Chapter 39 — Quiz

(b) the Simultaneity Trap. The value only appears if everybody on a fragmented project adopts at the same time, and any one holdout collapses the dataset — silently, which is the dangerous part. There is a Displaced Burden element too (the scanning falls on people who get nothing back), but the defining failure is that the GC bought a system whose data depends on parties it does not employ and cannot direct.

(c). §39.9.2 is explicit: if you cannot name the person and the decision, kill it regardless of the total. A 15 out of 20 with a D of 1 is a very well-structured way to produce information nobody will act on. The chapter's phrasing is worth memorizing: a 17 out of 20 with a D of 1 is a dashboard with good manners.

(b) capture is a day; modeling is a week. §39.2.4 puts registration and processing at 0.5–2× the capture time and scan-to-BIM modeling at 5–15×. The scan is fast and cheap. Turning billions of points into a modeled beam, wall, and duct somebody can work with is skilled labor, and it is where the money actually goes.

(b). Stick-built value $1,845,000; total prefabricated cost $1,820,000; net −$25,000, a 1.4% saving. Kestrel traded expensive field labor for cheaper shop labor and then spent almost all of the difference on coordination ($74,000), hanger and attachment engineering ($38,000), and transport and rigging ($96,000). If you sell a prefabrication program on cost reduction, you will be wrong and you will not get a second program.

(b). Site labor fell from 11,400 MH to 4,600 MH, and 4,300 MH of shop labor appeared. Total across both locations: 11,400 → 8,900, a 2,500 MH net gain, or 22%. The 6,800 hours are the safety and labor-market story — they moved from a lift in a corridor to a bench in a shop — and they are enormous, but they are not a cost saving. An honest program is built on the 2,500.

(c). The drone-versus-survey spread of 480 CY is more than a third of the disputed 1,290 CY, so the drone is not a defensible basis for withholding money. What it bought was the $3,100 decision: cheap evidence that the claim was probably high by a material amount, which is exactly enough to justify the survey you pay on. The drone is a screen, not a scale.

(c) zero. Foundations completed July 3, Year 1; steel erection was scheduled to start August 4, Year 1. There was float between them, so the nine days restored float rather than moving substantial completion. What the seven days were worth: $26,460 in labor (7 WD × 7-person crew × 10 hr × $54/MH), reduced form time, preserved float that mattered enormously five weeks later when the steel delay arrived — and, on two cold placements, a disaster avoided. Always run the float test before you book a schedule saving.

(d). The layout crew reported to the superintendent, the model was owned by VDC, and there was no named person, no standing time, and no deadline for producing tomorrow's layout file. So the crew pulled tape, because tape is always available and never late. The fix cost nothing: one named person, a standing Wednesday deadline, and two lines on the coordination agenda. Utilization went from occasional to daily inside a month. The technology was never the problem.

(a) rung 1. Roof and floor trusses, wall panels, rebar cages, architectural precast, and unitized curtain wall are all prefabrication. Northgate's 21,000 SF of architectural precast and 38,500 SF of unitized curtain wall are prefabricated components and nobody in the trailer calls them that. Rung 1 is universal and uncontroversial; rung 3 is where the argument actually is.

(c). Accountability does not transfer to a tool. This is a contract point, not a philosophical one. The framing the chapter recommends is that these systems are an analyst who is fast, tireless, cheap, extremely good at volume, occasionally confidently wrong, and requires supervision — and you would not let a new analyst issue a submittal review without checking it. Read the tool's terms of service with the attention you would give an indemnity clause, because that is what you are reading.

(b). It has "almost nothing to do with the elegance of the technology." The earthwork contractor buys the system, operates the machine, and captures the production rate improvement directly. Compare that with materials tracking, where the GC pays and fourteen subcontractors' suppliers do the work. The technologies that succeed in construction are overwhelmingly the ones where one party can adopt alone and capture the benefit alone. A second, real reason: it arrives already inside the dozer, so there is almost nothing to adopt.

False. The devices worked and the dashboard was genuinely beautiful. It was killed because in four months, 180 devices, and 2,100 logged proximity events, nothing changed — no work plan, no job hazard analysis, no route, no gate, no laydown area, no crew size. It failed on decision linkage, not on function. Bea Salgado did not need a count of proximity events; she needed a route change, and no device produces a route change.

