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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; V2509-September-2025

19.2 v25.09 September 2025 

Important Revisions

Most of this revision consisted of editing and rearrangement for clarity, consistency, and accuracy.

Other Edits and revisions

The rest of this update is taken up with minor edits and revisions for clarity, grammar, and spelling.

Important Notice:

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19.2A Revision Detail v25.09 - 2025 - September

CategoryClause Number (prior to update)Clause (As of current publication)Details
3 - Substantial change to recommendation5.4.2.15.4.2.1 Gutter Fall

Revision to clarify the acceptable and recommended amount of gutter fall.

3 - Substantial change to recommendation7.3.27.3.2 Roof Cladding Expansion Provisions

Revised 7.3.2A Favourable Circumstances for Controlling Expansion to show the correct recommendations for aluminium.

3 - Substantial change to recommendation14.19.214.19.2 Recommendations for Fixing Aluminium

Changed the recommendation for sheet lengths over 10 m to 3 m.

2 - Editing and rearrangement11 Introduction

New revision message for v25.09, published on 1 September 2025.

1 - Minor Errata4.6.34.6.3 Material Selection

Clarification of C4 and C6 fasteners.

1 - Minor Errata4.10.94.10.9 Gutter Leaf Guard

Grammar and typo fixes.

1 - Minor Errata4.15.14.15.1 Ground Clearance

Typo fix.

1 - Minor Errata5.4.75.4.7 Gutter Capacity Calculator

Updated label of "Span length of roof" on Secret Gutter for clarity.  This previously stated "Length of roof", which was ambiguous: calculations are unchanged.

The enforced minimum remains unchanged at 2.2.

2 - Editing and rearrangement5.6.25.6.2 Sumps

Clarifying edit.

2 - Editing and rearrangement5.75.7 Downpipes

This clause was renamed, and some content was moved to 5.6 Outlets. Minor edit for clarity: removed the reference to astragalus. No other changes to content or recommendations.

2 - Editing and rearrangement7.47.4 End Laps

Removed historical error regarding the use of rivets.

2 - Editing and rearrangement8.5.28.5.2 Barge And Verge

Added illustrations showing details for

1 - Minor Errata8.5.48.5.4 Apron Flashings

Deleted "optional cation" statements.

2 - Editing and rearrangement8.5.4.48.5.4.4 Eaves Flashing

Updated and renamed 8.5.4.4A Gutter-Eaves Flashing Option 1 and introduced option 2.

1 - Minor Errata10.10.1.210.10.1.2 Fascia Vents

Typo fix.

1 - Minor Errata10.10.210.10.2 Battens

Typo fix.

1 - Minor Errata10.11.110.11.1 Underlay Standards

Aligned some table items.

1 - Minor Errata10.11.610.11.6 Installing Underlay

Typo Fix.

1 - Minor Errata10.12.410.12.4 The Mechanics of Condensation

Typo fix.

1 - Minor Errata10.12.710.12.7 Water Vapour Pressure

Typo fix.

1 - Minor Errata1111 Natural Light

Typo fix.

1 - Minor Errata11.1.111.1.1 Compliance

Typo fix.

1 - Minor Errata11.3.111.3.1 Point Load on Translucent Sheets

Typo fix.

2 - Editing and rearrangement11.411.4 Thermal Resistance

Updated illustration: 11.4A Double-Skinned Rooflight.

1 - Minor Errata12.1.312.1.3 Thermal Noise

Grammar fix.

1 - Minor Errata12.212.2 Purlin Creasing

Punctuation fix.

1 - Minor Errata12.312.3 Flashing Buckling

Punctuation fix.

1 - Minor Errata12.4.312.4.3 Installation

Some grammar fixes.

1 - Minor Errata12.5.112.5.1 Touch-Up

Grammar fix.

1 - Minor Errata14.114.10 Overhang

Minor layout edit.

1 - Minor Errata14.114.1 Pre-Installation

Typo fix.

1 - Minor Errata14.514.5 Walking On Roofs

Typo fix.

1 - Minor Errata14.914.9 Marking and Cutting

Typo Fix.

 

1 - Minor Errata14.12.114.12.1 Nails

Punctuation fix.

1 - Minor Errata14.12.214.12.2 Screws

Punctuation fix and reformatted font in illustrations for consistency.

1 - Minor Errata14.13.214.13.2 Fastener Placement

Grammar fix.

1 - Minor Errata14.18.114.18.1 Roof Cladding Damage

Grammar fix.

1 - Minor Errata14.18.314.18.3 Correctly Installed Gutters

Typo fix.

1 - Minor Errata14.18.4.114.18.4.1 Preventing Swarf Damage

Formatting fix.

1 - Minor Errata14.1914.19 Fixing Aluminium Sheeting

Punctuation fix. Added clarifying statement for using aluminium screws.

1 - Minor Errata14.19.114.19.1 Painted Aluminium

Typo fix.

1 - Minor Errata1515 Other Products

Punctuation fix.

