A variation can be valued using the rates already in the contract or priced afresh as a new rate. Which applies decides the money, and the choice follows rules rather than preference.
Most contracts set a hierarchy for valuing change: use the contract rates where the work is of similar character and executed under similar conditions, adjust those rates where conditions differ, and only build a new rate where nothing comparable exists. Arguments about variations are usually arguments about which rung of that ladder applies. Understanding the test is worth more than being forceful about the number.
Valuation at existing contract rates at a glance
The varied work is measured and priced using the rates the contractor already tendered, either directly or with a proportionate adjustment where the quantity, timing or conditions differ. The attraction is that the rates were set competitively, so neither party is negotiating from scratch. The limitation is that a tendered rate carries assumptions about quantity, access and sequence, and applying it to work executed in very different circumstances produces an unfair answer in one direction or the other.
A new rate built from first principles at a glance
Where no comparable item exists, or where the conditions are so different that an adjusted rate would be unreasonable, the work is priced by building a rate from its components: labour at the agreed rates, plant, material at cost with the agreed addition, and the contractual percentages for overhead and profit. It takes longer, requires evidence and is the correct answer for genuinely novel work. It is also where a contractor can recover margin lost elsewhere if nobody checks the build up.
The test that decides which applies
Valuation at existing contract rates: Similar character and similar conditions of execution. Both limbs must be satisfied, and conditions include access, timing, sequence, quantity and any restriction on working.
A new rate built from first principles: Applies only once the first test fails, so the party arguing for a new rate has to show why the existing rate cannot reasonably be adjusted.
Evidence required
Valuation at existing contract rates: The measured quantity and the identification of the comparable bill item. Little else, which is why it settles quickly.
A new rate built from first principles: A full build up with labour constants, output assumptions, plant requirement, supplier quotations and the contractual percentages, each of which can be challenged.
Where the risk of error sits
Valuation at existing contract rates: In the assumption of similarity. A rate for 2,000 square metres applied to 40 square metres in a difficult location is arithmetically simple and commercially wrong.
A new rate built from first principles: In the build up. Generous labour constants or an inflated plant allowance are easy to insert and hard to spot without a benchmark.
Effect on time and disruption claims
Valuation at existing contract rates: A rate applied without adjustment may leave the contractor with a genuine disruption cost that the rate never contemplated, which then returns as a separate claim.
A new rate built from first principles: A properly built rate can absorb the local effect of the change, which reduces the scope for a later disruption argument on the same work.
Speed of settlement
Valuation at existing contract rates: Fast. Many variations can be agreed inside a single valuation cycle, which keeps the register short and the cost report honest.
A new rate built from first principles: Slow. Build ups go back and forth, and unresolved variations accumulate into the final account, where they are harder to settle.
Dependence on good tender documents
Valuation at existing contract rates: Heavily dependent. A thin activity schedule with lump figures provides nothing to apply, so every change becomes a new rate by default.
A new rate built from first principles: Dependent on having agreed labour, plant and percentage rates at tender. Without them the build up is negotiated from nothing.
Who it tends to favour
Valuation at existing contract rates: Usually the owner, because competitive tender rates are generally keener than a negotiated build up.
A new rate built from first principles: Usually the contractor, because a build up priced after award carries no competitive pressure.
When valuation at existing contract rates wins
- Additional work of the same character carried out in the same conditions, such as more of a finish already being installed.
- Omissions, where the tendered rate is the natural measure of what is being removed.
- Changes instructed early, before the sequence or access assumptions in the rate have been disturbed.
- Projects with a full bill of quantities, where a comparable item usually exists.
- Situations where speed matters more than precision, because the valuation can be settled in days.
When a new rate built from first principles wins
- Work with no equivalent in the pricing document, such as a new system or an unusual detail.
- Work executed in materially different conditions, for example in an occupied area or outside normal hours.
- Small quantities of something the rate assumed would be done at scale.
- Changes that alter method rather than quantity, such as a different sequence of installation.
- Any situation where applying a contract rate would plainly overcompensate or undercompensate one party.
How to decide
Work through the hierarchy in the order the contract states it, and resist jumping to a new rate because it is easier to calculate. Where a contract rate exists but conditions differ, the right answer is the adjusted rate: start from the tendered rate and adjust the specific component that has changed, with the adjustment explained in one line. Reserve new rates for work that genuinely has no equivalent, and insist on a build up you can benchmark against the labour and plant rates in the contract.
Keep a short internal note for every variation recording which limb of the hierarchy was applied and why. Over a project that note becomes the consistency record, and consistency is what stops the same argument being relitigated on each variation. It also means that if the matter reaches a formal dispute, you can show a method rather than a series of ad hoc settlements. The drafting of valuation clauses differs between forms and is revised periodically, so read your own clause and take advice from a licensed adviser where the interpretation is genuinely contested.
Domira builds and supervises projects across Saudi Arabia, and the commercial discipline above is how its projects stay inside their budget and their programme. Send the drawings, the contract or the site and Domira will tell you where the risk actually sits.
Frequently Asked Questions
How are variations valued in a construction contract?
Most forms set a hierarchy. First, use the rates in the contract where the work is of similar character and executed under similar conditions. Second, adjust those rates where the character is similar but the conditions differ. Third, build a fair new rate where neither applies. Dayworks are typically a last resort for work that cannot sensibly be measured at all.
What is a star rate in construction?
A star rate is a new rate agreed for varied work that has no comparable item in the pricing document. It is built from components: labour, plant, materials and the contractual additions for overhead and profit. Because it is priced after award with no competition, it should be supported by a build up and benchmarked against the labour and plant rates the contractor tendered.
Can a contract rate be adjusted for a smaller quantity?
Often yes, where the contract permits adjustment for a change in conditions of execution and the smaller quantity genuinely changes how the work is done. A rate tendered for a large repetitive area assumes a setup, a crew and a learning curve that do not apply to an isolated patch. The adjustment should address the specific component that changed rather than applying a blanket uplift.
Is extra work always a variation?
No. Work that is already required by the contract documents, read as a whole, is not a variation even if it is not drawn on the sheet the contractor was looking at. The question is whether the instruction changes the scope or merely clarifies it. That distinction is a matter of construing the documents, so where real money turns on it, get the view of a licensed legal adviser before conceding or refusing.
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