By the time a variation account is contested, the work has usually been built, covered and paid for at least once. What is left is a drawing, an instruction, and two parties with different recollections of what was actually done. The measurement that should have settled the matter was never taken.
Change is the most expensive thing to measure retrospectively and the cheapest to measure as it happens. The discipline that separates a clean final account from a contested one is almost entirely about when the measurement is taken, not how clever it is.
Measure against the contract quantities, not the drawing
A variation is a difference. It can only be quantified against a defined starting point, which is the contract Bill of Quantities or the contract drawings as priced. Measuring the varied work in isolation produces a number that cannot be reconciled with anything.
That means the omission must be measured with the same care as the addition. An instruction that substitutes one finish for another is not an addition of the new finish; it is an omission of the old at contract rates and an addition of the new. Accounts that record only the additions overstate the change and invite challenge on the whole submission.
Quantify at the point of instruction
An architect’s instruction, a site instruction or an RFI response should trigger a measurement while the design intent is fresh and the work is still visible. The measurement need not be agreed at that point — it needs to exist, dated, and tied to the instruction reference.
Where work is to be covered, the measurement has to be taken before it is. There is no later substitute for a record of what was in the ground, and a photographic record is not a measurement.
Keep dayworks as the last resort
Dayworks are appropriate where work genuinely cannot be measured, and they are routinely used where measuring would simply have been inconvenient. The commercial consequence is that the employer pays for resource rather than output, with no relationship to the value of the work.
Where dayworks are unavoidable, the sheets must be signed contemporaneously and the resource verified on site. A daywork sheet signed weeks later records an assertion, not an event.
Structure the account so it can be audited
A variation account that can be checked line by line gets agreed. One that arrives as a schedule of totals gets negotiated. Each variation should carry:
- The instruction reference and date
- The measured omission, at contract rates where they apply
- The measured addition, with the source drawing and revision stated
- The build-up of any new rate, showing how it relates to contract rates
- Any time or preliminaries consequence, priced separately
Pricing consequences separately matters. Conflating a quantity change with a prolongation claim makes both harder to agree, and the measured element is usually the part that is not actually in dispute.
Agree as you go
The strongest position at final account is a set of variations already agreed individually during the works. Change agreed at the time is priced against a live commercial relationship and a visible site. Change agreed at the end is priced against a closed project and an adversarial one.
Rolling agreement will not eliminate every dispute, but it reduces the final account to the small number of items where entitlement genuinely is contested — which is where the commercial effort belongs.
