Expert quantity surveying evidence after Warburton v County Construction
The judgment of Black J in Warburton v County Construction (NSW) Pty Ltd [2022] NSWSC 1281 is a useful illustration of how courts actually engage with expert quantity surveying evidence when liability is no longer the real issue.
The dispute had moved on to something more familiar and more difficult: how to value rectification works where competent experts disagree on scope and cost.
The Court was not critical of the experts themselves. The difficulty lay in the way the quantum evidence had been constructed.
As Black J observed, the quantification assumed that the Court would adopt one technical opinion in full, without adjustment. The joint reports were prepared on the basis that the Court would accept one or other expert “in its entirety and without modification” (para 227). That left the Court with little practical room to reason through the evidence, because the costings only worked if an all or nothing choice was made. As his Honour put it, the reports “do not allow costs to be determined unless I make a binary choice” (para 227).
That observation goes to methodology rather than outcome.
Courts rarely decide expert issues in a wholesale way. Findings tend to be incremental. Some aspects of an expert’s opinion are accepted, others are not. For quantum evidence to be useful, it must therefore show clearly how the figures are built up, so that a non technical decision maker can understand the pricing logic and adjust it sensibly if required.
The judgment also reinforces that the broader or more comprehensive rectification scope is not assumed to be the recoverable one.
“Where experts disagree, the Court will not simply prefer the more extensive solution. ”
Black J noted that there was “no basis to generally prefer” one expert over another where both were experienced and credible (para 226), and that the competing approaches were matters “as to which minds may reasonably differ” (para 240). Unless the evidence establishes why a wider scope is necessary, it may not be adopted.
Importantly, uncertainty was not treated as a reason to avoid pricing altogether. The Court accepted that uncertainty can be addressed within the costing exercise itself. As Black J stated, “the allowance of a provisional sum is a proper way to address uncertainty in the scope of the work” (para 245). The difficulty in this case was that alternative, narrower scopes had not been costed at all, leaving the Court to bridge the gap.
The judgment also reaffirms a familiar but often overlooked principle. Where loss is established, difficulty in quantification does not defeat recovery. The Court “must do the best it can to make a reliable assessment of damages” even where that assessment is difficult (para 255). Precision is required only to the extent that it is reasonably achievable on the available evidence (para 257).
Conclusion
In the end, the Court adopted one expert’s quantification but applied a discount to reflect unresolved uncertainty, recognising that “scientific or mathematical certainty is here not possible” (para 259). That outcome is a reminder that where uncertainty is not adequately addressed in the evidence, the Court will address it itself.
Seen in that light, Warburton is less about who was right on the numbers and more about how expert quantum evidence needs to be structured. Evidence that explains its reasoning clearly and allows for adjustment reflects how courts actually decide disputes and how rectification costs are ultimately assessed.
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