Chapter 12 Quiz — Estimating Fundamentals

B. 326 CY. 26,400 × (4 ÷ 12) ÷ 27 = 26,400 × 0.3333 ÷ 27 = 8,800 ÷ 27 = 325.9 CY. Answer D is the volume in cubic feet — the most common version of this error, and the one that produces a 27× overrun on a purchase order.

C. Formwork is measured in square feet of contact area — length × height × number of faces. Thickness does not appear in the formula (A affects tie hardware and bracing, not SFCA); strength and bar size do not affect surface area at all. This is the single most useful counterintuitive fact in concrete estimating.

B. $740,000. 32,000 BCY × 1.25 = 40,000 LCY; 40,000 × $18.50 = $740,000. Answer A is the uncorrected extension — a $148,000 error, and one of the most common unit-conversion failures in sitework estimating.

A. 1.484. $50.47 ÷ $34.00 = 1.484, i.e., a 48.4% burden. Answer D confuses the percentage of burden with the factor; multiplying a wage by 48.4 is a memorable disaster.

C. Workers' compensation is priced by class code, and excavation work carries a higher manual rate than interior carpentry. Same person, same wage, different work, different cost. An estimating system that carries one burdened rate per classification for an entire job is wrong somewhere.

C. 9.09%. Price = $1,100,000; profit = $100,000; margin = 100,000 ÷ 1,100,000 = 9.09%. Answer B is the markup you would need to achieve a 10% margin. Both formulas: markup = margin ÷ (1 − margin) and margin = markup ÷ (1 + markup).

C. Material per unit. Labor and equipment are time-based costs converted to unit costs by dividing by the production rate; slow the crew and both rise. Material is quantity-based — you install the same amount of it regardless of how long you take. This asymmetry is why a 15% production loss produces a 14.3% total unit-cost increase but a 17.6% increase on the time-based portion.

B. At LOD 300, geometry and location are generally reliable; materials, assemblies, and specification-driven properties are not. Extracting board layers, stud gauge, or ratings from a model built for spatial coordination produces a number with false precision — the most dangerous kind of wrong. See Chapter 35.

B. 3.80%. $1,804,800 ÷ $47,500,000 = 3.80%. The fee was negotiated as a 4.0% markup on the $45,120,000 subtotal. A 4% markup is never a 4% margin, and confusing the two on a $47.5M contract is a several-hundred-thousand-dollar conversation.

C. When the gap between first and second exceeds the gap across the entire rest of the field, six independent estimating departments have agreed with each other and disagreed with you. Buying power and overhead produce a few percent, not a step function at the top of the tab. Answer D would produce a wide overall spread, not a tight cluster with one outlier. Act on this immediately — the withdrawal window in most jurisdictions is short and evidence-hungry.

False. Applying waste in both places double-counts it. Pick one place — Kestrel's convention is the quantity, because a quantity you can see is a quantity you can audit — and make it a written company policy so the error is structurally impossible.

False. The factor is a stand-in for information you do not have. Once a reinforcing schedule and placing drawings exist, the only defensible quantity is bar-by-bar with laps and bends. A 15% factor error on Northgate's foundations is about $41,200.

True. General conditions are time-driven, not quantity-driven. On Northgate, forty added calendar days at $5,150/CD is $206,000 that appears on no takeoff sheet. This is why the estimate and the CPM schedule are produced together, not in series.

False. On-screen takeoff makes you faster at measuring the drawing you are looking at. Dani's nine missing footings on S-104 would have been missed just as cleanly in Bluebeam. What catches that error is a reconciliation — plan count against schedule total — not a tool.

False, emphatically. Jurisdictions differ on whether the contractor is the consumer of materials or whether the improvement is taxed, on public-work exemptions, on manufacturing exemptions, on use tax when materials cross a line, and on rates — and the rules change. Confirm the treatment for your jurisdiction and project type, and record the answer in the basis of estimate.

False — it depends on the procurement. On a negotiated or CM-at-Risk selection, clarifications are normal and expected. On many public hard bids, a bid that qualifies or conditions its price may be rejected as non-responsive; there, the mechanism for resolving an ambiguity is a pre-bid RFI and an addendum. Know which kind of procurement you are in before you write a single exclusion.

An estimate is produced before the work happens, from incomplete documents, by people who will not do the work, for conditions nobody has seen. Under those constraints no number can be reliably correct — but the statement of what the number assumed can be. A documented assumption is a claim that can be checked, priced, insured, negotiated, or transferred by contract; an undocumented one can only be discovered, usually by an owner's rep, at the worst possible moment. So the profession optimizes for the thing that can actually be made reliable: the documented set of decisions the number rests on.

Wall: 100 LF × 10 ft × 2 faces = 2,000 SFCA. Pad: perimeter 2 × (20 + 15) = 70 LF × 3.333 ft = 233 SFCA. An 8.6-to-1 difference on identical concrete volume, because formwork is driven by surface geometry — a wall is nearly all surface, a pad is nearly all interior. At $6.28/SFCA that is $12,560 versus $1,463; on the wall, the forms cost 40% more than the concrete.

(1) Quantities and their source; (2) unit costs and their source; (3) assumptions; (4) inclusions; (5) exclusions; (6) risks priced and not priced. The sixth is the one most often omitted — and it is the one every claim needs, because entitlement arguments turn on whether a risk was priced, was excluded, or was carried by allowance. Without it, the question "did you price this?" has no contemporaneous answer.

The conditions under which it was collected. A rate is meaningless without its context: clear access or congested, single trade or stacked, ground floor or lift-dependent, day shift or overtime, occupied building or empty shell. Ray's $310,000 mistake was applying a warehouse framing rate (1,180 SF/CD) to an occupied hospital corridor that produced 540 SF/CD. The rate was not the error; the undocumented rate was the error, because nobody could see the assumption in order to challenge it.

(a) Crew $66.54 + $151.41 + $39.51 = $257.46/hr; day × 8 = $2,059.68. Labor 2,059.68 ÷ 465 = $4.4295`; material `$1.18; equipment 310 ÷ 465 = $0.6667. Unit cost $6.2762/SFCA. Total 9,600 × 6.2762 = $60,252.

(b) Labor 2,059.68 ÷ 390 = $5.2812`; material `$1.18; equipment 310 ÷ 390 = $0.7949. Unit cost $7.2561/SFCA. Total 9,600 × 7.2561 = $69,659.

(c) Impact +$9,407. Production fell 16.1% but the unit cost rose only 15.6%, because material ($1.18/SFCA) is quantity-based and does not scale with time — only the labor and equipment terms inflate, and they inflate by 1 ÷ 0.839 = 19.2%.

(a) Nine missed footings = completeness (the measurement was right, the boundary was wrong). F-6 thickness = reading (the boundary was right, the input was wrong). No waste line = conceptual (both were right, and the model of what an estimate buys was wrong).

(b) Completeness: reconcile plan count against schedule total on every takeoff, and maintain a sheet index with a tick for every sheet opened. Reading: a straightedge under the active row on paper, or a highlighted active row on screen, plus a read-back by a second person on scheduled dimensions. Conceptual: a takeoff sheet template with a mandatory waste line that cannot be left blank, and a written company policy stating that waste is applied to the quantity and never to the price.

(c) $43,000 ÷ 0.0380 = $1,131,579 — about $1.13 million of revenue to earn back one line item on one sheet.