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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 v25.03:Revision-History; 2019-May

2019 – May

19.23 2019 – May

The following updates to the NZ Metal Roof and Wall Cladding Code Practice (COP), are effective 1 May 2019.

Important updates:

The main clause Roof Ventilation was renamed 10 Internal Moisture and completely revised and updated. The revised clause recommends designing and installing roof cladding to allow natural ventilation in residential buildings and requires design to enable ventilation in skillion, sarked, and low-pitched residential roofs.

Summary of other changes in this update

The main clause 14 Installation was revised and updated for clarity.
Some clauses from 13 Site Practice were moved to be included in the more relevant clause Installation. Site Practice now contains mainly 13 Safety.
Some clauses in 17 Testing were renamed and renumbered to fix broken links and reflect content more accurately. A major revision of 17 Testing is underway.
Other changes are Category 1 updates, which fixed minor errata such as grammar, spelling, and layout.

19.23A Revision Detail - 2019 - May

Category	Clause Number (at time of update)	Clause (As of current publication)	Details
2 - Editing and rearrangement	2.1	2.1 Definitions	Updated Glossary to include the terms: "Square Stopping".
2 - Editing and rearrangement	3.5.4	3.5.1.2 Load Distribution	Minor edit to drawing (3.5.1.2C Deflection and the Square of Depth )
1 - Minor Errata	3.12.1.1	3.8.2 Steel Purlins	Edited for Consistency – changed 1.1 mm to 1 mm.
1 - Minor Errata	4.1	4.1 NZBC Clause B2 (Extract)	Revised for clarity.
1 - Minor Errata	4.1.1	4.1.1 B2 Objective	Reformatting
1 - Minor Errata	4.1.2	4.1.2 B2 Functional Requirements	Reformatting
1 - Minor Errata	4.1.3	4.1.3 Performance Requirements	Reformatting
2 - Editing and rearrangement	4.11.6	4.10.6 Capillary Action	Changed minimum cover in 4.10.6B Roofing Sheet End Lap to closer reflect MRM recommendations and renamed the drawing.
1 - Minor Errata	5.3.2.3	5.3.2.3 Method 2: Gutter and Downpipe Capacity Determined by Calculations	Fixed broken link to E Standard Gutter Capacity and F Standard Down Pipe Capacity, and rewrote link copy for greater clarity.
2 - Editing and rearrangement	8.9.1	8.10.1 Flashing Expansion	First line revised for clarity.
2 - Editing and rearrangement	10	10 Internal Moisture	Clause renamed to Internal Moisture. Clause revised for clarity.
2 - Editing and rearrangement	10.1	10.9 Minimising Ingress of Water Vapour into the Ceiling Cavity	Clause renamed and revised for clarity.
4 - Clause Inserted	10.1.1	10.1.1 E3 Objective	New Clause
4 - Clause Inserted	10.1.2	10.1.2 E3 Functional Requirements	New Clause created
4 - Clause Inserted	10.1.3	10.1.3 E3 Performance Requirements	New clause created.
4 - Clause Inserted	10.2	10.2 Why Manage Internal Moisture	Newly created clause
2 - Editing and rearrangement	10.4	10.3 Special Requirements	Clause revised for clarity and relevance.
0 - Clause Removed	10.4	10.4 The External Environment	Clause removed, information has been revised and moved to other main clauses.
2 - Editing and rearrangement	10.5	10.4 Condensation	Clause completely rewritten.
2 - Editing and rearrangement	10.6	10.5 Building Airtightness	Clause completely rewritten.
0 - Clause Removed	10.6.1	10.6.1 Natural Ventilation	Clause removed. New drawings used in more relevant clauses.
4 - Clause Inserted	10.7	10.6 Insulation	Newly created clause.
4 - Clause Inserted	10.7.1	10.6.1 Insulation Position	Newly created clause
4 - Clause Inserted	10.7.2	10.6.2 Other Insulation	Newly created clause
0 - Clause Removed	10.7.4.1	10.7.4.1 Direction of Lay	Clause delted. Information is now discussed in Horizontal laying and Vertical laying.
