Privy Council reaffirms contractual orthodoxy on variations, engineer authority and conditions precedent Uniform Building Contractors Ltd v Water and Sewerage Authority of Trinidad and Tobago [2026] UKPC 2

In Uniform Building Contractors Ltd v Water and Sewerage Authority of Trinidad and Tobago [2026] UKPC 2, the Judicial Committee of the Privy Council has delivered a judgment of real significance for users of FIDIC-based construction contracts and other internationally deployed standard forms. The appeal concerned the proper characterisation of alleged variations, the limits of an engineer’s authority, and the operation of clause 20.1 as a condition precedent to entitlement.

The leading judgment was given by Sir Peter Coulson, with whom the rest of the Board agreed. The decision reiterates the importance of the contract to which the parties had agreed and provides authoritative guidance of particular importance to both international arbitration and common law courts.

Procedural and factual background

The dispute arose out of a lump-sum design-and-build pipeline contract dated 23 May 2007, governed by the FIDIC Yellow Book (1999 Edition). Uniform Building Contractors Ltd (“UBC”) undertook to design, supply and install 28.43 km of transmission pipeline from Rio Claro to Mayaro in Trinidad and Tobago, split into two packages valued at TT$15.9m and TT$12.6m respectively (approximately USD $4.3m total).

Disputes emerged during the works and both packages were terminated by the Water and Sewerage Authority of Trinidad and Tobago (“WASA”) in May–June 2009. UBC commenced proceedings in May 2013, close to the expiry of the applicable four-year limitation period.

At first instance, the High Court dismissed both UBC’s claim and WASA’s counterclaim. The Trinidad and Tobago Court of Appeal reversed that decision, awarding UBC TT$13.9m (approximately USD $2m) plus interest and costs, principally on the basis that four categories of work constituted variations and that it would be unfair for WASA to rely on strict contractual analysis given the manner in which the project had been administered on site.

WASA appealed to the Privy Council. The Board unanimously allowed the appeal and restored the High Court’s dismissal of UBC’s claim in full.

The Court of Appeal’s “flexible operation” approach

A central feature of the Court of Appeal’s reasoning was its conclusion that the contract had been operated flexibly on site, such that WASA could not later insist upon a strict contractual analysis. At paragraphs 47–50 of its judgment, the Court of Appeal emphasised that, although the FIDIC terms had been incorporated, the day-to-day management of the contract demonstrated flexibility, and that a return “after the fact” to the literal language of the contract would lead to an unfair outcome. It concluded that it would be “fundamentally unfair” for WASA to resile from the engineer’s treatment of the disputed works as variations.

That fairness-based approach was rejected in clear terms by the Privy Council.

Three key takeaways

1. Variations are determined by the contract, not by conduct or opinion

The Privy Council held that the Court of Appeal’s approach suffered from a fundamental error of principle. Whether work constitutes a variation is a matter of contractual construction. It does not depend upon how the works were administered in practice, nor upon the opinion of the engineer.

Sir Peter Coulson stated (at [15]) that “whether or not an item of work is a variation is primarily a function of the contract terms”, and that the absence of contractual analysis in the Court of Appeal’s reasoning was a “fundamental flaw”.

Having undertaken a detailed examination of the FIDIC conditions, the Employer’s Requirements and the Bill of Quantities, the Board concluded that none of the four disputed items fell outside the scope of UBC’s lump-sum obligations.

In reaching that conclusion, the Board relied expressly on the long-established principle in Sharpe v San Paulo Railway Co (1873) LR 8 Ch App 597, where it was held that an underestimate of work in a lump-sum contract is “precisely the thing which [the contractor] took the chance of”. That authority was applied to reinforce the orthodox position that contractual risk allocation in lump-sum design- and-build contracts is not to be diluted by hindsight or operational pragmatism.  Whilst there may be some sympathy for the Engineer, whose priority had been “getting the project done”, he only had the authority that the contract provided, and he was bound by its terms.

2. The engineer has no power to vary the contract or waive contractual rights

The Privy Council also declined to follow the Court of Appeal’s conclusion that the engineer’s conduct on site could waive contractual requirements or vary the parties’ obligations.

Clause 3.1 of the FIDIC Yellow Book expressly provides that the engineer has no authority to amend the contract or to relieve either party of any duties, obligations or responsibilities under it. Against that background, the Board held that the Court of Appeal was wrong to conclude that procedural requirements, including notice and claims provisions, had been waived.

Sir Peter Coulson explained that if the engineer purported to dispense with compliance with clause 20.1 or the determination procedure under clause 3.5, he would in effect be amending the contract, which he was not permitted to do. The engineer’s role is administrative and certifying, not constitutive of the parties’ contractual rights.

This aspect of the judgment will be of particular interest to international practitioners, given the frequency with which arguments are advanced that informal site practice or cooperative conduct has modified contractual risk allocation. The Board’s analysis firmly re-anchors the engineer’s role within the limits of the authority conferred by the contract.

3. Clause 20.1 is a hard condition precedent, with express approval of Obrascon

The most practically significant aspect of the decision concerns clause 20.1 of the FIDIC Yellow Book. The Privy Council held that the clause is drafted in classic condition precedent terms (“if X, then Y” – see [64]) and that failure to comply within the 28-day period bars entitlement to additional payment entirely.

The Board expressly approved the analysis in Obrascon Huarte Lain SA v Attorney General for Gibraltar [2014] EWHC 1028 (TCC), where clause 20.1 was treated as a condition precedent to recovery. Sir Peter Coulson confirmed that the language of clause 20.1 demonstrates the necessary dependency between compliance and entitlement.

The Board also rejected the Court of Appeal’s conclusion that termination of the contract rendered clause 20.1 inapplicable. Termination operates prospectively and cannot revive claims which were already time-barred prior to termination.

Conclusion

This judgment represents a clear and authoritative restatement of contractual orthodoxy at the highest level. Delivered by Sir Peter Coulson, it reinforces three principles of importance in international construction law: contractual scope is determined by the contract itself; engineers cannot vary contracts or waive rights absent express authority; and condition precedent clauses, including FIDIC clause 20.1, will be enforced as written, certainly in English law.

For international courts and tribunals, Uniform Building Contractors is a reminder that certainty, not flexibility, lies at the heart of sophisticated construction contracts, and that fairness arguments cannot readily be used to circumvent the contractual machinery the parties have chosen.