The same eight tonnes can cost you $8,987 or $15,783.

When a drawing changes, the work has to be valued, and the contract gives you a ladder of methods. They are not interchangeable. They are ranked, and the rank matters, because each rung up the ladder moves risk from the subcontractor to you.

Four bases, one piece of steel

The bill rate. If the change is more of something already in the bill, the agreed rate applies. Eight tonnes at the direct rate is $8,987, and it is the cleanest possible answer, because the price was fixed before anybody had an incentive to argue. This is always your opening position.

The star rate. When the changed work is similar but not identical — same steel, but in tighter conditions, or out of sequence — you take the bill rate and adjust it. Here it lands at the subcontract rate of $1,285, giving $10,280. The adjustment is a judgement, and the judgement is where the negotiation lives.

The quotation. The subcontractor names a price for the change before he does it. Eleven thousand six hundred. Clean, if you accept it, but you are accepting a number he built to be accepted — the Week 2 mark-up, applied to a captive change.

Dayworks. And then the one at the top of the ladder, the one he always wants: you pay for the men, the materials and the plant, measured by the hour, as they are spent. $15,783.

Same eight tonnes. A $6,795 spread — seventy-five percent of the cheapest price — created entirely by which basis you argue for. He will argue for dayworks every time. You will argue for the bill rate every time. And the contract has usually already decided who is right, in a clause nobody reads until they are fighting.

Why dayworks is dangerous

Dayworks looks the fairest of the four. You pay for exactly what was spent — the actual men, the actual hours, the actual steel. What could be fairer than that?

This.

Dayworks pays for time, not for output. Take the same eight tonnes. A gang tying five tonnes a day does it in 1.6 days and costs you $12,603. The same gang, tying two tonnes a day — slow, badly organised, three men where two would do — takes four days and costs you $15,783.

The worse the subcontractor performs, the more he is paid. It is the only pricing arrangement in construction with the incentive pointing exactly backwards, and a subcontractor who has talked you into dayworks has every reason to work slowly and none at all to work well.

Which is why the contract makes daywork sheets a daily ritual. Every sheet signed at the time, on the day, by your engineer — not because the paperwork is sacred, but because a daywork sheet you sign a week later is a record of hours you can no longer dispute. Sign it late and you have agreed to somebody else's account of how long it took.

The half of the change nobody prices

Now the real money, and it is the money almost nobody claims, because it is the hardest thing in construction to prove.

The eight-tonne change was not eight tonnes of damage. The column-head details arrived late, as a revision, into the middle of a running job. The gang that should have been fixing the core wall stopped and waited for them. Then it worked out of sequence, tripping over its own materials, doing tomorrow's work today because today's work was not ready.

The eight tonnes cost $10,280 to fix. But the disruption that change caused to the surrounding work — the whole 107-tonne superstructure dropping from five tonnes a day to three and a half — cost another $10,565. The true cost of that “small” change was $20,845, and only half of it is on any document.

This is disruption, and it is the single most disputed number in the industry. It has no rate, no line, no delivery note. It is not the direct cost of the changed work — it is the damage the change did to all the unchanged work around it. And because it lives only in the gap between how fast you should have gone and how fast the change let you, the only thing on earth that can prove it is a baseline.

The time-phased baseline from Week 8 — the one that seemed like an accounting exercise — is the document that turns “the job felt slow after that revision” into “the superstructure ran at 3.5 tonnes a day against a planned 5, here is the record, here is the date the revision landed, pay me.” Without it, disruption is a feeling, and you cannot invoice a feeling.

The rule that keeps it clean

Everything in this article is why a change never, ever gets priced inside an interim valuation.

A change is a separate event with its own life: notified, valued on the right basis, agreed, and only then added to the baseline as new scope with new money. It gets its own reference, its own record, its own instruction. The moment you let a variation be settled quietly inside a monthly certificate, you have lost the ability to price it properly, to claim the disruption, or even to prove later what was agreed.

Change control is not bureaucracy. It is the difference between getting paid for the change and absorbing it.

Practical insight

Take your three biggest variations and find, for each, the basis it was priced on. Bill rate, star rate, quotation, or dayworks.

If the big ones are on dayworks, ask why — because either the work genuinely could not be measured any other way, or a subcontractor won an argument he should have lost, and the difference is real money you are still paying for.

Then ask the harder question: for every change that delayed or disrupted other work, did we claim the disruption? If the answer is “we priced the change itself”, you have been collecting half of what each variation actually cost you, and giving the other half back for free — because nobody built the record while it was happening.

And the record is a baseline you already have. You just have to read it before the memory fades.

Key takeaways

✔ A change can be valued four ways: bill rate, star rate, quotation, dayworks — a $6,795 spread on eight tonnes of steel.
✔ The bases form a hierarchy. Each step up hands more risk to you. Bill rate is always your opening position.
✔ Dayworks pays for time, not output — the slower the subcontractor works, the more he earns.
✔ Sign every daywork sheet at the time. A sheet signed late is hours you can no longer dispute.
✔ Disruption is the change's damage to unchanged work: on this job $10,565, as big as the change itself.
✔ The “small” 8-tonne change really cost $20,845. Half of it is on no document.
✔ Only the time-phased baseline can prove disruption. That is what Week 8 was for.
✔ A change is never settled inside an interim valuation. It gets its own process, or you lose the right to price it.

What is coming next

Everything in Phase C has been about measuring one thing at a time — cost when it is incurred, progress when it is made, a subcontractor's claim, a change's true price.

But you cannot run a project by measuring everything twice: once for the accountant and once for the planner. The site does not have time, and the two sets of numbers never agree.

Next week: single data capture — the discipline of collecting cost and progress with one entry, at one moment, so that for the first time your CPI and your programme are telling the same story about the same day.