An NZS project may need several decisions arising from one change. Treating agreement on the physical work as agreement on time and delay cost can leave the commercial position unresolved.
One event can require several assessments
A changed design may increase the work, affect completion and cause additional time-related cost. Agreeing that the change is a variation does not, on its own, settle the other consequences. The team still needs to establish what happened to the programme and how the contract deals with the resulting cost.
This distinction matters when administering NZS 3910:2023 and NZS 3916:2025. The variation and extension of time procedures have their own requirements. A combined submission can only do both jobs if it contains the necessary information and satisfies the applicable procedures.
Establish the change to the work
Consider an instructed relocation of a pump chamber. Its variation valuation may include revised excavation, pipework and reinstatement. Those changed quantities can be assessed without first deciding whether completion is delayed. Conversely, agreement on those quantities does not establish the time-related cost of a later completion.
Identify the entitlement and valuation provisions in the executed NZS contract for each part of the assessment. Routine handling of instructions and quotations is covered in Managing Construction Variations During Delivery; the issue here is what each assessment needs to establish.
Explain the effect on completion
The time assessment needs a reasoned connection between the event and the relevant completion obligation. Identify the affected activities, their planned sequence and the work that could or could not proceed. Use the programme and contemporary records to explain the effect.
In the pump chamber example, the contractor might be able to build elsewhere while the revised design is completed. Alternatively, the chamber may control testing and commissioning. The physical change is the same; its effect on completion depends on the project circumstances.
Do not equate the duration of the changed work with the extension of time sought. Explain any available float, overlap with other work and practical measures taken to reduce the effect. Where the position is still developing, identify the assumptions and update the assessment as the facts become clearer.
Keep the notice requirements visible
Under these NZS forms, an extension of time application involves information about the estimated delay and further notification where delay continues. A variation submission that says only “time to be advised” should not be treated as completing that process.
Check the edition and special conditions before relying on a combined submission. Identify which part addresses the changed work, which seeks an extension of time and which supports time-related payment. The recipient should be able to assess each request without guessing whether another one is intended to follow.
Identify the basis for time-related cost
Extra time and extra payment are not interchangeable entitlements. The event giving rise to delay and the applicable valuation provisions determine whether time-related cost is recoverable and how it is assessed. An extension of time should not simply be multiplied by a daily rate without establishing that basis.
Prepare a clear account of the resources affected. Which costs continued because of the event? Which were already included in the variation valuation? Which would have been incurred in any event? These questions help both parties test the assessment and avoid duplication.
For the relocated chamber, the changed-work price might already include supervision and plant for the additional excavation. A further time-related assessment needs to show what additional cost remains, rather than charging those same resources again under a different heading.
Keep the three assessments distinct
In the chamber example, three positions may emerge: an agreed value for the changed construction, an assessed effect on completion and a separately assessed entitlement to time-related cost. Record the basis of each, including any matter still unresolved.
The purpose is to avoid treating one answer as proof of another. A variation can have no effect on completion; a delay can occur without a compensable variation; and an extension of time does not, by itself, determine additional payment. Assess the event under the relevant provisions rather than relying on its label.
