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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 v23.12:Maintenance; Scheduled-Maintenance

16.4 Scheduled Maintenance 

Scheduled maintenance is routine maintenance that is performed at pre-planned regular intervals. Inspection should always be an included part of scheduled maintenance.

Washing Cladding

The accumulation of deposits on a metal surface may increase the time of wetness of that surface and also increase the corrosivity of the wetness. Most exposed metal roofing will be adequately cleared of dirt by rain washing, but that is not the case with unwashed areas. Unwashed areas include all wall cladding. It is particularly applicable to areas directly sheltered from the rain, which includes all surfaces that are above a line drawn at 45° to an overhang, such as a soffit, underside of a canopy, under spouting, or garage door head.

Manual washing is required to prevent the accumulation of dirt, debris or other material not removed by rain on these surfaces, carried out at intervals as prescribed by the manufacturer.

Generally, metal wall cladding subject to some direct rain should be washed:

  • every 6 months in severe environments; and
  • every 12 months in moderate environments.

Generally, other unwashed areas should be washed:

  • every 3 months for severe environments; and
  • every 6 months for moderate environments.

Washing can be carried out with water and a sponge, soft brush or broom, or water blaster up to 20 mPa, directed away from the overlap of the sheets.  Detergent will help remove deposits if it can be applied without increasing the risk of slip and fall.