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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:Durability; Paint-Durability

4.8 Paint Durability 

New Zealand has a harsh level of ultraviolet light. Paint formulations that are successful overseas have sometimes been found lacking colour fastness in the Australasian environment. Proprietary pre-painted cladding products should give durability protection and keep its appearance for at least 15 years, and at the end of that period still have the anti-corrosive primers intact and present a good substrate for over-painting.

The performance of all paint coatings, however, can be affected by avoidable outside influences.

4.8.1 Touch-up Paint 

Colour match paint is sold in pre-colour matching accessories, such as soft edging or brackets, to match the pre-painted cladding. It should only be pre-applied before installation and should not be used to repair minor scratches and blemishes. These paints may closely match the pre-painted surface initially, but being an air drying acrylic, it is likely to weather differently to the pre-applied coating and cause unsightly blotches.



4.8.2 Sunscreen Lotions 

Sun screen lotions containing semi conducting metal oxides, such as titanium dioxide and zinc oxide, will cause discoloration of painted surfaces over time. There is no cure for such damage so contact of such chemicals with pre-painted cladding must be avoided.



4.8.3 Graffiti Removal 

Most Graffiti removal processes involve the use of strong solvents, abrasion, or extreme temperatures. It is generally difficult to remove graffiti without compromising an existing organic finish; the normal remedy is to overpaint as soon as possible. On a weathered pre-painted finish this can generally be achieved by washing and rinsing the surface to remove dirt and other contaminants, then applying two coats of acrylic paint.

It should be noted that such overpaint cannot, over time, be expected to match the appearance of existing pre-applied finishes.

4.8.4 Lichen 

Warm temperatures, dust, and rainfall can create an environment for lichens to flourish. Over time the root structures of lichen may infiltrate a painted surface and cause permanent damage.

Lichen growths retain moisture and, therefore, increase the time of wetness. They are fed by nutrients in the atmosphere and tend to occur more commonly in moist and unpolluted environments. Where lichen growth is present, it should be removed. See 16 Maintenance .

Physical removal is difficult to achieve completely, and recolonisation is usually rapid. Chemical treatment is recommended. New Zealand Steel publishes a formula for batching a 2% sodium Hypochlorite solution to be used for this.