1 - Minor Errata15.115.1 Curved Roofs

Grammar fix.

2 - Editing and rearrangement15.3.115.3.1 Design

This clause was revised as part of a comprehensive revision of the parent clause, 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.1.115.3.1.1 Durability

This clause was comprehensively edited during a comprehensive revision of 15.3 Pressed Metal Tiles.

 

4 - Clause Inserted 15.3.1.2 Structure

A new clause, created as part of a comprehensive revision of 15.3 Pressed Metal Tiles

2 - Editing and rearrangement15.3.1.215.3.1.3 Minimum Pitch

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.1.315.3.2.3 Underlay

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.1.415.3.2.1 Roof Framing

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.1.515.3.2.4 Tiling Battens

This clause was edited during a comprehensive revision of 19.2A Revision Detail v25.09 - 2025 - September. We introduced a table for 19.2A Revision Detail v25.09 - 2025 - September, replacing the multiple tables in 19.2A Revision Detail v25.09 - 2025 - September (which was removed).

0 - Clause Removed15.3.1.5Pullout resistance for different constructions

This clause was removed during an overall revision of 15.3 Pressed Metal Tiles, and replaced with 15.3.2.4A Batten Installation sizing and fixing requirements in accordance with NZS 3604: 2011 in 15.3.2.4 Tiling Battens.

2 - Editing and rearrangement15.3.215.3.1.4 Valleys

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

4 - Clause Inserted 15.3.2 Installation

A newly created clause as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.315.3.2.5 Roof Traffic

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.415.3.2.2 Valley Installation

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.515.3.2.6 Flashings

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.5.115.3.2.6.1 Ridge

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.5.315.3.2.6.3 Gable Ends

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.5.415.3.2.6.4 Flashing Metal Tile to Wall

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.5.515.3.2.6.5 Diverters

This clause was renamed and edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

1 - Minor Errata15.3.5.615.3.2.6.6 Penetrations

Typo fixes.

2 - Editing and rearrangement15.3.615.3.1.5 Longrun Tiles

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

1 - Minor Errata15.3.715.3.3 Sitework

Fixed links.

2 - Editing and rearrangement15.3.815.3.4 Laying Metal Tiles

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

2 - Editing and rearrangement15.3.915.3.5 Workmanship

This clause was edited as part of a comprehensive revision of 15.3 Pressed Metal Tiles.

1 - Minor Errata15.4.13.415.4.13.4 Finishing at Ridges and Eaves of Tray Roofing

Typo fix.

2 - Editing and rearrangement15.5.1.315.5.1.3 Insulated Panel Face Profiles

Updated profile illustrations.

1 - Minor Errata15.5.1.615.5.1.6 Insulation Panel Insulation Values

Typo and grammar fix.

2 - Editing and rearrangement15.5.1.1815.5.1.18 Insulated Panel Flashings

Replaced 15.5.1.18B Insulated Panels Barge Flashing detail for accuracy.

2 - Editing and rearrangement15.5.215.5.2 Composite Systems

Editing for clarity.

2 - Editing and rearrangement15.5.2.215.5.2.2 Composite System Installation

Edited for clarity and accuracy.

1 - Minor Errata16.116.1 Maintenance Compliance

Typo fix.

1 - Minor Errata16.616.6 Special Maintenance

Typo fix.

2 - Editing and rearrangement16.8.216.8.2 Paint Application

Clause renamed for clarity.

2 - Editing and rearrangement17.1.217.1.2 Test Requirements

Edit for clarification.

2 - Editing and rearrangement17.1.417.1.4 Test Report

Edit for clarification.

2 - Editing and rearrangement17.1.5.217.1.5.2 Interpreting UDL Load Results

Edit for clarification.

1 - Minor Errata17.1.5.317.1.5.3 Interpreting Point Load Results

Typo fix.

1 - Minor Errata17.2.3.117.2.3.1 Site Testing

Typo fix.

1 - Minor Errata17.2.517.2.5 Weatherproofing

Typo fix.

1 - Minor Errata17.3.117.3.1 Soft Edge Product Technical Statement Requirements

Typo fix.

1 - Minor Errata17.4.117.4.1 Part1: AS/NZS 2728:2013

Typo fix.

1 - Minor Errata17.4.417.4.4 Appendices of AS/NZS 2728:2013 included as Normative in the MRM Standard

Typo Fix

1 - Minor Errata17.4.517.4.5 Appendices of AS/NZS 2728:2013 considered Informative in the MRM Standard:

Typo fix.

1 - Minor Errata1818 Useful Information

Typo fix.

1 - Minor Errata18.118.1 Conversion Factors

Text styling.

1 - Minor Errata18.318.3 Material Density, Melting Point, Expansion And Modulus

Typo fix.

1 - Minor Errata18.418.4 Decadic Number System

Typo fix.

1 - Minor Errata18.818.8 Sheet Metal Work For Roofing Contractors.

Typo fix.

4 - Clause Inserted 19.2 v25.09 September 2025

Revision details for the update on 1 September 2025.