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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 v24.03:Revision-History; 2023-March

19.5 2023 – March 

The following revisions to the NZ Metal Roof and Wall Cladding Code of Practice were published on 1 March 2023.

Substantial changes to recommendations:

Editing and rearrangement:

Other changes consisted of small fixes for clarity and grammar.

19.5A Revision Detail - 2023 - March

CategoryClause Number (at time of update)Clause (As of current publication)Details
3 - Substantial change to recommendation5. Gutter Capacity CalculatorGutter Capacity Calculator now supports calculation where gutter fall is greater than 1:100, and has an option for Secret Gutters (i.e. where a roof slopes towards a raking wall or barge).
3 - Substantial change to recommendation7. Minimum Roof Cladding PitchRevised and renamed table 7.1.1A Minimum Pitch for Generic Metal Roofing.
4 - Clause Inserted 5.2 Roof Drainage TerminologyNew clause to clarify COP usage of terminology pertaining to Roof Drainage.
4 - Clause Inserted Designing for Climate ChangeNewly introduced clause, recommending NIWA's HIRDS-tool.
4 - Clause Inserted Bay WindowsNew clause discussing drainage for Bay Windows.
4 - Clause Inserted OutbuildingsNew clause to give guidance on roof drainage for outbuildings.
2 - Editing and rearrangement11 IntroductionUpdated Revisions Message
2 - Editing and rearrangement2.12.1 DefinitionsAdded definitions for Freeboard, Internal gutter, Hidden gutter, Secret gutter, and Raking Spouting.
1 - Minor Errata3. Wind LoadFixed broken link.
2 - Editing and rearrangement5. Internal Gutter Design FeaturesAdded clarifying text regarding scuppers.
2 - Editing and rearrangement5. Asymmetrical ValleysIncluded details drawing for installing a .
2 - Editing and rearrangement8.38.4 Flashing CoverAdded clarification of rib cover to 8.4K Apron Flashing Cover — Trapezoidal.
2 - Editing and rearrangement8. Barge And VergeAdded illustrations showing details for:8.5.3B Stepped Fascia Corrugate Under Barge; 8.5.3C Stepped Fascia Corrugate Over Barge; 8.5.3D Stepped Fascia Trapezoidal Under Barge; 8.5.3E Stepped Fascia Trapezoidal Over Barge; and 8.5.3F Tray Roofing-Wall Connection.
2 - Editing and rearrangement8. Apron FlashingsAdded illustration showing 8.5.5H Parapet — Reglet Flashing, Chase Cut and 8.5.5I Parapet — Reglet Flashing, Face Fixed.
1 - Minor Errata14.1614.16 Stop-endsMinor edit for clarity.
2 - Editing and rearrangement14.1714.17 Turndowns (Drip Forming or Drip Edging) Edited copy to provide guidance for difficult to turn down profiles, such as deep corrugated profiles.
4 - Clause Inserted 19.5 2023 – MarchRevision and updates active 1 March 2023.