Remuera aluminium joinery case study — the 12-week selection lock-in that saved the programme
Updated: Jul 9
A Remuera premium residential build had a joinery quote, an H1/AS1 thermal calculation, and a programme — but not a selection lock-in date. The 12-week lead time on premium thermally-broken aluminium turned a programme-comfortable build into a programme-critical one. Catching it at tender saved 8-12 weeks.
By Steve Parker · Trueworks · NZ construction estimation · 5 min
The joinery quote was fine. The thermal calculation was fine. The programme was fine. What wasn't fine: the date by which the selection had to be locked in to keep all three of them aligned. That date was eight weeks earlier than the builder expected.
By Steve Parker · Trueworks · NZ construction estimation · 5 min
What you'll learn in this case study
Why premium aluminium joinery lead times have become a programme-critical scope item
The H1/AS1 thermal performance lock-in that drives the selection date
The dollar and programme effect of catching the selection date at tender versus catching it at framing
Quick answer: A Remuera premium residential build had a $180-240k aluminium joinery quote that priced thermally-broken frames meeting the H1/AS1 thermal performance requirements. What the quote didn't make visible was the 12-week lead time on the selected joinery range, or the fact that the H1/AS1 calculation was tied to a specific frame profile that couldn't be substituted without re-running the calculation. Catching the selection lock-in date at tender saved 8-12 weeks of programme and $30-60k of value-engineering substitutions that would otherwise have been forced mid-build.
The build
A new-build premium residential on a Remuera ridge site, build value in the $3-4M range. Joinery scope was around 35-45 separate openings across two storeys including three large sliding doors, two corner stacker units, and a glazed stairwell. The architect's spec named a premium thermally-broken aluminium range with a specific frame profile, a specific glazing makeup, and an H1/AS1 thermal performance calculation tied to those choices. The head contractor sent the joinery quote across for review at tender stage.
A detail on the drawings that does not look right? Get the spec and the quote checked against the code before it becomes a build-stop. Send us your stamped drawings + the supplier's quote. We'll return a code-cited Quote-Check packet within 24 hours. Free for first-time customers. NDA available, NZ-hosted processing. → Get the free check at trueworks.co.nz/contact — or email hello@trueworks.co.nz
💡 Caught something similar on your job?
What we found in the quote
The quote read clean. The frame system was correctly named. The glazing makeup matched the architect's spec. The H1/AS1 thermal calculation was attached and the joinery system contributed the calculated U-value to the whole-building performance pathway. The pricing was within the band we'd expect for a premium thermally-broken range at this opening count.
What the quote didn't surface — and what nearly killed the programme — was the lead time and the selection lock-in cascade.
The quoted range had a stated lead time of 8-12 weeks from selection lock-in to delivery on site. "Selection lock-in" meant: every opening signed off on size, opening direction, hardware specification, glass makeup, and frame colour. The lock-in date had to precede delivery by 8-12 weeks. Delivery had to precede installation by 1-2 weeks for site staging. Installation had to follow weathertight closure of the wall framing and roof, which on this build was Week 18 of the programme.
Working backwards from Week 18 minus 1-2 weeks for staging minus 8-12 weeks for manufacture: the selection lock-in date was Week 4-9 of the programme. The build hadn't started yet. The architect's selection schedule showed selections being finalised at Week 12. There was a six- to eight-week gap between when the selections would be locked in and when they needed to be locked in.
The second issue was less obvious but more consequential. The H1/AS1 thermal calculation submitted to council was tied to the specific frame profile in the spec. The U-value of that profile, multiplied by the opening area, contributed a specific number to the whole-building H1/AS1 performance pathway. If the joinery range needed to substitute — for example, if the selected frame colour added 4-6 weeks of lead time and forced a swap to a faster-delivering range — the substitute range would carry a different U-value. The H1/AS1 calculation would need to be re-run. Council would need to be re-notified. Building consent could be reopened.
The Trueworks Per-Project pack (full estimation, risk register, contingencies table and pre-trade-start sheets across all major trades) is quoted per build. A Trueworks quote check starts at NZ$179 per quote — and your first one is free. Builders typically save NZ$10,000–20,000 of their own time per job. Get your first quote check →
📋 Want this kind of risk review on every trade?
How the code resolves it
H1/AS1 (Energy efficiency — Acceptable Solution) sets the framework for compliance with H1 (Energy efficiency) of the NZ Building Code. The acceptable solution provides a calculation pathway where the building's overall thermal performance is verified against a reference building, and the contributions of walls, roof, floor, and windows and doors are individually calculated.
The joinery contribution to the H1/AS1 calculation depends on three variables: the opening area (m²), the U-value of the frame system (W/m²·K), and the glazing makeup. A change in any of those variables changes the whole-building performance number. A substitution of a non-thermally-broken frame in place of a thermally-broken one — done quickly under programme pressure — can fail the H1/AS1 pathway and force a building consent amendment.
The selection lock-in is therefore both a programme item and a compliance item. The discipline at tender stage is to identify the lead-time-critical selections and lock them into the programme as named milestones with code consequences if missed.
