14.3 Material, Labor & Bid Estimating
Key Takeaways
- A bid is built from direct costs (material, labor, equipment, subcontractors), plus job overhead, plus a share of general overhead, plus profit — omitting any layer produces a bid that wins work and loses money.
- Labor is estimated with labor units, which are standard installation hours per unit of work, multiplied by quantity and adjusted for job conditions such as height, occupied buildings, and congested ceilings.
- The labor burden — payroll taxes, workers compensation, general liability, and benefits — is added on top of the base wage and commonly runs 25 to 40 percent, so a $28 wage costs the contractor roughly $35 to $39 per hour.
- Markup and margin are not the same: markup is figured on cost while margin is figured on selling price, so a 20 percent markup yields only about a 16.7 percent margin and a 20 percent margin requires a 25 percent markup.
- Selling price for a target margin is cost divided by (1 minus the margin), so $10,000 of cost at a 20 percent target margin must sell for $12,500, not $12,000.
14.3 Material, Labor & Bid Estimating
[!IMPORTANT] Why a licensing exam tests estimating: A Class A license authorizes unlimited-capacity contracting. The Board's interest is that licensees be competent to run a business that will still exist when the warranty is called. Chronic underbidding is a leading cause of contractor failure and of abandoned, unfinished mechanical work. The Plan Reading, Estimating & Math subject area tests the arithmetic that separates a bid from a guess.
Anatomy of a Bid
A complete bid is assembled in layers. Each layer is a distinct question, and skipping any one of them produces a number that looks competitive and is not.
| Layer | What it contains | Typical failure |
|---|---|---|
| 1. Direct material | Everything permanently installed: equipment, duct, pipe, fittings, insulation, hangers, grilles, controls, refrigerant | Forgetting consumables and hardware |
| 2. Direct labor | Field hours to install the above, fully burdened | Using the base wage instead of the burdened rate |
| 3. Equipment & tools | Crane picks, lifts, rigging, welders, scaffolding | Omitting the crane for rooftop units |
| 4. Subcontractors | Balancing, controls, crane service, roofing, electrical | Assuming another trade covers it |
| 5. Job overhead | Permits, plan review, dumpsters, temp power, jobsite supervision, mobilization, project management, bonds, jobsite-specific insurance | Treating supervision as free |
| 6. General overhead | The share of office rent, estimating, vehicles, software, accounting, and non-billable staff this job must carry | Not allocating it at all |
| 7. Profit | Return on the risk of performing the work | Confusing markup with margin |
Direct cost is layers 1–4. Total cost is layers 1–6. Selling price is total cost plus profit.
Estimating Labor with Labor Units
Material quantities come straight from the takeoff. Labor does not — it is derived by applying a labor unit, the standard number of installation hours for one unit of work, drawn from a published manual or from the contractor's own historical production data.
Representative form (always use your own or your manual's figures on a real bid):
| Item | Unit | Labor unit (hours) |
|---|---|---|
| Rectangular duct, fabricated and installed | per 100 lb | varies by gauge and height |
| Round spiral duct, 8 in. | per linear ft | fractional |
| Ceiling diffuser, lay-in | each | fractional |
| Rooftop unit, 10 ton, set and connected | each | multiple hours |
| Refrigerant line set, brazed | per linear ft | fractional |
Labor hours = quantity × labor unit × condition factors
Condition Factors
Published labor units assume favorable conditions: new construction, ground floor, open ceiling, normal working hours, cooperative sequencing. Real jobs deviate, and the estimator applies multipliers:
- Working height. Work above roughly 10–12 feet requires lifts and slows materially; the multiplier grows with height.
- Occupied buildings. Retrofit work in an operating facility carries protection, cleanup, and coordination penalties.
- Congested ceiling cavities. Ductwork threading between sprinkler mains, cable tray, and structure takes far longer than an open plenum.
- Off-hours or shift work. Night and weekend work carries both a premium wage and a productivity penalty.
- Crew size and learning curve. Repetitive work gets faster; one-off work does not.
- Weather. Arkansas summer rooftop work in July has a real, measurable productivity loss.
[!CAUTION] Condition factors are multiplied, not added. A job that is 15% slower for height and 20% slower for occupancy is 1.15 × 1.20 = 1.38, a 38% labor penalty — not 35%.
The Fully Burdened Labor Rate
The wage on the technician's paycheck is not what the hour costs the company. Labor burden adds:
- Employer FICA (Social Security and Medicare)
- Federal and state unemployment tax
- Workers' compensation insurance — significant in the mechanical trades and a required coverage for Arkansas employers with three or more employees
- General liability insurance allocable to payroll — Arkansas HVAC/R licensees must carry at least $250,000 in general liability coverage
- Health insurance, retirement contributions, paid time off
- Training, licensing, and continuing education — including the 8 hours of board-approved CE per International Mechanical Code cycle required under 17 CAR § 261-120
- Vehicle, fuel, and small-tool allowance where charged to labor rather than overhead
Burden commonly lands between 25% and 40% of base wage.
[!TIP] Worked burdened rate. Base wage $28.00/hr, burden 32%. Burdened cost = 28.00 × 1.32 = $36.96/hr.
On a 400-hour job, estimating at the bare wage understates labor cost by 400 × (36.96 − 28.00) = $3,584. That single omission can exceed the entire profit on a small commercial project.
