Chapter 27 — Exercises

Work these with a pencil, a calculator, and the canonical Northgate and Willow Street numbers in front of you. Several produce artifacts that belong directly in your Willow Street Project Notebook. Selected answers appear in Appendix J.

Difficulty legend: ⭐ basic · ⭐⭐ applied · ⭐⭐⭐ advanced judgment · ⭐⭐⭐⭐ research and extension

Canonical figures you will need:

The eight constraint categories (you will use these constantly): design information · submittals and approvals · material on site · labor available · equipment available · prerequisite work complete · permits and inspections · space and access.

Part A — Conceptual Understanding ⭐

A1. Explain, in your own words and in under 100 words, the difference between what a CPM schedule answers and what a constraint log answers. Give one specific question each one can answer that the other cannot.

A2. Write out SHOULD → CAN → WILL → DID and name the planning level, the horizon, the owner, and the artifact that goes with each word.

A3. Recite the eight constraint categories from memory. Then, for each one, name the person on the Northgate job most likely to own its removal.

A4. Why is percent plan complete measured on a binary basis with no partial credit? Give the reason from the receiving trade's point of view, not from the measuring party's.

A5. Define workable backlog and explain what happens to a project that runs a constraint screen without maintaining one.

A6. What does it mean to say that "the last planner" is the person who makes the final assignment before work is executed? On Northgate, name three people who plan and one person, for a given crew, who is the last planner.

A7. Name the eight categories of waste as they apply to a construction site, and give a one-line construction example of each that is not one of the Northgate examples in §27.2.

A8. Explain why construction is not a factory, using the three structural differences from §27.2. Then state which of the three is the root of most lean adoption failures, and why.

A9. What is a first-run study, and what is the minimum number of repetitions that makes one worth doing? Justify your number.

A10. In one sentence each, state what takt time planning, 5S, A3 problem solving, choosing by advantages, and target value design are for.

Part B — Applied Analysis ⭐⭐

B1. A project manager tells you: "Our PPC has been 91% every week for four months. We've mastered this." List the three questions you ask before you believe them, and say what answer to each would change your mind.

B2. Look at the Northgate reason-code Pareto in the chapter hook. Suppose a general contractor's Pareto instead looked like this: weather 31, labor 24, equipment 18, everything else 13. What would you conclude about (a) the type of project, (b) the quality of the constraint screening, and (c) where you would look first for a countermeasure?

B3. A subcontractor's foreman says in a pull-planning session that his scope will take 30 work days. His bid duration was 30 work days. When you ask what would have to be true for it to take 24, he says "nothing, it's 30." What are three plausible explanations for that answer, and how would you tell them apart?

B4. Kestrel's own PPC was below the job average in the first month, and Ray published it to fourteen subcontractors. Identify two specific ways that decision could have backfired, and describe the conditions under which you would not publish it.

B5. You inherit a job that runs a weekly work plan meeting with excellent attendance and no constraint log. PPC has never been measured. In one page, describe what you expect to find when you measure it for the first time, and why.

B6. A superintendent argues that the six-week look-ahead should be a two-week look-ahead because "six weeks out is fiction anyway." Evaluate the argument. Under what conditions is he right? Under what conditions is he badly wrong, and what evidence from his own job would settle it?

B7. The Northgate enclosure pull plan produced a sequence eight work days shorter than the office CPM. Wei Chen was an excellent scheduler and had all the same drawings. Explain precisely what information the foremen had that Wei did not, and why no amount of additional scheduling effort would have produced it.

B8. Rivermont Elementary #12's PPC rose from 62% to 89% while the job fell 17 calendar days behind. Explain the mechanism to someone who has never heard of the Last Planner System, in under 150 words, without using the word "gaming."

Part C — Calculations and Deliverables ⭐⭐–⭐⭐⭐

C1. Chain reliability. A sequence of trades hands off in a chain. Compute the probability that the last handoff is on time for each case, and show the arithmetic:

Then answer: for case (c), what per-trade reliability would be required to reach a 60% chance the chain holds? (Hint: solve for r in r⁸ = 0.60.)

C2. PPC arithmetic. A weekly work plan produces the following over eight weeks:

Compute PPC for each week and for the whole period. Then compute completed commitments per week for weeks 1–4 versus weeks 5–8. Write two sentences: one describing what PPC says about this team, and one describing what the raw counts say.

C3. Takt calculation. A five-story hotel has 12 similar guest-room zones per floor for a total of 60 zones. The trade train has 7 wagons. The available window is 24 weeks (120 work days).

(a) How many takts does the train require? (b) What is the calculated takt time? (c) What takt do you adopt, and why? (d) What is the resulting duration and buffer? (e) One trade tells you it cannot finish a zone in the takt you adopted. Name three things you can do about it, and rank them.

C4. Build a constraint log. Take any six activities from your Willow Street CPM (Chapter 14) scheduled in a six-week window. For each one, work all eight constraint categories and produce a log with columns for activity, constraint, category, named owner, need-by date, and status. Back-calculate every need-by date from the activity start, not from convenience. Then screen: ready or not ready.

C5. The money check, your version. Suppose Willow Street measures a slip rate of 0.6 calendar days per week over an eight-week baseline, with 18 weeks remaining to substantial completion.

(a) Project the total slip at that rate. (b) Determine Willow Street's extended general-conditions daily rate. (You will need to estimate the general-conditions budget for a $6.8M, 425-day job — 8% to 12% of contract value is a defensible range; state your assumption.) (c) Compute the exposure with and without liquidated damages at $1,200/CD. (d) Price a make-ready effort: one person, 12 hours a week, 18 weeks, at a fully burdened rate you justify. (e) How many calendar days must the effort save to break even on general conditions alone?