What it would have cost if caught later
| Stage caught | Cost range | Why | |---|---|---| | At tender (paper review) | $500-1,500 (one engagement) | Selection lock-in date identified and added to programme as named milestone; backup range pre-approved with matching H1/AS1 calculation; supplier confirmation requested in writing | | At framing (mid-build, Week 12) | $8,000-18,000 | Selection forced to faster-delivering substitute range; H1/AS1 calculation re-run; possible building consent amendment ($2-5k council fee plus consultant time); frame colour and hardware compromises | | At weathertight (Week 16-18) | $30,000-60,000 | Joinery substitution forced; possible programme delay of 4-8 weeks waiting for whichever range can deliver fastest; potential interim weatherproofing of openings; possible scaffold extension | | Post-completion (compliance failure) | $60,000-150,000 | Code Compliance Certificate withheld; remediation involves swapping in compliant joinery retrospectively; consequential damage to interior linings during swap; possible litigation between owner and head contractor |
The Remuera build was on track to hit the mid-build cost band — about $8-18k of forced substitutions and a building consent amendment — until the selection lock-in date was identified at tender. Catching it at tender cost a clarification email.
The clarification we recommended
The clarification packet to the head contractor named the joinery selection lock-in date (Week 4 of the build programme), referenced the H1/AS1 calculation lock to the specific frame profile, and recommended three actions: (1) confirm with the architect that selections could be finalised by Week 4 — if not, identify which selections were genuinely programme-critical versus which could be split across two delivery batches; (2) request the joinery supplier provide a written confirmation of the 8-12 week lead time and any seasonal variation in that window; (3) pre-approve a backup frame range with a matching H1/AS1 calculation, so that any forced substitution mid-build wouldn't trigger a consent amendment.
The architect agreed to bring forward the selection date by six weeks. The head contractor secured a written supplier confirmation of a 10-week lead time. The backup range was pre-approved on paper and the H1/AS1 calculation was re-run with both options in parallel so either could be installed without consent risk. The programme held.
What other Remuera premium residential builds should check
Joinery lead times on premium ranges have stretched from 4-8 weeks (pre-2022) to 8-14 weeks on current supply — the tender programme should be checked against current supplier confirmations, not historical averages
H1/AS1 thermal calculations tie the calculation to the specific frame profile in the spec — any substitution mid-build risks a consent amendment unless a backup range is pre-approved with matching U-value
The joinery selection lock-in date is a named programme milestone, not an architectural-discretion item; it should appear on the master programme with the consequences of missing it spelled out
The selection lock-in covers six elements per opening: size, opening direction, hardware, glass makeup, frame colour, sill detail — partial lock-ins don't start the manufacturing clock
Premium ranges often have batch-colour constraints; selecting a non-standard frame colour mid-build can add 4-8 weeks if the colour isn't in the supplier's current production run
FAQ — premium aluminium joinery on Remuera residential builds
Q1: Why have joinery lead times stretched so much in the last few years? A combination of factors: thermally-broken frame components are imported (mostly from Asia and Europe), powder-coating capacity has tightened, and demand from the H1 update (effective 2022-2023) shifted volume toward thermally-broken ranges. Premium ranges with bespoke colour or hardware sit at the upper end of the lead-time band.
Q2: Can the H1/AS1 calculation accommodate a backup joinery range without a consent amendment? Yes, if the backup range is named in the original consent submission with its own U-value calculation and the whole-building number is verified for both options. The consent then allows either range without amendment. This is a cheap insurance policy at consent stage and an expensive one to retrofit mid-build.
Q3: What's the difference between "selection lock-in" and "deposit paid" in lead-time terms? Most premium joinery suppliers don't start manufacturing until both have happened: full selection lock-in (all six elements per opening) and the deposit cleared. A signed quote with deposit pending isn't a manufacturing trigger. The selection lock-in date in the programme should be the date both happen.
Q4: How do we handle a joinery selection that changes mid-build for design reasons (not supply reasons)? A design-driven change after selection lock-in is a §14 variation under NZS 3910 with both cost and time impact. The time impact will typically be the full lead time of the changed item (8-12 weeks) added to the programme from the date of the change. The cost impact will include cancellation or remake of the original order plus the new order.
Q5: Should the joinery quote name the specific factory the frames are manufactured in? On a premium build, yes. The factory location and the powder-coating location both affect lead time and quality consistency. A quote that names "Australian-manufactured" versus "imported and powder-coated in NZ" is naming a real lead-time difference of 2-6 weeks and a real risk profile.
Get a free Quote-Check on your next job
Drawings + one supplier quote = a code-cited risk packet within 24 hours, ready for your pre-start meeting.
Free for first-time customers. No commitment. NDA available. Files NZ-hosted, deleted after 30 days unless you ask us to retain them.
→ Get the free check at trueworks.co.nz/contact — or email hello@trueworks.co.nz
About Trueworks
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.
Every report is checked and signed off by me personally before it goes out. If you've got a quote you want a second opinion on, the easiest way to find out if Trueworks is useful is to send it.
📧 hello@trueworks.co.nz · 🌐 trueworks.co.nz
Comments