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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 v26.09:Revision-History; V2609-September-2026

19.1 v26.09 September 2026 

In one of our busiest revisions yet, v26.09 of the Code of Practice features a long list of new and revised detail drawings. 

Important Revisions and New Content 

Editing and Rearrangement without changes to recommendations

The rest of the 26.09 revision consisted of minor errata and changes to layout to aid usability, with no changes to recommendations.


19.1A

CategoryClause Number (prior to update)Clause (As of current publication)Details
3 - Substantial change to recommendation8.108.10 Flashing Expansion and ContractionSubstantial revision with new recommendations and new details for expansion joints in flashings.
3 - Substantial change to recommendation8.10.18.10.1 Flashing Buckling Due to Timber ShrinkageThis clause was part of a complete revision of 19.1A .
4 - Clause Inserted 8.10.2 Flashing Buckling Due to Thermal MovementA new clause created during the revision of 19.1A .
4 - Clause Inserted 8.10.3 Recommended Expansion Joint Spacing for FlashingsNew clause created during the revision of 19.1A .
4 - Clause Inserted 8.10.4 Expansion Details for FlashingsA new clause for expansion joint details for flashings.
4 - Clause Inserted 8.11.1 Window Flashing DetailsA new clause showing window flashing details which were tested to comply with E2/VM. 
3 - Substantial change to recommendation5.4.25.4.2 Gutter Capacity DesignNow defining the minimum size for residential spouting overflow.  
2 - Editing and rearrangement1, 11 IntroductionNew revision message for v26.09, published on 1 September 2026.
2 - Editing and rearrangement2.1, 2.12.1 DefinitionsUpdated definition for Lap Tape.
4 - Clause Inserted 5.4.1.1 External Gutter DesignsNew illustrations showing different external gutter shapes.
1 - Minor Errata5.4.75.4.7 Gutter Capacity CalculatorChange illustration label from 'Depth' to 'Upstand' for consistency with input box and clarified instructions for calculator use.
2 - Editing and rearrangement5.5.35.5.3 Bifurcated Valleys 
2 - Editing and rearrangement7.1.17.1.1 Minimum Roof Cladding PitchChanged the minimum pitch for symmetrical trapezoidal > 30mm to 3° to bring it in line with manufacturers' recommendations.
2 - Editing and rearrangement8.48.4 Flashing CoverLayout changes to the cover tables to improve usability.
2 - Editing and rearrangement8.5.28.5.2 Barge And VergeAdjusted the layout of drawings into two columns to improve navigation. No changes to recommendations.
2 - Editing and rearrangement8.5.38.5.3 Parapet CappingsUpdated detail drawings for parapet caps.
2 - Editing and rearrangement8.5.4.18.5.4.1 Apron and Parapet Capping TerminationsTitle edit, layout change, and a new drawing showing details for Apron Terminations.
4 - Clause Inserted8.118.11 Wall CladdingNew drawing showing a Proprietary Wall Vent Cover.
1 - Minor Errata9.4.2.69.4.2.6 Penetration Flashings on Trapezoidal ProfilesImage resizing.
3 - Substantial change to recommendation9.4.2.79.4.2.7 Over-Flashing More Than 1m WideNew drawings showing alternative details.
1 - Minor Errata9.4.39.4.3 Dormer DetailsReformatting of 19.1A . No other edits or changes to recommendations.
2 - Editing and rearrangement10.10.1.410.10.1.4 Vented Soft EdgeEditing to remove ambiguity
2 - Editing and rearrangement10.10.210.10.2 BattensEditing of 19.1A .
2 - Editing and rearrangement14.18.514.18.5 Colour Matching PaintRevised for clarity.
2 - Editing and rearrangement1616 Maintenance Added a link the home page of the Exterior Cleaning Industry Association.
2 - Editing and rearrangement16.716.7 WashingAdded link to ECIA homepage.
4 - Clause Inserted 19.1 v26.09 September 2026Latest revision.