Constraint Analysis in Construction
Constraint analysis is the step inside the Last Planner lookahead that identifies every upstream blocker on upcoming work — design that is not final, materials that have not arrived, prerequisite work that has not cleared — and assigns owners and dates to resolve each one before the committing week. It is the make-ready engine of LPS, and the single most under-practised step on projects that report low PPC.
What is constraint analysis?
Constraint analysis is the Last Planner System screening step that systematically tests every candidate activity in the lookahead window against the eight standard constraint categories, assigns an owner and a date to every open constraint, and only promotes constraint-free activities into the weekly commitment set. The output is a filtered plan and a working make-ready action list.
Also known as: constraint screening, make-ready planning, screening and pulling, constraint-free screening. In the LPS literature the terms are used interchangeably; “constraint analysis” refers to the identification work and “make-ready” to the resolution work on top of it.
The eight constraint categories
Most mature LPS implementations screen against the same eight categories so trends can be read week over week. Any additional project-specific category (commissioning, environmental) is treated as a ninth.
Design
Drawings issued, RFIs closed, submittals approved, coordination model up to date.
Materials
Procured, on order, delivered to site, stored in the right staging area.
Labour
Crew available, correct trades, certifications current, inductions complete.
Equipment
Plant on site, inspection in date, consumables stocked, lifting plans in place.
Prerequisites
Upstream trade complete to the agreed handoff condition, inspections signed off.
Permits & inspections
Statutory permits held, hot-work and confined-space permits raised, inspector availability booked.
Access
Area cleared, lifts and hoists booked, lay-down space allocated, services isolated if needed.
Safety
Method statement issued, risk assessment signed, exclusion zones agreed, PPE and rescue plans in place.
Running the constraint register through the week
A constraint register is only useful if it is reviewed, owned and worked between the weekly screening meetings. The cycle below is what separates teams whose PPC climbs from teams whose constraint log just accumulates stale entries.
- 1
Screen on Monday (or chosen cadence)
Walk the lookahead window with the last planners. For each candidate activity, test the eight categories. Any open constraint goes on the register with the activity reference, the category, the owner and a clearing date.
- 2
Chase daily, not weekly
Constraints clear through small daily actions, not through Friday heroics. The planner owns following up on the clearing dates — a short daily check keeps the register working rather than letting it drift to the next weekly meeting.
- 3
Escalate on the escalation date, not on reflection
Every constraint has an escalation date distinct from the clearing date. If a constraint is not closed by its escalation date, it moves to the project director immediately rather than being rolled to next week with a shrug.
- 4
Promote to the weekly plan only when closed
On the committing day (usually Friday), activities with any open constraints at the two-weeks-out line are either resolved immediately or pulled out of the commitment plan. The weekly plan is a promise set, not a wish list.
- 5
Review the reason-code trend each Monday
Last week's missed commitments carry reason codes. If one category (materials, say) is the top reason three weeks running, this Monday's lookahead gives materials-related constraints an earlier screening date and a tighter clearing timeline. This is what turns the register into a learning loop.
Worked example: a mid-project constraint register
Monday morning on a 14-storey residential project. The lookahead covers weeks three through six. The register below is a slice of what the screening surfaced and how make-ready assignments were made.
| Activity | Category | Owner | Clear by |
|---|---|---|---|
| Curtain wall install L7 | Materials | Logistics | Mon close |
| MEP first-fix L5-6 | Design (RFI 142) | Design manager | Fri close |
| Partition boarding L4 | Prerequisite — slab inspection | Inspector + concreter | Tue 10:00 |
| Facade mast-climber permit | Permits | H&S lead | Thu close |
| Painter 2nd coat L3 | Prerequisite — snagging incomplete | Fit-out foreman | Wed close |
| Lift commissioning witness | Permits — engineer unassigned | Lift vendor | Fri close |
What the register did for next week's commitment set
Six activities screened, six constraints logged, six owners and six clearing dates. By Friday's committing meeting, four were closed, one was pulled from the next week (curtain wall shipment slipped), and one was replaced with an alternate (facade work re-sequenced while the permit cleared). The weekly plan that went into Friday's meeting had no activities with open constraints — PPC rose from 62% the previous week to 86% on the first week with disciplined screening.
Where constraint analysis fails in practice
The template is in most project handbooks; the practice is rarer. Four failure modes come up repeatedly on teams that have the register but low PPC.
