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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; Tools-Trade

14.22 Tools Of The Trade 

14.22A Hand Seamers

Hand Seamers are used to hand fold small flashings, by progressively working along the edge of a sheet.

14.22B Seaming Pliers

Various shapes of seaming pliers may be required to execute complex sheet metal work, particularly with standing seam roofs.


14.22C Crimping Tools

These can be used to form a small end in downpipes, or by reducing the length of a down-turn on a flashing to cause a curve in the adjacent surface.

14.22D Shears (Straight and Curved)

Shears are normally purchased in left-hand and right-hand sets.  Both may be required to cut through complex shapes.  They may be solid or articulated (“aviation snips”)


14.22E Roller Bender

This can be used for onsite manufacture of flashings.

14.22F Portable Folding Machine

Portable folding machines are useful for onsite sheetmetal work.

14.22H Joint Sealing by Hand Seaming

All metal joints that are to be sealed should be mechanically joined. Seaming is one acceptable method of joining two pieces of metal. 

The two pieces are folded so each hooks into the other and then they are locked together by the means of a hand seamer or groover. 

The material allowance depends on the hook dimension, but it is usually 6 mm. That means the extra allowance for the is 18 mm, because there are four thicknesses of material.

This type of seam can be used on a flat surface or round surface.


14.22I Setting Hammer

A nylon faced hammer can be used to reduce damage when dressing flashings.