Near-Critical Paths
Last reviewed 9 September 20262,012 words9 min read
The chains that become critical next month
🟩 In one line: A near-critical path is any chain with total float below the threshold you set — commonly 10 or 20 working days — and it matters because on a live project the critical path changes almost every month, and the chain at +8 days today is the one that fails you in six weeks. Report the critical path and everything under 20 days float, every update.
👤 Who this is for: Mid-level planners writing the monthly narrative; juniors who report only the zero-float path; seniors deciding where to put management attention. You should know total-float and critical-path-vs-longest-path.
First, let's be honest about why this page exists
Planners report the critical path because that's what the report template asks for. Then the critical path recovers, everyone relaxes, and the project is delayed by a chain nobody was watching — façade procurement, an authority approval, a single long-lead switchgear item — that had 9 days of float and quietly ran out.
The critical path tells you what's late now. The near-critical paths tell you what's going to be late. One is a report; the other is management.
🟨 The standard — what "good" looks like
| Source | What it says (paraphrased) |
|---|---|
| DCMA 14-Point, Metric 12 (Critical Path Test) | Tests whether the network responds correctly — an artificial delay on a critical activity should move completion by the same amount |
| DCMA 14-Point, Metric 12 (Critical Path Length Index, CPLI) | Measures the efficiency of the critical path against remaining time |
| GAO Schedule Assessment Guide, Best Practice 6 (establishing the critical path) and Best Practice 7 (identifying float) | Explicitly requires identification of near-critical paths as well as the critical path |
| AACE RP 49R-06, Identifying the Critical Path | Discusses float thresholds and multiple near-critical paths; recommends analysing more than the zero-float path |
| SCL Protocol 2nd ed., Guidance Part B | Updates should identify the current critical path; changes in the critical path should be explained |
| Typical Gulf client specifications | Often require reporting of all paths with total float below 20 or 30 days |
| PMI Practice Standard for Scheduling, 3rd ed. | Near-critical path identification as part of schedule analysis |
🟢 Rule to remember: set the threshold once, state it in the schedule basis, and report every path under it every month. 20 working days is the default that works on most jobs.
How it actually works
Choosing the threshold. There is no universal number. Match it to your update cycle and project length.
| Project length | Update cycle | Sensible near-critical threshold |
|---|---|---|
| Under 12 months | Weekly / fortnightly | 5–10 working days |
| 12–36 months | Monthly | 15–20 working days |
| Over 36 months | Monthly | 20–30 working days |
| Shutdown / turnaround | Daily or shift | 1–2 shifts |
Rule of thumb: the threshold should be about one to two update cycles' worth of typical slippage. If you're losing 6 days a month, anything under 12–15 days can be critical by the next report.
Two ways to find them in P6.
| Method | How | What you get |
|---|---|---|
| Float threshold filter | Filter: Total Float ≤ 20d, Activity Status ≠ Completed. Group by WBS or by float band | Fast, simple, works everywhere. But it returns activities, not paths — you have to read the chains yourself |
| Multiple float paths | Tools > Schedule > Options > tick Calculate multiple float paths; choose Free Float or Total Float; set number of paths (e.g. 10); specify the end activity | Returns genuine ranked paths in the Float Path and Float Path Order columns — path 1 is the longest path, 2 is the next, and so on |
Multiple float paths settings that matter:
| Setting | Options | Use |
|---|---|---|
| Calculate multiple float paths using | Free Float / Total Float | Free Float gives cleaner, more distinct paths and is the usual choice. Total Float tends to sweep in whole branches |
| Specify the number of paths to calculate | 3–10 | 10 is plenty; more than that slows F9 noticeably on large files |
| Display multiple float paths ending with activity | Completion milestone (or a sectional milestone) | If you leave it at the default project end it may pick an activity you don't expect. Set it explicitly |
Then add columns Float Path and Float Path Order, group by Float Path, and you can read each chain top to bottom.
Float bands for reporting. A simple table in the narrative, every month:
| Band | Meaning | Action |
|---|---|---|
| Negative float | Behind the contractual date | Recovery required; EOT position stated |
| 0 to +5 d | Critical in practice | Weekly management |
| +6 to +20 d | Near-critical | Monitor; named owner; report trend |
| +21 to +60 d | Watch | Review quarterly or on change |
| Over +60 d | Not a concern now | Check it isn't a logic gap or missing constraint |
Reading the trend, not the snapshot. A path at +14 days is only interesting if you know it was +26 last month. Track float on each named path across updates:
| Path | Aug | Sep | Oct | Nov | Trend |
|---|---|---|---|---|---|
| Structure → finishes → handover | 0 | 0 | -4 | -6 | Critical, worsening |
| Façade procurement → installation | +32 | +24 | +15 | +7 | Fastest deteriorating — will be critical next month |
| Substation → energisation → T&C | +19 | +18 | +18 | +17 | Stable, watch |
| External works → landscaping | +48 | +45 | +44 | +41 | No concern |
The façade row is the one to put in front of the PM, even though it isn't critical yet.
