Most civil engineers in New Zealand have signed off on NZS 3910 paperwork at some point. Most have never read the standard cover-to-cover. That’s a reasonable trade-off — the document runs to a few hundred pages of cross-referenced clauses, and the parts you actually deal with on a contract are a small slice of the whole.
This guide is the slice. What NZS 3910 is, what it covers, who the four parties are, how the mechanics work in practice, where teams get tripped up, and what’s new in the 2023 edition. Written by a civil engineer who’s been working under NZS 3910 (in some form) for 27 years.
If you’re a project manager, contract administrator, or junior engineer coming up to speed — this is the cheat sheet. If you’re a Principal or Contractor wanting to know what the Engineer actually does, the four-parties section is the part to read.
What is NZS 3910 in one sentence?
NZS 3910 is the standard form of Conditions of Contract for Building and Civil Engineering Construction, published by Standards New Zealand. Most major New Zealand infrastructure contracts use it — Waka Kotahi NZ Transport Agency, regional councils, KiwiRail, water utilities, and private developers all reference it as the framework that governs how the contract is administered.
It’s not the law. The Construction Contracts Act 2002 (CCA) is the law that governs construction payment timing and dispute rights. NZS 3910 is the contract document that most parties choose to adopt to give structure to the CCA’s framework, plus everything the CCA doesn’t address (variations, defects liability, insurances, programme, completion certificates, and so on).
A quick history
NZS 3910 first appeared in 1969 as NZS 623. The numbering shifted to 3910 in 1987. Major revisions have followed in 2003, 2013, and most recently 2023. Each revision tightens ambiguities exposed by case law, adds clauses for things the previous edition didn’t anticipate (digital contract administration, sustainability reporting, alignment with updated CCA timelines), and occasionally restructures the General Conditions to read more cleanly.
If your contract references “NZS 3910:2013,” you’re working under the previous edition. Both 2013 and 2023 are valid — the contract itself nominates which one applies. Always check the front sheet.
The four parties
NZS 3910 names four distinct roles in any contract. Getting these clear in your head saves an enormous amount of confusion.
The Principal is the party paying for the work. A government agency, council, developer, or any organisation commissioning construction.
The Engineer is the contract administrator. An Engineer is named in the contract and represents the Principal’s interests in technical decision-making, certification of payments, issue of variations, assessment of claims, and final acceptance of the work. The Engineer is typically an external consulting firm — independent of both the Principal and the Contractor — appointed because contract administration is a specialist task and impartiality matters.
The Engineer’s Representative is the Engineer’s day-to-day delegate on site. The person walking the works, attending site meetings, signing off daily inspections, and feeding decisions back to the Engineer. The Engineer remains formally responsible for everything the Representative does, but the Representative handles the operational tempo.
The Contractor builds the work. They have the direct contractual relationship with the Principal.
A common confusion: people merge “Engineer” and “Engineer’s Representative” into a single role, or treat the Engineer as just another arm of the Principal. NZS 3910 is explicit that these are four separate parties. The Engineer has a duty of impartiality under the contract, even though paid by the Principal — that impartiality is what makes the contract administration credible to the Contractor and defensible if it ever ends up in adjudication.
What NZS 3910 covers
The standard is organised in three main parts.
General Conditions of Contract (Part A). The rules of engagement. Clauses covering definitions, the Engineer’s authority, Contractor obligations, programme and time, site possession, variations, insurances and risk allocation, defects liability, payment and retentions, and disputes. This is the part you’ll reference most often.
Special Conditions of Contract (Part B). Project-specific overrides and additions. The standard pattern reads: “Where General Conditions clause X.Y says [boilerplate], this contract shall instead read [project-specific]”. Special Conditions usually live at the front of the contract document.
Schedules. Physical artefacts: the Schedule of Prices, the Schedule of Preliminary and General Items, the list of insurances, the construction programme, drawings, specifications. These are the project-specific data that the General Conditions reference but don’t define.
The mechanics every engineer needs to know
Quick reference for the parts you actually deal with weekly.
Variations
A variation is any change to the Contract Works after the contract is signed. Three flavours exist in practice:
- A Variation Order issued formally by the Engineer (NZS 3910:2013 Clause 9.3). The clean path.
- A Variation by direction (Clause 9.4) — issued verbally or informally on site, formalised in writing later. The pragmatic path.
- A Constructive variation — where the Contractor claims a change happened by implication or instruction even though no formal Variation Order was issued. The disputed path.
Every variation needs a cost impact and a time impact assessed. If the parties can’t agree on the price, the Engineer determines under Clause 11. The cleaner the paper trail — written Variation Order, agreed price, agreed time impact, signed by both parties — the less likely the variation re-emerges as a dispute six months later.
Payment claims
Monthly payment cycle, governed by both NZS 3910 (Clause 12) and the CCA 2002:
- The Contractor submits a Payment Claim at the agreed cycle date (typically end-of-month).
- The Engineer reviews and issues a Payment Schedule within the working-day window specified in the Special Conditions (which cannot be shorter than the CCA statutory floor).
- The Net Certified Value is calculated: gross work done, minus retentions, minus prior payments, minus deductions.
- The Principal pays the Net Certified Value.
Late payment triggers CCA penalties and summary debt-recovery rights for the Contractor. The CCA timeline is statutory — Special Conditions can lengthen it (within reason) but cannot shorten it below the floor. If the Engineer fails to issue a Payment Schedule within the required window, the Contractor’s claim amount can be “deemed” certified in full, which can be expensive.
