Variations under Clause 13, valued as they happen
On a FIDIC job the Engineer can instruct change up to practical limits, and how that change is valued is set out in Clause 13. The discipline is to value it now, not at the final account.
QScope Team · 8 March 2026 · 6 min read
Change is normal on the scale of work Qatar has been building. A FIDIC contract expects it and gives the Engineer the power to instruct it under Clause 13, together with the rules for valuing it. Understanding those rules is the difference between change that is paid month by month and change that becomes a lump argued over at the close.
Where the power comes from
Under Clause 13 the Engineer may instruct a Variation, whether by instruction or by requesting a proposal, and the Contractor is bound to carry it out unless it falls outside the defined limits. A Variation can add work, omit work, change the character or quality, or change the sequence. What it cannot do is arrive without an instruction, so the first task is always to tie the change to an instruction that exists on paper.
How Clause 13 values the change
The valuation follows an order. Where the Bill or Schedule contains a rate for work of the same character executed under the same conditions, that rate applies. Where work is of similar character but not the same conditions or quantity, the contract rate is used as the basis and adjusted. Where there is no applicable rate, a new rate is derived from the cost of the work plus reasonable margin, or the work is carried out on a Daywork basis where the contract provides for it.
- Same character, same conditions. Apply the existing rate. No argument to be had.
- Similar work, changed conditions. Start from the contract rate and adjust for the difference, showing the adjustment.
- No comparable rate. Build a new rate from first principles, or price on Daywork where the contract allows and the records support it.
- Omissions. Value what is being taken out at the rate it was priced at, and watch for the effect on Preliminaries and on rates that assumed the omitted quantity.
Carry it into the IPC
A valued Variation is part of the interim measure. It belongs in the next Statement under Sub-Clause 14.3 and, if the Engineer accepts it, in the next IPC. The instinct to hold Variations back for the final account is a cash-flow mistake. Every month a valued change stays out of the Statement is a month the Contractor funds the Employer change for free.
The record that makes it stick
Because Qatar has no statutory adjudication scheme sitting behind the contract, an unvalued Variation has no quick remedy. It waits for the contractual claim and, ultimately, the dispute mechanism. The protection is contemporaneous records: the instruction, the measure of what was done, the resource where a new rate or Daywork is involved, and the valuation reasoning. Build the record as the work happens and the Clause 13 valuation almost writes itself.
QScope prices each Clause 13 Variation as it is instructed and carries it into the next Statement, so change is certified in the cycle rather than banked for a fight at the end.