Job Overhead vs. General Overhead
These are distinct and are handled differently.
Job overhead is caused by this job and is estimated directly for it: the mechanical permit, plan review, jobsite supervision hours, mobilization, temporary power and heat, dumpsters, jobsite trailer, project management time, and any bond required for the project. In Arkansas, remember that a commercial project of $50,000 or more requires an Arkansas Contractors Licensing Board commercial license in addition to the ADLL trade license, and ACLB licensure carries its own bonding and financial-statement obligations that belong in this layer.
General overhead is the cost of being in business regardless of any one job: office rent and utilities, estimating and administrative salaries, accounting and legal, insurance not allocable to a job, software, vehicles, marketing, and annual license renewals. It is allocated across all jobs, most often as a percentage of direct cost or of direct labor.
[!TIP] Worked overhead allocation. A contractor's annual general overhead is $300,000 and expected annual direct cost is $1,500,000. Overhead allocation rate = 300,000 ÷ 1,500,000 = 20% of direct cost. A job with $40,000 of direct cost must therefore carry 40,000 × 0.20 = $8,000 of general overhead before any profit is added.
Markup vs. Margin — The Central Arithmetic Trap
This distinction appears on trade licensing exams more often than any other estimating topic, because contractors get it wrong in the field constantly.
- Markup is computed on cost: Price = Cost × (1 + markup)
- Margin (gross profit percentage) is computed on selling price: Margin = (Price − Cost) ÷ Price
They are not interchangeable.
[!TIP] Worked comparison at $10,000 of total cost.
Applying a 20% markup: Price = 10,000 × 1.20 = $12,000 Gross profit = $2,000 Margin = 2,000 ÷ 12,000 = 16.7% — not 20%.
Achieving a 20% margin: Price = Cost ÷ (1 − margin) = 10,000 ÷ 0.80 = $12,500 Gross profit = $2,500 Check: 2,500 ÷ 12,500 = 20% ✓ The required markup was 2,500 ÷ 10,000 = 25%.
The formula to memorize:
Selling price = Total cost ÷ (1 − desired margin)
| Desired margin | Required markup on cost |
|---|---|
| 10% | 11.1% |
| 15% | 17.6% |
| 20% | 25.0% |
| 25% | 33.3% |
| 33.3% | 50.0% |
| 50% | 100.0% |
A contractor who believes a 20% markup delivers a 20% margin is short 3.3 percentage points on every job — which, on a business running an 8% net, is most of the profit.
Full Worked Bid
A 10-ton rooftop replacement on a single-story Arkansas retail building.
| Layer | Calculation | Amount |
|---|---|---|
| Equipment (RTU-1, 10 ton) | from schedule and quote | $14,200 |
| Curb adapter, duct transitions, hardware | takeoff | $1,850 |
| Refrigerant, controls, misc. material | takeoff | $700 |
| Direct material subtotal | $16,750 | |
| Labor: 62 hours × $36.96 burdened | 62 × 36.96 | $2,292 |
| Condition factor (rooftop, occupied store): × 1.25 | 2,292 × 1.25 | $2,865 |
| Crane pick (subcontract) | quote | $1,400 |
| Test and balance (subcontract) | quote | $850 |
| Direct cost (layers 1-4) | 16,750 + 2,865 + 1,400 + 850 | $21,865 |
| Job overhead: permit, supervision, disposal, protection | direct estimate | $1,600 |
| General overhead at 20% of direct cost | 21,865 × 0.20 | $4,373 |
| Total cost (layers 1-6) | 21,865 + 1,600 + 4,373 | $27,838 |
| Selling price at a 20% target margin | 27,838 ÷ 0.80 | $34,798 |
| Gross profit | 34,798 − 27,838 | $6,960 |
| Margin check | 6,960 ÷ 34,798 | 20.0% ✓ |
Note what a 20% markup would have produced instead: 27,838 × 1.20 = $33,406, a margin of 16.7% and $1,392 less profit on one small job.
Common Exam Traps
- Trap: Markup equals margin. They never do. Price = Cost ÷ (1 − margin).
- Trap: Bare wage as labor cost. Always burden the wage.
- Trap: Adding condition factors. They multiply.
- Trap: Overhead omitted. General overhead must be allocated to every job or it is paid out of profit.
- Trap: Forgetting the ACLB threshold. A commercial job at $50,000 or more (or a residential job at $2,000 or more) requires ACLB licensure in addition to the ADLL trade license — a compliance cost that belongs in the bid.
- Trap: Subcontractor scope gaps. Balancing, crane service, roofing penetrations, and electrical are frequently assumed to be someone else's; confirm in writing.
A contractor computes $10,000 of total cost on a job and wants a 20 percent gross margin. What must the selling price be?
A technician earns a base wage of $28.00 per hour and the company carries a 32 percent labor burden. What is the fully burdened hourly cost, and what does estimating at the base wage cost on a 400-hour job?
An estimator determines that a retrofit job will run 15 percent slower because of working height and 20 percent slower because the building is occupied. What total labor factor applies?
A contractor has $300,000 of annual general overhead and expects $1,500,000 of annual direct cost. Using direct cost as the allocation base, how much general overhead must a job with $40,000 of direct cost carry?