A longrun takeoff is a sheet-and-flashing order from measured planes, not square metres of steel. You need effective cover, slope length including eaves, hips and valleys, fastener pattern, and the NZMRM Code of Practice row for that profile. NZ Roof Tools turns those measurements into a CoP-aware estimate. It is still not a quote, a consent check, or an LBP sign-off.
What the order should list
Longrun is sold by the lineal metre of named profile, cut to length. The merchant needs:
- Sheets: brand, profile, BMT, coating, colour, cover width, cut length, count per plane
- Ridge, hip, barge, apron, valley and penetration flashings as lineal metres (and piece count if stock lengths apply)
- Fasteners, washers, stitching screws, closures, tape and sealant as their own lines
- Waste as a separate allowance, not buried inside the sheet count
Satellite area or one footprint figure will look tidy and still miss a valley, a 50 mm verge, or a garage at a different pitch. Split the house, garage and porch. Write the assumptions next to the numbers so a merchant can argue with them.
A takeoff omits labour, scaffold, freight, merchant margin and availability. Those belong on a quote. Check the current product sheet and the NZMRM Code of Practice before anyone cuts coil.
Measurements to take first
For each plane, record plan length along the ridge, eave-to-eave span, pitch in degrees, eave overhang and barge/verge overhang. Sheet run is slope length: horizontal run including the eave drip, divided by cos(pitch). NZ drawings and CoP tables are in degrees, not 4/12.
A symmetric gable is two rectangles. A skillion is one. A hip, L-shape or broken-back roof is several planes plus extra flashing length. The roof area calculator shows plan area beside sloped area so the pitch factor is visible.
Mark valleys, hips, ridges, barges, roof-to-wall junctions, internal gutters, and every penetration (skylight, flue, vent). A valley means diagonal sheet cuts. A penetration needs a soaker or proprietary flashing above and below the hole.
“Longrun iron” is not a spec. Confirm profile, BMT, coating (Colorsteel, Zincalume or other) and colour before you count. Cover width is the laid width after the side lap — 760 or 762 mm on common corrugate, not the 851 mm overall blank. The sheet calculator counts from cover. Using overall width under-orders by about 10%.
Sheet count and length
Across a gable plane: ridge-direction width including verges, divided by cover, round up, once per plane, then multiply by two on a symmetric gable. Example: 7.200 m on 762 mm cover is 9.45 → 10 sheets per plane.
The longrun roofing calculator uses manufacturer cover widths from Dimond, Metalcraft and Stratco and lets you override the coil tag. Length is slope length, rounded up 50 mm so it reads like a merchant cut. If that length exceeds the CoP “check capacity after …” figure for the profile height, you get a drainage warning rather than a silent pass.
True longrun is usually one sheet ridge-to-eave. End laps only appear if you hit a truck, site or expansion cap. Two short sheets with a guessed overlap are not the same as one specified length.
Do not convert total area into sheets and stop. Two roofs with the same m² can differ by a sheet because one plane is 12.1 m on 762 mm cover (16 per side, not 15.9) or because hips throw diagonal offcuts.
Flashings, waste and small materials
Measure ridge, barge, hip, valley, apron and penetrations separately. Extra High wind zone is Category B flashing cover at every pitch — a 200 mm ridge cover, not the 130 mm residential default. The takeoff lists those as lineal metres on top of the sheet order.
Hips start around 12% cutting waste of sloped area; each valley adds more; a clean gable is mostly the per-plane round-up plus a small handling spare. A flat 10% is how hip roofs run short and simple gables get over-ordered. Use the waste calculator rather than hiding flashings inside the percentage.
Fastener counts follow the profile’s fixing pattern, purlin spacing, edge zones and wind zone. Pick screws for the substrate and coating, not by colour. Closures, butyl and approved sealant are cheap next to coil and they stop the job if they are missing.
CoP, pitch, wind and the truck
NZMRM CoP 7.1.1A tables are cladding pitch after deflection, not the degrees on the truss ticket. Standard 16.5 mm corrugate is 8° minimum and a run check after 15 m. A 6° garage needs a deeper trapezoidal or tray, or a re-pitch — not extra waste. See minimum pitch for corrugated iron in NZ and the pitch calculator.
Manufacturer sheets can be stricter than the generic table (Metalcraft corrugate 9° past 30 m at ≤100 mm/hr is one example). Coastal and industrial sites change coating choice. High and Extra High wind zones change fixings and flashing covers. None of that should be inferred from a US roof-pitch widget.
Long sheets also have to fit a truck and a driveway. Confirm the yard’s maximum length before you treat a 18 m run as one piece. Split lengths, lifting and storage (no trapped moisture, no incompatible metals) belong in the assumptions list.
Checklist before you send it to a merchant
- Label each plane; do not add footprints at one pitch.
- Use slope length including eaves, not plan span alone.
- Lock profile, cover, BMT, coating and colour, then count.
- Round sheets up per plane; list cut lengths separately if you cap them.
- Measure ridge, hip, barge, valley, aprons and penetrations as their own lines.
- State waste and flashing overlaps; do not fold them into area.
- Check cladding pitch, run length and wind zone against the current CoP row and product sheet.
- Note what you excluded (dormers, labour, freight).
Open the takeoff with those numbers, screenshot the result, and have the roofer or merchant read the warnings before anyone orders coil.