C6. Re-cut a look-ahead. Take the four largest activities in your Willow Street six-week window and break each one into area-based pieces small enough that one crew could complete one in a week. State how many lines you started with and how many you ended with. Then answer: which of your original four activities was impossible to verify as "complete" by walking the building, and why?

C7. Reason-code Pareto. You have run six weeks of measurement on a job and collected 74 misses:

prerequisite work 9 · material 22 · information 6 · labor 11 · space and access 4 · inspection 3 · submittals 15 · owner/design change 2 · weather 1 · equipment 1

(a) Build the Pareto and compute cumulative percentages. (b) Identify the two categories that account for the most misses and name the specific management system that owns each. (c) Write the two countermeasures you would present on Friday, each with a named owner and a date. (d) This job's profile is very different from Northgate's. What does that difference tell you about the two projects?

Part D — Judgment and Ethics ⭐⭐⭐

D1. You are a project manager with a live delay exposure. Your PPC log contains twelve information-related misses over six weeks, most traceable to a single unanswered RFI from the architect. Your attorney wants the log. Argue both sides, then decide — and state what you would say to the fourteen foremen who created that data, either way.

D2. A subcontractor's project manager will not permit his foreman to decline a commitment in the weekly meeting. The foreman is therefore promising things he knows he cannot do, in public, week after week. You have watched him do it for two months. What do you do, in what order, and what is the line you will not cross in doing it?

D3. Your general superintendent proposes that any subcontractor whose PPC falls below 60% for three consecutive weeks be put on notice of default under the subcontract. Evaluate this proposal on three grounds: whether it would improve the job, whether the data would survive it, and whether it is contractually sound.

D4. A trade partner tells you privately that his bid duration for a scope contains eight days of buffer, and asks you not to tell anyone. Is that information you are entitled to? What do you do with it? What would you have to change about how you run the job for him to be willing to give up those days openly?

D5. Your company mandates the Last Planner System across all projects, funds nothing, changes no subcontract terms, and asks for monthly PPC reporting. You are a project manager and you can see exactly where this goes. Write the memo you send back — 300 words, to a vice president, in a company where "that won't work" is not a well-received sentence.

Part M — Mixed and Interleaved Practice ⭐⭐–⭐⭐⭐

M1. Ch. 27 + Ch. 14 + Ch. 29. Take six activities from your Willow Street CPM. Run the forward and backward pass to establish early and late dates and total float (Chapter 14). Then run the eight-category constraint screen on the same six. Produce a two-column comparison: scheduled to start versus actually ready to start. Where the two disagree, state what the difference is worth in float consumed, and what you would put in a schedule narrative (Chapter 29).

M2. Ch. 27 + Ch. 25. Take your Willow Street submittal log and RFI log. For every open item, determine which look-ahead activity it gates and back-calculate the need-by date from that activity's start. Re-sort both logs by need-by date rather than by number. How many items move from the middle of the list to the top? That reordering is the single highest-value hour in this exercise set.

M3. Ch. 27 + Ch. 16 + Ch. 18. Pick one long-lead item on Willow Street. Trace it through three chapters: the buyout decision that set its lead time (Chapter 16), the site logistics that determine where it lands and how far it gets carried (Chapter 18), and the constraint-log entry that makes it visible six weeks out. Which of the three would you fix first if you could only fix one?

M4. Ch. 27 + Ch. 19 + Ch. 20. Construct a scenario in which an unscreened weekly work plan produces trade stacking, and the trade stacking produces a measurable labor productivity loss. Use the man-hour and productivity concepts from Chapter 20 to put a dollar figure on it. State every assumption you make and mark the ones you could not defend to an opposing scheduling expert.

M5. Ch. 27 + Ch. 24. Take the three findings from the Northgate scaffold near-miss investigation. For each one, state whether a functioning six-week constraint screen would have made it less likely, more likely, or made no difference — and explain the mechanism. Be honest where the answer is "no difference."

M6. Ch. 27 + Ch. 3 + Ch. 11. Compare how the Last Planner System would actually run on three delivery methods: hard-bid design-bid-build (Willow Street), CM at Risk with a GMP (Northgate), and integrated project delivery (Chapter 3). For each, identify who pays for the system, who captures the benefit, and what one contract change would most improve the alignment. Then connect target value design back to the preconstruction services described in Chapter 11.

Part E — Research and Extension ⭐⭐⭐⭐

E1. Find the proceedings of the International Group for Lean Construction, which are published openly. Locate two papers on percent plan complete or the Last Planner System from different years and different countries. Compare how each one defines a "commitment" and how each computes PPC. Then write 400 words on why cross-project PPC benchmarking is harder than practitioners generally assume, using what you found. Do not accept any number you cannot trace to a stated method.

E2. Attend or arrange to observe a real weekly work plan or pull-planning session — through an employer, an internship, a student chapter, or a local contractor. Record, without judgment: how many people attended, how many of them controlled a crew, how many commitments were made, whether misses were scored, whether reasons were categorized, and whether anyone in the room could tell you how many constraints were closed last week. Then evaluate the session against the four conditions in §27.9 and write one page on which of the four is weakest and what it would take to fix it.

E3. Take a real jurisdiction — your own — and build the "permits and inspections" branch of a constraint log for a mid-size commercial interior project. For each inspection type, find the actual required notice period, the prerequisites for calling it, and what happens when it fails. Note where the requirements are published and where they are only known by asking. Then state how far ahead your look-ahead would have to run for that jurisdiction's inspection lead times, and compare it to the standard six weeks.