P6 Multiple Float Paths
Last reviewed 16 September 20267 min read
Second and third critical paths — the setting that turns "what's near-critical?" from a guess into a list
🟩 In one line: Multiple Float Paths (Tools → Schedule → Options → Advanced) makes P6 trace the driving chain to a chosen end activity, then the next most critical chain, and the next, and stamps each activity with a Float Path number and its order in that path; set to Free Float, 5–10 paths, ending at the contractual completion milestone, it is how the top-three near-critical table in every narrative is built.
👤 Who this is for: J/M. Prerequisites: near-critical-paths, critical-path-vs-longest-path, scheduling-options.
First, let's be honest about why this page exists
"Sort by Total Float ascending" is what most planners do to find the second critical path. On a single-calendar job it roughly works. On a job with a 6-day site calendar, a 7-day curing calendar and a 24-hour shutdown calendar, activities on the same chain show different float values, the sort scatters them, and the "second path" in the narrative is a list of unrelated activities that happen to share a float number.
Multiple Float Paths traces logic, not float values. It is the only P6 feature that produces an actual chain, and it is switched off by default.
🟨 The standard — what "good" looks like
| Source | What it asks for (paraphrased) | What the setting delivers |
|---|---|---|
| GAO Schedule Assessment Guide, BP 6 | Confirm the critical path is valid; identify near-critical paths | Path 1 = longest path; Paths 2–n = near-critical chains |
| DCMA 14-Point, Metric 12 (Critical Path Test) | The critical path responds as a continuous chain to a pushed activity | Path 1 must be continuous from data date to completion |
| DCMA Metric 6 (High Float) | ≤ 5% of incomplete tasks with TF > 44 days | Paths beyond the near-critical threshold are where high float lives; the setting shows where the threshold falls |
| AACE RP 49R-06 (Identifying the Critical Path) | Longest path method; secondary paths identified | Same |
| PMI Practice Standard for Scheduling, 2nd ed. | Near-critical paths monitored | Same |
| Convention (scheduling-options; near-critical-paths) | Free Float; 5–10 paths; end at the contractual completion milestone; top 2–3 paths in every narrative with float trend | This page's settings |
🟢 Rule: Multiple Float Paths on Free Float, 5–10 paths, ending at the contractual completion milestone; grouped by Float Path in a dedicated layout; top three paths reported every month with their float at the milestone and the trend from the previous three updates.
How it actually works
1. The settings
| Field (Tools → Schedule → Options → Advanced tab) | Value | Why |
|---|---|---|
| Calculate multiple float paths | Ticked | Off by default — on every project, every schedule run |
| Calculate multiple paths using | Free Float | Traces the driving relationships (zero relationship float) back from the end activity — a genuine chain. Total Float groups activities by float value and mixes paths on multi-calendar jobs |
| Display multiple float paths ending with activity | Contractual completion milestone (e.g. MIL-CC-010) | Paths to an interim key date are run separately when that date is the question |
| Specify the number of paths to calculate | 5 (buildings); 10 (fast-track, shutdowns, EPC) | More paths, slower schedule; 5 covers the near-critical threshold on most jobs |
The paths are calculated during F9 and stored until the next F9. Change the end activity, reschedule, and the columns repopulate.
2. Reading the result
| Column | Meaning |
|---|---|
| Float Path | 1 = the most critical driving chain to the end activity (equals the longest path when the end activity is the completion milestone); 2 = the next chain, found by removing Path 1 and tracing again; and so on |
| Float Path Order | Sequence of the activity within its path, from the end activity backwards |
| (blank) | Activity is not on any of the n paths calculated |
Layout 04b Float Paths: filter Type ≠ LOE/WBS Summary and not Completed; Group & Sort by Float Path, then sort by Float Path Order; columns ID, Name, Cal, TF, Float Path, Float Path Order, Early Start, Early Finish. Each group reads top to bottom as a chain.
3. From paths to the narrative table
| Path | Reported as | Float at the milestone | Driver (first activity behind DD) | Trend (last 3 updates) |
|---|---|---|---|---|
| 1 | Written as an activity sequence with IDs (schedule-narrative) | 0 (or negative) | — | — |
| 2 | One-line description + IDs | e.g. 8 | e.g. Façade L3 brackets | 21 → 15 → 8 |
| 3 | Same | e.g. 5 | e.g. MEP first fix L6 | 18 → 12 → 5 |
Float is read at the contractual completion milestone — the path's end — never mid-path (multiple-calendars-and-float). The trend is the point of the table: a Path 3 losing 6 days a month is next month's Path 1.
