walk the in-wall blocking against the casework shops before rock goes up. A buffer isn't slack you're wasting — it's the shock absorber that keeps one trade's slip from cascading into three.
Labor and Equipment
For labor, the constraint is often lead time, not headcount — the sub has the guys, they're just on another job and need two weeks' notice. Flag specialty crews early. For equipment, the trap is sharing: one lift covering three areas looks fine on paper until two foremen both need it Wednesday. Confirm availability against the actual dates, and keep a backup plan for anything you can't fully control.
Read the Patterns, Then Fix the Process
Once you've been logging constraints for a few months, the data starts talking. Sort your resolved and failed constraints and look for the shape of your problems: Which category shows up most — materials, information, predecessors? Which sub consistently owns the constraints that go overdue? How long does each type actually take to clear, so you can set realistic need-by dates instead of hopeful ones?
Then close the loop with your Percent Plan Complete. When PPC drops, don't just note the number — pull the variances and count how many plan breaks traced back to an unresolved constraint, and what type it was. If half your misses are information constraints, your problem isn't the field, it's the RFI turnaround, and no amount of yelling at foremen fixes that. Constraint data plus PPC variance tells you exactly where to spend your management attention next month. That feedback loop is the entire point of running the system — you're not just planning the next week, you're getting measurably better at planning.
The Bottom Line
Constraints don't resolve themselves, and pretending they will is what wrecks schedules. The practice is old and boring and it works: screen every activity against the seven categories, give every constraint a person and a date, chase them down in the daily huddle, verify they're actually clear before you commit, and only let genuinely ready work into the weekly plan. Software's role is to hold that list where the whole team can see it and to nag you about the overdue ones — LookAheadWall and tools like it are built to keep constraints attached to the work they threaten so nothing falls off the back of a truck. But the tool doesn't do the make-ready. You do. Do it honestly, and your weekly plan starts meaning something — because for once, the work you promised is the work that can actually happen.