What is the minimum roof pitch in NZ for each roof cladding?
Published · Updated · By Sai Nath
E2/AS1, 4th edition, sets the minimum pitch by cladding: corrugated metal 8°, trapezoidal 4° (3° with crests 27 mm or higher), trough 3°, pressed metal tiles 12° (15° for shingle profiles), concrete tiles 15° to 25° by profile with underlay, and butyl or EPDM membrane roofs 2°.
Minimum pitch for each roof cladding
Acceptable Solution E2/AS1, 4th edition, covers four roof claddings: masonry tiles, pressed metal tiles, profiled metal and membranes (8.1.1.2). Its minimums:
| Cladding | Minimum pitch | Ratio E2/AS1 gives | Limits | Where |
|---|---|---|---|---|
| Corrugated profiled metal (crest 16.5 mm or more) | 8° | 1:7 | Roofs up to 18 m long without end laps | 8.4.4.1(a) |
| Trapezoidal metal, crest under 27 mm | 4° | 1:14 | As above | 8.4.4.1(c) |
| Trapezoidal metal, crest 27 mm or higher | 3° | 1:20 | As above | 8.4.4.1(c) |
| Trough profile metal (ribs 38 mm or more) | 3° | 1:20 | As above | 8.4.4.1(b) |
| Pressed metal tiles, standard profile | 12° | 1:4.75 | Rafters up to 12 m; add 1° per extra 0.5 m | 8.3.3.2, 8.3.3.3 |
| Pressed metal tiles, shingle or shake profile | 15° | 1:3.75 | As above | 8.3.3.2, 8.3.3.3 |
| Concrete tiles, Type I (two watercourses) | 15° with underlay, 20° without | – | Rafters up to 4.5 m; add 1° per extra 0.5 m | Table 8.2.3.1 |
| Concrete tiles, Type II (one watercourse) | 20° with underlay | – | As above | Table 8.2.3.1 |
| Concrete tiles, Type III (flat, or slate, shake or shingle look) | 25° with underlay | – | As above | Table 8.2.3.1 |
| Clay tiles | 20° or 25° with underlay, by profile; 25° for the one row allowed without | – | As above | Table 8.2.3.1 |
| Butyl or EPDM membrane roof | 2° fall | 1:30 | On plywood | 8.5.1.2(a) |
| Butyl or EPDM membrane deck | 1.5° fall | 1:40 | Up to 40 m² | 8.5.1.2(b) |
Underlay is needed under any tile roof that takes water from a spreader, and on tile roofs in Very High or Extra High wind zones (Table 8.2.3.1, Note 3), and all pressed metal tile roofs have one (8.3.4.1). Masonry tiles tested to AS 4046.9 for dynamic weathertightness may go lower than the table, but not under 15° (8.2.3.4). A maker’s own instructions can ask for more than these minimums; E2/AS1’s comments say to follow them where they do.
Anything else, including timber shingles, asphalt shingles and curved metal, is outside E2/AS1 (8.1.1.3, 8.4.1.2). Its pitch then comes from the maker’s literature and whatever route to compliance your building consent authority accepts.
Set out from the degrees, not the ratio
The ratios E2/AS1 prints beside the degrees are rounded, and several are flatter than the angle: 1:20 is 2.86°, under 3°; 1:4.75 is 11.89°, under 12°; 1:3.75 is 14.93°, under 15°; 1:30 is 1.91° and 1:40 is 1.43°. Work from the angle. Rise per metre of run is 1000 × tan(angle):
| Pitch | Rise per metre of run | Rise over a 4 m run |
|---|---|---|
| 1.5° | 26.2 mm | 104.7 mm |
| 2° | 34.9 mm | 139.7 mm |
| 3° | 52.4 mm | 209.6 mm |
| 4° | 69.9 mm | 279.7 mm |
| 8° | 140.5 mm | 562.2 mm |
| 12° | 212.6 mm | 850.2 mm |
| 15° | 267.9 mm | 1071.8 mm |
| 20° | 364.0 mm | 1455.9 mm |
| 25° | 466.3 mm | 1865.2 mm |
Worked example: a skillion with 300 mm of rise over 4 m
A lean-to roof runs 4000 mm from the high wall to the low one and the plans give 300 mm of rise. Which claddings does that allow?
- Pitch: arctan(300 ÷ 4000) = arctan(0.075) = 4.29°.
- Corrugated metal needs 8°: not enough. Trapezoidal metal with crests under 27 mm needs 4°: passes, with 0.29° to spare. Trapezoidal with taller crests, trough profile and membrane: pass. Any tile: no.
