Roof Pitch Chart Australia - Degrees, Ratio & Percentage

Need to calculate a specific pitch from rise and run? Use the roof pitch calculator for instant NCC 2022 compliance checking.

Material Pitch Ranges at a Glance

Each roofing material has a minimum and practical maximum pitch under NCC 2022. Rows in the chart below are colour-coded by material zone.

Complete Roof Pitch Conversion Table

Rows shaded blue fall within the Custom ORB® range (5°–35°). Rows shaded green are low-slope profiles (1°–4°). Rows shaded amber are tile-range pitches (15°+).

End Lap: NCC 2022 Housing Provisions Part 7.2 - pitch ≥ 15° requires 150 mm end lap; pitch 5°–15° requires 200 mm. Rafter Multiplier: Multiply your horizontal run by this factor to get the true rafter length. Example: 4,000 mm run at 22° × 1.079 = 4,316 mm rafter.

How to Read This Chart

Degrees

The angle between the roof surface and a horizontal plane. Used by architects and certifiers on construction drawings. The most internationally consistent measurement. Calculated as: degrees = arctan(rise ÷ run).

x:12 Ratio (Pitch Ratio)

The traditional trade format: the number of units of rise for every 12 units of run. A 5:12 pitch rises 5 mm for every 12 mm of run. This format dominates in AU roofing specifications and Lysaght / COLORBOND product guides. Convert from degrees: ratio = tan(degrees) × 12.

Slope Percentage

Used by hydraulic engineers and stormwater designers. Expresses rise as a percentage of run. A 100% slope is exactly 45°. Convert from degrees: slope % = tan(degrees) × 100.

Rafter Multiplier (Pitch Multiplier)

The factor by which horizontal run must be multiplied to get true rafter length. Calculated as: multiplier = 1 ÷ cos(degrees). This is the same result as the Pythagorean theorem but expressed as a single number for quick site calculation. At 5°, the rafter is just 0.4% longer than the run. At 45°, it is 41.4% longer.

Quick Pitch Conversion Reference

NCC 2022 Compliance Zones by Material

The National Construction Code 2022 - Housing Provisions Part 7.2 - sets mandatory minimum pitches for each roofing material. Using a pitch below the minimum for your material voids the manufacturer warranty, breaches the NCC, and causes waterproofing failures. See the full NCC minimum pitch guide for code references and enforcement context.

Most Common Roof Pitches in Australia

5° - COLORBOND Corrugated Minimum

The most important pitch in Australian residential construction. Five degrees is the minimum allowed for Custom ORB® (the standard corrugated COLORBOND profile). The majority of shed roofs, carports, and pergola roofs sit between 5° and 10°. Below 5°, water ponds in the corrugation valleys and drives through the sheet overlaps by capillary action.

10° - Skillion and Contemporary Home Standard

Ten degrees (2.1:12) is the go-to pitch for contemporary skillion-roof homes in AU. It provides adequate drainage, works for both corrugated and concealed-fix profiles, and reads as visually flat from street level. Common in Melbourne's inner suburbs and Sydney's outer growth corridors.

15° - Tile Minimum and End Lap Change Point

Fifteen degrees triggers two things: (1) concrete and terracotta tile systems are permitted at this pitch, and (2) the NCC end lap requirement reduces from 200 mm to 150 mm for metal roofing. This is the pivot point between low-slope and standard-slope roof design in Australian practice.

22° – 25° - Traditional Gable Range

The dominant pitch for tile-roofed homes built in Australia from the 1950s to 2000s. The standard fibrous cement and terracotta tiles of that era were optimised for this range. If you're adding to or matching an existing suburban home, this is the most likely pitch you'll encounter.

30° - Steep Gable (Heritage and Period Homes)

A 30° pitch (6.9:12) appears in homestead-style roofs and some Victorian/Federation period housing in Melbourne and regional NSW and SA. The steeper pitch was driven by the use of corrugated iron (pre-COLORBOND) with shallow ribs - the steeper angle provided the drainage the material needed. Heritage overlays often require matching this pitch exactly when extending or restoring.

Pitch and Bushfire Attack Level (BAL)

Under AS 3959 (Construction of Buildings in Bushfire-Prone Areas), roof pitch intersects with ember and flame attack provisions:

• Pitches above 18° create larger eave cavities - increased ember entry risk unless eaves are sealed or removed
• Pitches below 10° may require specific valley and gutter detailing in BAL-FZ (Flame Zone) to prevent debris accumulation
• The BAL rating on the allotment (from your council's bushfire overlay) determines the required detailing, not pitch alone - pitch only modifies the risk context

If your site has a BAL rating, engage a BAL assessor before finalising roof pitch. The calculator result is a starting point for compliance checking, not a BAL assessment.

Optimal Roof Pitch for Solar Panels in Australia

Solar panel output depends on the angle between the panel and the sun. For a fixed-tilt rooftop system:

• Sydney (latitude 34°S): optimal tilt ≈ 30°–34°, but 15°–25° delivers within 5% of optimal
• Melbourne (latitude 38°S): optimal tilt ≈ 34°–38°, but 20°–30° within 5% of optimal
• Brisbane (latitude 27°S): optimal tilt ≈ 23°–27°, but 15°–22° within 5% of optimal
• Perth (latitude 32°S): optimal tilt ≈ 28°–32°, but 15°–25° within 5% of optimal

Most 15°–30° residential roofs are within the acceptable solar range. Very low pitch roofs (5°–10°) can still work but benefit from panel tilt-up frames to improve angle. The CEC (Clean Energy Council) guidelines recommend a minimum panel angle of 10° to ensure self-cleaning by rain.

Frequently Asked Questions