Constraints logged but not owned
The spreadsheet has an ‘open constraints’ column that accumulates entries week over week with no name or date against them. The register has become a diary of problems rather than an action list — identification without resolution.
No daily chase between weekly meetings
Constraints get reviewed on Monday and forgotten until Friday. Items that could have been cleared with a Wednesday phone call sit open through to the committing meeting, where they get rolled into next week with new dates.
Escalation path missing
A constraint without an escalation owner stalls when the designated owner cannot clear it alone. The register needs both a clearing owner and an escalation path from day one — otherwise difficult constraints disappear into inboxes.
Register maintained in a side spreadsheet
When the register is a document in SharePoint and the master schedule lives in P6, they drift. By week three, the register's view of ‘ready’ disagrees with the master's view of ‘scheduled’, and the weekly meeting burns time reconciling the two.
How VisiLean supports constraint tracking
VisiLean Planner maps constraints against the master schedule as part of collaborative planning, so the identification and resolution loop runs on the same source of truth as the CPM master and the weekly commitment plan.
- Review lookahead plans, map constraints and monitor commitments in real time against the master schedule — no side spreadsheet to drift from the plan.
- Constraints are mapped against the master schedule, with owners, dates and escalation notes captured on the activity itself.
- Make-ready updates and progress flow between the office and the field via LiveSite — the mobile app the last planners use to update completion.
- Reason-code trends from the previous week's PPC are visible as the next lookahead meeting opens, so the screening priority adjusts to what is actually breaking.
- Weekly commitment conversations work from the filtered constraint-free set, keeping the plan aligned with what the trades say is actually ready.
Related methods
Lookahead Planning
The six-week horizon that constraint analysis operates inside. Lookahead sets the window; constraint analysis fills it with actionable screening.
Read moreLast Planner System
The production-control system constraint analysis sits inside. The five conversations, PPC and the full LPS loop.
Read morePPC — Percent Plan Complete
The reliability metric that reveals when constraint analysis is working. Low PPC is almost always the symptom of broken make-ready.
Read moreVisiLean Planner
The product that maps constraints against the master schedule and tracks commitment reliability in one place.
Read moreFrequently asked questions
What is constraint analysis in construction?
Constraint analysis is the Last Planner System step that systematically identifies anything blocking an upcoming activity before the activity reaches the committing week. Each candidate activity in the lookahead window is tested against the eight standard constraint categories — design, materials, labour, equipment, prerequisites, permits, access, safety — and every open constraint is assigned an owner and a date for clearing. The output is a filtered set of activities that are genuinely ready to be committed to, plus a working action list for everything that is not.
What are the eight standard constraint categories?
Most mature LPS implementations use the same eight: design (drawings, RFIs, submittals, coordination model), materials (procurement, delivery, site storage), labour (crew, certifications, inductions), equipment (plant, tools, inspection), prerequisites (upstream trade handoff), permits and inspections (statutory and project-specific), access (areas, lifts, lay-down space) and safety (method statements, risk assessments, exclusion zones). Project-specific categories like commissioning or environmental are added on sectors that need them (data centres, infrastructure, water utilities).
What is the difference between constraint analysis and make-ready?
Constraint analysis is the identification half — walking through each upcoming activity and flagging what is not ready. Make-ready is the resolution half — the active work of assigning owners and dates to clear each flagged constraint, chasing those actions through the week, and either closing the constraint or pulling the activity out of the plan. Both are needed. An LPS team that only identifies constraints has a diary of problems; a team that identifies and clears them has reliable commitments.
Who runs the constraint analysis meeting?
The main-contractor planner facilitates. The last planners for the trades inside the lookahead window attend — the foremen and subcontractor leads who actually commit crews. Design representatives join when design-category constraints dominate the week. The meeting runs weekly, usually 30 to 60 minutes, and sits at the top of the lookahead cycle — the output drives both the make-ready action list for the week and the filtered constraint-free set that feeds the Friday weekly-commitment meeting.
How is constraint analysis different from a risk register?
A risk register tracks what might happen; a constraint register tracks what is blocking work that is otherwise scheduled to start. Risks are probabilistic and project-level; constraints are concrete and activity-level. A risk register asks “what should we worry about?”; a constraint register asks “what has to be true for this activity to start next week?” Both are useful artefacts, but they answer different questions and live in different places in a project — risks in the PM's office, constraints in the lookahead meeting.
See constraint tracking on a live schedule
VisiLean maps constraints against the master schedule and keeps the make-ready loop on the same source of truth as the CPM master and the weekly commitment set.