Chapter 14 — Key Takeaways

A one-page reference card. Keep it where you can find it before your next schedule meeting.

Key Takeaways

  • The critical path is calculated, not designated. It is the longest path through the network. Nobody chooses it, and it moves the moment a duration or a relationship changes.
  • Float belongs to a path, not to an activity. Four days of float on a five-activity chain is four days total — not four days each. It is spent exactly once, by whoever gets to it first.
  • Total float protects the project; free float protects your successor. An activity with total float and no free float is spending somebody else's room. That difference — interfering float — is where most schedule disputes actually live.
  • A duration and a cost come from the same two numbers: quantity and production rate. Duration = quantity ÷ (production rate × crews). This is why the schedule and the budget are one conversation and why $10,650 a calendar day is a schedule number on Northgate.
  • A schedule does four jobs — prove the work fits, tell people what to do next, price change, and prove entitlement. Most baselines are built for the first and fail at the other three.
  • Label every duration WD or CD. Contract time, liquidated damages, and extended general conditions run on calendar days. Crew productivity runs on work days. Fifteen work days is twenty-one calendar days of general-conditions burn.
  • Weather goes in the calendar, not in an activity. A contingency bar in the middle of a network is a lie the schedule tells about itself.
  • Ask of every relationship: "what physically prevents this from starting?" If the honest answer is "nothing, we'd just rather not," it is soft logic — write that in the activity note. That note is worth more in a claim than the relationship is.
  • A small float number on a chain that ends at an unbuyable constraint is not comfort. A mill slot, a permit, a utility cut-in, or an owner-furnished delivery cannot be accelerated with a second crew on a Saturday. Manage those chains as critical whatever the float column says.
  • Acceleration is capped by the float on the parallel path. Buying six days of compression on a path whose neighbor has four days of float delivers four days. Run the network before you write the check.
  • The software calculates; it does not think. Every catastrophically wrong schedule was arithmetically perfect.

Action Items — do these on your job this week

  1. Filter your current schedule to total float = 0 and print it. Read the critical path out loud as a narrative. Listen for the sentence that does not make physical sense.
  2. Count your open ends. Activities with no predecessor and activities with no successor. There should be exactly one of each.
  3. Count your constraints and list them with a written reason. Delete every one nobody can justify. Confirm you have zero mandatory constraints.
  4. Run the critical path test. Add 100 days to one critical activity on a copy of the file. The finish must move exactly 100 days. If it moves less, find out what is absorbing the delay.
  5. Find every chain that ends at something you cannot buy back — long-lead fabrication, a permit, an owner-furnished item, a utility company outage window. Add them to your critical report regardless of float.
  6. Compute your daily exposure. Extended general conditions per calendar day plus liquidated damages per calendar day. Write the number on the whiteboard. Every schedule conversation gets easier once everyone in the room knows it.
  7. Report float consumption in this month's OAC minutes, by name and by number: "This change consumes nine of the eleven days on the imaging suite path." Do it every month, starting now.

Common Mistakes and the Fix

Mistake What it costs The fix
Reporting only zero-float activities The near-critical chain that becomes critical in four days is invisible until it stops the job Manage everything at or below a stated float threshold — and every chain with an unbuyable downstream constraint
Activities 40–120 days long Progress becomes unverifiable; every activity sits at 90 percent complete for six weeks Cap field activities at ~15–20 work days; one party, one work type, one area
A lag standing in for real work Ten days with no owner, no resource, and no way to report status Convert any lag over 5 days into a real activity or document the reason
Negative lags (FS−10) Unpredictable behavior when durations change; indefensible in a claim Model overlap as SS + positive lag
Constraint on the finish milestone Every path in the schedule gains phantom float equal to the offset — silently Audit constraints first, every month; keep the finish milestone tied to the contract date
Confusing work days with calendar days Extended general conditions understated by ~40 percent Label every duration; run 5-day, 7-day, and weather calendars
Padding every duration 10–15 percent Contingency you cannot see, manage, allocate, or report — and it gets spent anyway Honest durations plus a named, visible project buffer that you report monthly
Soft logic modeled as hard A critical path that collapses under cross-examination, taking the credible parts of your claim with it Tag every relationship hard / soft / resource in the activity notes, contemporaneously
Accepting a subcontractor schedule as a PDF No logic to check, no float to verify, no ability to insert a change and recalculate Ask for the file. If the answer is "PDF only," you have your answer about whether a network exists
Buying acceleration without re-running the network Paying for six days and receiving four Recalculate first; find the knee where a parallel path takes over

Decision Framework

When somebody says "there's float there, just absorb it"

  1. Total or free? If the float is total but not free, you are spending a downstream party's room. Say whose, out loud, in the meeting.
  2. How much is on the path, and how much would this consume? Get the number, not an adjective.
  3. What is downstream? If the chain ends at a mill slot, a permit, an inspection window, a utility outage, or an owner-furnished delivery, the float is not spendable — it is protection against something you cannot fix later.
  4. What is a day worth here? Extended general conditions + liquidated damages, per calendar day. Multiply.
  5. Who owns the float under this contract? Find the clause. If the contract is silent, say so in writing today, before it matters.
  6. Write it in the minutes either way. The contractor who has reported float consumption every month for fourteen months is in a completely different position from the one who discovers the concept in month sixteen.

The thirty-minute schedule review, in order

  1. Ask for the file, not the PDF.
  2. Six numbers: activity count and average duration · activities with no predecessor · activities with no successor · constrained activities (and zero mandatory) · activities with very high float · percentage of activities critical.
  3. Logic quality: relationship-type mix · every lag over 5 days · any negative lag · out-of-sequence work in an update.
  4. Filter to zero float, print the critical path, and narrate it out loud. Listen for the break in the story.
  5. Run the critical path test — 100 days added to a critical activity must move the finish 100 days.
  6. Then, and only then, form an opinion about the durations. The checks find defects. Judgment finds lies.