Which lifespan number are you looking at?
| Measure | What it describes | What it does not prove |
|---|---|---|
| Building Code durability requirement | Required performance period under the applicable conditions. | The roof needs replacement when that period ends. Sources: NZMRM durability guidance. |
| Manufacturer warranty | A remedy for defined failures, subject to exclusions and maintenance. | Every component or every cause of a leak is covered. Sources: New Zealand Steel. |
| Condition-based service life | Whether the installed assembly remains fit for use. | A fixed national average applying to all metal roofs. Sources: NZMRM maintenance guidance. |
The NZ Metal Roofing Manufacturers’ discussion of B2 describes the 15-year requirement for relevant accessible cladding applications and distinguishes it from longer durability requirements for some building elements. It should not be reworded as “metal roofs last 15 years”. Sources: NZMRM durability guidance.
What do current manufacturer examples show?
New Zealand Steel lists 20-year ZINCALUME roofing warranty cover in moderate environments and 25 years in mild environments. Those are warranty periods, not roof-expiry dates. The same page excludes more severe exposures from its recommendations, so site classification belongs in product selection. Sources: New Zealand Steel.
COLORSTEEL’s newer MAXAM material replaced Endura and Maxx in its range. A warranty statement about an older product cannot simply be pasted onto a new specification, or vice versa. Match the exact product and applicable warranty document. Sources: COLORSTEEL.
- Which product and manufacturing period does the warranty apply to?
- Does it cover perforation, paint performance, workmanship or something else?
- What maintenance records are required?
- Which flashings, fasteners and rainwater components are included?
- Does the warranty transfer to a new owner? Ask for the written terms.
What information helps decide between maintenance and reroofing?
Ask for a condition report that distinguishes isolated repairable details from widespread deterioration. It should identify the affected roof planes and components, describe the findings, and explain why the recommended scope addresses them. A useful report is more specific than an age estimate or a sales claim.
Record the roof’s approximate age if known, past repairs, current leaks, coating, coastal or industrial exposure, and any inaccessible or unwashed areas. Manufacturer maintenance requirements are relevant to both performance and warranty compliance. Sources: NZMRM maintenance guidance.
Does maintenance mean replacing the roof?
Not necessarily. Treat inspection, maintenance, local repair and whole-roof replacement as separate options to be evaluated. Ask for the remaining uncertainties and the expected purpose of each recommendation, rather than assuming that a coating refresh automatically renews the whole roofing system.
NZMRM guidance explains that maintenance must reflect the material, environment and manufacturer instructions. Areas not naturally rain-washed can need different attention. Do not substitute a generic cleaning frequency for the instructions for the installed product. Sources: NZMRM maintenance guidance.
Why age alone is an incomplete answer
Publisher-reported project
Damage uncovered under the old roof
Tamahere, Waikato · Gerard CF Shake
Gerard describes replacing asphalt roofing and dealing with damaged plywood and framing beneath it.
What it illustrates: Hidden substrate work belongs in a contingency and variation process, not an assumed fixed removal rate.
- Roof price
- Not published
- Measured area
- Not published
The lesson is not that every old roof has the same concealed damage. It is that a visual age estimate cannot establish the state of everything beneath the covering. Budget decisions should account for the evidence available and the work needed to confirm it.
What should you request from a roofer?
- A roof-specific condition report, ideally with annotated photographs taken safely.
- Separate options for urgent work, planned repairs and replacement where appropriate.
- Clear identification of the product and site exposure.
- A scope for flashings, fixings and substrate, not just the visible sheets.
- A written explanation of warranties and exclusions.
Sources and review notes
Prepared by RoofHub editorial team. Reviewed . A source check confirms what a page states, not an independent inspection or invoice audit. Published project accounts are attributed to their publishers.
- primaryNZ Metal Roofing Manufacturers: NZ Building Code clause B2 and durability - Page checked 2026-09-28. Publication date not stated. · industry-technical
- primaryNZ Metal Roofing Manufacturers: Maintenance compliance - Page checked 2026-09-28. Publication date not stated. · industry-technical
- primaryNew Zealand Steel: ZINCALUME product information - Describes the 2025 transition to the AM125 aluminium/zinc/magnesium coating. Historical AZ specifications are not treated as current. Page checked 2026-09-28. Publication date not stated. · manufacturer
- primaryCOLORSTEEL: The evolution of COLORSTEEL - Page checked 2026-09-28. Publication date not stated. · manufacturer
- primaryGerard: Tamahere transformation with CF Shake (2022-03-03) - Page checked 2026-09-28. Publication date shown above. · manufacturer
Original calculations are labelled as examples. Historical prices stay dated, missing fields stay unknown, and conflicting specifications are flagged. Sources are not endorsements or paid rankings. Read our methodology or report a correction.
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Apply this to your roof
Have measurements or a project question?
Use your dimensions in the detailed estimator, or send your question to the RoofHub team. A roofing contractor still needs to confirm the site, specification and final price.