Chapter 35 Exercises

Work these with the chapter closed where you can. Selected answers appear in Appendix J; a few calculation answers are given here in <details> blocks so you can check your arithmetic without checking your reasoning.

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

Part A — Conceptual Understanding ⭐

A1. Define level of development in one sentence. Then give an example of a highly detailed element you may not rely on, and a crude element you may.

A2. Name the three models in §35.1. For each: who makes it, who is legally responsible for it, and — the part people skip — what it is not for.

A3. The chapter calls Northgate's model-extracted gypsum board "correct and unusable at the same time." Explain that without using the words error or mistake, and name the four line items that produced the 17.8 percent gap.

A4. Distinguish a hard clash, a soft clash, and a workflow (4D) clash. Which one can a geometric test never find, and what is the reason — not the symptom?

A5. List the routing-priority convention from most to least constrained. State the principle that produces the order, and name the thing that sits above all six and is not a routable system.

A6. Grace's funnel took 1,840 raw results to 61 decisions. Name the four filters and the count each removed. Which one carries a signature, and why does it need one?

A7. What does a 4D model calculate? Give one question only CPM logic can answer and one only 4D can answer.

A8. Which two rungs of the digital-twin spectrum pay today, and what has to be true about the owner before rung 5 is worth selling?

A9. Why is a reverse-engineered model worse than no model at all? Answer in terms of what a manager can and cannot see.

Part B — Applied Analysis ⭐⭐

B1. A design model shows a 30-inch chilled-water main with visible flanges. The execution plan puts piping at LOD 200 in design development. Your superintendent wants to confirm the pipe clears the air handler with it. State your answer, your reason, and your next action — including what form that action takes and who it goes to.

B2. Round three shows fewer clashes than round two. Comparing rule sets, you find the duct-to-pipe tolerance was loosened from 0.5 inch to 1.5 inches between rounds, with no note and no approval. Describe what has actually happened to the report, what you do this afternoon, and what professional line has been crossed.

B3. Your sheet-metal subcontract ties fabrication release to coordination sign-off. Level-two sign-off will slip nine days. The subcontractor offers to release anyway "at our own risk." Write the two-sentence response, and state the one condition under which you would agree.

B4. Your company requires a full execution plan and four clash rounds on every job. You are handed a $2,000,000 tenant fit-out — existing grid, two systems, one congested mechanical room. Write the paragraph recommending a deviation to your VP of Operations, and name the three things you would still do.

B5. The first federation puts the mechanical model 1,140 feet northeast of the building and rotated 21 degrees. Name two ways this gets "fixed." Say which one is dangerous, exactly what it breaks, and how you would detect it afterward.

B6. A trade contractor's models are clean, organized, and on time. Their foreman has never opened one. Name three observable symptoms that the model was reverse-engineered from paper, and what you would do on the day you became sure.

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

C1. Triage a raw clash report ⭐⭐⭐

Grace hands you the Northgate level-four report the afternoon before the round-two meeting. Level 4 is ambulatory surgery, its support corridor, and the level-four mechanical room.

(a) Triage all twelve into must resolve, resolve if convenient / route elsewhere, and false positive. For each false positive name the rule that suppresses it — and say why you record the rule rather than deleting the item.

(b) Four are true routing conflicts. Identify them, apply the routing-priority convention, and state which system gives way and why, in degrees of freedom rather than volume of complaint.

(c) Identify the one 4D conflict. State the test you used and why no geometric run — at any tolerance, at any LOD — will ever report it.

(d) Two items are not clashes at all. Name them and the log each belongs on.

(e) Two items cannot be ruled on until somebody confirms a level of development. Identify them and write the one-line request you send before Thursday.

C2. The Willow Street kitchen cavity budget ⭐⭐

The commercial kitchen sits on the first floor under the wood-framed second floor. Floor-to-floor 13'-0"; total structural depth of the wood floor system including subfloor and underlayment 16 inches; required finished ceiling 9'-0". At the worst crossing, where the grease exhaust duct passes over the makeup-air duct:

Then run the plan width check over the cook line, where the clear zone between the hood and the walk-in cooler wall is 9'-4". It carries the grease duct envelope (32"), the makeup-air duct (30"), gas piping with hangers (8"), domestic hot and cold water (10"), and 3 inches of separation at each of three interfaces.

