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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-December

2019 – December

19.21 2019 – December

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

Major Revisions

For this update, the COP section 5 Roof Drainage and all its sub-clauses have been substantially revised. The updates focussed heavily on creating new online tools for calculating Roof Drainage, Gutter Capacity, Downpipe Capacity and Valley Capacity, which are located in 5.4.7 Gutter Capacity Calculator.

Summary of other changes in this update

All the content in 5 Roof Drainage has been updated to provide clarity and brevity, and detail drawings are updated.
The previous methods of capacity calculations, using two distinct methods based on standard sizes, have been removed and replaced by online calculator in 5.4.7 Gutter Capacity Calculator.
New clauses have been added for 17.1.3.2 Point Load Testing and 17.1.1.2 Point Load Testing Standard under 17.1 Metal Cladding Testing.
The Glossary has been updated with 2.1A Definitions for Swiss Gable, Finial, and Profiled Washer; and some minor edits to refine definitions and grammar fixes.

19.21A Revision Detail - 2019 - December

Category	Clause Number (at time of update)	Clause (As of current publication)	Details
2 - Editing and rearrangement	1	1 Introduction	Update Revisions Message
2 - Editing and rearrangement	2.1	2.1 Definitions	Revised definition of "Load Spreading Washer", added a new item "Profiled Washer", added definition for "Finial", minor grammatical fixes.
2 - Editing and rearrangement	5	5 Roof Drainage	The entire Roof Drainage-clause had been revised.
1 - Minor Errata	5.1	5.1 NZBC: Clause E1 — Surface Water	Formatting
4 - Clause Inserted		5.4 Gutters	New clause.
4 - Clause Inserted		5.4.1 External Gutters (Spouting)	New clause.
2 - Editing and rearrangement	5.5.5	5.4.4 Concealed Fascia Gutters	This clause had been completely revised and renamed.
2 - Editing and rearrangement	5.5.4	5.4.5 Internal Gutters	Clause completely revised.
4 - Clause Inserted		5.4.5.1 Internal Gutter Design Features	New clause.
2 - Editing and rearrangement	5.6	5.5 Valleys	Valleys had been completely revised and divided into smaller, more specific, sections.
4 - Clause Inserted		5.5.1 Valley Fixing	New clause.
4 - Clause Inserted		5.5.2 Valley Design	New clause.
4 - Clause Inserted		5.4.3 Internal Corners	New clause.
2 - Editing and rearrangement	5.6.2	5.5.3 Bifurcated Valleys	The clause had been revised. Valleys are now discussed in smaller, more specific, clauses.
4 - Clause Inserted		5.5.5 Changing Angles in Valleys	New clause.
4 - Clause Inserted		5.5.6 Asymmetrical Valleys	New clause.
4 - Clause Inserted		7.1.3 Roof Drainage Capacity	New clause.
3 - Substantial change to recommendation	5.5.7	5.4.6 Secret Gutters	Clause revised, for brevity and clarity.
4 - Clause Inserted		5.6 Rainwater Heads, Sumps, and Overflows	New clause.
2 - Editing and rearrangement	5.8.1	5.6.1 Rainwater Heads	Clause revised, now providing more information.
2 - Editing and rearrangement	5.8	5.6.2 Sumps	This clause has been revised.
2 - Editing and rearrangement	5.8.2	5.6.3 Overflows	Clause renamed, Outlets are now discussed under Outlets and Downpipes.
4 - Clause Inserted		5.7 Outlets and Downpipes	New clause.
4 - Clause Inserted		5.7.1 Placement of Downpipes	New clause.
4 - Clause Inserted		5.7.2 Capacity Table for Common Size Downpipes	New clause.
2 - Editing and rearrangement	5.5.1	5.4.2 Gutter Capacity Design	Clause has been revised and edited.
