Access the Code of Practice online

This registration will be required once-only per browser/device, which is achieved using a cookie stored on your device.

There is no password required, and your information will not be shared with any third parties.

Please register and accept the terms for the NZMRM online COP
By ticking this box you confirm that you have read and accept the Terms listed below


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; 2020-December

19.14 2020 – December 

The following revisions to the NZ Metal Roof and Wall Cladding Code of Practice were published on 1 December 2020.

Summary of Changes in this update:

We introduced three more responsive tools to aid in roof drainage design. They are:

The rest of this update consisted of fixing minor errors and improvements for clarity.

19.14A Revision Detail - 2020 - December

CategoryClause Number (at time of update)Clause (As of current publication)Details
2 - Editing and rearrangement11 IntroductionUpdate Revisions Message
1 - Minor Errata1.31.3 Standards and Related DocumentsClause renamed.
1 - Minor Errata4. Dissimilar MetalsFormatting fix.
1 - Minor Errata4. Compatibility TableRemoved reference to Butly Rubber into its own clause 4.9.3 Compatibility with Non-Metallic Substances.
2 - Editing and rearrangement4.124.11 Inert CatchmentInserted photo "Localised Damage due to Inert Catchment".
1 - Minor Errata5. Asymmetrical ValleysPunctuation fix.
2 - Editing and rearrangement5. Roof Drainage CapacityClause renamed to more accurately reflect its content.
4 - Clause Inserted5. Maximum Area Above Spreader CalculatorNew online tool for calculating maximum drainage areas for spreaders.
1 - Minor Errata5.55.4.2 Gutter Capacity DesignGrammar fix.
2 - Editing and rearrangement5. Rainfall IntensityRainfall intensity maps have been added to this clause. Links to rainfall maps have been included in the calculators.
1 - Minor Errata5. Allowance for Short-Term IntensitiesUpdated short-term intensity multiplication factors.
2 - Editing and rearrangement5.75.4.7 Gutter Capacity CalculatorRenamed the clause. Other capacity calculators have been moved closer to the relevant information dealing with each topic.
0 - Clause Removed5.7.1North Island 50-year ARI, 10-minute Rainfall Intensity MapMap moved to 5.3.2 Rainfall Intensity.
0 - Clause Removed5.7.2South Island 50-year ARI, 10-minute Rainfall Intensity MapMap moved to 5.3.2 Rainfall Intensity.
3 - Substantial change to recommendation7. RunoffClause completely revised.
4 - Clause Inserted7. Maximum Run CalculatorNew online tool to calculate maximum run for drainage of different roofing profiles.
2 - Editing and rearrangement8. Eaves FlashingInserted a paragraph recommending eaves flashings in Marine Environments.
1 - Minor Errata9. Curb DesignIntroductory copy added.
4 - Clause Inserted9. Maximum Area Above Penetration CalculatorNew online tool for calculating the maximum area above a penetration.
1 - Minor Errata17. Site TestingUpdated the graph.
4 - Clause Inserted 4.9.3 Compatibility with Non-Metallic SubstancesA new clause, previously part of "4.10.3 Compatibility Table". Information was split since this is not part of the table or online tool.
4 - Clause Inserted 5.5.7 Valley Capacity CalculatorNew clause created for Valley Capacity Calculator. The calculator was previously part of Capacity Calculators.
4 - Clause Inserted 5.7.3 Downpipe Capacity CalculatorNew clause for Downpipe Capacity Calculators.
4 - Clause Inserted 19.14 2020 – DecemberNew clause showing updates effective on 1 December 2020.