Experience is Not Evidence: The Quantum Lesson from Santos v Fluor

For years in Australia, clients have routinely engaged quantum experts in construction disputes who are not quantity surveyors.

Often they are delay experts dabbling in costs, former tradespeople, site supervisors or construction managers who have moved into senior operational roles. Their evidence is framed around experience. It is expressed in phrases such as “in my experience” or “on projects of this type”. 

The Queensland Supreme Court’s decision in Santos Ltd v Fluor Australia Pty Ltd shows why that approach is dangerous. 

This was not a marginal dispute. It was one of the largest construction cases ever litigated in Australia. When the quantum evidence was tested, the difference between disciplined construction quantum analysis and experience-based opinion mattered. 

Courts do not decide quantum by reference to experience alone 

A central theme of the judgment is that courts cannot act on opinions that are not explained. The Court reaffirmed that an expert must expose assumptions and reasoning: 

“The facts upon which an expert’s opinion is based must be available for scrutiny by the tribunal. A court can hardly be expected to act upon an opinion the basis for which is not explained.” ([259]) 

That principle is fatal to the style of evidence that relies on industry experience without analytical working or evidence. Construction experience is not evidence. It must be translated into a structured methodology the court can test and review. 

This was not QS evidence versus QS evidence 

What is striking about Santos is that the competing quantum evidence was not given by two quantity surveyors. 

One side presented construction quantum evidence grounded in QS analysis. It identified time-related indirect costs, linked them to site activity, validated records against contemporaneous project material, and explained the calculations step by step. 

The other side relied on a different type of witness. The evidence focused on critique rather than construction costing. It challenged assumptions, questioned aggregation, and relied heavily on professional judgment and experience. 

The Court did not accept that as a substitute for quantity surveying expertise. 

Criticism is not a methodology 

A recurring mistake exposed by the judgment is the belief that attacking the other side’s numbers is enough. 

The Court repeatedly characterised the non-QS evidence as criticism of reasoning rather than proof that the underlying assumptions were wrong. At [272], the Court made clear that these were attacks on reasoning, not failures of foundation. 

That distinction is critical. Courts expect a quantum expert to do more than say “this looks wrong”. They expect the expert to demonstrate why it is wrong and to replace it with a better construction cost based analysis. 

That did not happen. 

Construction quantum requires construction costing skills 

Many of the assumptions challenged in Santos were not accounting assumptions. They were construction assumptions. How supervision behaves during delay. How labour dominates indirect costs. How site resources respond to disruption. 

Those are precisely the matters quantity surveyors are trained to analyse and quantify. They are not resolved by seniority, past roles, or anecdotal experience. 

The Court accepted evidence where conclusions were reached by calculation and explained transparently ([268]–[271]). It gave little weight to experience-based critique that did not engage with construction costing logic. 

Not every QS is fit for purpose 

Santos also illustrates a point that is often missed in the Australian market. 

This is not simply about engaging a quantity surveyor rather than a non-QS. It is about engaging the right quantity surveyor. 

Courts expect quantum evidence to reflect an understanding of how costs arise on site, how delay and disruption play out in real time, and how variations are dealt with during live project delivery. That understanding comes from having delivered projects, worked for contractors, and dealt with time and cost issues as they occur, not in hindsight or in theory. 

A QS who has never worked on site, never delivered projects for contractors, or never dealt with delay and variation in practice is unlikely to provide the kind of evidence courts now expect. 

Even then you need a QS who understands that their opinion needs to be grounded in evidence demonstrating cause and effect. 

How does it apply to the Australian market?

The lesson from Santos v Fluor is clear in that if one party instructs a qualified quantity surveyor with real contractor delivery experience and the other does not, the outcome is rarely neutral. The court will prefer the evidence that explains how costs arise on site and how the figures are actually built that uses evidence to support their position. 

For years, Australian market has treated construction quantum as a discipline that can be filled by general construction experience. Santos shows that approach failing at the highest level. 

This is not about labels or professional protectionism. It is about evidentiary fitness for purpose. 

Construction quantum is a specialist discipline. If you do not instruct a properly qualified QS with real construction delivery experience, the other side will. And when the evidence is tested, that choice may determine the result. 

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At Accura Consulting, our team of experts work with clients to create a tailored solution to problems. If you have an issue and want expert support, get in touch.

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