Even well-developed project plans are vulnerable to unforeseen disruptions. At critical "forks in the road" — teams must choose between alternative paths, each carrying distinct risks and potential schedule impacts. The decisions made at these points can significantly influence project outcomes.
Extension of Time (EOT) claim negotiation is a core aspect of project delivery, regardless of contractual position, driven by schedule impacts, the need to establish causation and the selection of an appropriate delay analysis methodology.
Which method to use and when?
Selecting an appropriate delay analysis method is critical to accurately assessing schedule impacts and establishing EOT entitlement. The choice of methodology should be guided by the nature of the delay, the availability and quality of progress data and the contractual requirements. While both prospective and retrospective approaches are generally permissible, the selection often reflects stakeholder perspectives as well as contractual terms.
Contractors can typically favour prospective analysis methods such as IAP and TIA, as it allows entitlement to be determined early, providing clarity around exposure to liquidated damages (LDs).
Conversely, principals may prefer retrospective methods, opting to assess actual delay outcomes over time using a ‘wait and see’ approach, considering mitigation efforts, concurrent risks and whether forecasted delays materialise.
The following comparison table, informed by the Society of Construction Law Delay and Disruption Protocol (2nd Edition, 2017), outlines the key characteristics, strengths and limitations of commonly used delay analysis techniques.
| Method | Type | Approach | Best Used For | Strengths | Limitations |
| Impacted As-Planned (IAP) | Prospective | Inserts delay events into baseline schedule. | Early-stage claims. | Simple, easy to model. | Ignores actual progress; theoretical. |
| Time Impact Analysis (TIA) |
Prospective / Contemporaneous | Adds delay fragments to current schedule and reschedules. | Ongoing projects with updates. | Widely accepted; reflects schedule logic. | Requires detailed records and accurate updates. |
| Windows Analysis |
Retrospective | Compares planned vs. actual progress across time windows. | Complex, completed projects. | Reflects real progress; handles multiple delays. | Time-consuming; needs frequent schedule updates. |
| Collapsed As- Built |
Retrospective | Removes delay events from as-built schedule to assess impact. | Forensic analysis. | Using actual data; good for proving causation. | Can be speculative; logic changes hard to justify. |
| As-Planned vs. As-Built | Retrospective | Compares baseline schedule to actual completion. | Simple projects or limited data. | Straight forward, minimal data required. | Doesn't account for logic or concurrent delays. |
What about Australian Contracts?
Many modern Australian contracts — AS 4000 and AS 4902 being common examples — require contractors to keep the client informed as delays develop, rather than providing a single report after the fact. This means contractors often need to provide ongoing updates during the delay and later submit a retrospective explanation of what occurred and how it impacted the schedule. In contrast, some contracts, such as GC21 (NSW Government), impose strict timeframes for deciding on an initial Extension of Time (EOT) claim based on prospective analysis, even when the full extent of the delay is not yet known.
In Australian construction contracts, additional complexity is introduced when a contractor experiences a delay and any entitlement to damages, usually in the form of time-related costs (e.g. site overheads, supervision, equipment hires). Not all contracts treat these costs the same way and the following table demonstrates a preference for retrospective methodology in certain contracts when submitting EOT claims:
| Contract | Approach to Delay & Damages |
| AS 4000 / AS 4902 | Allows EOT claims and delay costs if the contractor can prove entitlement. Damages must be actually incurred, not estimated. |
| GC21 (NSW Government) | Requires detailed substantiation of delay costs. Often includes clauses requiring retrospective proof of actual costs. |
| HIA / MBA Domestic Contracts | Generally simpler; may not allow for time-related damages unless specifically agreed. |
| Bespoke D&C Contracts | Often include strict notice and substantiation requirements. May limit damages to actual costs only, excluding estimates or forecasts. |
At first glance, it may seem straightforward. If the contract permits or even encourages a ‘wait and see’ approach, then why consider submitting or awarding EOTs prospectively?
But...
Before dismissing the value of prospectively awarded EOT claims, it is important to recognise that recent Australian case law has found contractors not only entitled to relief from liquidated damages due to the improper denial of extensions of time, but also eligible for acceleration costs — having been forced to expedite works as a direct consequence of the superintendent’s failure to properly assess and grant those claims.
Could these cases have been avoided? Quite possibly. EOTs assessed and awarded prospectively, may have prevented costly and onerous disputes:
| Case | Could Prospective EOTs Have Prevented the Dispute? | Reasoning |
| V601 Developments v Probuild [2021] VSC 849 | Likely | The superintendent rejected EOTs and failed to act impartially. If EOTs were assessed and granted prospectively, the contractor wouldn’t have been forced to accelerate, and the dispute over LDs and damages may have been avoided. |
| Lahey Constructions v Dept of Education [2014] NSWSC 1011 / [2021] NSWCA 69 | Possibly | The dispute involved retrospective substantiation of time-related costs. A prospective EOT assessment could have clarified entitlement early and reduced the need for expert determination and litigation. |
| Brewarrina Shire Council v Beckhaus Civil [2005] NSWCA 248 | Possibly | The dispute over payment and completion could have been mitigated if EOTs and associated costs were assessed during the delay, rather than after. |
| Peninsula Balmain v Abigroup Contractors [2002] NSWCA 211 | Likely | The superintendent’s failure to act impartially and procedural issues around notice led to the dispute. A timely, prospective EOT process could have clarified entitlement and reduced reliance on the prevention principle. |
Final Thoughts
Recent Australian court decisions highlight that unfairly rejecting or delaying Extension of Time (EOT) claims can result in significant financial consequences. Acting promptly and, where the contract permits, granting EOTs on a prospective basis can reduce the risk of disputes and costly litigation.
Effective planning and maintaining accurate records — such as updated schedules, site diaries and correspondence — are critical. Without strong documentation, even legitimate claims can be difficult to substantiate.
In short, managing EOTs fairly, promptly and with proper record-keeping isn’t just best practice; it safeguards all parties involved in the project.
Written by Danya Pearce.
If you want to know which Delay Analysis Methodology is most suitable for your firm? Reach out to Zancon, your Construction Planning Experts. We're here to help.