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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 v26.03:Revision-History; V2603-March-2026

19.1 v26.03 March 2026 

In the March 2026 revision of the Code of Practice the focus was heavily towards clarification with some substantial changes.

Important Revisions

Editing and rearrangement

Most editing and rearrangement for this update concentrated on clarifying and removing ambiguities throughout the Code of Practice. 

19.1A Revision Detail v26.03 - 2026 - March

CategoryClause Number (prior to update)Clause (As of current publication)Details
2 - Editing and rearrangement11 IntroductionNew revision message for v26.03, published on 1 March 2026.
2 - Editing and rearrangement2.12.1 DefinitionsUpdated definition for Lap Tape.
3 - Substantial change to recommendation4.10.74.10.7 Crevice Corrosion/Wet Storage StainAdded guidance for scaffolding support on roofing.
2 - Editing and rearrangement4.19.14.19.1 Fastener DurabilityEdited for clarity. No changes to recommendations.
2 - Editing and rearrangement8.68.6 Fastening FlashingsEditing for clarity.
2 - Editing and rearrangement8.88.8 Profile ClosuresEditing for grammar and clarity. No changes to recommendations.
1 - Minor Errata9.4.1.19.4.1.1 Overflashed BackflashingsRenamed clause, for linking purposes. 
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 Errata9.4.39.4.3 Dormer DetailsReformatting of 9.4.3B Gable Dormer Valley: Corrugate. No other edits or changes to recommendations.
2 - Editing and rearrangement9.5.19.5.1 Boot Flashings to an Over FlashingReplaced details drawing: 9.5.1C Over-flashed Boot with Arrowhead Soaker on Trapezoidal Profile
0 - Clause Removed9.5.2Other Applications for Boot FlashingsRemoved empty clause.
3 - Substantial change to recommendation10.110.10 Ventilation PathwaysThis clause and its sub-clauses have been substantially revised.
1 - Minor Errata10.10.1.110.10.1.1 Soffit VentsSmall layout fix.
2 - Editing and rearrangement10.10.1.210.10.1.2 Fascia VentsThis clause has been revised as part of the larger revision of 10.10 Ventilation Pathways.
2 - Editing and rearrangement10.10.1.310.10.1.3 Ridge VentsThis clause has been revised as part of the overall revision of 10.10 Ventilation Pathways.
1 - Minor Errata10.10.1.410.10.1.4 Vented Soft EdgeSpacing fixes.
2 - Editing and rearrangement10.10.210.10.2 BattensThis clause has been revised during the overall review of 10.10 Ventilation Pathways and the drawings have been updated.
4 - Clause Inserted 12.3 Clip Marking on Trough SectionsNew clause.
1 - Minor Errata15.4.715.4.7 SarkingText formatting.
2 - Editing and rearrangement15.4.1215.4.12 Canning and Purlin CreasingRevised definition (see 2 Glossary ), and added a specifications for lap tape and HD tape as an alternative backer for tray roofing.
2 - Editing and rearrangement17.1.3.217.1.3.2 Point Load TestingRemoved wrongly placed image.
1 - Minor Errata17.1.5.217.1.5.2 Interpreting UDL Load ResultsTypo Fix.
2 - Editing and rearrangement1818 Useful ToolsRenamed the clause to 18 Useful Tools.
1 - Minor Errata18.518.5 Geometry And MeasurementReplaced some illustrations with better waulity ones. No changes to recommendations.
1 - Minor Errata18.618.6 VelocitiesRemoved superfluous captions.
1 - Minor Errata18.718.7 Cricket Penetration PatternsReplaced copied drawings with original illustrations. No changes to recommendations.
1 - Minor Errata18.818.8 Sheet Metal Work For Roofing Contractors.Replaced copied drawings with original illustrations. No changes to recommendations.
4 - Clause Inserted 19.1 v26.03 March 2026Revision detail for the update on 1 March 2026