Most people who administer construction contracts in New Zealand know NZS 3910 well, and many now know the 2023 edition’s Contract Administrator and Independent Certifier. Fewer have read NZS 3915, even though councils use it often. Its full title explains it: Conditions of contract for building and civil engineering construction, where no person is appointed to act as Engineer to the contract.
That is the whole idea. Take NZS 3910, remove the Engineer, and let the Principal run the contract directly through a Principal’s Representative. It is a plain-English form with its own conditions of tender, special conditions, contract agreement and bonds, and it is aligned with the Construction Contracts Act 2002. It is also, as of today, the only member of the family still on its 2005 edition.
What changes when there is no Engineer
Under NZS 3910 the Engineer wears two hats: the Principal’s agent for instructions and administration, and an impartial decision-maker on the matters the contract entrusts to it. The 2023 edition split those hats into two people. NZS 3915 does something different. It keeps the Principal’s agent and drops the impartial decision-maker altogether.
The Principal’s Representative issues the instructions, assesses the payment claims, values the variations and decides the extensions of time. The form does not require that person to act independently or impartially between the parties. They act for the Principal, and the contract says so. The contractor knows that going in, which is why contractors tend to regard NZS 3915 as a form that works well for them: when the Principal gets it wrong, the consequences land on the Principal.
Three practical differences follow.
Payment schedules are the Principal’s job. There is no Engineer’s certificate to rely on. The Principal, through its Representative, must issue a payment schedule that meets the Construction Contracts Act and pay inside the time allowed. Miss the schedule and the claim is payable in full. That is true under every form, but under NZS 3915 there is no consultant in the chain whose diary catches it.
Variations are valued on a clock. The parties are expected to agree the value of a variation first. If they cannot, the Principal has a fixed window after receiving the contractor’s estimate to value it. Let the window pass and the contractor’s figure is treated as accepted. On a busy council desk, that is the clause that costs money.
Disputes go straight to an outsider. With no Engineer to give a first decision, the form sends unresolved disputes to an agreed expert, whose written determination binds the parties unless one of them takes it on to mediation or arbitration. Adjudication under the Construction Contracts Act is available at any time, as it is on every construction contract.
Where it earns its keep
The honest case for NZS 3915 is cost. On a $150,000 carpark resurfacing or a $400,000 toilet block, an Engineer’s fee is a visible line in a thin budget, and a council with a capable project manager can run the job itself. Where the works are simple, the contractor is known, and the client has somebody who understands payment schedules and variations, the form does what it was written to do.
It also suits principals who would rather own their decisions than delegate them to an impartial third party. There is nothing improper in that. It is simply a different allocation of risk, and the contractor prices it.
Where it bites
It is twenty years old. NZS 3915:2005 was written to match NZS 3910:2003. The 2013 revision of NZS 3910 was never carried across. Neither were the 2023 changes: the two-role split, the target-price option, the fault-based contractor indemnity and liability cap, the simplified dispute process, the health and safety clauses rewritten for the Health and Safety at Work Act 2015. NZS 3916 and NZS 3917 were both brought into line in 2025. NZS 3915 was not. The committee said in 2023 that it would be dealt with separately because it is so different from the others, and no timetable has been published since. Any special conditions a council has developed for its 2023-edition contracts will not drop onto a 3915 contract without rework.
Somebody still has to do the work. Removing the Engineer does not remove the administration. The registers, the site instructions confirmed in writing, the payment schedule within the statutory window, the variation valued on time, the extension of time decided with reasons: all of it still has to happen, and now it has to happen inside the council. Where the in-house capacity is not there, the saving on the Engineer’s fee is spent on the first disputed variation.
No impartial decision, no cover. When a contractor challenges a Principal’s Representative’s decision, there is no independent certificate to point to. The decision was made by the client’s own agent, and it will be tested as such. Councils that value being seen to deal fairly with contractors, or that expect to work with the same contractor again next year, should weigh that.
The name on the door matters. There is no Engineer, no Contract Administrator and no Independent Certifier under NZS 3915. A consultant engaged to help can act as the Principal’s Representative or support one, and should describe the role in those words. Promising “independent certification” on a 3915 contract promises something the form does not contain.
Three things to settle before you use it
- Who is the Principal’s Representative, and do they have the time? Name a person, not a team. Check their diary against the payment-schedule and variation clocks before award.
- Is the job simple enough that an impartial decision-maker is not worth paying for? If the ground is uncertain, the scope is loose or the contractor is new to you, it usually is worth paying for, and NZS 3910 is the better form.
- Which special conditions are you carrying over, and were they written for 2003? Have someone who knows both editions read them against the 3915 text.
Where we fit
We administer small works under NZS 3915 as the Principal’s Representative, or sit beside a council officer who holds the role and carry the registers, the schedules and the valuations for them. The discipline is the same one we apply as Engineer or Contract Administrator on larger contracts: every instruction in writing, every decision with reasons, every clock watched. The difference is that under NZS 3915 we say plainly whose side we are on, because the contract does.
If you are choosing between NZS 3915 and NZS 3910 for a small project, tell us the scope, the budget and who on your side would hold the role. We will give you a straight view on which form fits.