Trade Exam · Module 2
Labor Estimating Basics
Labor is usually the hardest part of a plumbing estimate to get right. This lesson shows you how to break a job into tasks, estimate man-hours from your own production records, turn man-hours into cost with a loaded rate and into a schedule with a crew size, adjust for productivity and job conditions, and price overtime under California Labor Code 510. Production rates and adjustment percentages in this lesson are example numbers for practice math, not industry standards.
Key Takeaways
- CSLB lists "cost estimation for materials, equipment, labor, and overhead" and "coordination of projects" under Planning and Estimating, about 22% of the C-36 trade exam.
- A man-hour (MH) is one worker for one hour. Labor cost = man-hours x loaded labor rate.
- Duration = man-hours / number of workers. 40 MH is 20 hours for a crew of 2 or 10 hours for a crew of 4, if they stay equally productive.
- Production rates should come from your own job cost records. Published or rule-of-thumb rates are a starting point, not a fact.
- Adjusted hours = base hours / productivity factor. At 75% productivity, 372 base hours become 496 hours.
- Remodels, poor access, occupied buildings, weather and tight schedules usually cost more hours. Measure how much from your own jobs.
- California overtime (Labor Code 510): at least 1.5 times the regular rate after 8 hours in a day or 40 in a week, and at least 2 times after 12 hours in a day.
Why This Matters
CSLB's C-36 study guide lists "cost estimation for materials, equipment, labor, and overhead" and "coordination of projects" as subjects in Planning and Estimating, about 22 percent of the trade exam. Material prices come from a supplier's quote. Labor comes from your judgment, which is why it is where most estimates go wrong.
Units You Will Use
- Man-hour (MH), also called a worker-hour or labor-hour: one worker for one hour.
- Labor unit or production rate: the man-hours a task takes, per item (MH per fixture) or per quantity (MH per 100 feet of pipe).
- Crew-hour: one hour of the whole crew. A crew of 3 working 8 hours spends 3 x 8 = 24 man-hours.
- Duration: calendar or working time. Duration (hours) = man-hours / workers on the task.
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