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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:Flashings; Fastening-Flashings

8.6 Fastening Flashings 


Flashings must be fastened in one of three ways.


  • By primary fastening – fastening into the main structure.
  • By secondary fastening — fastening into the cladding.
  • By means of clips, cleats or seams to allow for differential movement of the roof cladding and the flashings.

For full details on fixings, see 14.13 Fasteners.


8.6.1 Primary Fasteners 

Primary fasteners are fixings that attach flashings to the structural building frame and which should withstand all the loads applied to the cladding, including expansion provisions. Primary fasteners are relied on for structural performance. Flashings should be fastened at a point within 25 mm from the exposed edges of the flashing, and the primary fastener spacing should be to each structural member it crosses.

Flashings should be fixed on both edges.

Putting bonded or embossed washers under all primary fasteners through the horizontal upper surface of flashings improves weathertightness.

8.6.2 Secondary Fasteners 

Secondary fasteners are fixings that attach flashings to sheets and one another to transfer loads and provide lap sealing. Rivets and stitching screws are secondary fasteners used to fasten flashing laps. They are subject to shear loading due to expansion and differential movement.

Sealing washers are required on all secondary fasteners, except under rivets which should themselves be sealed or self-sealing.

8.6.3 Flashing Cleats 


A flashing cleat is a continuous metal under-flashing installed behind the leading edge of a metal capping or flashing. Cleats secure cladding or flashings to the substrate or structure using a slip joint or by crimping the leading edge of the flashing to the cleat.
Cleats and clips should be accurately aligned and clinched after fixing to avoid vibration or chatter, but should still allow for expansion of the flashing.

Cleats are fastened to the substrate using mechanical fasteners and should be made from the same metal as the flashing or sheeting.

To allow for differential expansion and contraction, the flashing should be securely hooked to the drip edge of the cleat but should not be attached directly to it.


8.6.4 Seams 

Flashings can be joined together by various types of seam to avoid a plain lap joint without sealant. If the joint is likely to retain moisture and it is required to be sealed, the sealant should be introduced into the joint before it is completed.