Retentions vs Bond in Lieu
NZS 3910:2013’s default retention bands are 10% on the first $200,000 of contract value, 5% on the next $800,000, and 1.75% on amounts over $1,000,000 (with caps and project-specific tweaks possible via Special Conditions). Retentions are released on Practical Completion (half) and Final Completion / end of Defects Liability Period (the rest).
An alternative mechanism is Bond in Lieu of Retentions: the Contractor provides a bond from an approved insurer or bank to the value that would otherwise have been retained, and no cash is withheld. This frees up the Contractor’s working capital.
Important domain rule: a contract uses either retentions or bond in lieu — never both simultaneously. This is one of the most common accounting mistakes in contract administration. Pick one mechanism per contract.
Notices, RFIs, NCRs, Transmittals
NZS 3910 itself doesn’t prescribe detailed flows for Requests for Information (RFIs), Non-Conformance Reports (NCRs), or Transmittals — it mostly references generic “written notice” requirements scattered through the General Conditions. In practice every contract develops its own register flow, often inherited from the Principal’s standard procedures.
The principle that matters: every change, every clarification, every non-conformance, every issued document gets timestamped and tracked. The audit trail is what decides disputes years later. If it isn’t in the register, it didn’t happen.
Common pitfalls
Patterns I’ve seen repeated across 27 years on civil works in NZ and AU:
- Verbal variations. A site engineer informally directs a change. The Contractor builds it. Six weeks later they claim time and cost. No written Variation Order exists. Always issue a written Variation Order — even retroactively after a verbal direction.
- Missed Payment Schedule deadlines. The Engineer takes too long to review a Payment Claim. The CCA default kicks in: the Contractor’s claim amount is deemed certified. Expensive and avoidable.
- Mixing retentions and bond in lieu. Accounting error — typically when a contract is amended mid-stream from one mechanism to the other. Pick one and stick with it.
- Schedule of Rates ambiguity. Items priced “per unit” without precise unit definitions. Variations later involve disputes over whether the rate covered X or didn’t.
- Treating the Engineer as the Principal’s arm. The Engineer must remain impartial under the contract. A “captured” Engineer who acts purely as the Principal’s advocate compromises the contract’s integrity and can be challenged in dispute.
NZS 3910 vs AS 4000
Australian projects use AS 4000-1997 (and AS 4902 for design-and-construct contracts) as the equivalent standard form. The concepts overlap with NZS 3910 but the structure differs.
AS 4000 calls the equivalent of the Engineer the Superintendent. The Superintendent has similar contract-administration duties but the impartiality requirement is framed slightly differently in Australian case law. AS 4000 separates “directions” and “variations” more cleanly than NZS 3910. AS 4000 retention bands are typically negotiated project-by-project rather than tied to a default schedule the way NZS 3910:2013 is.
For trans-Tasman firms running projects under both standards, most modern contract administration software handles both out of the box. The mental model carries over once you know the role-name mapping (Engineer ↔ Superintendent, Principal ↔ Principal, Contractor ↔ Contractor, Engineer’s Representative ↔ Superintendent’s Representative).
NZS 3910:2023 — what’s new
The 2023 edition modernises several areas:
- Tighter alignment with CCA 2002 payment-schedule timelines
- New provisions for digital contract administration (electronic notices, digital signatures, audit-trail expectations)
- Clearer treatment of sustainability and environmental obligations
- Updated dispute resolution pathway — adjudication first, then arbitration if unresolved
- More explicit definition of the Engineer’s impartiality duty
Many contracts still reference NZS 3910:2013, particularly those signed before late 2023 or where Principal procurement teams haven’t updated their template clauses. Both editions are valid — the contract itself states which one applies. If you’re starting a new contract today, NZS 3910:2023 is the better baseline.
Tools that help
You can run NZS 3910 contracts on spreadsheets. Most NZ firms do, and it works — until the volume of artefacts compounds. A single live infrastructure contract typically generates dozens of variations, hundreds of RFIs, monthly payment claims, ongoing NCRs and notices, and a transmittal register that just keeps growing. Spreadsheet-only workflows become fragile around the point where two team members start editing in different versions.
Contract administration software handles the mechanics (retention bands, fluctuations, certified amounts, approval routing) and the audit trail in one place. Gnosis is built specifically for NZS 3910 and AS 4000 — captures every artefact, calculates retentions automatically, routes approvals to the right people in the right order, and supports both NZ and AU jurisdictions in the same workspace. See the features or book a 15-minute walkthrough.
FAQ
Where can I buy NZS 3910? Through the Standards New Zealand website (standards.govt.nz). Both NZS 3910:2013 and NZS 3910:2023 are available as PDF or hard copy.
Is NZS 3910 mandatory? No. Parties to a construction contract can adopt any form they like, or write a bespoke one. NZS 3910 is the de facto default for major NZ infrastructure work because clients, contractors, and engineers are all familiar with it.
What’s the difference between NZS 3910 and NZS 3915? NZS 3910 is for one-off construction contracts. NZS 3915 is for term-service or maintenance contracts where the same Contractor performs ongoing work across a number of years. Different mechanics for variations, payment, and term.
Does the Engineer have to be an external firm? Not strictly, but in practice almost always. Internal-Principal Engineers create perception-of-impartiality issues that are hard to defend if a dispute escalates.
Alexios Kavallaris is the founder of Gnosis, a contract administration platform built for civil engineers working under NZS 3910 and AS 4000. He’s spent 27 years in civil infrastructure across Greece, the UK, New Zealand and Australia — including eight years on New Zealand’s Waikato Expressway programme — and is a 2020 Engineering Science Award recipient (KuDos).
