Introduction
The NZ Metal Roof and Wall Cladding Code of Practice (COP) is published by NZ Metal Roofing Manufacturers Inc. (MRM), to provide:
- acceptable trade practice for fixing metal roofing, metal wall cladding, and accessories,
- prescriptive detailing for designers, and
- sets a benchmark for the standard of detailing and workmanship required over and above that required to comply with the NZBC.
The COP does not describe or dismiss alternative methods, which may need specific acceptance by the Building Consent Authorities.
It is published in accordance with current technology, materials, and building codes. The COP will be periodically updated to reflect changes in legislation and standards or improvements in technology and available materials.
The most current Code of Practice is available on the MRM website, www.metalroofing.org.nz/cop, as Code of Practice Online (MRM COP Version 25.06).
The latest update to the NZMRM Metal Roof and Wall Cladding Code of Practice, v25.06 was published on 1 June 2025.
This update focused on clarification and usability.
Important Changes
We replaced the illustration for Cricket Under-Soaker: Trapezoidal to show the width of the cricket flashing correctly.
In Profile Closures, we removed a repeated paragraph and added illustrations showing vermin closures, and we removed a statement from Compatibility with Non-Metallic Substances that neither AZ-coated steel nor Aluminium should be used as a flashing embedded in concrete or masonry.
In Flashing Expansion, we clarified the required moisture content of timber and removed a recommendation for using aluminium rivets in place of expansion joints.
Other Notable Revisions
We renamed three clauses: Runoff, Rainwater Heads, Sumps, and Overflows, and Outlets and Downpipes, with no changes to recommendations.
In another bid to improve clarity and usability, we introduced an interactive table to Lichen And Mould. The table gives improved guidance on water/bleach ratios to achieve a 2% chlorine solution for treating lichen and mould on roofs.
The rest of the updates and revisions consisted of minor edits for clarity, grammar, and spelling. There were no other changes to recommendations.
For a detailed list of revisions, please visit v25.06 June 2025.
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