0 - Clause Removed	10.7.5	10.7.5 Non-Residential Buildings	Clause removed. Information is discussed elsewhere.
2 - Editing and rearrangement	10.8	10.7 Climate	Clause revised for clarity.
0 - Clause Removed	10.8	10.8 Wall Underlay	Clause removed and content discussed i other relevant clauses.
4 - Clause Inserted	10.8.1	10.7.1 Humidity	Relative humidity (RH, given in per cent [%]), is the most widely known method: It gives the content of water vapour in the air relative to the maximum amount of water this parcel of air can hold at its present temperature. Other measures are absolute humidity and water vapour pressure.
2 - Editing and rearrangement	10.9	10.8 Moisture Sources	Renamed and revised clause for clarity. Lead clause for various "Sources of Internal Moisture"
4 - Clause Inserted	10.9.1	10.8.1 Occupant Behaviour	Newly created clause, combining new information with some from revised "Managing Water Vapout at the Source" (renamed Sources of Internal Moisture).
4 - Clause Inserted	10.9.2	10.8.2 Heating	Newly created clause
2 - Editing and rearrangement	10.9.4	10.8.4 Construction Moisture	Clause revised for clarity.
4 - Clause Inserted	10.9.5	10.8.5 Ground Moisture	Newly created clause
2 - Editing and rearrangement	10.11	10.10 Ventilation Pathways	Clause revised for clarity.
4 - Clause Inserted	10.11.1	10.10.1 Methods of Ventilation	Newly created clause
4 - Clause Inserted	10.11.1.1	10.10.1.1 Soffit Vents	Newly created clause.
4 - Clause Inserted	10.11.1.2	10.10.1.2 Fascia Vents	Newly created clause
4 - Clause Inserted	10.11.1.3	10.10.1.3 Ridge Vents	Clause renamed and revised for clarity.
2 - Editing and rearrangement	10.11.1.4	10.10.1.5 Turbine Vents	Clause revised for clarity.
4 - Clause Inserted	10.11.2	10.10.2 Battens	Newly Created clause.
2 - Editing and rearrangement	10.12	10.11 Underlay	Clause revised and expanded for clarity.
4 - Clause Inserted	10.12.1	10.11.2 Underlay Requirements	Newly created clause.
2 - Editing and rearrangement	10.12.2	10.11.3 Types Of Underlay	Clause revised for clarity.
4 - Clause Inserted	10.12.3	10.11.4 Underlay Usage	Clause revised for clarity.
2 - Editing and rearrangement	10.12.4	10.11.5 Underlay Durability	Clause revised and expanded.
2 - Editing and rearrangement	10.12.5	10.11.6 Installing Underlay	Clause revised and expanded.
4 - Clause Inserted	10.12.5.1	10.11.6.1 Horizontal Laying	Newly created clause.
4 - Clause Inserted	10.12.5.2	10.11.6.2 Vertical Laying	Newly created clause.
2 - Editing and rearrangement	10.12.5.3	10.11.6.3 Underlay Support	Clause revised.
2 - Editing and rearrangement	10.13	10.12 Additional Information	Clause renamed to Additional Information.
2 - Editing and rearrangement	10.13.1	10.12.1 Cold Roofs	Clause revied for clarity.
2 - Editing and rearrangement	10.13.2	10.12.2 Warm Roofs	Clause revised for clarity.
2 - Editing and rearrangement	10.13.3	10.12.3 Night Sky Radiation	Clause revised for clarity.
2 - Editing and rearrangement	10.13.4	10.12.4 The Mechanics of Condensation	Clause revised and renamed, it is now: The Mechanics of Condesation.
4 - Clause Inserted	10.13.5	10.11.1 Underlay Standards	Newly created clause.
4 - Clause Inserted	10.13.6	10.12.5 Relative Humidity	Newly created clause
4 - Clause Inserted	10.13.7	10.12.6 Absolute Humidity	Newly created clause
4 - Clause Inserted	10.13.8	10.12.7 Water Vapour Pressure	Newly created clause
2 - Editing and rearrangement	13.2	13.1.13 Roof Access During Construction	Clause movved to 13 Safety
0 - Clause Removed	13.4	13.4 Acceptance Of Materials	class="views-field views-field-field-revision-message-revision-id">
0 - Clause Removed	13.4.1	13.4.1 Presence Of Moisture Between Sheets	Clause combined with 14.3.2 Wet Storage Damage
0 - Clause Removed	13.4.2	13.4.2 Colour Match	Clause combined with 14.18.5 Colour Matching Paint
0 - Clause Removed	13.4.3	13.4.3 Storage Stain	Clause removed.
