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v26.06 June 2026

Substantial changes to recommendations

  • The Downpipe Capacity Calculator and Downpipe Capacity Table have been updated with common dropper sizes, which resulted in a decrease in downpipe capacity in many cases. The calculator now automatically selects the minimum dropper size relevant to a chosen downpipe size.
  • The calculations in the Maximum Area Above Penetration Calculator for corrugate profiles now assumes that there is no lap in the discharge trough. This resulted in an increase in the maximum area above penetrations recommendations in the CoP.
  • We improved general labelling and descriptions of conditions and dimensions for Asymmetrical Valley designs.
  • The clause Metal Wall Cladding Flashings now contains details for wall cladding flashings, including internal and external corners, and vermin proofing.
    Window details for Corrugate Horizontal on Cavity, Corrugate Vertical on Cavity, and Corrugate Vertical Direct fixed have been tested to comply with E2/VM1. Details are available from roofmattersnz@gmail.com and will be published the next Code of Practice revision on 1 September 2026.

Editing and rearrangement

 

Revision Detail v26.06 - 2026 - June

Category Clause Number (prior to update) Clause (As of current publication) Details
2 - Editing and rearrangement 1 Introduction New revision message for v26.06, published on 1 June 2026.
2- Editing and rearrangement   Capacity Table for Common Size Downpipes Revised the Downpipe Capacity Table to use dropper sizes and linked the table to the Downpipe Capacity Calculator.
1 - Minor Errata   Material Selection Fixed table content alignment.
3 - Substantial change to recommendation   Secret Gutters Revised Secret Gutter Detail to clearly show the height of the gutter.
1 - Minor Errata   Gutter Capacity Calculator Grammar fix.
2 - Editing and rearrangement   Asymmetrical Valleys Added clarification for asymmetrical valley dimensions.
 
3 - Substantial change to recommendation   Valley Capacity Calculator Improve labeling and conditions for asymmetrical valley designs and fix label positioning.
Clarifies requirement for valley baffle in some asymmetrical designs.
1 - Minor Errata   Outlets Correction for clarity.
1 - Minor Errata   Capacity Table for Common Size Downpipes Fixed link to Downpipe Capacity Calculator.
3 - Substantial change to recommendation   Downpipe Capacity Calculator Updated for in-place selection of common downpipe sizes, and now uses measured dimensions of standard droppers.
This may result in reduced capacity vs previous calculations.
2 - Editing and rearrangement   Maximum Area Above Spreader Calculator Grammar fix and additional callout on illustration to Condition 3
1 - Minor Errata   Maximum Run Calculator Grammar fix.
2 - Editing and rearrangement   Roof Cladding Expansion Provisions Revised Favourable Circumstances for Controlling Expansion to show the correct recommendations for aluminium.
1 - Minor Errata   Flashing Cover Removed requirement for a baffle in Category C in Transverse Apron Flashing Cover Table.
2 - Editing and rearrangement   Profile Closures Illustrations for vermin flashings have been moved to Metal Wall Cladding Flashings.
3 - Substantial change to recommendation   Wall Cladding Flashings Renamed clause and added illustrations for wall cladding flashings and vermin closures.
3 - Substantial change to recommendation   Maximum Area Above Penetration Calculator For corrugate profiles this now assumes flow to top of profile (no freeboard), which increases area but requires that there be no discharge to lap row.
2 - Editing and rearrangement   Fascia Vents This clause has been revised as part of the larger revision of Ventilation Pathways.
2 - Editing and rearrangement   Battens Editing of Ventilation Pathway: Top Plate with Underlay to clearly show a baffle.
1 - Minor Errata   Overhang Edit for clarity. No changes to recommendations.
1 - Minor Errata   UDL Testing Minor edit for clarity.
2 - Editing and rearrangement   MRM Fastener Performance Requirements and Testing Added recommendation fastener identification stamped on the head.
2 - Editing and rearrangement   Revision History PDF Download of the Code of Practice now contains detailed revision history for only changes made to the current edition. 
1 - Minor Errata   April 2026 Correction to clause links
4 - Clause Inserted   v26.06 June 2026 Latest revision.
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Clause: 
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Clause Number: 
19.1
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Revision Category: 
4 - Clause Inserted
Revision Detail: 

Latest revision.