Roofing quote per m² in NZ: the re-roof priced below cost and the sanity check that caught it
Updated: Jul 9
A roofing business asked us to review a long-run steel re-roof quote before it went to the homeowner. The headline rate looked like market. Net of the scaffold line, it sat below our mid-case cost stack — a margin of roughly −5 to −10%, a four-figure loss baked in before a single sheet was lifted. One sanity check caught it before the quote left the office.
By Steve Parker · Trueworks · NZ construction estimation · 7 min
What you'll learn in this case study
Why a headline $/m² rate can hide below-cost pricing once the scaffold line is stripped out
Why flashing metres, not plan area, drive cost on complex multi-level roofs
The exposure-zone fixings check (NZS 3604, E2/AS1) that protects the warranty as well as the margin
Quick answer: The job was a long-run steel re-roof on a multi-level house in a coastal North Shore suburb of Auckland — flashing-heavy, with about 60 lineal metres of flashings, and scaffold priced as its own line. The headline rate came out in the low $120s per m² excluding GST including scaffold, which reads as respectable. Net of the scaffold line, the roofing works landed around the mid $90s per m² — at or below the realistic floor for that roof type in that market. Our mid-case cost stack (materials, labour, disposal, and margin on the flashing work) slightly exceeded the quoted revenue: an estimated margin of about −5 to −10%, a four-figure loss on one job, with a plausible band of roughly −10% to +12% depending on trade buying power and scaffold ownership. We also caught a durability mismatch: sea-spray exposure zone, marine-grade cladding called up in places, but non-marine fixings specified. Both issues were corrected before the quote went out.
The quote that came across the desk
A roofing business sent us a re-roof quote for review before it went to the homeowner — the only stage where a pricing error costs almost nothing to fix.
The job: long-run steel over a multi-level house in a coastal North Shore suburb of Auckland. The roof was the complicated kind — multiple levels, hips, junctions against upper-storey cladding, penetrations, and about 60 lineal metres of flashings once we took off the drawings properly. Scaffold was priced as its own line item — good practice.
The headline number: low $120s per m² excluding GST, scaffold included. At a glance, that sits inside the band most Auckland roofers would recognise for long-run work — and the glance is where the problem hides. A headline rate says what the customer pays per square metre, not what the job costs you per square metre.
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What we found
First, we netted the scaffold line out of the total and divided by the measured roof area. The roofing works came out around the mid $90s per m² excluding GST — for a multi-level, flashing-heavy long-run roof in the Auckland market, at or below the realistic floor.
Then we built a mid-case cost stack: sheet and underlay at typical trade pricing, clips and fixings, folded flashings priced per lineal metre, strip and disposal of the existing roof, crew hours weighted for the flashing work, and a normal overhead-and-margin allowance. The mid-case cost slightly exceeded the quoted revenue: a margin of about −5 to −10%, a four-figure loss signed up the moment the homeowner accepted.
The honest version carries a band: roughly −10% to +12%. A firm with strong trade buying power and its own scaffold could scrape a small positive margin; a firm hiring scaffold and paying near-list locks the loss in. A quote that only works if everything breaks your way is not a price — it is a bet.
The number driving the miss was not plan area. It was the 60 lineal metres of flashings: flashing work carries the labour hours on a complex roof, and a flat $/m² rate carried over from simpler jobs quietly under-recovers it.
The second finding was a durability mismatch. The house sits in a sea-spray exposure zone. The quote called up marine-grade material in places — correctly — but the fixings specified were standard, not marine-spec. Mixed durability like that fails at its weakest point, which is almost always the fixing head.
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The per-m² sanity check, and the code behind the fixings call
The sanity check we ran takes about twenty minutes with a calculator and the drawings:
Net off every non-roofing line — scaffold, access, gutters if priced separately — and divide what remains by the measured roof area, not the plan area. Compare that net rate against your own floor for the roof type in your market: the rate below which your last few completed jobs say nothing is left after cost. Then count the flashing lineal metres off the drawings and check the labour allowance against them, because flashing metres — not area — set the hours on a cut-up roof.
