Concurrent Delay: What Does Effective Cause Require?
True concurrent delay is rarer than the term suggests. Two genuinely independent causes, each capable on its own of causing the same period of critical delay, running at exactly the same time.
It’s clear to anybody, that is a narrow set of facts. Thomas Barnes & Sons PLC v Blackburn with Darwen Borough Council [2022] EWHC 2598 (TCC) is a useful case precisely because it shows what happens when a court is satisfied those facts are actually present, and how it then has to choose between competing tests for dealing with them.
The facts behind the principle
The case concerned the construction of Blackburn bus station, under an amended JCT contract. The project suffered significant delay and the Council terminated the contract before completion, engaging a replacement contractor to finish the works. Thomas Barnes brought a claim for additional extension of time and prolongation costs of 209 days, on top of the 84 days already granted during the works.
Both parties' delay experts referred to the SCL Protocol, and both purported to use a windows analysis — Thomas Barnes's expert favouring an as-planned versus as-built approach, the Council's expert a hybrid of time-slice and time-impact analysis. HHJ Stephen Davies, sitting as a High Court judge, found that neither expert had in fact followed their chosen method loyally, and made a point that is easy to miss in summaries of the case:
“It would be wrong to attach too much importance to a close analysis of whether each had properly chosen or loyally followed the particular method selected. The SCL Protocol itself discourages such an approach.”
The Judge went further, making clear that deviation from a stated method is not automatically fatal — but it is not free of consequence either:
“…if an expert selects a method which is manifestly inappropriate for the particular case, or deviates materially from the method which he… [chose] without providing any, or any proper, explanation, that can be a material consideration in deciding how much weight to place on the opinions expressed by the expert.”
Two genuinely concurrent causes
The real substance of the case was a dispute over which of two events was driving the critical path during a specific window: a hub steelwork deflection issue (the employer's risk) and delay to the roof coverings (the contractor's risk). Thomas Barnes's expert said the steel deflection issue was critical throughout. The Council's expert said the critical path had, in fact, switched to the roof covering delay by early December 2014, which reduced the period of employer-caused delay to 27 days.
HHJ Davies found that, for a defined period, both events were genuinely critical and genuinely concurrent — a relatively unusual factual finding, and one reached only after detailed scrutiny of when each event actually started affecting the sequence of work, not simply when each was first identified.
The test the Court applied
Having found true concurrency, the Court had to choose between two long-standing approaches: the “dominant cause” approach, which asks which of the concurrent causes was the more significant driver of the delay, and the “effective cause” approach, drawn from the current edition of Keating on Construction Contracts, under which a contractor is entitled to an extension of time if an employer-risk event was an effective cause of the delay, even where a contractor-risk event was a concurrent cause of the same delay.
The Court adopted the Keating effective cause approach, while also holding that the contractor was not entitled to loss and expense for the period of concurrency itself — time was extended, but the contractor's own concurrent culpability meant it did not recover money for that same window.
Why this is not a wholesale shift
It would overstate the case to describe Thomas Barnes v Blackburn as a rejection of “first in time” thinking generally. The case did not need to resolve that debate, because the Court's finding was that two events were concurrent for a defined window regardless of which started first — the “effective cause” question was about significance, not chronology. What the case does confirm is that English courts will engage directly with the Keating effective-cause framework once true concurrency is established, and that doing so can produce a split outcome: time extended, money not recovered for the concurrent period.
For Australian practitioners, the case is instructive rather than binding, but the underlying caution applies equally here: genuine concurrency is rare, and proving it requires the same forensic discipline as proving any other delay — a clear account, grounded in the contemporaneous record, of exactly when each cause started to bite on the critical path, not an assumption that two delayed events occurring in the same general period must automatically be concurrent.
References
Thomas Barnes & Sons plc (in administration) v Blackburn with Darwen Borough Council [2022] EWHC 2598 (TCC) (17 October 2022), Technology and Construction Court, England and Wales (HHJ Stephen Davies).
At Accura Consulting, our team of experts work with clients to create a tailored solution to problems. If you have an issue and want expert support, get in touch.
Back to News and Insights
Related News and
Insights from Accura
True concurrent delay is rarer than the term suggests as delay experts understand. Two genuinely independent causes, each capable on its own of causing the same period of critical delay at the same time.