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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 v25.12:Revision-History; V2512-December-2025

19.1 v25.12 December 2025 

In this update, we made few substantial changes to recommendations. Most of the revision consisted of editing and rearrangement for clarity, consistency, and accuracy. We have also linked all published Bulletins to the relevant content in the CoP.

Important changes

Editing and rearrangement

  • 15.1.1A Spring Curving Calculator has been updated and can now work from either height or desired radius to enable profile selection and calculate the total length of seal required.
  • We made some edits for clarity and added a reference to wall cladding to 17.1.3.2 Point Load Testing.
  • In 4.6.3 Material Selection, we changed materials endorsed as complying with AS/NZS 2728 coating types to align with the current product range.

19.1A Revision Detail v25.12 - 2025 - December

CategoryClause Number (prior to update)Clause (As of current publication)Details
2 - Editing and rearrangement11 IntroductionNew revision message for v25.12, published on 1 December 2025.
2 - Editing and rearrangement3.7.63.7.6 Construction LoadsAdded a photo showing severe damage, causing splitting on the rib.
2 - Editing and rearrangement3.10.23.10.2 Maximum Spans and Fastening Patterns for Corrugate Wall CladdingInserted a link to: 19.1A Revision Detail v25.12 - 2025 - December
2 - Editing and rearrangement4.6.34.6.3 Material SelectionMaterials endorsed as complying with AS/NZS 2728 coating types have been changed to align with the current ColorsteelⓇ product range.
1 - Minor Errata4.9.24.9.2 The Electrochemical or Galvanic SeriesFixed image format, no changes to recommendations.
2 - Editing and rearrangement4.9.34.9.3 Compatibility with Non-Metallic SubstancesInserted link to bulletin: 19.1A Revision Detail v25.12 - 2025 - December.
2 - Editing and rearrangement4.10.64.10.6 Capillary ActionRevised 4.10.6B Roofing Sheet End Lap for clarity and accuracy. No changes to recommendations.
2 - Editing and rearrangement4.10.94.10.9 Gutter Leaf GuardInserted a link to: 19.1A Revision Detail v25.12 - 2025 - December
2 - Editing and rearrangement4.15.14.15.1 Ground ClearanceInserted a link to:  19.1A Revision Detail v25.12 - 2025 - December
2 - Editing and rearrangement4.16.34.16.3 AluminiumFormatting change to 4.16.3A Aluminium Hardness End-use and inserted a link to: 19.1A Revision Detail v25.12 - 2025 - December No changes to recommendations.
1 - Minor Errata5.3.25.3.2 Rainfall IntensityMinor formatting fix. No changes to content.
2 - Editing and rearrangement5.6.25.6.2 SumpsRenamed 5.6.2B Sump with Overflow. No changes to recommendations.
1 - Minor Errata5.85.8 Downpipe SpreadersLayout fixing. No change to content or recommendations.
2 - Editing and rearrangement7.4.17.4.1 Wall Cladding End LapsInserted a link to: 19.1A Revision Detail v25.12 - 2025 - December.
3 - Substantial change to recommendation8.4.28.4.2 Clearances and Minimum SlopeThis clause was substantially revised and renamed. 
1 - Minor Errata8.5.18.5.1 Ridge and Hip IntersectionsUpdated illustrations for clarity. No changes to recommendations.
2 - Editing and rearrangement8.5.38.5.3 Parapet CappingsAdded a new drawing to show 8.5.3B Parapet Expansion Joint Details, renamed 8.5.3C Parapet Corner Detail, and corrected the titles of 8.5.3D Clip-fixed Parapet Cross-section Detail and 8.5.3F Cap-fixed Parapet Cap to Smooth Profile Inner
2 - Editing and rearrangement8.5.4.28.5.4.2 Change Of PitchUpdated illustrations for clarity. No change to recommendations.
2 - Editing and rearrangement8.68.6 Fastening FlashingsEditing for clarity.
2 - Editing and rearrangement8.88.8 Profile ClosuresInserted a link to bulletin: 19.1A Revision Detail v25.12 - 2025 - December
3 - Substantial change to recommendation9.4.1.19.4.1.1 Overflashed (Watershed) BackflashingsChanged limitations for wide over-flashings behind penetrations and given guidance on how they should be constructed, and added a new illustration in support.
1 - Minor Errata9.4.39.4.3 Dormer DetailsReformatting of 9.4.3B Gable Dormer Valley: Corrugate. No other edits or changes to recommendations.
1 - Minor Errata9.5.2.19.5.2.1 Plant Room And Conduit PenetrationsReformatted illustration of 9.5.2.1A PVC and E.P.D.M Flashing. No changes to recommendations.
1 - Minor Errata9.5.2.29.5.2.2 Mechanical ServicesReformatted illustrations. No change to recommendations.
2 - Editing and rearrangement10.110.10 Ventilation PathwaysInserted new illustrations to show typical ventilation pathways and link to a bulletin:  19.1A Revision Detail v25.12 - 2025 - December
2 - Editing and rearrangement10.10.1.410.10.1.4 Vented Soft EdgeReplaced the photographs with more modern versions.
2 - Editing and rearrangement10.1110.11 UnderlayInserted a link to bulletin:  19.1A Revision Detail v25.12 - 2025 - December
2 - Editing and rearrangement12.212.2 Purlin CreasingInserted a link to bulletin: 19.1A Revision Detail v25.12 - 2025 - December.
2 - Editing and rearrangement14.714.7 Double LappingInserted link to bulletin 19.1A Revision Detail v25.12 - 2025 - December.
1 - Minor Errata14.1514.15 Stop-endsInserted a title for Dog-eared Stop-ends
1 - Minor Errata14.18.114.18.1 Roof Cladding DamageMinor fix for clarity. No changes to recommendations.
1 - Minor Errata14.2114.21 Tools Of The TradeReformatted some drawings of 14.21G Hand Jenny Edger and 14.21H Joint Sealing by Hand Seaming
2 - Editing and rearrangement15.2.1 This clause was reviewed for clarity, and the 15.1.1A Spring Curving Calculator was updated to have improved functionality.
1 - Minor Errata15.3.2.6.515.3.2.6.5 DivertersInserted a title for Metal Tile Wall-to-Roof Junction.
2 - Editing and rearrangement17.1.3.217.1.3.2 Point Load TestingAdded reference to point load testing for wall cladding.
4 - Clause Inserted 19.1 v25.12 December 2025New clause detailing the revisions published on 1 December 2025.