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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; 2018-October

19.22 2018 – October 

The NZ Metal Roof and Wall Cladding Code Practice (COP), has been updated effective 1 October 2018.

Summary of Changes in this Update

In this update there are Category 1 - Minor Errata corrections only, for spelling and grammar - no clauses have been substantially revised, nor any recommendations altered.


19.22A Revision Detail - 2018 - October

CategoryClause Number
(at time of update)
(As of current publication)
1 - Minor Errata1. Mediation1. Inserted "a" before settlement. 2.Corrected spelling of "available" in the second paragraph.
1 - Minor Errata2.12.1 DefinitionsGeneral tidy up; Fix spelling: Intersection, surface, heights, dewpoint, six-sided, practitioners, seashore, rainwater, coatings, trademark, components, electromagnetic, skylight, sawtooth, embedded, cross-section, violently, stop end, fibreglass, change. Changed: Low Pitched 15° to 10°, and Pitch Roof 15° to 10°. Remove some extra spaces. Removed some commas. Inserted comma. Changed "newton" to "Newton". Reworked Pop Rivet definition. Removed semi-colon. UPdated "boot Flashings.
1 - Minor Errata3. Section PropertiesMoved paragraph: "Symmetrical corrugate or trapezoidal profiles have the advantage of being more easily curved around a radius. Because the ribs are necessarily close together, they have the disadvantage of roof traffic loads having to be spread over two crests or along the purlin line, and they have a lower run-off capacity."
1 - Minor Errata3. ContinuityUpdated Drawing. Arrows were not displaying correctly.
1 - Minor Errata3. Point LoadRemoved empty paragraph spacing
1 - Minor Errata4. Graffiti RemovalFixed typo "Grafitti"
1 - Minor Errata4. Compatibility TableInserted "online" in the description of the online interactive tool.
1 - Minor Errata4. Capillary ActionTypo — Changed 80 to 8°.
1 - Minor Errata4. MicrocrackingReplaced drawings a through to e
1 - Minor Errata5.75.7 DownpipesReplaced drawing "Collecting Rainwater"
1 - Minor Errata66 External Moisture OverviewFixed typo: "conductionand" to "conduction and"
1 - Minor Errata9.3.310.12.1 Cold Roofsfixed typo: inserted " is ..."
1 - Minor Errata9.510.11 Underlay1. Added new new photo – 9.5C Condensation on Synthetic Underlay. 2. Typo: corrected spelling of 9.5B "Condesation.." to "Condensation"
1 - Minor Errata9.5.510.7.5 Non-Residential BuildingsFixed typo: deleted extra "in"
1 - Minor Errata1011 Natural LightFixed typos: "thermal", "installation" and "available"
1 - Minor Errata10.111.1 Clause G7 NZBCFixed typos: "through", "enough"
1 - Minor Errata10.211.2 Natural Light MaterialsFixed typos: "a varying mass" and "square"
1 - Minor Errata10.311.3 Types Of Roof LightsFixed typos: "single" and removed extra space after comma.
1 - Minor Errata10.511.5 Weathering And DurabilityFixed typo: "not"
1 - Minor Errata13.1.214.17 Turndowns (Drip Forming or Drip Edging) changed "downturns" to "Turn-downs" and inserted "drip forming or drip edging" in the heading.
1 - Minor Errata13.3.314.13.2 Screws1. Fixed typos: "hardwoods", 2. Fixed broken links" "Fastener Performance" and "Secret Fixing Clips"
1 - Minor Errata13.5.314.5.3 Expansion FixingsFixed link: "favourable conditions for expansion"
1 - Minor Errata14.1.515.1.5 Purlin SpacingFixed typo: "subjected", removed comma.
1 - Minor Errata14.4.2.415.4.2.4 Types Of JointsRemoved unnecessary link: (See drawing 11.2.4)
1 - Minor Errata16.1.317.1.3 Resistance for wind pressuresReplaced incorrect numbering reference (section 15.7) with correct link (Wind and Point Load Testing)
1 - Minor Errata16.217.2 Background to ScopeCorrected heading "Commentary on 16.1"
1 - Minor Errata16.417.4 Commentary On 16.3Corrected heading: "Commentary On 16.3"
1 - Minor Errata16.917.9 Background to wind load testingCorrected heading: "Commentary On Section 16.6"