New Zealand · metal roofing
Minimum pitch for corrugated iron in NZ
Eight degrees. Cladding pitch. After deflection. That sentence is the whole product for a lot of searches.
NZMRM CoP 7.1.1A: corrugate 16.5 mm rib — 8° minimum, check capacity after 15 m; 21 mm — 4° / 20 m; 35 mm — 3° / 65 m. The table is explicit that these are cladding pitches, not building-design roof pitches. Buildings with wide purlins or portals may need a steeper design pitch so the as-laid sheet still meets the table.
Manufacturer sheets can be stricter than the generic table. Metalcraft corrugate: 8° up to 30 m sheets, 9° beyond that (to 50 m) at ≤100 mm/hr. Stratco CGI: 8°, plus thermal-expansion joints on long dark sheets. None of that appears on a US-centric “roof pitch calculator.”
Exceptions in the CoP (curved roofs, penetration back curbs, some trough reroofs) are specialist. This tool will not bless a 6° corrugate garage because the internet said drainage is fine.
FAQ
Is E2/AS1 the same as the CoP table?
E2/AS1 and the CoP agree on 8° for standard corrugate in common residential details, but you still follow the manufacturer’s current sheet. This site is not an Acceptable Solution checker.
What if my garage is already 6°?
Use a profile whose tabulated minimum is ≤6° (typically a deeper trapezoidal or tray), or re-pitch. Putting corrugate on it because the last roof was corrugate is how leaks get designed in.