0 - Clause Removed	13.5	13.5 Roof Loading	Clause combined with 14.3.1 Unloading
2 - Editing and rearrangement	14	14 Installation	Clause revised for clarity.
2 - Editing and rearrangement	14.1	14.1 Pre- Installation	Clause revised for clarity.
2 - Editing and rearrangement	14.1	14.10 Overhang	Clause revised for clarity
0 - Clause Removed	14.1	14.10 Metal Roof Defects	Clause removed. See 14.18.1 Roof Cladding Damage
0 - Clause Removed	14.1.5	14.1.5 Cutting And Drilling	Clause deleted. Information was spread through other clauses, mainly 14.18.4.4 Repairing Swarf Damage
4 - Clause Inserted	14.2	14.2 Product Selection	Newly Created Clause
2 - Editing and rearrangement	14.2	14.20 Completion	Clause revised for clarity.
4 - Clause Inserted	14.2.1	14.2.1 Measuring	Newly created clause
0 - Clause Removed	14.2.1	14.2.1 Swarf Removal	clause removed, subject is now discussed in 14.18.4.1 Preventing Swarf Damage.
4 - Clause Inserted	14.2.2	14.2.2 Ordering	Newly created clause.
2 - Editing and rearrangement	14.2.3	14.2.3 Transportation	Clause revised for clarity and moved to 14 Installation.
4 - Clause Inserted	14.3	14.3 Accepting Delivery	New created clause, combining Acceptance of Materials, previously in Site Practice.
4 - Clause Inserted	14.3.1	14.3.1 Unloading	Newly created clause
0 - Clause Removed	14.3.1	14.3.1 Primary Fasteners	Clause removed. Information is now discussed in various shorter and newly created clauses.
4 - Clause Inserted	14.3.2	14.3.2 Wet Storage Damage	Newly created clause
0	14.4	14.4 Secondary Fasteners	class="views-field views-field-field-revision-message-revision-id">
0 - Clause Removed	14.4.2	14.4.2 Monel Rivets	clause removed, information is now discussed in other clauses.
0 - Clause Removed	14.4.3	14.4.3 Aluminium Rivets	Clause removed, information now in 14.12.4 Rivets
0 - Clause Removed	14.4.4	14.4.4 Stainless Steel Rivets	Clause deleted. See 14.12.4 Rivets
0 - Clause Removed	14.4.6	14.4.6 Fastener Frequency	Clause removed. See 14.13.1 Fastener Spacing
2 - Editing and rearrangement	14.5	14.5 Handling	Clause revised for clarity and moved to Installation.
0 - Clause Removed	14.5.2	14.5.2 Pan Fixing	Clause Removed. See 14.12.2 Screws
0 - Clause Removed	14.5.3	14.5.3 Expansion Fixings	Clause removed. See 14.13.4 Fastener Allowance for Expansion
0 - Clause Removed	14.5.4	14.5.4 Lap Stitching	Clause removed. Information absorbed in other clauses.
2 - Editing and rearrangement	14.6	14.5 Walking On Roofs	Clause revised for clarity and moved to 14 Installation.
0 - Clause Removed	14.6	14.6 Installation	Empty heading removed. See 14.13 Fastener Installation.
4 - Clause Inserted	14.6.1	14.5.1 Footwear	Newly created clause
2 - Editing and rearrangement	14.7	14.6 Strippable Films	Clause revied for clarity.
0 - Clause Removed	14.7	14.7 Re-Roofing	Clause removed. Information absorbed in other clauses.
4 - Clause Inserted	14.7.1	14.6.1 Storing Product with Strippable Film	Newly created clause
2 - Editing and rearrangement	14.8	14.8 Setting Out	Clause revised for clarity.
0 - Clause Removed	14.8.2	14.8.2 Side Lap Fixing Between Purlins	Clause removed.
0 - Clause Removed	14.8.6	14.8.6 Purlin Protection	clause removed
0 - Clause Removed	14.8.7	14.8.7 Drainage	Clause removed
0 - Clause Removed	14.8.8	14.8.8 Condensation	Clause removed.
4 - Clause Inserted	14.9	14.9 Marking and Cutting	Newly created clause
2 - Editing and rearrangement	14.11	14.11 Sealing and Joining	Clause revised for clarity
4 - Clause Inserted	14.11.1	14.11.1 Sealing End Laps	Newly created clause
2 - Editing and rearrangement	14.12	14.12 Fasteners	Clause revised for clarity.
0	14.12.1	14.12.1 Nails	class="views-field views-field-field-revision-message-revision-id">
2 - Editing and rearrangement	14.12.2	14.12.2 Screws	Clause revised for clarity.
4 - Clause Inserted	14.12.3	14.12.3 Clip Fasteners	Newly created clause.