(a) Available cavity. (b) Required stack. (c) Surplus or shortfall. (d) Width check result. (e) The one change that produces the largest gain for the least cost, and what it costs you contractually. (f) One sentence on what this single location says about whether a $6,800,000 community center needs a coordination program.

On code numbers: grease-duct slope, permitted clearance to combustibles, and minimum ceiling height in a food-preparation area all depend on your adopted code edition, on the listing of the enclosure you actually buy, and on your health department. Confirm all three. Do not carry a number out of this book.

C3. Build two LOD matrix rows ⭐⭐⭐

Using the §35.2 format — Schematic · Design development · Construction documents · Coordination · Fabrication · As-built delivered — build a complete row for each system below. Add two columns the chapter's table does not have: who owns the coordination cell (a role, not a company) and a one-sentence justification.

(a) Kitchen grease exhaust — hood, grease duct, listed enclosure, roof fan. (b) Gym roof — open-web steel joists, rooftop-unit curbs, roof drains and overflow drains.

Then: why is the coordination cell higher than the construction-documents cell in both rows? And name one Willow Street system whose coordination cell should stay at 300, and defend keeping it low against somebody who thinks higher is always better.

C4. The funnel and the matrix as diagnostics ⭐⭐

(a) Northgate level one, round two. Raw geometric result 2,410. Tolerance rules remove 812; the self-clash filter 604; grouping 691; already-assigned items from round one 214. Compute the items requiring a human decision. Then split it the way Grace splits hers — detailer-closed 51, trade-to-trade 34, escalated to design 4 — and check that it reconciles.

(b) Level one, round three. Total 1,708.

Stop looking at the total and read the table. Produce four specific actions, and say for each whether it is a process problem or a building problem. For the 388, give two candidate explanations and describe how you would tell them apart in five minutes.

C5. Price the same conflict twice, then find the break-even ⭐⭐

Willow Street gym roof. RTU-3's curb as detailed conflicts with the top chord of joist J-14 and with the roof-drain sump. Found in the model in month 3: relocate the curb 3'-6" west, revise the joist reinforcement with the fabricator, move the drain — $3,850, zero days.

Found in the field, joists erected and deck placed:

(a) Total the direct cost. (b) Add 6 CD at Willow Street's canonical daily exposure, and state that rate. (c) State the total and the amount avoided. (d) If your scoped program costs $61,000, how many findings of this size does it take to break even? (e) Is that a good argument or a fragile one, and what does it tell you about how to talk to an owner?

C6. Reconcile a model extraction against a hand takeoff ⭐⭐⭐

Willow Street gypsum board. Two numbers arrive the same morning.

(a) Compute the gap in SF and as a percentage of the hand takeoff. (b) Explain each of the four differences, and for each say whether the model is wrong or answering a different question. (c) Price the gap at Chapter 12's installed rate, $4.19/SF, as a percentage of the $6,800,000 contract. (d) Say which number goes in the estimate and write the stamp beside it. (e) Willow Street is prevailing wage and Northgate is not. Is $4.19/SF defensible here?

Part D — Judgment and Ethics ⭐⭐⭐

D1. Which document governs. A mechanical subcontractor installs a duct main exactly where the signed coordinated model puts it. The mechanical drawing shows it four feet away, and the owner's representative says the contract documents govern. Work the analysis: what does the drawing govern, what does the model govern, and which of them ever resolved the third dimension? Draft the sentence you want in every MEP subcontract — then say who wins on a job where no such sentence exists, and on what basis.

D2. Who pays a trade contractor to model. A public hard-bid project requires LOD 400 coordination models from every MEP trade. The bid form has no line for it and your low mechanical bid obviously contains none. Work the decision at three moments — before bids are due, after award but before buyout, and in month seven when you find the sub detailing on paper — and state what is available at each. Name the ethical line around asking a subcontractor to absorb an unpriced scope, and explain why "they signed the subcontract, it's their problem" is both contractually arguable and managerially useless.

