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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 v24.06:Installation; Product-Selection

14.2 Product Selection 

The profile must be suitable for the strength requirements of the building, and appropriate for the minimum pitch, and the material selected must be suitable for the environment and be compatible with adjacent building materials. See 4 Durability.

Aluminium requires special installation details to achieve durability. See  14.20 Fixing Aluminium Sheeting for more details.

14.2.1 Measuring 

Measuring should take place once sufficient structure is in place to enable accurate calculation of lengths required. It is beneficial to make more than one measurement of any run to identify discrepancies and avoid errors.

14.2.2 Ordering 

Cladding materials should be ordered with enough time to allow for manufacture and transport. Profile, thickness, colour, grade, and any requirements for labelling of bundles should all be clearly identified.

Do not mix products; different manufacturers use different paint formulations. Where different brands of pre-painted material are used on the same building, differences in colour, gloss, and weathering performance may appear immediately or over time.

14.2.3 Transportation 

Load safety and protection is primarily the driver’s responsibility.

Short sheets should be packed on top of longer ones, which should have end and edge protection to avoid cut-end damage to the sheets below them. Dunnage should be evenly spaced in vertical alignment. Bundles must be placed and secured to protect against damage from other materials.

For sheets that are exposed on the underside in situ, such as for unlined wall cladding applications, or have double-sided or fleece-lined coatings, protection must be given to prevent the dunnage from damaging the bottom sheet.  This is normally achieved by the application of a short slip sheet with paper overlay.

On longer distances, extra protection or packaging may be required to protect the material from fretting during transport.

For longer lengths, when a long boom is required for off-loading, a suitable boom should accompany the load unless otherwise arranged.