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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.


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 v24.06:Revision-History; 2021-September

19.11 2021 – September 

The following revisions to the NZ Metal Roof and Wall Cladding Code of Practice were published on 1 September 2021.

Summary of Changes in this update:

The rest of this update consisted of fixing minor errors.

19.11A Revision Detail - 2021 - September

CategoryClause Number (at time of update)Clause (As of current publication)Details
2 - Editing and rearrangement 1 IntroductionUpdate Revisions Message
4 - Clause Inserted 3.10.1 G550 Steel Roof Fastening Pattern TablesNew clause aimed at easy reference of fastening patterns.
4 - Clause Inserted 3.10.3 Aluminium Fastening Pattern TablesNew clause for easy referencing of fastening patterns for aluminium cladding.
1 - Minor Errata 3.7.4 Roof TrafficChanged "tradesman" to trades people for gender neutrality.
1 - Minor Errata 3.6.2 Uniformly Distributed Load (Wind or Induced Action)Corrected spelling of "Uniformly. Included a full term before the abbreviation for UDL in the first sentence.
2 - Editing and rearrangement 5.4.3 Internal CornersClause moved from Valleys to Gutters.
3 - Substantial change to recommendation 5.4.7 Gutter Capacity CalculatorThe minimum Freeboard on internal gutter calculations has been changed to 30mm to align with E1/AS1 and E1/AS2.
1 - Minor Errata 5.5.2 Valley DesignInserted cross-reference link to Internal Corners.
4 - Clause Inserted 5.5.4 Intersecting ValleysNew clause showing the correct way to intersect valleys.
2 - Editing and rearrangement 5.8 Downpipe SpreadersReplaced Downpipe Spreader Design-drawing with a more detailed one.
3 - Substantial change to recommendation 9.1 Penetrations Minimum PitchRevised first sentence to make allowance for modern profiles and proprietary profiles.
4 - Clause Inserted 14.8 Double LappingNew clause.
4 - Clause Inserted 19.11 2021 – SeptemberNew Revision clause