Unit price work: measuring and agreeing quantities
The owner's inspector has certified 430 m³ of rock excavation on your sewer extension for March; you claimed 610 m³. Her figure comes from the rock line on the geotechnical drawings, yours from truck tickets, and the trench was backfilled two weeks ago. Nobody surveyed the rock before the first blast.
Agree how each item will be measured, then measure it with the owner's representative at every stage — before the surface is disturbed and before the work is covered — and sign the quantity the same day. A unit-price contract pays the measured quantity at the agreed rate, so the measurement is the invoice. Once rock is blasted or pipe backfilled, nobody can measure it again, and the argument moves to drawings and memory.
- Read the measurement clauses: the unit, whether it is measured in place, loose or by weigh ticket, the pay lines, and what the rate includes.
- Agree with the owner's representative who measures, how, at which stages, and on what sheet you both sign.
- Survey the starting surface together, and both sign the plot.
- Measure each stage before it is covered or removed, with photos tied to stations or gridlines, as in documenting concealed work.
- Record each quantity the same day on a joint sheet with both signatures; note a disputed quantity rather than leave it off.
- Track running totals against the estimate, and warn the owner in writing when an item runs well over or under.
- Reconcile before each progress claim with the owner's representative; carry each agreed quantity from the signed sheets and identify any disputed amount separately.
Common mistakes
- Billing truck counts when the contract pays for rock in place.
- Letting the inspector measure alone and seeing the figure first on the certificate.
- Backfilling before the quantity is signed, to keep the crew moving.
Checklist
Before unit-price work is covered
- Unit, method and pay lines confirmed
- Starting surface surveyed and signed
- Each stage measured before it is covered
- Quantity sheet signed the same day
- Running totals checked against the estimate
- Differences settled before the progress claim
Check your understanding
The inspector is away the day the last blast is mucked out, and the crew wants to pour the base slab tomorrow. What do you do?