Why paths go near-critical. Usually one of: a long-lead procurement item quietly slipping; an approval cycle taking longer than assumed; a path across different calendars where float behaves oddly (multiple-calendars-and-float); or a resource-constrained soft chain nobody is resourcing.
🟥 Where people go wrong
- Reporting only the zero-float path. The board hears "the critical path is on track", and the project is sunk by a chain at +6 days. If your narrative only names one path, it's incomplete.
- Filtering on total float and calling the result "paths". A float filter returns a scattered set of activities across the whole job. You still have to trace which ones form continuous chains. Use multiple float paths if you want actual paths.
- Setting the threshold too low. A 3-day threshold on a monthly cycle catches almost nothing, because typical monthly slippage exceeds it. Match the threshold to your slippage rate.
- Not naming the paths. "Path 3" means nothing to a PM. Name them: "façade path", "energisation path", "lift installation path". Named paths get owners; numbered paths get ignored.
- Ignoring near-critical when assessing a delay claim. An EOT is assessed on the critical path — but if the event pushes a near-critical path past the critical one, the critical path switches and the impact is different from the obvious calculation. Check both.
- Leaving multiple float paths switched on and forgetting. It slows F9 and, on some versions, the Float Path values persist confusingly after logic changes. Recalculate before reading them, every time.
- Not looking at very high float. A path with +180 days of float on a 30-month job is usually not lucky — it's missing logic, a dangle, or an activity with no real successor. High float is a quality signal too.
⚖️ When you're challenged
"The critical path is recovering. Why are you still worried?" "Because the façade path has gone from +32 to +7 in four months. At that rate it's critical before the next report, and it's a procurement chain — once the fabrication slot is lost we can't crash it. That's the one I'd act on this month."
"What threshold are you using and why?" "20 working days, stated in the schedule basis, section 11. We update monthly and typical monthly slippage on this job has been 5 to 8 days, so anything under 20 can be critical within two cycles."
"You've got six critical paths. That can't be right." "There's one critical path at -6 days. There are five near-critical paths between +4 and +18 days, which is normal on a job with parallel zones. Section 4 lists them separately with float and trend."
"The variation only hit a path with 12 days float, so there's no delay." "There's no delay to completion this month, correct — 12 days of float absorbed it. But that float was the project's cushion and it's now gone, and if anything else hits that path we're in negative float immediately. I'm reporting it as a float consumption, not an EOT."
📄 Related pages
- Total float — the measure this page bands
- Critical path vs longest path — what path 1 actually is
- P6 Multiple Float Paths — the P6 mechanics in full
- Multiple calendars and float — why float misreads across calendars
- Slippage and Trend Analysis — reading float across three months
- CPLI and BEI — the indices that summarise this
- Schedule compression — what you do when a near-critical path turns
- Monthly update checklist — where this check sits in the cycle
✏️ Worked example
A hospital in Doha, Update 18, monthly cycle. Multiple float paths run with Free Float, 8 paths, ending at Taking Over.
| Path | Description | Total float | Last month | Change | Owner |
|---|---|---|---|---|---|
| 1 | Ward block structure → MEP → finishes → T&C | -9 d | -3 d | -6 | Construction Manager |
| 2 | Medical gas system procurement → install → validation | +4 d | +21 d | -17 | Procurement Manager |
| 3 | Substation → DEWA-type energisation → functional testing | +11 d | +12 d | -1 | MEP Manager |
| 4 | Operating theatre fit-out specialist package | +16 d | +19 d | -3 | Fit-out Manager |
| 5 | Lift installation → commissioning → inspection | +22 d | +23 d | -1 | MEP Manager |
| 6 | External works → car park → landscaping | +58 d | +60 d | -2 | Civil Manager |
| 7 | Signage and wayfinding | +74 d | +74 d | 0 | — |
| 8 | Landscaping irrigation | +91 d | +91 d | 0 | — |
What the narrative said: the critical path is path 1 at -9 days, driven by ward block MEP first fix. But the item requiring action this month is path 2 — 17 days of float lost in one period because the medical gas supplier's approval cycle ran long. At that rate it becomes the critical path within the next update, and it is a procurement chain with a 14-week fabrication slot that cannot be compressed.
Management focus shifted to path 2. Approval was expedited, the fabrication slot was held, and by Update 20 path 2 was back to +12 days. Path 1 was recovered separately by adding a second MEP crew. Neither would have been caught by reporting only the zero-float path.
📖 References
- DCMA 14-Point Assessment, Metrics 7 and 12
- GAO, Schedule Assessment Guide (GAO-16-89G), Best Practices 6 and 7
- AACE RP 49R-06, Identifying the Critical Path
- SCL Delay and Disruption Protocol, 2nd ed. (2017), Part B Guidance
- PMI, Practice Standard for Scheduling, 3rd ed.
- Oracle, P6 Professional User Guide — Scheduling Options, multiple float paths
From the field
Experience from working planners. Unreviewed — read it as experience, not guidance.
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