True. $520 amortized camera and mount, $6,840 of hosting and plan-linking subscription over 19 months, and about 104 hours of Dani Okonkwo's time at roughly $6,240 burdened. That is 0.029% of a $47,500,000 contract, and the record was used substantively eleven times — once ending a disputed above-ceiling conversation that had already burned about six thousand dollars of three people's time.

False. It removed 6,800 man-hours from the site and added 4,300 in a shop. Total labor fell from 11,400 MH to 8,900 MH — a 2,500 MH reduction, or 22%. Confusing "removed from the site" with "saved" is the single most common overstatement in prefabrication business cases.

False, and this is the failure mode that gets people. One badly placed control point does not add noise — it tilts the whole surface, producing a smooth, confident, professional-looking, completely wrong volume. It does not look like an error. That is precisely why it survives review.

True, and the conditions typically include all of: the owner's specific written consent, evidence of insurance covering the material where it sits, evidence that title has passed, segregation and marking of the material, and sometimes a bond. The specific requirements vary by contract form and by jurisdiction, and public payment provisions are frequently more restrictive and set by statute or standard form rather than negotiable. If the owner declines, you are financing your subcontractor's shop inventory at your own carrying cost — which is a cash-flow event, not a rounding error, on a program with a million-plus dollars of racks under construction.

False. The bench-height argument is real and it is hazard elimination, which sits at the top of the hierarchy of controls. But a shop is not automatically safe; it has its own hazards. If your subcontractor's shop safety program is weaker than your site program, you have moved risk rather than removed it. Ask to see the shop's program before you send eleven hundred man-hours into it. And note what prefabrication creates: setting a two-thousand-pound assembled rack in a partially built corridor is a suspended-load and struck-by operation, fifty-nine times over.

1. What problem does it solve? Name the decision or the cost — not "visibility," not "insight."
2. What does it cost, all in? License, hardware, training, and the internal hours nobody puts in the proposal, over three years, with the renewal price.
3. What does it return, and to whom? In dollars, days, or man-hours, landing on a named party.
4. What does it break? Workflow, contract, relationship, liability.
5. What has to be true here before it works at all? Including who owns it on a Tuesday when the champion is on vacation.

"A stop, not a discount" means you do not proceed with a lower expectation when a gate question has no answer. An unanswered gate is not a risk you have priced; it is a risk you have not identified. The temptation is always to say "we'll figure that out during the pilot," and questions 4 and 5 are the ones that get deferred that way — which is exactly why they account for most of the money that gets wasted.

The loop is: coordinated model → work installed → scan → deviation map → correction back into the model → next installation. Its whole value is that it catches divergence while the correction is still cheap — in the model, with lead time, before the trades stacked behind it have committed. On Northgate, one bay found before MEP was hung cost about $2,100 to fix; the same condition found after duct was hung would have cost about $18,400 plus three days of sequence.

If the gap between "installed" and "compared" is six weeks, everything downstream has already been built on the wrong condition, and there is no lead time left to use. At that point you have produced an as-built record, which has real value at closeout, but you have not produced a control. Same scan, same cost, entirely different product.

Removes work: machine control (the grade checker no longer walks in front of the blade); a rack assembled at a bench instead of overhead on a lift; equipment telematics (the machine reports itself; nobody types); current drawings on a device (the crew stops building off a superseded sheet); a demolition robot in a hazardous space.

Moves work: a system where a foreman types installed quantities for twenty minutes at the end of a ten-hour day so the office can read a chart; a gate-scanning protocol imposed on suppliers who get nothing back; any subcontractor data-entry requirement whose only consumer is upstream.

The test, in one question: does the person doing the additional work get anything back from it, on their own timescale? If a foreman enters a number and sees a same-day productivity figure he can act on tomorrow, you have changed where existing work lands. If he enters a number and the output goes to a monthly report the office reads, you have created a burden, and it will decay — usually in about six weeks.

Both are sold with the same vocabulary. Being able to tell them apart in four questions is, the chapter argues, the single most valuable skill in it.

