Wellington Te Aro contract-admin case study — the §14.4 valuation method the QS chose vs the contractor's claim

Steve Parker
Jun 22
7 min read

Updated: Jul 9

A Wellington Te Aro inner-city alteration produced a structural variation claim the head contractor priced at $145-180k. The QS's §14.4 valuation method, applied in the right order, resolved the variation at $85-110k — and survived the contractor's challenge.

By Steve Parker · Trueworks · NZ construction estimation · 5 min

NZS 3910 §14.4 sets a hierarchy of valuation methods for variations. The dollar gap between method 1 and method 4 is the difference between a defensible determination and a determination that gets appealed.

By Steve Parker · Trueworks · NZ construction estimation · 5 min

What you'll learn in this case study

The contract-admin scope ambiguity in a variation claim
The NZS 3910 §14.4 valuation hierarchy applied correctly
The cost-of-catching-it-later table from issue to final account dispute

Quick answer: On a Wellington Te Aro inner-city alteration, a structural variation claim from the head contractor came in at $145-180k built on the contractor's preferred §14.4(d) valuation method (fair valuation including overhead and profit). The QS applied the §14.4 hierarchy in the correct order — schedule of prices first, then rates, then fair valuation as a last resort — and determined the variation at $85-110k. Caught at the variation determination stage the difference was a working paper and a one-page determination letter. Caught at final account it would have meant a $35-70k disputed claim heading to adjudication under the Construction Contracts Act 2002.

The build

A Wellington Te Aro inner-city alteration: a three-storey commercial-to-residential conversion of a 1960s reinforced-concrete shell, 1,400 m² gross floor area across the three levels. Head contract NZS 3910:2023 lump sum in the $4.8-5.6M envelope. Engineer to the contract a senior structural engineer; CA-role held by an external QS firm.

Mid-build, the engineer issued a structural instruction adding two transfer beams at level 2 to support a programme-driven layout change the client had requested. The engineer's revised structural sheets dropped onto the head contractor, who priced the change as a §14 variation and submitted at $145-180k. The QS's job was to value the variation under §14.4 and issue a determination.

The variation claim crossed our desk for a peer review before the determination was issued.

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What we found in the quote

The head contractor's variation submission opened with a methodology statement nominating §14.4(d) of NZS 3910:2023 as the basis for valuation: "fair valuation including a reasonable allowance for overheads and profit." From that starting point, the submission built up a daywork-style calculation: hours of structural steel fabrication labour at the workshop, hours of site erection labour, materials at retail pricing, plant hire at retail rates, and a 22% combined overhead-and-profit mark-up on the total.

That methodology assumes the variation has no contractual reference points. §14.4 of NZS 3910:2023 does not work that way. The clause sets a hierarchy.

The contract documents themselves carried a schedule of prices in the priced bills (Section 5 of the contract documents) with rates for structural steel supply at $X per tonne and site erection labour at $Y per hour. The variation work — two transfer beams, structural steel — was directly comparable to scope already priced in the schedule. The §14.4 hierarchy required the QS to apply those rates first, not move to fair valuation as a starting point.

The dollar gap was the gap between (a) structural steel valued at the schedule rates with the schedule overhead-and-profit allowance baked in, versus (b) structural steel built up from retail pricing with a 22% mark-up applied on top.

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How the code resolves it

NZS 3910:2023 §14.4 sets four valuation methods, applied in order:

§14.4(a) — Where rates and prices in the contract are applicable to the varied work, those rates and prices apply. This is the primary method. The QS must consider whether the schedule rates are applicable before moving down the hierarchy.

§14.4(b) — Where rates and prices are applicable as a basis but require adjustment, those rates adjusted to reflect the difference in scope, quantity or conditions apply. This is the secondary method. Rates exist but the new work differs in scale, sequence, or site conditions enough to warrant adjustment.

§14.4(c) — Where no applicable rates or prices exist, the Engineer (or CA) determines a fair valuation built up from first principles. This is the tertiary method.

§14.4(d) — Where the work cannot reasonably be valued under (a), (b) or (c), the Engineer may direct that the work proceed on a daywork basis and the variation is valued at actual cost plus a fee per the daywork schedule.

The contractor's submission applied (d) as if it were the default. The schedule of prices in the contract carried rates directly applicable to structural steel. The correct primary method was §14.4(a), with possible adjustment under (b) for the level-2 site-access difficulty (working at a higher floor than the schedule rate assumed).

