Extra High (NZS 3604 EH) does not usually change how many sheets fit across the ridge. It changes flashing cover and edge fixings. This takeoff treats EH as CoP 8.4 Category B at every pitch: 200 mm ridge cover, 100 mm profiled barge cover, two barge upstands. Category A residential default is 130 mm ridge / 75 mm barge.
Very High and pitch under 10° is also Category B here. SED is out of scope.
Set wind zone on NZ Roof Tools to Extra High and read the flashing warning. Related: flashing checklist.
What to write on the order
- Wind zone EH (do not guess from “near the coast”).
- Flashing type Category B / Extra High cover — not a standard 130 mm ridge because the sheets look the same.
- Fixing pattern and edge zones from the current manufacturer sheet and span tables (not calculated here).
- Same cover-width sheet count unless you also changed profile or width.
A standard barge on an EH house is how the edge fails while the coil looks right. This is not an E2/AS1 or LBP sign-off. NZMRM CoP 8.4 and the product flashing detail win.