D3. The ratio on the slide. Marketing wants to use Northgate's numbers as "Kestrel's BIM program delivers a 5-to-1 return." Show with the arithmetic why you refuse, write the two sentences you would let them use, and say what happens to your credibility three years from now if you do not.

D4. The deviation that was better. A subcontractor deviates from the signed model without written approval, and the deviation is genuinely better. What do you do, and why is the answer not "nothing, it's better"? Now change one fact: the deviation is worse and already above a closed ceiling. Does your process change, or only your mood?

D5. Reliance past the stated LOD. A project manager extracts a quantity from the architect's design model and puts it in a guaranteed maximum price. Trace what went wrong and name every party with exposure. Then the harder turn: at what point does relying past a stated level of development stop being a technical error and become a misrepresentation to your own owner?

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

M1. (Ch 35 + Ch 10.) Take Corridor C: 30 inches available, 39 required. Chapter 10 solved it with arithmetic; Chapter 35 solved it with a model. Build a two-column table listing, for each of the four options, what the model contributed and what a human still had to decide. Then: which option could a model have eliminated without a meeting, and why does that matter more than the ones it kept alive?

M2. (Ch 35 + Ch 12.) Write the LOD stamp — one sentence, Grace's format — for five extractions: footing concrete at 300; steel tonnage at 400; gypsum board at 300; sprinkler pipe length at 350; and slab-on-grade concrete for a purchase order. For the last, say what the stamp must additionally warn about and why the model cannot know it.

M3. (Ch 35 + Ch 14.) Six activities from a conventional schedule: Erect structural steel · Place metal deck · Place lightweight topping · Set precast panels · Install curtain wall · MEP overhead rough-in. None can be linked to a model. Recode all six so a 4D simulation is possible, state your coding scheme, and answer the question that decides whether this is worth doing: when must the recoding happen, and what does it cost to attempt it in month eight?

M4. (Ch 35 + Ch 25 + Ch 33.) Stonebridge closed with 441 RFIs, of which 258 were later categorized as coordination questions; Vantry claimed 34 days and recovered none as compensable. Name the three separate proofs a delay claim requires and, for each, the specific contemporaneous record Vantry needed to create during the job. Then name the single field on an RFI log that would have changed the outcome, and when it must be filled in.

M5. (Ch 35 + Ch 6 + Ch 16.) Northgate's risk R-07 carried a $230,000 exposure at 50 percent — a $115,000 expected value — mitigated to 30 percent and $140,000. Trace that one register line into procurement: write the coordination exhibit you would attach to an MEP subcontract, naming the obligation, the deliverable, the LOD, the schedule, meeting attendance, sign-off, the detailing allowance, the fabrication-release tie, and the remedy. One page.

M6. (Ch 35 + Ch 40.) Build the asset-data field list for one Willow Street packaged rooftop unit. For each field, name where the data comes from and when it is available. Mark the fields that become expensive or impossible after the ceiling closes.

Part E — Research and Extension ⭐⭐⭐⭐

E1. Score a real specification. Public agencies, districts, and state facilities departments post complete bid documents online. Find one with a Division 01 BIM or digital-data section and score it against the sixteen-part outline in §35.3: which sections does it decide, and which does it merely mention? Watch four — the LOD matrix, the coordinate origin, sign-off authority, and whether trade detailing is a paid scope. Then write the pre-bid RFI you would send, and predict the answer.

E2. Find the current documents. (i) Identify the level-of-development framework contracts in your region actually reference, who maintains it, and how often it is revised. (ii) Find the current release of the open exchange standard (IFC) and its maintaining body, and identify what an IFC file does not preserve. (iii) Find one standard-form BIM addendum or digital-data exhibit and list the five decisions it forces the parties to make. Write a page on where the three overlap and where they leave a gap.

E3. Watch a real coordination meeting. Ask a contractor or a VDC group whether you can sit in on one. Note five things: how many people are in the room; how many can move their own company's work without a phone call; what clash count is reported and whether anybody says the raw number out loud; how a disagreement actually gets settled; and whether anybody writes down what was decided. Then write one page on the gap between §35.4 and the meeting you watched — and be honest about which parts of the real meeting were better than the book.