What it would have cost if caught later

| Stage caught | Cost range (ex GST) | Why | |---|---|---| | Variation determination (where we caught it) | $0-1k | One-page determination letter citing §14.4(a) with the schedule rate and a §14.4(b) adjustment for level-2 access, working paper attached | | First post-determination challenge | $2-4k | Contractor formally disputes; QS prepares a written response with rate-build-up and §14.4 reasoning; matter resolved in correspondence | | Carried to final account | $35-70k | Variation sits unresolved through the build; contractor lodges a §22 payment claim under Construction Contracts Act 2002; PI-defensibility of the determination tested | | Adjudication under CCA 2002 | $55-100k+ | Adjudicator's fee, both parties' legal and expert costs, plus the underlying difference between the determination and the contractor's claim if the determination is overturned in part |

The bottom row depends on whether the QS's working papers and citation chain hold up under independent adjudicator review. A §14.4(d) determination with no consideration of §14.4(a) or (b) does not hold up — that is exactly the PI exposure the QS persona we were supporting needed to avoid.

The clarification we recommended

A two-page variation determination letter to the head contractor under §14, structured as follows. First, the variation work is described against the engineer's revised structural sheets. Second, the §14.4 hierarchy is named in order with each sub-clause considered explicitly. Third, the determination is reasoned: §14.4(a) applies because the contract schedule carries structural steel rates directly comparable to the variation work; §14.4(b) applies a 12% adjustment for the level-2 access penalty over the ground-floor rate baseline; §14.4(c) and (d) do not apply because rates exist. Fourth, the dollar figure of the determination is shown with the rate build-up appended.

Total determination: $85-110k against the contractor's $145-180k claim. Difference of $55-75k. Documented, reasoned, PI-defensible.

The contractor accepted the determination after one round of correspondence. No adjudication.

What other Wellington inner-city alteration variations should check

The §14.4 hierarchy applied in order — never start at (d) without exhausting (a) and (b)
The contract's schedule of prices read for applicable rates before any first-principles build-up
The adjustment under §14.4(b) reasoned in writing where the schedule rate needs modification for new conditions
The §13 time-impact assessment kept separate from the §14 cost variation
The variation determination letter structured to survive a Construction Contracts Act 2002 adjudication if challenged

FAQ — NZS 3910 §14.4 variation valuation on Wellington inner-city alterations

Q1: Why does the §14.4 hierarchy matter — isn't a fair valuation always defensible? A fair valuation under §14.4(c) or daywork under §14.4(d) is defensible only where the higher methods don't apply. Where applicable rates exist in the contract, the contract requires those rates to be used. Skipping straight to fair valuation is a contract administration error and is reversed on adjudication.

Q2: How does a QS evidence the §14.4(b) adjustment? The CA writes the adjustment with a stated reason — different floor level, different access, different sequencing, different quantity. The adjustment is typically a percentage applied to the base rate, with the percentage justified against either market practice or the contractor's own published productivity factors. The reasoning is the defence.

Q3: What's the typical PI exposure on a QS-acting-as-CA variation determination in Wellington? A determination that misapplies §14.4 and is overturned on adjudication exposes the QS firm to a professional negligence claim from the principal for the difference between the determination and the adjudicator's award. PI policies typically respond, but the policy excess and the deductible can sit at $25-50k.

Q4: Does the Construction Contracts Act 2002 timeline pressure the determination? Yes. The CCA sets 20 working days for a payment schedule response after a payment claim. A variation that flows into a payment claim must be valued within that window or the claimed amount is treated as the scheduled amount by default (§21). The §14 determination has to keep pace with the §12 payment cycle.

Q5: What happens if the engineer's instruction was issued without naming it as a §10.3 instruction? Under §10.3 the engineer's instruction has to be in writing and named as an instruction. An instruction issued informally (verbal site direction, marked-up sketch without an instruction notation) leaves the contractor open to argue the work was outside the contract and value it on §14.4(d) daywork. Tightening §10.3 process protects the §14.4 hierarchy downstream.

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Trueworks is built by Steve Parker — 20 years on the analytical side of NZ construction. Variation reviews, contract advisory, programme review, and AI-augmented document workflows. Trueworks is the productisation of that practice for builders: same defensible analysis, at a price and pace a NZ builder can actually use.

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