4. Where else it is used
| Use | How |
|---|---|
| Compression / recovery | Re-run F9 after each lever; the path that moves to Float Path 1 is the next target (schedule-compression) |
| TIA | Compare Float Path 1 before and after the fragnet; a fragnet that creates a new Path 1 is the delay |
| Review of a received file | Path 1 continuous from DD to completion with no constraint or open end holding it = DCMA Metric 12 pass |
| Interim key dates | Set the end activity to the key-date milestone; run; report its own top 3 |
5. Limits
- Only one end activity per run. Several key dates = several runs; note which run each table came from.
- Paths trace driving logic. A path held by a constraint rather than a predecessor stops at the constraint — which is the diagnostic, not a fault.
- Completed activities appear in paths with Float Path Order values; filter them out for the forward-looking table.
- The Free Float option ignores activities with relationship float > 0 into the path, so a near-critical chain joined by a 1-day non-driving link may appear as a separate path. That is correct; report it as such.
🟥 Where people go wrong
- Setting left off. The narrative's "second critical path" is a float sort. Ticked in the SBM's scheduling-options screenshot, checked on every received file.
- Total Float instead of Free Float. On a multi-calendar job the paths interleave and Path 2 contains activities from three chains. Free Float traces links; Total Float groups numbers.
- End activity left as the last activity in the file. On many schedules that is a closeout or O&M manual activity with 60 days of float. End at the contractual completion milestone, always.
- Float read mid-path. A curing activity on the 7-day calendar shows 3 days; the chain's float at the milestone is 0. Read at the end.
- Paths reported once, never trended. A single month's Path 3 at 5 days is a fact; three months of 18 → 12 → 5 is a warning. Table carries the previous three values.
- Ten paths on a 400-activity schedule. Paths 6–10 have 40+ days of float and clutter the layout. Five is enough until the job is fast-track.
⚖️ When you're challenged
"Just sort by float. Why the extra setting?" Float sort puts a 7-day-calendar curing activity and a 6-day blockwork activity on the same chain 3 days apart, and puts two unrelated chains together because they share a number. Float Path traces the links, so what I report as Path 2 is an actual sequence of work — that's what the site can act on.
"Your Path 2 has 8 days float. Why are you worried?" It had 21 in June and 15 in July. At that rate it's critical before the structure recovers, and it ends in the façade — a trade with a 6-week mobilisation. The number today isn't the story; the direction is.
📄 Related pages
- Near-Critical Paths — why the second and third paths matter
- Critical path vs longest path — Path 1 = longest path
- Multiple calendars and float — why float sort fails across calendars
- Scheduling options — the Advanced tab in context
- Schedule compression — the re-run after every lever
- Slippage and Trend Analysis — the trend column
- P6 Layouts and Filters — layout 04b
✏️ Worked example
Doha office tower, Update 09, DD 1 October, contract completion 31 March, 5 paths on Free Float ending at MIL-CC-010:
| Float Path | Chain (first activity behind DD → milestone), IDs abbreviated | TF at milestone | Trend Jul → Aug → Sep → Oct | Note |
|---|---|---|---|---|
| 1 | STR-L14-SLB → STR-L15 … L22 → FAC-L18-INST → FIN-L18 … → TC-SYS → HO → MIL-CC-010 | −40 | −18 → −25 → −32 → −40 | Structure cycle 9 vs 7 days |
| 2 | ELE-TRF-DEL (Employer transformer) → ELE-MV-ENERG → TC-SYS → MIL-CC-010 | −25 | — → — → −15 → −25 | Employer delay; claim C-118 |
| 3 | FAC-L03-BRKT → FAC-L04 … → FIN-L10 → … | 8 | 21 → 15 → 12 → 8 | Held by structure release; becomes Path 1 after recovery |
| 4 | MEP-FF-L06 → MEP-FF-L07 … → FIN-L06 → … | 5 | 18 → 12 → 9 → 5 | Finishing sub not yet mobilised |
| 5 | LFT-INST-01 → LFT-TEST → HO | 29 | 33 → 30 → 29 → 29 | Stable |
Table went into the narrative as the top-3 near-critical paths (Paths 2, 3, 4 — Path 1 is the critical path written in full above it, Path 5 is beyond the 15-day threshold). Run time on 2,860 activities: 11 seconds.
📖 References
- GAO Schedule Assessment Guide (GAO-16-89G), Best Practice 6
- DCMA 14-Point Schedule Assessment, Metrics 6, 12
- AACE International RP 49R-06, Identifying the Critical Path
- PMI Practice Standard for Scheduling, 2nd ed.
- Oracle Primavera P6 Professional User Guide — Schedule Options → Advanced (Multiple Float Paths); Float Path and Float Path Order fields (field labels as in P6 Professional v20; earlier versions differ)
From the field
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