Chapter 9 — Exercises

Work these with the chapter closed where you can. Retrieval is worth more than rereading, and it will feel worse. Selected answers appear in Appendix J.

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

Part A — Conceptual Understanding ⭐

A1. Name the four control layers in order of consequence, and state what each one controls.

A2. Explain, in two sentences, why "dried-in" is described in this chapter as a decision rather than a date. Who makes it on Northgate, and what document supports a partial version of it?

A3. What is a drainage plane, and why is the cladding on a rainscreen wall not the water control layer?

A4. Define thermal bridging. Explain why a wall with R-19 batt insulation between metal studs performs at a fraction of R-19, and what continuous insulation does about it.

A5. Distinguish positive-side from negative-side waterproofing. Which is preferred, and name two situations that force you to the other one.

A6. A roofing manufacturer offers three warranties: a material warranty, a workmanship warranty, and an NDL system warranty. Explain what each covers and who issues it. Which one does an institutional owner actually want, and what conditions come with it?

A7. What is the difference between stick-built and unitized curtain wall? Give one advantage and one disadvantage of each.

A8. Explain the purpose of backer rod. Name the three jobs it does, and explain why three-sided adhesion causes premature sealant failure.

A9. What is the difference between a field mockup and a performance (laboratory) mockup? At what point in the schedule must each be complete to be useful?

A10. Name the two inspection hold points in the interior sequence and explain, in one sentence each, why a hold point behaves differently from an ordinary schedule activity.

Part B — Applied Analysis ⭐⭐

B1. Margo finds water on Level 3 of Northgate at a location forty feet from the nearest exterior opening, running along the underside of the metal deck. Give two plausible sources, explain the mechanism by which water travels horizontally in a metal deck, and describe how you would prove which source it is.

B2. A curtain-wall unit is installed and water appears at the slab directly below its centerline. The unit's exterior gaskets appear intact. Explain what is probably happening inside that unit, why the design expects some water to get past the outer seal, and what field action likely caused the failure.

B3. Your roofing subcontractor proposes substituting a different cover board that saves $19,000 and improves delivery by two weeks. List the four questions you ask before you evaluate the price, and explain what the two-week delivery improvement probably tells you about the original submittal.

B4. A mechanical contractor sets a 4,000-pound rooftop air handler on its curb three days before the roofer arrives to flash the curb. Describe the specific quality problem this creates, name whose failure it is, and write the schedule logic that prevents it.

B5. Vantage offers a glass substitution on Northgate that saves $1.85/SF on 38,500 SF but changes the assembly SHGC from 0.27 to 0.38. Trellis Engineering says the change requires roughly 40 additional tons of chiller capacity at about $1,900 per installed ton plus a $14,500 redesign fee. Show whether the substitution saves or costs money, and state the additional consequence that does not appear in the arithmetic.

B6. A drywall subcontractor asks to install ceiling tile on Level 2 on Monday, ahead of final paint, because otherwise their crew has a gap. Give your answer, give two independent technical reasons, and then describe what you owe the subcontractor in exchange for saying no.

B7. On Rivermont Elementary School #12, a life-safety plan shows a two-hour rated corridor wall. The drywall subcontractor built the wall to the underside of the ceiling grid. Explain what is wrong, what code concept has been violated, and what it will cost to correct after the ceiling is closed versus before.

B8. Explain why sealant joints, rather than membranes or glass, generate the most warranty callbacks on commercial buildings. Include the movement-capability arithmetic in your answer: a joint must accommodate 0.25 inches of movement and the sealant is rated ±25%. What is the minimum joint width?

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

C1. Enclosure slip cost, done honestly. Northgate's enclosure slips 18 calendar days. The window between dried-in (March 28, Year 2) and substantial completion (September 18, Year 2) is 174 CD; the driving downstream work needs 168 CD. Extended general conditions are $5,150/CD, liquidated damages are $5,500/CD, and winter temporary heat and enclosure maintenance run $2,400/CD.

(a) How much contract time is actually lost? (b) What is the cost of the lost contract time? (c) What is the total direct cost of the slip? (d) Write the one sentence you would say in the owner-architect-contractor meeting that captures what this slip cost beyond the dollars.

C2. Back-schedule a long-lead facade package. Using the Northgate curtain-wall chain from §9.5.1 (shop drawings 6 wk → review 3 wk → resubmit and re-review 4 wk → material procurement 10 wk → fabrication 12 wk → shipping and staging 3 wk overlapped, giving 38 weeks from award to first unit set), determine:

(a) The latest subcontract award date if the first unit must be set on January 5, Year 2. (b) How many days of float that leaves against a Notice to Proceed of March 3, Year 1 and an actual award of April 9, Year 1. (c) Rebuild the chain assuming a design-assist engagement that completes the transition details during design, eliminating the resubmittal cycle. What is the new award-to-first-unit duration, and what is the new latest award date?