- For corrugated, the rise must be at least 4000 × tan 8° = 562.2 mm. Set at 1:7 instead, 4000 ÷ 7 = 571.4 mm, a little steeper, which also passes.
- The trap is 3°: 4000 × tan 3° = 209.6 mm, but 1:20 gives 4000 ÷ 20 = 200 mm, which is 2.86°, under the minimum.
- The sheet length on the slope is √(300² + 4000²) = 4011.2 mm before any overhang, well under the 18 m limit for one sheet.
Worked example: long rafters on a tile roof
The table minimums for tiles hold for rafters up to 4.5 m long. Take Type I concrete tiles on rafters 6.0 m long.
- Extra length: 6.0 − 4.5 = 1.5 m, which is 1.5 ÷ 0.5 = 3 steps of 0.5 m.
- With underlay: 15° + 3 × 1° = 18°. Without underlay: 20° + 3° = 23°.
- In a Very High or Extra High wind zone, underlay is required, so the figure there is 18° with it.
- At 18° a 6.0 m rafter covers a run of 6.0 × cos 18° = 5.71 m and rises 6.0 × sin 18° = 1.85 m.
Pressed metal tiles work the same way from 12 m: a 13 m rafter is 2 steps over, so standard profiles need 12° + 2° = 14°.
Valley and hidden gutters
Gutters inside the roof set a minimum of their own (8.1.6.1 and Table 8.1.6.1): a 250 mm wide valley gutter needs a roof pitch of 8° or more and drains up to 25 m², and a 160 to 249 mm valley gutter needs 12.5° and drains up to 16 m². Hidden gutters need a slope of at least 8°, and internal gutters at least 1:100 (8.1.5.1, and 8.5.1.2(c) on membrane roofs). Eaves gutters get a minimum cross-section of 2500 mm² and must overflow to the outside, but no fall figure (8.1.4.2); see the minimum fall for a gutter.
Doing it in MeisterCalc
Open Home ▸ Pitch and choose Rise + Run. Enter Rise 300 mm and Run 4000 mm: it shows Angle 4.29°, % Grade 7.50%, Slope Ratio 0.0750 and Hypotenuse 4011.2 mm. To find the rise a cladding needs, choose Run + Angle and enter Run 4000 mm and Angle 8: the diagram’s Rise label reads 562.2 mm. Pitch comes with Pro. It has no table of claddings and doesn’t know E2/AS1, so compare the Angle with the minimums above yourself. It doesn’t do rafter cuts or roof area either.
Which edition applies?
E2/AS1 4th edition took effect on 28 July 2025 and was the current version on building.govt.nz on 1 November 2026. The 3rd edition (amendment 10) could be used for building consent applications made before 1 August 2026. The 4th edition renumbered the paragraphs and tables, so a detail sheet that cites a 3rd edition table points to a different number now. E2/AS1 applies to timber-framed buildings within the scope of NZS 3604, up to 3 storeys and 10 m high, with roofs no steeper than 60° (1.1.1.1). It is one way to comply with clause E2; your building consent authority decides what it accepts, and where the cladding maker asks for a steeper pitch, follow the maker. Check with your building consent authority where the wind zone, roof length or cladding is outside the table. More NZ rules are on the NZ Building Code page.
Sources
Checked on 1 November 2026. These pages explain the rules; the code itself, your plans and your council, building consent authority, building control body or certifier decide what a job needs.
- MBIE, Acceptable Solution E2/AS1 External moisture, 4th edition (PDF): 1.1.1.1 scope; 8.1.1.2 and 8.1.1.3 claddings covered; Table 8.2.3.1 and 8.2.3.4 masonry tiles; 8.3.3.2, 8.3.3.3 and 8.3.4.1 pressed metal tiles; 8.4.1.2, 8.4.3.1 and 8.4.4.1 profiled metal; 8.5.1.2 membranes; 8.1.4.2 eaves gutters, 8.1.5.1 internal gutters, 8.1.6.1 and Table 8.1.6.1 valley and hidden gutters; preface on the 3rd edition’s transition (checked 1 November 2026)
- MBIE, E2 Acceptable Solutions and Verification Methods: lists E2/AS1 4th edition, effective 28 July 2025, as the current version, and the 3rd edition (amendment 10) as effective until 31 July 2026 (checked 1 November 2026)
Do the maths in MeisterCalc
MeisterCalc does the arithmetic behind these rules on an Android phone, with no signal needed: Stairs, Concrete and Check Square are free, and the other calculators come with Pro. It runs on Android 7.0 or later.