Proving Disruption: The Hardest Claim in the Final Account

Ask any quantum practitioner which head of claim is hardest to prove and the answer rarely varies: disruption. It appears in nearly every substantial final account dispute, it is frequently the largest single figure on the schedule, and it fails more often than any other. The reason is structural. Disruption is a claim about productivity, and productivity is invisible until it is measured.

The two are routinely conflated, and the distinction matters. Delay is about time: the works finished later than they should have. Disruption is about efficiency: the works cost more to build than they should have, because labour and plant achieved less per hour than the contractor was entitled to expect. The SCL Delay and Disruption Protocol draws the line precisely, recognising that disruption can occur without any delay to completion at all.¹ A contractor can hold the completion date by flooding the site with additional resource and still carry a substantial disruption loss for the cost of doing so.

That is also why the compensation route differs. There is no extension of time to claim. Disruption is recovered as loss and expense under the contract, or as damages for breach, and the claiming party bears the full burden of establishing cause, effect, and quantum.

The most persuasive method remains the measured mile: identify a period or section of the works unaffected by the events complained of, measure productivity there, and compare it with the impacted work. Done properly, the comparison strips out matters that sit at the contractor's own risk: tender optimism, poor supervision, defective workmanship. The logic has judicial pedigree reaching back to Whittall Builders v Chester-le-Street District Council, where output achieved in an undisrupted period provided the yardstick for valuing the disrupted one.²

The difficulty is that the method presumes a clean comparator, and complex projects rarely offer one. Where the whole site was impacted from the first week, or the works are too heterogeneous to compare, the analysis must reach for alternatives: earned value analysis, work sampling, programme-based studies, or, at the bottom of the evidential hierarchy, published industry productivity factors.³ None of these is illegitimate. Each is judged by the same test: does it demonstrate, rather than assert, the causal link between the event and the lost productivity?

A disruption claim is won or lost in the project records, long before an expert touches it.

The case law is a catalogue of self-inflicted wounds. In Van Oord v Allseas, claims presented with apparent sophistication collapsed on contact with the contemporaneous record: the witness evidence was contradicted by the documents, and the quantum evidence had taken the pleaded figures largely on trust.⁴ The judgment remains the standard citation for what happens when a disruption claim is built top-down from the overspend rather than bottom-up from the records.

The pattern repeats because the arithmetic is seductive. Actual cost minus tender allowance equals claim. But that formula assumes the tender was adequate, the site was otherwise efficient, and every unproductive hour traces to the respondent. Tribunals do not extend that courtesy, and opposing experts are retained precisely to withhold it.