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An extension-of-time (EOT) claim is only as reliable as the programme used to assess it. A detailed analysis can fail if the underlying activities, durations or dependencies do not reflect a credible (baseline) plan.
Clarke Energy (Australia) Pty Ltd v Alinta Energy Transmission (Roy Hill) Pty Ltd [2026] NSWSC 1124 examines programme selection, changes in logic and the relevance of how work was ultimately performed.
Time impacted analysis and the intended work
At [407]– [408], Rees J considered time impacted analysis, drawing on Alstom Ltd v Yokogawa Australia Pty Ltd (No 7) [2012] SASC 49 at [1268]–[1271]. The method assesses a delay event’s effect on the contractor’s intended future work, taking account of progress when the event occurred.
This requires more than inserting a delay into a scheduling model. The selected programme must provide a reliable starting point, with logic that explains the intended sequence and progress information that supportsthe assessment. Later programme revisions may help test that starting point, but their significance depends on why the logic changed.
When a later programme exposes an earlier weakness
At [832], the Court accepted that a substantive change in subsequent programme logic, retained over an extended period, supported questioning the earlier programme’s suitability. However, the fact that the works were ultimately performed differently did not undermine the time impacted analysis: [834]–[835].
The distinction is between later evidence that exposes an unrealistic assumption and later events that lead to a different, but workable, approach.
For example, a programme might allow installation to overlap with adjacent structural work, before a safety review requires that work to finish first. The analyst should establish whether the original overlap was achievable, why the dependency changed and when the constraint became known.
A revision may correct unrealistic planning or reflect a new restriction, mitigation, a different resource strategy or a commercial choice. Programme files, revision narratives, workshop minutes and correspondence help distinguish these explanations. A departure from the planned sequence is not, by itself, proof that the analysis fails.
Comparable judgments: evidence and hindsight
This emphasis on the evidence behind programme logic is echoed in White Constructions Pty Ltd v PBS Holdings Pty Ltd [2019] NSWSC 1166. At [18]–[26], Hammerschlag J rejected the assumption that one of the competing expert approaches must be correct and described the complexity introduced by the analyses as a distraction.
The lesson is to make the reasoning accessible: identify the dependency said to cause delay, explain its factual basis and show its effect on completion.
Alongside that need for clear reasoning sits the question of how later events should inform the assessment. As discussed in Clarke Energy at [12]–[14], Built Qld Pty Ltd v Pro-Invest Australian Hospitality Opportunity (ST) Pty Ltd [2022] QCA 266 at [115]–[117] and V601 Developments Pty Ltd v Probuild Constructions (Aust) Pty Ltd[2021] VSC 849 recognise scope for retrospective judicial assessment.
Accordingly, [834] is not a universal prohibition on considering actual events. The applicable contract, theassessment method and the purpose for which later evidence is used remain central.
Presenting a persuasive EOT claim
Taken together, these decisions point to a practical approach: identify the contractual assessment method, explain why the selected programme is suitable, disclose relevant logic changes and demonstrate the resulting movement in forecast completion. Tie any later records to the assumptions they test. The aim is a traceable account of the plan, its dependencies and the reasons it changed, not simply a precise calculation.
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