Sheets can be right and the roof still unbuildable if ridge, barge, hip and valley are missing. This site lists those as lineal metres on top of the sheet order. Extra High wind zone is CoP Category B at every pitch — 200 mm ridge cover and two barge upstands, not the 130 mm / 75 mm residential default.
Measure the weathering line
Plan length is not barge length. Barge, hip and valley follow the slope (same figure as the common rafter / hip length on the rafter calculator). Ridge is the ridge-direction length including verges.
Name each line (R1, B1, H1, V1). Split at a change of pitch or a wall. A 8 m plan ridge with two barges is three different lengths.
Order length = measured line + joints + end details, then round to what the yard actually folds. A 9 m ridge in one piece has no mid joint; three pieces have two laps. Do not hide that in a percentage.
Cover, not catalogue width
Match the flashing to the named profile. Extra High (and Very High under 10°) forces Category B covers. The takeoff warning on NZ Roof Tools is that check — not an E2/AS1 consent.
Apron, back flashing and penetrations belong on the same schedule even if the brief only said “ridge and barge”. Valleys are not a hip with a different name: width, freeboard and discharge matter. CoP v26.09 (1 September 2026) updated flashing expansion, valley freeboard and hip details.
Waste is not flashing
Hip and valley sheet cuts sit in waste. Flashing laps sit here. Mixing them is how a hip roof is short of trim and long on coil.
Checklist: every edge named; slope vs plan labelled; wind zone written; Category B if EH; penetrations listed; current NZMRM CoP and product sheet open. Then run the takeoff and read the flashing lines before anyone folds metal.