Applying Productivity Factors (PF) to Labor — 30-Minute Class
Construction Queen / Intern Academy • Build. Learn. Preserve.
Learning Objectives
- Define base manhours and productivity factors (PF).
- Build a composite PF for real-world constraints.
- Apply PF to Electrical, HVAC, and Plumbing examples.
- Check reasonableness and document assumptions.
30-Minute Agenda
- 0–5 min Why PF matters + formula
- 5–10 Typical PF categories & ranges
- 10–18 Worked examples (E/H/P)
- 18–25 Mini exercises + calculator
- 25–30 Field checks + quick quiz
Core Formula
PF > 1.00 = slower (more hours) • PF < 1.00 = faster (less hours)
Typical PF Categories (Guide Ranges)
| Category | Example | PF (guide) |
|---|---|---|
| Height / Access | Lift/scaffold work | 1.05–1.25 |
| Congestion | Multiple trades, tight space | 1.05–1.30 |
| Occupied Facility | Hospital/school live areas | 1.05–1.25 |
| Weather | Heat, cold, wind, rain | 1.05–1.20 |
| Overtime / Shift | Night work / long OT weeks | 1.05–1.20 |
| Security / Badging | Check-in delays | 1.02–1.10 |
| Learning Curve | Green crew early weeks | 1.05–1.15 |
| Prefab / Kitting | Shop-built skids | 0.80–0.95 |
Use your company standards when available. Document chosen PFs in your estimate notes.
Worked Examples (with math)
Electrical — 2" EMT, 250 ft
Base MH/ft = 0.12 • PFs: Height 1.20 × Congestion 1.15 × Overtime 1.10 → Composite PF = 1.518
Hours = 250 × 0.12 × 1.518 = 45.5 MH
Plumbing — 80 rough-in fixtures
Base MH/unit = 0.50 • PFs: Learning 0.90 × Prefab 0.85 → Composite PF = 0.765
Hours = 80 × 0.50 × 0.765 = 30.6 MH
HVAC — 1,200 sq ft duct
Base MH/sqft = 0.08 • PFs: Lift 1.10 × Confined 1.20 × Heat 1.10 → Composite PF = 1.452
Hours = 1,200 × 0.08 × 1.452 = 139.4 MH
Mini Exercises (2–3 min each)
- Pipe rack: 180 ft, base 0.10 MH/ft, PFs = height 1.15, congestion 1.10. Compute hours.
- VAV boxes: 12 units, base 1.6 MH/unit, PF = occupied 1.10. Compute hours.
- Branch wiring: 40 drops, base 0.75 MH/drop, PFs = prefab 0.90, OT 1.10. Compute hours.
Show suggested answers
- 1) 180 × 0.10 × (1.15×1.10=1.265) = 22.8 MH
- 2) 12 × 1.6 × 1.10 = 21.1 MH
- 3) 40 × 0.75 × (0.90×1.10=0.99) = 29.7 MH
Interactive PF Calculator
Enter your base and PFs. Values > 1.00 add time; < 1.00 reduce time.
Hours = —
Trade-Specific Examples (Extended)
NOTE: Base manhours are illustrative. Replace with your company standards when available. Formula reminder: Hours = Qty × Base MH per Unit × Composite PF.
Electrical
| Scope | Qty | Base MH/U | PFs | Comp PF | Hours |
|---|---|---|---|---|---|
| 2" EMT install | 400 lf | 0.120 | 1.15 × 1.10 × 1.10 | 1.391 | 66.79 |
| Branch circuit drops | 60 ea | 0.650 | 1.10 × 1.10 × 0.90 | 1.089 | 42.47 |
| Panelboard set & make-up | 2 ea | 8.000 | 1.10 × 1.05 | 1.155 | 18.48 |
| Cable tray install | 200 lf | 0.200 | 1.10 × 1.15 | 1.265 | 50.60 |
| Troffer fixtures | 150 ea | 0.250 | 1.10 × 0.95 | 1.045 | 39.19 |
| Fire alarm devices | 100 ea | 0.350 | 1.15 × 1.05 × 1.10 | 1.328 | 46.49 |
| Generator rig/term | 1 ea | 60.000 | 1.10 × 1.15 × 1.05 | 1.328 | 79.69 |
| Feeder pulls (sets) | 6 sets | 6.000 | 1.10 × 1.20 | 1.320 | 47.52 |
HVAC
| Scope | Qty | Base MH/U | PFs | Comp PF | Hours |
|---|---|---|---|---|---|
| Rectangular duct (sf) | 1,400 sf | 0.080 | 1.10 × 1.20 × 1.10 | 1.452 | 162.62 |
| Spiral duct (lf) | 300 lf | 0.220 | 1.15 × 1.10 | 1.265 | 83.49 |
| VAV box install | 18 ea | 1.600 | 1.10 × 1.05 | 1.155 | 33.26 |
| RTU set & connections | 3 ea | 16.000 | 1.15 × 1.10 | 1.265 | 60.72 |
| Hydronic pipe 2" | 500 lf | 0.120 | 1.20 × 0.90 | 1.080 | 64.80 |
| Controls wiring (lf) | 800 lf | 0.050 | 1.10 × 1.05 | 1.155 | 46.20 |
| Fan coil units | 10 ea | 6.000 | 1.10 × 1.15 | 1.265 | 75.90 |
| Grilles/registers | 120 ea | 0.200 | 1.05 × 0.95 | 0.997 | 23.94 |
Plumbing
| Scope | Qty | Base MH/U | PFs | Comp PF | Hours |
|---|---|---|---|---|---|
| Domestic copper 1" (lf) | 600 lf | 0.100 | 1.10 × 1.10 | 1.210 | 72.60 |
| Waste & vent PVC 4" (lf) | 300 lf | 0.090 | 1.15 | 1.150 | 31.05 |
| Fixture rough-ins (ea) | 45 ea | 0.500 | 0.85 × 0.95 | 0.807 | 18.17 |
| Carrier toilets (ea) | 20 ea | 2.500 | 1.10 × 1.15 | 1.265 | 63.25 |
| Gas pipe 1-1/2" (lf) | 400 lf | 0.130 | 1.10 × 1.10 | 1.210 | 62.92 |
| Underground DWV (lf) | 200 lf | 0.200 | 1.10 × 1.05 × 1.05 | 1.213 | 48.51 |
| Water heater set (ea) | 4 ea | 4.000 | 1.10 × 1.05 | 1.155 | 18.48 |
| Insulation (lf) | 800 lf | 0.040 | 1.10 × 0.95 | 1.045 | 33.44 |
Instructor Tips
- Have students pick any row and recreate the math with the on-page calculator.
- Ask: which PF would you tighten or relax with prefab or better access?
- Replace Base MH/U with your ConstructIQ tables to align training with your estimating workflow.
© Construction Queen / Intern Academy — S F Johnson Enterprises, LLC • info@sfjohnsonconsulting.com • 844-261-9737