4 - Clause Inserted		5.4.2.2 Maximum Gutter Length	New clause.
2 - Editing and rearrangement	5.5.2	5.4.2.3 Spouting Support Systems	Clause revised.
4 - Clause Inserted		14.18.9 Gutter Installation	New clause.
2 - Editing and rearrangement	5.2	5.3 Roof Drainage Design	Clause had been completely revised.
2 - Editing and rearrangement	5.3.1	5.3.1 Catchment Area	Caluse has been completely revised. All calculations are now under a new clause Capacity Calculations.
2 - Editing and rearrangement	5.5.8	5.4.2.1 Gutter Fall	Clause revised and renamed.
3 - Substantial change to recommendation	5.3	5.3.2 Rainfall Intensity	Clause had been completely revised, with updated Rainfall Intensity Maps at the end of the main Clause, Roof Drainage.
4 - Clause Inserted		5.3.2.3 Allowance for Short-Term Intensities	New clause.
4 - Clause Inserted		5.3.2.2 Duration	New clause
2 - Editing and rearrangement	5.3.2	5.4.7 Gutter Capacity Calculator	The old clause, Capacity Calculations, replaced by a new clause of the same name but including new online tools.
4 - Clause Inserted		5.7.1 North Island 50-year ARI, 10-minute Rainfall Intensity Map	New clause.
4 - Clause Inserted		5.7.2 South Island 50-year ARI, 10-minute Rainfall Intensity Map	New clause.
4 - Clause Inserted	8.3	8.4 Flashing Cover	Adjusted spacing in Table 8.3A
2 - Editing and rearrangement	8.4.4.3	8.5.5.3 Step Apron	Removed reference to "Fortress Fasteners" in drawing A: Step Apron Details.
4 - Clause Inserted	8.4.4.4	8.5.5.4 Eaves Flashing	Drawing 8.4.4.4A renamed to Gutter Flashing.
2 - Editing and rearrangement	12.2	12.2 Purlin Creasing	Inserted photograph.
4 - Clause Inserted	17.1.2	17.1.1.2 Point Load Testing Standard	New Clause.
4 - Clause Inserted	17.3.2	17.1.3.2 Point Load Testing	New clause.
1 - Minor Errata	18.8	18.8 Sheet Metal Work For Roofing Contractors.	Clause revised for gender neutrality. No significant changes.
4 - Clause Inserted		19.21 2019 – December	Summary of Changes – December 2019
0 - Clause Removed	5.3.2.1	Method 1: Gutter and Downpipe Capacity Determined by Graph	These methods have been replaced by online capacity calculating tools.
0 - Clause Removed	5.3.2.3	Method 2: Gutter and Downpipe Capacity Determined by Calculations	These methods have been replaced by online capacity calculating tools.
0 - Clause Removed	5.3.3	Roof Cladding Capacity	These methods have been replaced by online capacity calculating tools.
0 - Clause Removed	5.4	Snow	Clause removed, Snow and hail are comprehensively discussed in Snow Loads.
0 - Clause Removed	5.4.1	Hail	Clause removed. Leaf guards and maintenance are discussed under Gutter Maintenance.
0 - Clause Removed	5.5	Gutters	The clause had been removed. Gutters are now discussed in more detail in a separate clause for each type, under the main clause Types of Gutter.
0 - Clause Removed	5.5.3	Eaves Gutters	Clause deleted. Now discussed under External Gutters.
0 - Clause Removed	5.6.1	Valley Catchment	This clause had been replaced with the newly developed online tool in Valley Capacity Calculations.
0 - Clause Removed	5.7	Downpipes	Information previously contained in this clause is now discussed in Outlets and Downpipes.
Out-of-band updates 16/12/2019
2 - Editing and rearrangement	5.4.2A	5.7.2 Capacity Table for Common Size Downpipes	Removed obsolete column for Roof Area Drained as the online calculator replaces this.
2 - Editing and rearrangement	5.7	5.4.7 Gutter Capacity Calculator	Added link to Common Sized Downpipes.