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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 v24.03:Trash; Nzs-3604

NZS 3604

18.3 NZS 3604 

NZS 3604 is an acceptable solution for compliance with the NZBC for light timber frame buildings not requiring specific design. It contains prescriptive dimensions for purlin spacings and fasteners , based on maximum design wind speeds of Low ( 32 m/s ) , Medium ( 37 m/s ) , High ( 44 m/s ) , Very High ( 50 m/s ) , or Extra High ( 55 m/s ) .

Some limitations of the scope of NZS3604 are:

  • Timber frame construction .
  • Height from lowest ground to the highest point on the roof not to exceed 10 m .
  • A snow load not exceeding 1.0 kPa ( although Section 15 of NZS 3604 does provide additional criteria for 1.5 kPa and 2.0 kPa snow loads).
NZS 3604 includes:
  • private dwellings, hostels, hotels and nurse's homes ,
  • factories with restricted floor loadings , and
  • institutional and educational buildings with restricted floor loadings .
NZS 3604 excludes:
  • buildings dedicated to the preservation of human life ,
  • buildings which may host crowds ,
  • publicly owned buildings containing high value contents , and
  • curved roof construction .

NZS3604 uses conservative figures to arrive at a design load. Th e NZ Metal Roof and Wall Cladding Code of Practice uses the same philosophy to prescribe a value known to perform , either historically or by test , and will comply with the NZBC.

The price for this conservatism is small in comparison the overall cost of the whole of the building, and unless the building is specifically designed, designers and contractors should not deviate from the loading requirements of this section of the Code of Practice.

Classification of Wind Zones in NZS 3604 are specific to the site, because the buildings covered by this standard are limited in size. Design tables (but not design wind speed) include a local pressure factor of 1.5 over the entire structure rather than varying factors according to the position on the roof. ( see section 3.3.2 )