Our standing recommendation to any roofer: build a simple one-page cost sheet before sending any quote over about $15,000. Five lines is enough — materials, labour, disposal, subcontract and hire, overhead-plus-margin. It converts "the rate feels right" into "the rate covers the cost stack," and it would have caught this quote in the office rather than on the site.
On the fixings: NZS 3604 defines exposure zones by proximity to the coast, and a sea-spray zone triggers the highest durability demands; E2/AS1 governs external moisture. The practical rule is simple — fixings must match or exceed the corrosion resistance required for the cladding's zone. Specify marine-grade sheet with standard fixings and you have built the failure point into the quote, and most manufacturers' warranties are conditional on zone-appropriate fixings. Not just a durability issue — a warranty and callback liability priced at less than cost.
What it costs when it's caught late
| Stage caught | Cost range | Why | |---|---|---| | Before the quote goes out | The cost of a review, low hundreds | Repricing is a document edit; nothing has been promised | | After the homeowner accepts | Low four figures | You wear the loss or reopen an accepted price — one costs margin, the other costs the job and goodwill | | Mid-job | Four figures, trending up | Labour and materials committed; a variation cannot rescue your own pricing error | | At completion | The full four-figure loss plus unrecovered overhead | The job is done and the loss lands on the year-end accounts | | Years later, at the fixings | Five figures | Premature corrosion in a sea-spray zone means re-fixing or re-roofing, on the wrong side of the warranty argument |
Five checks before you hit send on a re-roof quote
Net the scaffold out. Strip scaffold, access and any non-roofing lines from the total, then compute the true roofing $/m² — that is the only rate worth benchmarking.
Compare against your own floor, not the market average. Know the rate below which your crew, your buying and your overhead leave nothing — and treat anything at or under it as a red flag, not a competitive edge.
Count the flashing metres. Take off the lineal metres of flashings from the drawings and check the labour allowance against them; on multi-level roofs they drive cost harder than area does.
Match the fixings to the exposure zone. Confirm the NZS 3604 zone, then confirm every fixing meets the cladding manufacturer's requirement for that zone — mixed spec voids warranties and builds in callbacks.
Run a one-page cost sheet on anything over about $15,000. Materials, labour, disposal, hire, overhead-plus-margin — five lines that turn a feel into a number before the number becomes a promise.
FAQ — pricing a re-roof per square metre
Q1: What should a long-run steel re-roof cost per m² in NZ? There is no single honest number — region, roof complexity, access and material grade all move the rate. The useful benchmark is not a market average but your own floor: the net-of-scaffold rate at which your last few completed jobs actually covered their cost stack. A new quote below that floor needs a specific reason, not a hope.
Q2: Should scaffold be a separate line on a roofing quote? Yes — it is transparent for the customer and lets you, or a reviewer, benchmark the roofing rate honestly. Just net it off before comparing $/m² figures, because a scaffold-inclusive rate always flatters the roofing price underneath it.
Q3: Why do flashing metres matter more than roof area? Because flashings are where the hours are. Sheet laying is fast and predictable; flashings involve measuring, folding, cutting, fitting and sealing at every junction. About 60 lineal metres of flashings can add crew-days a flat area rate never sees.
Q4: What is a sea-spray exposure zone and why do fixings matter there? NZS 3604 classifies sites into exposure zones based mainly on distance from the sea; the closest zones face airborne salt that attacks steel aggressively. Fixings must carry at least the corrosion protection the cladding's zone requires — a standard fixing in marine-grade sheet corrodes first and gives the manufacturer grounds to decline the warranty claim.
Q5: How do I sanity-check a quote without a full estimating system? A one-page cost sheet: materials at your actual trade pricing, labour from honestly estimated crew-days, disposal, hire, and an overhead-plus-margin line. If quoted revenue minus that stack is negative or barely positive, stop and reprice. Twenty minutes, and the cheapest insurance in the trade.
Who this helps
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About Trueworks
Trueworks is built by Steve Parker — 20 years on the analytical side of NZ construction. Variation reviews, contract advisory, programme review, and document-heavy estimation work. Trueworks is the productisation of that practice for NZ trades and builders: the same defensible analysis, at a price and pace a working contractor can actually use.
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hello@trueworks.co.nz · trueworks.co.nz
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