In construction disputes, delay and disruption are often treated as interchangeable concepts, despite addressing different issues. Delay refers to the point at which completion is achieved later than planned. Disruption commonly results in a loss of productivity or efficiency. Loss of productivity arises when more resources or time are required to achieve a given output. Loss of efficiency, on the other hand, reflects the difference between the work actually achieved and the level of performance that was planned. It is therefore necessary to demonstrate what resources were used, how they were deployed, and the performance achieved relative to the original plan.
Disruption is often thought of not as a ‘blow-out’ but as a ‘slow-puncture’ that is not noticed until the tyre runs flat. Its effects may accumulate unnoticed until productivity losses become substantial. Because disruption is experienced while work is ongoing, it can be difficult to identify in real time and even harder to document accurately.
What Needs to be Demonstrated
The bar for demonstrating disruption is high. A contractor must demonstrate, on the balance of probabilities, that identifiable events outside its responsibility interfered with the execution of the works and directly resulted in additional expenditure.
Although the courts1 have confirmed that claims based on aggregated evidence (global claims) are not automatically invalid, this does not remove the contractor’s obligation to establish causation. Broad-brush approaches remain exceptional and rarely successful. The contractor must still connect the alleged disruptive event with a measurable loss. Where this link is missing or inadequately supported, the claim risks being dismissed as speculative rather than grounded in fact.
How Do You Measure Disruption?
The Society of Construction Law (SCL)2 suggests that methods for measuring disruption can be divided into two broad groups: those based on productivity analysis and those derived from cost comparison.
Productivity-Based Methods
Measured Mile Analysis
A measured mile analysis is widely regarded as a reliable means of assessing productivity because it compares performance during a disrupted period with a representative, undisrupted ‘baseline’ from the same project. Ideally, the baseline should be as close in time and nature to the disrupted work as possible to account for learning curves and seasonal weather variations, which often complicate how comparable the baseline is. By focusing on actual outputs rather than estimates, this approach seeks to minimise arguments about tender assumptions or general inefficiency.
However, the credibility of a measured mile assessment depends on careful implementation. Where planned outputs are used as the reference point, it must be shown that these outputs were genuinely achieved in unaffected areas and were not influenced by variations or other external factors3. Identifying a truly comparable, disruption-free period is often the most significant practical difficulty, particularly on large or complex projects where multiple influences overlap.
Earned Value Analysis (EVA)
Earned value analysis compares the resource allowance associated with a defined scope of work against the actual resources consumed in completing that work. Any excess may indicate reduced productivity. For this approach to be persuasive, the original allowances must be realistic, and the recorded actuals must be free from inefficiencies attributable to the contractor.
Some analyses extend this approach by using resource-loaded programmes to model intended versus actual resource deployment. While potentially informative, these exercises remain subject to the same underlying assumptions and limitations as traditional earned value assessments. EVA is typically less persuasive than a measured mile but stronger than a pure cost comparison.
Project-Comparison and Industry Studies
Where project records are insufficient, contractors may attempt to rely on comparisons with other projects or published industry data. These approaches are inherently vulnerable to criticism, as differences in scope, complexity, and working conditions make true comparability difficult to achieve. As a result, such methods are often treated as indicative at best rather than determinative4 and rarely sufficient on their own.
Cost-Based Methods
Cost-based methods generally present the greatest evidential challenge and are considered a last resort. Cost-based methods represent the most precarious route for a contractor. The SCL notes that they provide the “least robust support5” for a disruption claim, as they assume that any difference between the planned and actual costs is attributable to disruption.
Decision-makers tend to approach such claims with caution, implicitly assuming that the original pricing was accurate and that the contractor’s performance played no part in the cost overrun. To have any prospect of success, a contractor adopting this approach must be willing to provide detailed financial transparency, demonstrating both the sufficiency of the tender and the absence of any defaults.
Practical Implications and Records
Focusing solely on critical path activities is unlikely to capture the true impact of disruption. Productivity losses often arise in non-critical workstreams, consuming resources without immediately affecting the overall completion date.
To support a disruption claim, contractors should maintain records that go beyond basic site diaries or weather logs. Effective records may include:
- Clear identification of work locations and tasks with instances of idle time or unplanned redeployment, together with explanations.
- Regular measurement of actual output against planned rates.
- Evidence of compliance with contractual notice requirements.
- Progress reporting that distinguishes between delay and disruption effects.
Digital tools and integrated information management systems (such as BIM-integrated systems or automated site sensing) may assist in capturing this data, but the method is less important than the consistency and accuracy of the records maintained.
Conclusion
If disruption is the ‘slow puncture’ of construction disputes, then a contractor has to check the tyres frequently. Contractors must look beyond programme milestones and focus on how work is being carried out on site. Without contemporaneous evidence linking disruptive events to reduced productivity and resulting cost, recovery becomes increasingly difficult, if not impossible. Robust record-keeping remains the most effective means of preserving that link.
Author
Mick Cahill, MSc, FCIOB, MCIArb
Director, Delay
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Mick is a Chartered Construction Manager specialising in planning, project controls, and delay analysis for major construction and infrastructure projects. His career has spanned site engineering, project management, pre-construction, and design management, giving him a practical understanding of project delivery from inception through to completion. He now acts as an expert on delay and planning matters, producing delay analyses and expert reports across a range of contract forms, including JCT, NEC, FIDIC, ICE, and bespoke contracts.
References
- Walter Lilly & Company Ltd v Mackay & Anor [2012] EWHC 1773 (TCC). ↩︎
- Society of Construction Law Delay and Disruption Protocol 2nd Edition ↩︎
- Amey LG Ltd v Cumbria County Council [2016] EWHC 2856 (TCC) ↩︎
- Society of Construction Law Delay and Disruption Protocol 2nd Edition, Paragraph 18.20 ↩︎
- Society of Construction Law Delay and Disruption Protocol 2nd Edition, Paragraph 18.21 ↩︎