C3. Roof penetration and drainage check. Northgate has 34,000 SF of TPO roofing with eight primary roof drains, tapered insulation at ¼ inch per foot, and 214 penetrations.

(a) Water weighs about 5.2 pounds per square foot per inch of depth. Compute the load added by three inches of ponding across the full roof area, in pounds and in tons. (b) Explain why this number is a structural concern and what overflow drainage is for. (c) A mason builds the parapet to a "round number" that places the overflow scuppers two inches higher than detailed. Explain the consequence in terms of (a).

C4. The gypsum finish decision. Northgate has 412,000 SF of gypsum board (all faces, all layers), of which about 268,000 SF is finished visible surface: 46,000 SF at Level 5, 198,000 SF at Level 4, and 24,000 SF at Level 1 above ceilings. Use $0.72/SF as the Level 4-to-Level 5 premium.

(a) What does it cost you if you bid Level 4 everywhere and the finish schedule requires Level 5 in the three specified areas? (b) What does it cost you if you bid Level 5 across all finished surface? (c) Which document tells you the level and which tells you the location? What do you do if the finish schedule specifies semi-gloss paint in a corridor the specification assigns to Level 4?

C5. Price a failed above-ceiling inspection. On Level 2, 212 of 1,840 rated penetrations are rejected. Correction runs $38 per penetration, the re-inspection fee and coordination cost $650, and the zone stops for four work days. Remobilizing a six-person ceiling grid crew costs $6,200. Two calendar days of project float are consumed.

(a) Compute the "visible" cost that lands on the cost report. (b) Compute the realistic total exposure including the float, valued at $10,650/CD. (c) Design the firestop management plan that eliminates this category of failure. Name at least five specific elements.

C6. Write the RFI. On the Willow Street Community Center, the second-floor wood-framed wall detail (Detail 6/A-402) shows the self-adhered air/water-resistive barrier terminating at the top of the wall sheathing, and the roof detail (Detail 2/A-403) shows the roof membrane terminating under the coping. No transition membrane is shown connecting them over the parapet.

Write the RFI. Include: reference documents, a factual statement of the conflict, the technical consequence in terms of control layers, a proposed resolution, a cost-impact statement, a dated schedule-impact statement, and the attachments you would send. Keep it under 300 words in the body.

C7. Build the interior sequence for one zone. Northgate has 18,600 LF of metal-stud partition and 412,000 SF of gypsum board across four 33,000 SF floors, each divided into three work zones. Using the sequence table in §9.8:

(a) List the sixteen steps in order, with the trade responsible and the single most important predecessor for each. (b) Mark the two hold points and state, for each, exactly what must be true before you will call the inspector. (c) Sum the zone durations for steps 1 through 8. Then explain why that sum is much larger than the calendar time available between dried-in (March 28) and MEP rough-in complete (May 30), and what zoning does about it. (d) The in-wall inspection on Zone 2 fails. The correction takes one day. Estimate the total schedule impact on that zone and justify each component of your estimate.

C8. Enclosure quantity takeoff, Willow Street. Using the Willow Street package in Appendix K, take off the envelope: brick veneer (SF), CMU back-up (SF), fiber-cement panel (SF), insulated metal panel (SF), TPO roofing (SF), standing-seam metal roofing (SF), storefront (SF), punched windows (EA), through-wall flashing (LF), coping (LF), exterior sealant joint (LF), and roof drains plus overflows (EA). For each line, state your takeoff method, your waste factor, and one assumption you made. Then flag the three quantities you are least confident in and say what you would need to firm them up.

Part D — Judgment and Ethics ⭐⭐⭐

D1. A value-engineering item proposes deleting the through-wall flashing, end dams, and weeps at a brick shelf angle, saving $88,000. The architect's job captain says it "should be fine with a good sealant joint." You believe it will leak in three to five years, after your warranty period ends. Describe exactly what you do, in what order, and in what form. What is the difference between protecting the owner and protecting yourself, and can one document do both?

D2. Your roofing subcontractor is three weeks behind and asks to install membrane over insulation that got rained on over the weekend. He says it "will dry out." The moisture is between the cover board and the insulation, and it will be sealed under a fully adhered membrane for thirty years. He is a good sub, you like him, and he is right that the delay hurts you both. What do you do, and what do you write down?

D3. The specification says field water testing shall be performed "as directed by the Architect," and the Architect has directed none. You know the clause is dead. Testing three assemblies would cost about $14,000 out of your own general conditions and is not required of you. The owner has not asked. Argue both sides, then decide, and state the principle behind your decision.

