NZ Metal Roof and Wall Cladding Code of Practice

The New Zealand Metal Roof and Wall Cladding Code of Practice (COP) is a technical guide published by the New Zealand Metal Roofing Manufacturers Inc. (NZMRM). It covers the design, installation, performance and transport of metal roof and wall cladding in New Zealand and is used by roofers, designers, building consent authorities and manufacturers.

Scope

The COP applies to buildings designed under NZS 3604 (the standard for timber-framed buildings), AS/NZS 1170 (structural loadings) and specific engineering design. It is presented as a means of meeting the performance provisions of the New Zealand Building Code and supports compliance with the Health and Safety at Work Act 2015, including safe handling and installation.

Topics include:

• roof pitch and profile selection
• fastener types, spacing and wind load resistance
• flashings, penetrations, gutters and spouting
• thermal expansion, condensation and underlay
• corrosion, environmental categories and material compatibility (for example dissimilar metals and run-off)
• foot traffic, handling, storage and transport
• maintenance requirements

Versions and access

The COP is a living document, revised regularly. Version v26.09 was issued on 1 September 2026, described by NZMRM as one of its busiest revisions. It is available online after a simple one-time registration per device, and as a PDF for offline use.

Relationship to E2/AS1

The NZBC Acceptable Solution E2/AS1 includes basic metal roofing details, but within limits. The COP goes much further, covering more profiles, steeper and lower pitches, curved and crimped roofing, and specific situations such as severe marine environments. Designers often cite the COP in specifications, and it is widely treated as the reference for good practice.

Why it matters

New Zealand's climate combines high winds, heavy rainfall, strong UV and, in many areas, salt-laden coastal air. Metal roofing is the dominant residential roof covering in the country, so correct detailing has a large effect on building durability. The COP brings together manufacturer research and field experience, including the durability statements and environmental classifications that affect product choice and warranty conditions.

Comparable documents

In Australia, metal roofing design and installation is covered mainly by Australian Standards referenced through the National Construction Code, supported by manufacturer installation guides.