By Charles Humphries

Article summary

COVID‑19 continues to shape construction disputes, raising complex questions around causation, evidence, and valuation. Drawing on both on‑site experience and subsequent expert witness work, the article explores:

• Competing and simultaneous causative events.
• How impacts can be identified, linked, and particularised.
• The role of factual and contemporaneous evidence in establishing the chain of causation required to recover costs.
• Practical considerations for the preparation and presentation of claims.

Introduction

The term ‘COVID’ is likely to feature in most change accounts for projects that were live across England and Wales in early 2020 and onwards, with their effects still being tested within the disputes industry against established principles of causation, proof, and entitlement.

For context, traditional disruption events, such as reduced working areas, restricted access, or changes to defined workface constraints, although challenging to quantify, often present a principal or readily identifiable causative event upon which a claim can be advanced.

However, for many COVID‑impacted projects, the effects involved multiple and overlapping causes occurring simultaneously, which, in practice, increase the difficulty in establishing clear and distinct links between cause and effect. This is because live projects often suffered from many simultaneous effects, which include but are not limited to:

1. Reduced labour availability and output productivity due to safety concerns with varying restrictions and guidance;
2. Out‑of‑sequence working for the same reasons;
3. Material and supply-chain constraints; and
4. Weakened coordination as remote working removed the quick day‑to‑day problem-solving conversations that typically keep projects moving.

These overlapping causes tend to blur the relationship between cause and effect in a way which many construction professionals and projects had rarely experienced before.

The challenge becomes even greater if these pressures also manifested themselves on top of pre‑existing issues. In some instances, COVID became an explanation for commercial and delivery pressures which may have been already present.

Causation

From a commercial perspective, a practical starting point when assessing COVID‑related claims is the principle that a party may only recover loss actually caused by the event relied upon, and that an event which merely provides the opportunity for loss does not ordinarily suffice.^[1]  The “but for” test is also conventionally a starting point for factual causation, requiring that the loss would not have occurred absent the event relied upon, however, the courts have recognised that this test is not inflexible and may be challenging where simultaneous causes are at play.^[2]

Secondly, where several causes overlap, a party should endeavour to understand the effect of each cause. However, the courts recognise that in practice such causes may be difficult to disentangle, and that this difficulty goes to the assessment of quantum, rather than operating as an automatic bar to recovery.^[3]  However, where multiple factors operate simultaneously, care is required to avoid attributing all claimed disruption to a single cause by inference or high‑level narrative without proper engagement with other potentially operative factors.^[4]

Thirdly, where damage was already present, a subsequent event which does not add to the injury already caused does not give rise to recoverable loss, because the loss was already present and cannot be said to flow from the later event.^[5] Furthermore, the fact that two events occur concurrently does not mean that one negates or excuses the causal effect of the other, and that thorough analysis is still required to determine whether, and to what extent, each event caused delay or disruption.^[6]

Against this backdrop, before bringing a dispute to proceedings, parties should consider whether:

1. The activity was actually disrupted because of COVID;
2. The project was already disrupted for another reason; or
3. It was a combination of both?

These questions may be basic, but they are often the basis upon which COVID claims either succeed or fail. If the honest answer is “a combination,” the claim’s strength typically depends on whether a party can separate the impacts and demonstrate the effects using facts and records.

Effect

Despite the volume of COVID-related issues arising on construction projects, there remains a limited number of publicly reported case law addressing how the courts approach COVID‑related disruption and loss of productivity. This is largely because many such claims are still within adjudication or arbitration.

Whilst not legally binding, the SCL Delay and Disruption Protocol remains an industry benchmark for prescribing how to evidence cause and effect, particularly in relation to disruption and productivity loss. The Protocol sets out a clear preference for project‑specific analysis, with a properly executed measured‑mile analysis recognised as the most reliable method.^[7]

However, many projects do not have a sustained unimpacted baseline period to measure against prior to COVID. Furthermore, the prolonged duration and evolving nature of COVID meant that many traditional methods of demonstration were unavailable, especially as projects moved through new phases where prior activities could no longer be meaningfully compared with follow-on activities.

In my experience, this was compounded by the practical reality on site. Whilst working on projects operating under these exceptionally challenging conditions, I often heard that ‘the site teams are focused on doing everything possible to keep the works progressing, rather than dedicating additional time and resources to claim preparation and record‑keeping’. This is because these were often perceived as matters for quantity surveyors or commercial teams. This practical reality goes some way to explaining why COVID‑era disruption claims are, in many cases, more difficult to substantiate than claims arising from more traditional events. However, a failure to keep records in circumstances where they reasonably could have been kept will rarely excuse a party from the evidential burden of substantiating causation and quantum.^[8]

A lesson learnt, is that where a sustained unimpacted comparator period does not exist, projects, even during challenging conditions, should consider implementing sustained and prescriptive time‑and‑motion style records during disruption periods, perhaps coupled with structured observations of lost time and constrained working. These can later be compared against follow‑on works, or other similar historical projects and expected output, and can, when done robustly, provide be a very useful basis for a claim.

