The Clause 13 Variation, valued and certified
On the giga-projects driving Vision 2030 the scope moves constantly. FIDIC Clause 13 is the route every change has to travel, and the surveyor who prices it promptly keeps it out of the dispute pile.
QScope Team · 9 February 2026 · 6 min read
No project the size of a Vision 2030 development is built to the drawings it started with. Design develops, ground conditions surprise, and the Employer changes its mind. On a FIDIC Red or Yellow Book contract, every one of those changes is a Variation under Clause 13, and how you value it decides whether it gets paid this cycle or fought over at the final account.
What counts as a Variation
Under Clause 13 the Engineer may instruct changes to the Works: alterations to quantities, quality, levels, sequence or timing. An instruction that changes the scope is a Variation and carries a right to be valued. An instruction that merely clarifies what was always required is not. The first discipline is telling the two apart, because pricing a clarification as a Variation invites a rejection that taints the genuine changes alongside it.
The valuation hierarchy
FIDIC gives an order for valuing a Variation, and it is worth following in that order rather than jumping to a quotation.
- Bill rates. Where the varied work is of similar character and executed under similar conditions, the rate in the Bill of Quantities applies.
- Pro-rata rates. Where the work is similar but conditions differ, the Bill rate is adjusted to suit.
- Fair valuation. Where no rate reasonably applies, a new rate is built from first principles, from labour, plant and materials.
Get it into the certificate
A valued Variation does not pay itself. It has to be included in the next Statement so the Engineer can certify it in the Interim Payment Certificate. A Variation that is agreed in value but left out of the Statement is money sitting idle, and on a long job that idle money is a cash flow problem the Contractor created for itself.
Instructed, then priced
On a giga-project the pressure to keep building often means work goes ahead on a verbal or emailed instruction while the paperwork catches up. FIDIC requires the instruction to come from the Engineer, and the safe practice is to confirm any instruction in writing before valuing it. An unconfirmed instruction is a valuation with no anchor, and it is exactly the kind of item that survives to the final account unresolved.
The discipline
Log every instruction, confirm it in writing, value it against the Bill in the correct order, and carry the agreed value into the next Statement. A Variation handled this way is paid in the ordinary cycle. A Variation left loose becomes a claim, and a claim is slower, more adversarial and worth less.
QScope prices each Variation against the Bill rates and carries it into the Statement, so approved changes flow into the certificate instead of stacking up as a claim.