Estimating Lost Labor Productivity in Construction Claims
You never see lost productivity — you calculate it against a fair benchmark. Learn the reliability ladder, the gold-standard Measured Mile, and how a 0.80→1.20 hr/m drop becomes a six-figure quantum. Built on AACE 25R-03.
What "lost productivity" means
Productivity is output ÷ input — on site, work installed per labour hour. Engineers usually flip it to the unit rate: hours to install one unit (one metre of pipe, one m² of drywall). Lower is better. When a crew suddenly needs more hours per unit than planned, that gap is lost productivity, and it almost always means lost money.
A ladder ranked by reliability
There's a recognised ladder of quantification methods, ranked by how defensible they are — and the rank is not arbitrary. The most reliable methods demand the best contemporaneous records. The better your data, the higher you climb, and the harder your number is to attack.
| Method | What it does | Reliability |
|---|---|---|
| Measured Mile | Compares a clean, unimpacted stretch of the same work against the impacted stretch. The gold standard. | Highest |
| Baseline productivity | Builds the benchmark from the project's own best periods when no clean "mile" exists. | High |
| Earned value | Uses the project's EVM data to expose productivity variances over time. | Good |
| Comparison / industry studies | Benchmarks against other projects or published research (MCAA, NECA, Leonard) when your data is thin. | Moderate |
| Modified total cost | Total overrun, adjusted to strip out the contractor's own faults and bid errors. | Low |
| Total cost | "All our overrun is the owner's fault." Rarely accepted — a last resort. | Lowest |
The Measured Mile
The most defensible method compares a clean, unimpacted period of the same work against the impacted period. Because both samples share the same crew, scope and conditions, the change environment is the only material difference — which is what makes the comparison persuasive and hard to attack.
Worked example — a Measured Mile
A piping subcontractor hit a wall of owner changes mid-project. Earlier, in a clean window, the same crews installed pipe at a steady rate. Compare the two.
Unimpacted "mile" vs. impacted period
Worked example| Step | Unimpacted (the "mile") | Impacted period |
|---|---|---|
| ① Pipe installed | 5,000 m | 8,000 m |
| ② Labour hours used | 4,000 hr | 9,600 hr |
| ③ Unit rate = ② ÷ ① | 0.80 hr/m | 1.20 hr/m |
| ④ Extra hours per metre = ③ impacted − ③ mile | 0.40 hr/m | |
| ⑤ Lost hours = ④ × impacted m | 3,200 hr |
The crew was 50% less efficient in the impacted window (0.80 → 1.20). Because we benchmarked against the same crews on the same work, the contractor's own baseline ability is already baked in — there's no argument they were simply "slow." That's why the Measured Mile is so hard to attack.
Measured Mile calculator
The benchmark "mile" is fixed at 0.80 hr/m. Drag the sliders to see how the impacted productivity drives the lost hours and the bill.
Measured Mile calculator
Try it yourselfThe benchmark "mile" is fixed at 0.80 hr/m. Drag the sliders to see how the impacted productivity drives the lost hours and the bill.
Ten things to remember
- Lost productivity is invisible — you calculate it against a benchmark, you never see it.
- Unit rate (hr/unit) is the working measure — lower is better.
- Methods form a ladder ranked by reliability — and by the records they demand.
- The Measured Mile is the gold standard — same work, same crew, clean vs impacted.
- The mile must be genuinely unimpacted — not merely "less bad."
- Exclude ramp-up and ramp-down — claim only the abnormal steady-state loss.
- Apply the loss factor to hours worked in the impacted window, not the whole job.
- Strip out your own inefficiency — owning your share builds credibility.
- Avoid bare total cost — tribunals discount it; use modified total cost at best.
- Productivity ≠ delay — a loss-of-efficiency number won't recover time.
Glossary
- Baseline productivity
- A benchmark built from the project's own best-performing periods.
- Blended labour rate
- An averaged crew cost per hour, used to value lost hours.
- Loss factor
- (impacted rate − benchmark) ÷ benchmark — the proportional drop in efficiency.
- Lost productivity
- Extra hours caused by disruption, measured against a fair benchmark.
- Measured Mile
- Comparing a clean, unimpacted window of the same work to an impacted one.
- Modified total cost
- Total overrun adjusted to remove the contractor's own faults — a last resort.
- Productivity
- Output ÷ input; on site, work installed per labour hour.
- Unit rate
- Hours needed per unit of work. Lower is better.