Metal roofing dominates the Australian roofing market, and for good reason. It is lightweight, durable, fire-resistant, and available in a huge range of profiles and colours. Whether you are building a new home, replacing an existing roof, or simply want to understand what is on top of your house, this guide covers everything you need to know about metal roofing.
These are the two main metal roofing products manufactured by BlueScope Steel, and understanding the difference is important.
Zincalume is a steel sheet coated with an alloy of 55 percent aluminium, 43.5 percent zinc, and 1.5 percent silicon. This coating provides excellent corrosion resistance. Zincalume has a distinctive silver-grey metallic finish. It is an unpainted product - what you see is the raw coating. It is typically cheaper than Colorbond and is often used where appearance is not the primary concern, such as sheds, garages, and industrial buildings.
Colorbond starts with the same Zincalume base but adds a baked-on paint finish. This paint system consists of a primer, a base coat, and a topcoat, providing both decoration and additional protection. Colorbond is available in over 20 standard colours plus a Matt finish range, and is the standard choice for residential roofing across Australia.
For residential homes, Colorbond is almost always the better choice. The paint finish provides additional corrosion protection, UV resistance, and obviously a much wider range of colour options. The cost premium over Zincalume is typically $3 to $8 per square metre - a small price for significantly better aesthetics and protection.
The profile of a metal roof sheet refers to its cross-sectional shape - the pattern of ribs, pans, and corrugations. The profile affects both appearance and performance. Here are the most common profiles used in Canberra:
Corrugated (Corro): The classic Australian roof profile with its regular sinusoidal waves. Still widely used and suits both traditional and contemporary homes. Corrugated profile is versatile, relatively inexpensive, and available from most suppliers. It can be used at pitches as low as 5 degrees.
Standing Seam (Klip-Lok, Snap-Lock): A modern profile with concealed fixings - the screws are hidden between the ribs rather than being exposed on the face of the sheet. This gives a clean, contemporary appearance and eliminates the risk of fixing-point leaks. Standing seam is increasingly popular in new Canberra builds, particularly in Molonglo, Denman Prospect, and Whitlam. Minimum pitch varies by product but is typically 1 to 3 degrees.
Trimdek: A popular profile with five ribs per sheet, giving a strong, linear appearance. Used extensively on residential and commercial buildings. Minimum pitch is 5 degrees, and it handles high water flows well, making it a solid choice for larger roof areas.
Custom Orb: BlueScope's branded corrugated profile, similar to traditional corro but manufactured to specific dimensions. It is the most commonly specified corrugated profile for residential roofing in the ACT.
Colour choice is partly aesthetic and partly functional. In Canberra's climate, the colour of your metal roof affects heat absorption, energy efficiency, and even the longevity of the paint system.
Lighter colours like Surfmist, Shale Grey, and Windspray reflect more solar radiation, keeping your roof cavity cooler in summer. This translates directly to lower cooling costs. In our experience, lighter-coloured roofs in Canberra suburbs with good insulation can reduce summer cooling energy use by 10 to 20 percent compared to dark colours.
Darker colours like Monument, Basalt, and Ironstone absorb more heat but provide a striking visual contrast. They are popular in modern architectural designs but do put more thermal stress on the roof structure and increase cooling costs.
For Canberra, we generally recommend medium to light colours unless there is a strong design reason for a dark roof. The energy savings and reduced thermal stress make it a practical choice.
One of the major advantages of metal roofing is low maintenance. However, low maintenance does not mean no maintenance. Here is a recommended schedule:
Every 6 months:
Annually:
Every 5 to 10 years:
Every 20 to 30 years:
While metal roofs are generally very reliable, certain problems can develop over time:
Screw fixings working loose: Thermal expansion and contraction can gradually back screws out of the timber. Loose screws allow water in at the fixing point and allow the sheet to lift in wind. This is the most common maintenance item on metal roofs.
Corrosion at cut edges: When metal roofing sheets are cut on site (as they often are around valleys, ridges, and hips), the cut edge exposes raw steel without the Colorbond coating. Over time, this edge can corrode. Good practice is to seal cut edges with touch-up paint, but this is often overlooked during installation.
Ponding water: On very low-pitch roofs, water can pond in the pans of the sheeting. Prolonged ponding leads to premature coating failure and eventually corrosion. Ensuring your roof has adequate fall and that gutters drain properly prevents this issue.
Dissimilar metal corrosion: When two different metals are in contact in the presence of moisture, galvanic corrosion can occur. This is most commonly seen where copper pipes or fittings contact Colorbond steel, or where old lead flashings meet new steel sheets. Keeping dissimilar metals isolated with appropriate separators prevents this.
Because metal is a good conductor of heat, insulation is critical for comfort and energy efficiency under a metal roof. The minimum insulation requirement for ceilings in the ACT is R4.0 for new builds, but higher values (R5.0 to R6.0) provide noticeably better comfort in Canberra's extreme temperature range.
Sarking (a reflective membrane under the roof sheets) is also important - it provides a secondary water barrier, reduces condensation risk, and adds to the thermal performance. Sarking is a code requirement for new metal roofs in the ACT and is highly recommended when re-roofing.
Whether you are considering a new metal roof, need maintenance on an existing one, or want to convert from tile to Colorbond, we can help. Book a free estimate or call (02) 5133 5608. We cover all ACT suburbs, 7 days a week.
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