8° on cited systems
Metalcraft Corrugate and Steel & Tube Custom Orb publish 8° minimum pitch, subject to their detailed limitations.
Roof geometry
Roof pitch: how degrees change area, products and access
Roof pitch affects both how much roof surface exists above a plan footprint and which roofing profiles can be used. For a simple roof plane, actual sloping area is approximately plan area ÷ cos(pitch).
A 200 m² plan area is about 207 m² at 15°, 221 m² at 25° and 244 m² at 35° before allowing for overhangs and irregular geometry.
- Input
- Pitch in degrees
- Area formula
- plan area ÷ cos(pitch)
- Safety breakpoint
- >25° needs more slip control
- Reviewed
- 26 Sep 2026
Pitch factors
How pitch changes a 200m² plan area
| Roof pitch | Area factor | 200m² plan becomes | Notes |
|---|---|---|---|
| 0° | 1.000 | 200 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 5° | 1.004 | 201 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 10° | 1.015 | 203 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 15° | 1.035 | 207 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 20° | 1.064 | 213 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 25° | 1.103 | 221 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 30° | 1.155 | 231 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 35° | 1.221 | 244 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 40° | 1.305 | 261 m² | Simple single-pitch conversion before overhangs/complex geometry |
| 45° | 1.414 | 283 m² | Simple single-pitch conversion before overhangs/complex geometry |
Worked calculation
Plan measurement vs actual measurement
200m² plan-view roof at 25°
- Plan area
- 200 m²
- cos(25°)
- ≈ 0.9063
- Calculation
- 200 ÷ 0.9063
- Simple sloping area
- ≈ 220.7 m²
This works for a simple roof plane. A real roof may also include overhangs, multiple pitches and geometry that should be measured directly when possible.
Product limits
Minimum pitch belongs to the exact roof profile
3° on cited systems
Metalcraft MC760 and Dimond Hi Five publish 3° minimum pitch for the cited systems.
12° on cited Gerard systems
Gerard Bond and Milano publish 12° minimum pitch.
These are manufacturer examples, not a generic legal rule for every product. Use the selected manufacturer's current specification and the relevant Building Code compliance pathway.
Safety matters too: WorkSafe notes that roofs above 25° have greater sliding risk and recommends additional controls; for slopes over 35°, edge protection should be specifically designed. Roof pitch therefore affects both quantity and access planning.
For measurement methodology, continue to roof area and measurement.
Sources
Technical references
- primaryMetalcraft Roofing — Corrugate — 760 mm cover; 8° minimum pitch stated by manufacturer · manufacturer
- primaryMetalcraft Roofing — MC760 — Five-rib trapezoidal profile; 760 mm cover; 3° minimum pitch stated · manufacturer
- primaryMetalcraft Roofing — Espan 470 — 470 mm cover; concealed fixing; 3° minimum pitch stated · manufacturer
- primaryGerard Roofs — Bond — Pressed steel tile; 0.47 m² cover per panel; 12° minimum pitch · manufacturer
- primaryWorkSafe — Working on roofs good practice guidelines — Fall prevention, roof access and edge-protection guidance · government
- primaryBuilding Performance — E2 External Moisture — New Zealand Building Code external-moisture requirements · government
FAQ
Roof pitch questions
Does roof pitch increase roof area?
Yes. A sloping roof surface is larger than its plan-view projection. For a simple roof plane the conversion is plan area divided by the cosine of the pitch angle.
If I already measured the actual roof surface, should I apply pitch again?
No. Pitch conversion is only for plan-view measurements. Applying it to an actual sloping measurement would double-count the slope.
What is a normal NZ roof pitch?
There is no single normal pitch. Product choice and architecture vary widely. RoofHub asks for the actual pitch or a broad pitch category because both area and product suitability can change.