Corrugated Iron Roofing NZ: The Complete Guide

Few things are more quintessentially New Zealand than the sound of rain on a corrugated iron roof. It's been the roofing material of choice for Kiwi homes, farms, and industrial buildings for well over a century — and modern developments in steel and coating technology mean it's better than ever. Whether you're considering a re-roof or just want to understand your existing roof better, here's what you need to know.

What Is Corrugated Iron (Long-Run Steel)?

What we casually call "corrugated iron" today is actually modern long-run steel roofing — cold-rolled steel coated with a metallic substrate (usually zinc/aluminium) and a high-quality paint system. It's no longer iron at all. The term has simply stuck around as a colloquial description of the profile.

Modern long-run steel comes in a variety of profiles, including:

• Corrugated — The classic sinusoidal (wave) profile. Timeless, suitable for a wide range of pitches, and very popular on both residential and rural buildings.
• Trapezoidal (trough/rib profiles) — Such as Corrugate, Hi-Rib, or similar. Higher ribs provide greater spanning ability and a more angular, contemporary look.
• Standing seam — A concealed-fix profile where fixings are hidden under raised seams. Popular on low-pitch roofs and premium contemporary designs.

What Is It Made Of?

Modern long-run steel roofing in NZ is typically produced using:

• New Zealand Steel's Colorsteel® — Steel substrate, hot-dip coated with a zinc/aluminium alloy (Zincalume®), then finished with a baked-on paint system available in a wide range of colours. The most widely used residential roofing steel in NZ.
• SSAB's Greencoat® — A Swedish steel product used by Edwards & Hardy in some applications. Features a bio-based paint system offering excellent durability and colour retention.

Thickness is measured in gauge or BMT (Base Metal Thickness). Residential roofing is typically 0.40mm BMT, while commercial applications often use 0.55mm BMT for added strength and spanning capacity.

How Long Does It Last?

Modern Colorsteel® long-run roofing carries manufacturer warranties of 30–50 years for perforation and significant colour fading depending on the product grade, installation environment, and maintenance. Real-world lifespans can comfortably reach 40–60 years with appropriate maintenance. Key factors affecting longevity include:

• Distance from the sea — Salt spray significantly accelerates corrosion. If you're within 500m of the coast, specify a marine-grade product and ensure the roof is rinsed with fresh water regularly.
• Maintenance — Annual washing, keeping gutters clear, and checking/resealing flashings dramatically extends roof life.
• Installation quality — Incorrect fixings, insufficient laps, or poorly installed flashings can result in leaks and premature corrosion long before the material itself fails.

Advantages of Long-Run Steel Roofing

• Lightweight — Much lighter than concrete or clay tiles, reducing structural loads.
• Low pitch capability — Can be installed on pitches as low as 3–5° depending on profile.
• Low maintenance — An annual wash-down is typically all that's required.
• Wide colour range — Colorsteel® is available in dozens of colours to complement any home exterior.
• Cost-effective — Generally less expensive to supply and install than tiled alternatives.
• Recyclable — Steel is 100% recyclable at the end of its life, making it an environmentally responsible choice.

Potential Drawbacks to Consider

• Noise — Rain on a steel roof is louder than on tiles, though modern insulation installed during a re-roof can dramatically reduce this.
• Thermal expansion — Steel expands and contracts with temperature changes, which can cause creaking and requires proper allowance in installation.
• Condensation — In certain conditions, condensation can form on the underside of steel roofing. A correctly installed anti-condensation layer or ceiling insulation mitigates this.

How Much Does a Corrugated Iron Roof Cost?

Long-run steel is typically among the most cost-effective roofing options in New Zealand. For a full residential re-roof (supply, remove old roof, and install), expect indicative pricing in the range of $15,000–$35,000 depending on the size and complexity of your home. For an accurate quote, contact Edwards & Hardy.

Choosing a Colour

Roof colour has a surprisingly large impact on your home's street appeal — and on its thermal performance. Lighter colours reflect more heat and keep ceiling spaces cooler in summer; darker colours absorb more heat. In New Zealand, popular residential longrun colours include Ironsand, Flaxpod, Titania, and Classic Roofing shades. Check out the Colorsteel® selector tool to visualise options on a NZ home.

Ready to Re-Roof with Long-Run Steel?

Edwards & Hardy has been installing long-run steel roofing across New Zealand for decades. Our teams are members of the Roofing Association of New Zealand (RANZ), and we work to the highest standards of installation and health and safety. Get a free quote today.