D4. At the eleven-month warranty walk on a completed building, two tenants on different elevations report staining at the base of exterior walls. Your service department wants to cut out forty feet of sealant, re-caulk, and close the items — total cost about $2,800 and two days. Investigating properly means an exploratory opening, a water test, and a consultant: roughly $22,000, plus the risk that you find something you then have to fix. Make the call. What changes your answer?

D5. Kestrel's assistant superintendent, under acceleration pressure, allows a curtain-wall crew to work a swing stage in gusting wind because "they've been out there all week and they know what they're doing." Nobody is hurt. Should this appear in a report? Who writes it, who reads it, and what does the answer say about whether this project's safety culture is real?

D6. The Northgate acceleration decision table had two columns: cost and days recovered. It did not have a column for how many workers would be in how little space. Bea Salgado's investigation of the week-34 near-miss listed schedule pressure as the third and most important finding, and that finding was the one nobody wanted to write down. As the project manager, what do you owe the field before you sign an acceleration? Draft the two sentences you would add to Kestrel's acceleration approval form.

D7. Your masonry crew is cutting brick with a dry saw and no dust shroud because the water supply on that elevation was shut off for a repair and the crew is behind. The foreman tells you it is "one afternoon." Silica exposure is cumulative and irreversible, and this crew has been on this job for four months. Describe the conversation, the immediate action, and the systemic fix — and be honest about which of the three is hardest.

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

M1. (Chapters 6, 7, and 9.) Build a five-line enclosure risk register for the Willow Street Community Center in the format from Chapter 6: named risk, probability, impact in dollars, risk owner, response, and contingency amount. At least two lines must trace to a document conflict of the kind you learned to find in Chapter 7. Then state which lines you would draw down first and what event triggers each drawdown.

M2. (Chapters 8 and 9.) In Chapter 8 you learned that the long pole on a structural package is the submittal and fabrication lead time, not the field duration, and that the anchor-bolt submittal cost Northgate 23 calendar days of steel start. Demonstrate that the same pattern holds for enclosure by building a side-by-side table: for structural steel and for unitized curtain wall, show the field duration, the paper-and-fabrication duration, and the ratio between them. Then state the management rule that follows.

M3. (Chapters 7, 9, and 16.) The precast-to-curtain-wall vertical joint on Northgate belonged to no subcontract, which cost $148,000 to resolve. Write the scope-sheet language for both subcontracts that closes the gap. Then list four other interface conditions on a typical commercial envelope that live between two subcontracts, and say who you would assign each to and why.

M4. (Chapters 9 and 14.) Take the interior sequence table from §9.8 and convert the first eight steps into a small precedence network for one zone: activity, duration, and predecessors. Run a forward pass and a backward pass. Identify the critical path through the zone and compute the total float on the insulation activity. Then explain what happens to your network when the in-wall inspection fails.

M5. (Chapters 9, 23, and 25.) Design the enclosure portion of an inspection and test plan for Northgate: the conditions tested, the frequency, the party performing, the party witnessing, the pass/fail criteria source, the funding source, and the retest cost responsibility. Then write the submittal-log entries for the three enclosure submittals whose lead times most threaten the dried-in milestone, back-scheduled from March 28, Year 2.

M6. (Chapters 9 and 24.) The Northgate acceleration put two crews on the north elevation in weeks 33 through 37, and the scaffold near-miss happened in week 34. Add a third column to the acceleration decision table from §9.5.1 — beyond cost and days — that captures trade density. Propose a specific, measurable way to express it (workers per 1,000 SF of work area, simultaneous trades per elevation, or something better), and describe how you would use it in a go/no-go acceleration decision.

Part E — Research and Extension ⭐⭐⭐⭐

E1. Find a real construction specification for a commercial project — many public owners post full bid documents online — and read Division 07 (Thermal and Moisture Protection) and Division 08 (Openings). Locate the field-testing requirements. For each one, determine whether it has a frequency, a selection method, a funding source, a consequence for failure, and a deliverable. Write a one-page assessment of which requirements will actually happen on that job and which are decorative.

E2. Contact or research the building department in your own jurisdiction and find out what enclosure-related inspections it performs, in what order, and what triggers each one. Then find out whether your jurisdiction has adopted a whole-building air-leakage testing requirement, and if so, what target and what test protocol. Note that adoption of energy-code provisions varies widely by state and by local amendment; report what you find and cite the actual adopting document, not a summary.

E3. Choose one real building near you that you can walk around. Photograph five transitions: base of wall, a window head, a system change from one cladding to another, a roof-to-wall condition, and any exterior penetration. For each, write what you can see, what you cannot see, and the one question you would ask the person who built it. Then find the oldest visible sealant joint on the building and estimate its age from its condition.