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Disclaimer

Although the information contained in this Code has been obtained from sources believed to be reliable, New Zealand Metal Roofing Manufacturers Inc. makes no warranties or representations of any kind (express or implied) regarding the accuracy, adequacy, currency or completeness of the information, or that it is suitable for the intended use.

Compliance with this Code does not guarantee immunity from breach of any statutory requirements, the New Zealand Building Code or relevant Standards. The final responsibility for the correct design and specification rests with the designer and for its satisfactory execution with the contractor.

While most data have been compiled from case histories, trade experience and testing, small changes in the environment can produce marked differences in performance. The decision to use a particular material, and in what manner, is made at your own risk. The use of a particular material and method may, therefore, need to be modified to its intended end use and environment.

New Zealand Metal Roofing Manufacturers Inc., its directors, officers or employees shall not be responsible for any direct, indirect or special loss or damage arising from, as a consequence of, use of or reliance upon any information contained in this Code.

New Zealand Metal Roofing Manufacturers Inc. expressly disclaims any liability which is based on or arises out of the information or any errors, omissions or misstatements.

If reprinted, reproduced or used in any form, the New Zealand Metal Roofing Manufacturers Inc. (NZMRM) should be acknowledged as the source of information.

You should always refer to the current online Code of Practicefor the most recent updates on information contained in this Code.

Scope

This Code of Practice provides requirements, information and guidelines, to the Building Consent Authorities, the Building Certifier, Specifier, Designer, Licensed Building Practitioner, Trade Trainee, Installer and the end user on the design, installation, performance, and transportation of all metal roof and wall cladding used in New Zealand.

The calculations and the details contained in this Code of Practice provide a means of complying with the performance provisions of the NZBC and the requirements of the Health and Safety at Work Act 2015.

The scope of this document includes all buildings covered by NZS 3604, AS/NZS 1170 and those designed and built under specific engineering design.

It has been written and compiled from proven performance and cites a standard of acceptable practice agreed between manufacturers and roofing contractors.

The drawings and requirements contained in this Code illustrate acceptable trade practice, but recommended or better trade practice is also quoted as being a preferred alternative.

Because the environment and wind categories vary throughout New Zealand, acceptable trade practice must be altered accordingly; in severe environments and high wind design load categories, the requirements of the NZBC will only be met by using specific detailing as described in this Code.

The purpose of this Code of Practice is to present both Acceptable Trade Practice and Recommended Trade Practice, in a user-friendly format to ensure that the roof and wall cladding, flashings, drainage accessories, and fastenings will:

  • comply with the requirements of B1, B2, E1 E2 and E3 of the NZBC;
  • comply with the design loading requirements of AS/NZS 1170 and NZS 3604 and with AS/NZS 1562;
  • have and optimised lifespan; and
  • be weathertight.

COP v24.12:Revision-History; V2412-December-2024

19.1 v24.12 December 2024 

The following revisions to the NZ Metal Roof and Wall Cladding Code of Practice were published on 1 December 2024.

Substantial change to recommendations:

Notable Editing and rearrangement:

The rest of the updates consisted of minor corrections and edits.

19.1A

CategoryClause Number (prior to update)Clause (As of current publication)Details
2 - Editing and rearrangement11 IntroductionNew revision message for V24.12, published on 1 December.
3 - Substantial change to recommendation3.7.23.7.2 DeflectionAdded a statement:
Temporary deflection under load is not considered for roof load tables as it has not been found to affect weathertightness. Temporary deflection under load of wall cladding is a recommended limitation for aesthetic reasons, but it is not mandatory.
3 - Substantial change to recommendation3.10.23.10.2 Maximum Spans and Fastening Pattern for Corrugate Wall CladdingChanged "span/120 + P/20" to "span/120 + P/30".
3 - Substantial change to recommendation5.4.5.15.4.5.1 Internal Gutter Design FeaturesAdded a recommendation to align with 5.6.3 Overflows, for the cross-sectional area of a scupper to be 1½ times that of the downpipe.
2 - Editing and rearrangement5.5.15.5.1 Valley FixingRearranged layout. Clarified statement about positive (through) fixing. Replaced the old illustration for Clip System with 5.5.1A Correct Valley Fixing, Allowing for Thermal Movement.
Added illustrations for Valley Junction at the Apex.
3 - Substantial change to recommendation5.5.65.5.6 Asymmetrical ValleysChanged recommendation: A valley baffle is required in all cases where a valley has a change of angle or difference in roof  pitch exceeds 10 .
3 - Substantial change to recommendation5.6.35.6.3 OverflowsChanged the recommended cross-sectional area of a scupper to align with BRANZ recommendation.
2 - Editing and rearrangement9.4.2.69.4.2.6 Penetration Flashings on Trapezoidal ProfilesUpdated the illustration to show the apron of the cricket covering the penetration apron.
1 - Minor Errata10.110.10 Ventilation PathwaysTypo fix: changed through to trough. No changes to recommendations.
2 - Editing and rearrangement10.12.510.11.1 Underlay StandardsMoved clause to 10.11 Underlay for relevance. Fixed table formatting. No changes to recommendations.
4 - Clause Inserted 19.1 v24.12 December 2024Revision details for v24.12; published on 1 December 2024.