2 - Editing and rearrangement	14.12.4	14.12.4 Rivets	Clause revised for clarity
2 - Editing and rearrangement	14.13	14.13 Fastener Installation	Clause renamed and revised for clarity.
2 - Editing and rearrangement	14.13.1	14.13.1 Fastener Spacing	Newly created clause
4 - Clause Inserted	14.13.2	14.13.2 Fastener Placement	Newly created clause
4 - Clause Inserted	14.13.3	14.13.3 Fastener Seating	Newly created clause
4 - Clause Inserted	14.13.4	14.13.4 Fastener Allowance for Expansion	Newly created clause
4 - Clause Inserted	14.14	14.14 Modes Of Fastener Failure	Clause revised for clarity
4 - Clause Inserted	14.15	14.15 Stop-ends	Clause revised for clarity.
2 - Editing and rearrangement	14.16	14.16 Turndowns (Drip Forming or Drip Edging)	Clause revised for clarity.
4 - Clause Inserted	14.17	14.17 Soft edging and Flashing	Newly created clause
4 - Clause Inserted	14.18	14.18 Avoiding Problems	Newly created clause heading
2 - Editing and rearrangement	14.18.1	14.18.1 Roof Cladding Damage	Clause revised for clarity and moved to 14 Installation
4 - Clause Inserted	14.18.2	14.18.2 Water Ponding	Newly created clause
4 - Clause Inserted	14.18.3	14.18.3 Correctly Installed Gutters	Newly created clause
0	14.18.4	14.18.4 Swarf Damage	class="views-field views-field-field-revision-message-revision-id">
4 - Clause Inserted	14.18.4.1	14.18.4.1 Identifying Swarf Stains	Newly created clause
4 - Clause Inserted	14.18.4.2	14.18.4.1 Preventing Swarf Damage	Newly created clause
4 - Clause Inserted	14.18.4.3	14.18.4.3 Swarf Effect on Performance	Newly created clause.
2 - Editing and rearrangement	14.18.4.4	14.18.4.4 Repairing Swarf Damage	Clause revised for clarity and renamed.
4 - Clause Inserted	14.18.4.5	14.18.4.2 Severe or Extensive Swarf Staining	Newly created clause.
4 - Clause Inserted	14.18.5	14.18.5 Colour Matching Paint	Newly created clause
4 - Clause Inserted	14.18.6	14.18.6 Field Painting	Newly created clause.
4 - Clause Inserted	14.18.7	14.18.7 Sunscreen	Newly created clause.
4 - Clause Inserted	14.18.8	14.18.8 Removing Lichen	Newly created clause.
2 - Editing and rearrangement	14.21	14.21 Tools Of The Trade	Claused revised for clarity.
4 - Clause Inserted	14.21.1	14.22.1 Spacing	Clause removed. See 14.13.1 Fastener Spacing
4 - Clause Inserted	14.22.1	14.23.1 Crest Fixing	Clause removed. See 14.12.2 Screws
4 - Clause Inserted	14.23	14.6.2 Tools	Clause removed. See 14.12.2 Screws
4 - Clause Inserted	14.24	14.8 Translucent Sheeting	Clause removed.
4 - Clause Inserted	14.24.1	14.8.1 Side-Lap Fixing	Clause removed.
4 - Clause Inserted	14.24.2	14.8.3 End Laps	Clause deleted.
4 - Clause Inserted	14.24.3	14.8.4 Midspan Supports	Clause removed
4 - Clause Inserted	14.24.4	14.8.5 Stopends	Clause removed.
4 - Clause Inserted	14.24.5	14.8.9 Pitch	Clause removed.
2 - Editing and rearrangement	17	17 Testing	Edited for clarity.
2 - Editing and rearrangement	17.1	17.1 Scope	Clause revised for clarity
1 - Minor Errata	17.1.2	17.1.2 Resistance to point load	Fixed typos – "serviceability" and "strength".
2 - Editing and rearrangement	17.2	17.2 Background to Scope	Heading changed from "Commentary on 16.1" and clause revised for clarity and brevity.
4 - Clause Inserted	17.4	17.4 Commentary On 16.3	Clause removed
2 - Editing and rearrangement	17.5	17.5 Determining Wind load Span Graphs	Minor grammatical edits and clause renamed to "Determining Wind Load Span Graphs" to avoid confusion with 3.11.2 Steel Cladding Wind Load Span Graphs.
1 - Minor Errata	17.6	17.6 Specific Methods Of Testing Sheet Roof And Wall Cladding	Clause moved (renumbered) to follow 17.7 Wind and Point Load Testing.
4 - Clause Inserted	17.7.1	17.7.1 Commentary On Section 15.5	Clause Removed. 17 Testing to undergo major revision.
2 - Editing and rearrangement	17.9	17.9 Background to wind load testing	Renamed "Clause from Commentary on 16.6".