Proportionality: The Hidden Principle That Organises NZS3910
For years, practitioners have debated the meaning of fairness under NZS3910. We argue over variations, extensions of time, working day rates, percentage recoveries, liquidated damages, and valuation methods. Yet beneath these individual mechanisms lies a recurring theme that rarely receives explicit attention. The theme is proportionality.
My proposition is simple. Proportionality is not merely a valuation tool. It is the organising principle that links together many of the most important mechanisms in NZS3910. When disputes arise, the dispute is often not really about notice, entitlement, rates, percentages, or timing. It is about whether the outcome remains proportionate to the bargain the parties originally struck.
The word proportionality appears only sparingly throughout construction contracts. However, many contractual mechanisms cannot be understood properly without it.
Consider variations.
The contract seeks to value varied work using existing rates and prices where possible. If identical work is performed in different quantities, the preferred outcome is that identical rates are applied. The objective is not merely administrative convenience. The objective is preservation of the contractual bargain. The Contractor receives the same commercial outcome for the same work, while the Principal pays no more and no less than would have applied had the work formed part of the original scope.
This concept extends beyond measured work.
Working Day Rates provide another example. Time-related costs arise because time itself has a value. The contract allows recovery through a nominated Working Day Rate, except where doing so would produce an inequitable outcome. This exception is often viewed as a narrow adjustment mechanism. I suggest it reflects something much broader.
The existence of an equity override recognises that strict application of a contractual formula can sometimes generate outcomes that become disconnected from the underlying bargain. The contract therefore introduces flexibility, not to rewrite the bargain, but to preserve it.
This same tension appears in percentage recoveries.
A percentage applied to a variation assumes a roughly proportional relationship between the value of varied work and the Contractor's overhead recovery. Sometimes that assumption holds. Sometimes it does not. The contract therefore permits alternative approaches in circumstances involving significant time-related effects.
Again, the objective is proportionality between cause and compensation.
Perhaps the clearest example is liquidated damages.
The liquidated damages mechanism assumes that each day of delay has a consistent value. Everyone understands reality is more complicated than this. The financial consequences of delay may fluctuate enormously throughout a project. Yet the contract deliberately adopts a linear valuation model.
Why?
Because the purpose is not perfect accuracy. The purpose is proportional allocation of risk. Both parties know their exposure from the outset and can price accordingly. The same reasoning helps explain why NZS3910 places such importance upon contemporaneous valuation, early notice, mitigation, and cooperation. Each mechanism seeks to maintain a reasonable relationship between contractual cause and contractual effect. Left unmanaged, that relationship can quickly become distorted.
Viewed through this lens, many disputes become easier to understand.
Arguments about Working Day Rates are often arguments about proportionality. Arguments about overhead percentages are often arguments about proportionality. Arguments about whether a variation rate remains applicable are frequently arguments about proportionality.
Even natural justice principles exhibit the same characteristic. Impartial decision-making seeks a proportionate relationship between the facts and the outcome reached.
This perspective may also help explain the recurring use of the phrase "fairly compensate" throughout construction law commentary. Fair compensation does not necessarily mean perfect compensation. It means compensation proportionate to the contractual bargain the parties actually made.
Proportionality, the Hidden Organising Principle of the Bargain
If this analysis is correct, proportionality is not merely another principle operating within NZS3910. It is the thread connecting many of its most important provisions.
The challenge for contract administrators is therefore not simply to apply contractual mechanisms mechanically. The challenge is to apply them in a manner that preserves the proportional relationship between risk, responsibility, and reward established at tender stage.
Perhaps that is why disputes arise whenever that relationship is lost. Not because the contract has failed. But because proportionality, the hidden organising principle of the bargain, has been forgotten.
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“Celebrating 50 years of New Zealand Building Economist 1972 to 2021”
By Matthew Ensoll
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Editor New Zealand Building Economist.
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