Records, Records, Records

The onus of proof remains with the party seeking the claim,^[9] and entitlement generally depends on contemporaneous records demonstrating what actually occurred, when it occurred, and why it had a material impact on progress or cost, rather than on abstract, reconstructed or theoretical analysis.^[10]

The key question is not “Do we have records?,” but “Do we have meaningful records?”

Records that typically make the difference include but is not limited to detailed daily allocation sheets, contextualised photographs, detailed trackers, periodically accepted programmes, and contemporaneous communications which can later be relied upon i.e., can a decision maker who is not as close to the intricacies of the project easily interpret them?

Ultimately, a decision‑maker is likely to examine whether contemporaneous records demonstrate the alleged effects of COVID, or whether the assessment relies on assumptions to address evidential gaps. The quality of records not only underpins entitlement, but directly constrains the extent to which quantum can be demonstrated.

Notwithstanding this, there may be circumstances in which detailed contemporaneous records are not available, particularly for fast-moving situations. In those cases, an assessment may still be undertaken, but it will typically limit the confidence with which the causation, effects, and quantum can be established, and may require any assessment to be framed by reasonable and appropriate assumptions.

Quantum

It is often tempting for a party to advance a claim by reference to actual costs less the pricing document, which may, in substance, resemble a global or total‑cost approach. Where practicable, parties should endeavour to distinguish between excusable delay, compensable delay, self‑driven delay, neutral events, and any concurrency, in order to demonstrate causation and responsibility.

It is worth bearing in mind that in other jurisdictions, it has been decided that where inefficiency arises from a combination of contributing factors, recovery is not precluded merely because precise apportionment is difficult, provided the evidence establishes a rational and proportionate connection between the relevant causative events and the loss claimed.^[11]

Overall, the period linked directly to the causation(s) is most likely to give rise to recoverable cost, with anything outside of this period being reduced as remoteness to the causation increases.

Expert Witness (and best practice)

When presenting information to a decision‑maker, clarity should be preferred over unnecessary complexity. Transparency as to areas of uncertainty enhances credibility and is to be preferred over overstating precision.

An expert witness’s duty is to assist a decision‑maker objectively, to identify clearly the factual foundations and assumptions relied upon, and to explain alternative conclusions where outcomes may reasonably differ depending on the underlying facts.^[12]

Closing thoughts

From the perspective of a Chartered Quantity Surveyor who worked both on-site during COVID and subsequently acted in expert witness on COVID‑related matters, the lessons learned are, in many respects, no different from those arising from traditional disruption events. Experience consistently reinforces a familiar adage: the clearer the causation, the stronger the records, the more robust the quantum.

---

[1] Galoo Ltd v Bright Grahame Murray (a firm) [1993] EWCA Civ 3

[2] The Financial Conduct Authority v Arch Insurance (UK) Ltd [2021] UKSC, paragraphs 177 to 185

[3] Walter Lilly & Co Ltd v Mackay & Anor [2012] EWHC 1773 (TCC), paragraphs 362 to 371.

[4] Amey LG Ltd v Cumbria CC [2016] EWHC 2856 (TCC), paragraphs 17.13 to 17.15.

[5] Performance Cars v Abraham [1962] 1 QB 33.

[6] Royal Brompton v Hammond [2001] EWCA Civ 206, paragraphs 11 to 12.

[7] Society of Construction Law, Delay and Disruption Protocol, 2nd Edition (February 2017), paragraphs 18.16 to 18.19.

[8] Franco Mastrandrea, ‘Are Global and Total Cost Claims Still Viable?’ (2026) The International Construction Law Review 194.

[9] Robins v National Trust Co Ltd [1927] AC 515, PC.

[10] Bluewater Energy Services BV v Mercon Steel Structures BV [2014] EWHC 2132 (TCC), paragraph 324.

[11] John Doyle Construction Ltd v. Laing Management (Scotland) LTD [2004] ScotCS 141, paragraphs 16 to 18.

[12] National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The “Ikarian Reefer”) [1993] 2 Lloyd’s Rep 68.

---

About the Author

Charles Humphries is a Chartered Quantity Surveyor with nearly 15 years’ experience spanning main contracting and construction dispute resolution, and is a Fellow of the Royal Institution of Chartered Surveyors and the Chartered Institute of Arbitrators.

He brings significant practical experience from commercial lead roles on major infrastructure projects in excess of £1 billion.

Charles has also supported named quantum experts on over fifteen occasions across litigation, international and domestic arbitration, adjudication, and mediation, contributing to disputes in excess of £500 million.

His experience includes termination valuations, variations, prolongation, disruption, defects, and loss and expense.

About HKA’s Construction Quantum services

In high-stakes construction disputes, expert quantum analysis is critical to defending or determining value with precision.

HKA is the trusted global leader in quantum expertise – delivering robust, evidence-based insights that stand up to scrutiny. With a proven track record on major projects worldwide, our specialists provide the clarity, credibility, and confidence clients need to resolve disputes and protect project outcomes.