Before anything goes on a belt: say exactly what is collected, say exactly who can see it, say exactly what it will and will not be used for, put it in writing, and put it in the subcontract. (That is five; four of them are the minimum.)

The credibility commitment is this: commit in writing that the data will not be used in discipline or in a termination decision — and then honor that the first time it would be convenient not to. If you cannot make that commitment, do not deploy the technology.

Three complications you must not skip. A location-reporting device reports location all day, including breaks and the restroom, and someone will eventually look at that data for a reason it was not deployed for. Most of the people on your site work for another employer, so you are proposing to monitor another employer's employees, which is a labor and employment question that varies enormously by jurisdiction and by collective bargaining agreement — take it to counsel before deployment, not after. And biometric and location data may be separately regulated where you work; those laws vary widely and change.

The practical argument closes it: a workforce that believes a device is a surveillance tool will defeat it, and will be right to distrust you if you were not straight about it. You will have traded a functioning safety culture for a dashboard.

$5,150/CD, for a total of $15,450.

Liquidated damages are only owed if you finish late. On a job projected to finish on time there are no LDs to avoid — there is only extended general-conditions burn you stop paying. Applying the full $10,650 would be claiming credit for avoiding a penalty that was never going to be assessed.

The $10,650 rate is the right one when you are valuing days on a job that is already projected late and the days buy you back out of an exposure you are actually facing — which is exactly how the steel-delay acceleration analysis was framed. Same project, same two rates, and the question of which one applies is answered by the schedule, not by preference. Check whether the rate you are applying is a cost you are actually incurring.

(i) Fund it. Kestrel installs it alone, Kestrel captures the benefit, nobody types anything (the instrument reports itself), and D is unusually strong: a named threshold triggers a named action by a named person — stop the operation, adjust the method, notify the clinic. It is also, and this is the point, evidence. A continuous record on a property line twenty feet from a clinic that sees patients five days a week is Chapter 26's documentation logic applied to a physical quantity, and it is worth far more than $19,000 the first time somebody next door claims damage.

(ii) Kill it on the gate. A=4 and B=4 are fine; C=3 is acceptable. D=1 ends it. A project executive with fourteen jobs already knows which three are in trouble. Worse, the score is computed from data whose quality varies by project — a job whose schedule has not been meaningfully updated in six weeks reports green, and those are the jobs you actually needed to find. Killing it on the gate means the argument is arithmetic rather than a verdict on the person who proposed it.

(iii) Kill it, or narrow it to what you control. B=1 is the Simultaneity Trap in its purest form: the value requires suppliers who have no contract with you and no reason to stop at a gate podium. The salvageable version is the one §39.7.3 describes — adopt it for your own property: your gang boxes, your tools, your yard, your owned material. That version has a completely different score because the party doing the work and the party benefiting are the same company.

(a) Site man-hours removed:

Stick-built site labor = 380 LF × 9.66 MH/LF = 3,670.8 MH Prefabricated site labor = 380 LF × 3.90 MH/LF = 1,482.0 MH Removed from the site = 2,188.8 MH

(b) Net labor across both locations:

Shop labor = 380 LF × 3.64 MH/LF = 1,383.2 MH Total prefabricated = 1,482.0 + 1,383.2 = 2,865.2 MH Net saving = 3,670.8 − 2,865.2 = 805.6 MH As a percentage = 805.6 ÷ 3,670.8 = 21.9%, which is the same 22% Northgate produced

(c) It fails gate question 5 — what has to be true here before it works at all. A multi-trade rack program requires a real design freeze, and a corridor with two unselected pieces of owner-furnished equipment does not have one. This is the CO #14 problem exactly: an equipment vendor selected after the money was set, landing on a fabrication run somebody has already started.

The recommendation is not "no." It is: proceed only if the owner will commit in writing to a freeze date for this corridor, with the change consequences stated. If they will, the labor numbers above are attractive and the safety case is strong. If they will not, decline and stick-build it — and say plainly that you declined for an organizational reason, not a technical one, so that nobody concludes prefabrication does not work.

Recall what the Northgate freeze breach actually cost: $18,400 for one change nine weeks after freeze, on six modules, from an owner who signed the freeze and documented the change contemporaneously the same week. On a corridor with no freeze at all and two pending equipment selections, that is your floor, not your ceiling.