Variations under Clause 13: how to instruct and value them

No major project runs exactly to the original design. Quantities change, new requirements appear, site conditions surface. FIDIC provides a lawful mechanism for this — the Variation under Clause 13.

What a Variation is

A Variation is a change to the Works made under Clause 13: adding, omitting or changing the quantity, quality, sequence or character of the work. This is not a claim or a dispute — it is the normal tool for managing the contract.

Who initiates it

The right to initiate a change belongs to the Employer’s side — usually through an Engineer’s instruction (in the Silver Book, the Employer’s Representative). The Contractor may propose a change (value engineering), but the Employer’s side puts it into effect.

The Contractor must carry out reasonable Variations — but within the contract and with the right to an adjustment of price and time.

The procedure (Sub-Clause 13.3)

1. Initiation. The Engineer either instructs a Variation or asks the Contractor for a proposal.
2. Contractor’s proposal. The impact on design, programme and price; justification.
3. Agreement or determination. Through the Sub-Clause 3.7 mechanism — the valuation of cost and time.

How it is valued

Valuation generally follows this order of priority:

• at the contract rates (BoQ/Schedule), if the work is similar;
• at adjusted rates, if the character or quantity differs significantly;
• at a reasonable cost (new rates), if there are no comparables.

This also covers adjustments for changes in legislation and cost (Sub-Clause 13.6/13.7 depending on the edition).

Where the line between a Variation and a claim lies

This is a frequent source of disputes:

• Variation — the employer/Engineer instructed the change. Handled under Clause 13.
• Claim — a party has acquired a right (to payment/time) because of an event or breach. Handled under Clause 20 with a 28-day notice.

Sometimes one event gives rise to both. If work is done “on instruction” but not formally treated as a Variation, record it and, if necessary, submit a claim so you don’t lose the right to payment.

Practical tips

• Do not perform significant extra works without a written instruction — verbal directions are hard to prove.
• Calculate the impact on the programme, not just on cost.
• If the instruction exceeds the Engineer’s authority, note it.
• Keep contemporaneous records — they decide the outcome of the valuation.

For more on claims, see “The 28-day rule”. Need a specific change valued? Contact our experts.