Solar on corrugated iron roofs in Perth: what to know

Older Perth homes — particularly character homes in suburbs like Subiaco, Fremantle, North Perth, Leederville, Victoria Park, and Mount Lawley — often have corrugated iron roofing, sometimes referred to as CGI (corrugated galvanised iron) or zincalume if more recent. Solar can be installed on corrugated iron, but the age and condition of the roofing significantly affect the approach.

Corrugated iron vs Colorbond: the difference

Modern Colorbond (BlueScope steel) is a coated steel product with a pre-painted finish and a 36-year warranty. Corrugated iron refers to older, typically bare galvanised or painted steel sheeting installed before Colorbond became standard (broadly pre-1990s).

The key distinction for solar: Older corrugated iron is often at or near end of life. Installation of solar racking (with roof penetrations) on roofing that will need replacement in 3–7 years creates an unnecessary cost burden: the solar would need to be removed, the roof replaced, and the solar reinstalled.

Assessing your corrugated iron roof before solar

Before proceeding with solar on corrugated iron, a condition assessment is essential:

Signs of end-of-life corrugated iron:

• Visible surface rust (orange staining or pitting on the steel surface)
• Holes or perforations in sheeting
• Previous patch repairs (indicates past leak history)
• Sheets that flex or "oil-can" under light foot pressure (loss of structural integrity)
• Chalky, flaking paint on painted corrugated iron

Signs of serviceable corrugated iron:

• Intact galvanised or Zincalume surface (silver-grey, without rust staining)
• No visible holes or patches
• Paint still adhering (for painted iron)
• Stiff under pressure (retains structural integrity)

Professional assessment: A roofer's inspection costs $200–$400 in Perth. The roofer can give an estimated remaining life for your iron sheeting — anything under 10 years remaining is a strong argument to replace before solar installation.

Mounting solar on corrugated iron

The standard approach for corrugated iron:

Top-fix brackets: Brackets that attach over the corrugation ridges and fix down to the purlin/batten below via a self-drilling screw or lag bolt. The bracket foot sits on the ridge of the corrugation; the penetration goes through the valley (lowest point) of the sheeting with appropriate sealing.

Lap-screwing into purlins: Direct screwing through the corrugation crest into the structural purlin below. This requires accurate rafter/purlin location (not always straightforward in older homes with non-standard framing) and appropriate sealing with EPDM or Neoprene washered screws to prevent water ingress.

Sealing quality: Every penetration through corrugated iron must be properly sealed. The sealant degrades over time in Perth's UV and heat conditions — a quality sealant (neutral cure silicone, or manufacturer-specified EPDM washered screws) is essential. Cheap sealing approaches will fail.

Age-related structural considerations

Older corrugated iron homes (pre-1960) may have non-standard rafter spacing and lighter purlin/batten sizing than modern construction. A structural engineer should review the roof framing if:

• The building appears to have non-standard construction
• The iron sheeting shows significant sag between purlins (indicating structural deflection)
• The original plans suggest light-gauge framing

Solar panels add approximately 10–15kg per panel to the roof structure. A 10kW system (24–28 panels) adds 240–420kg distributed across the roof area. Standard 1980s+ Australian residential framing is designed for this; older framing may not be.

The roof replacement decision

For Perth character home owners with corrugated iron, the decision framework:

If iron sheeting has 15+ years remaining: Solar on existing roofing is reasonable. Use quality mounting with proper sealing, and accept that the system will need temporary removal when the roof is eventually replaced.

If iron sheeting has 5–15 years remaining: Assess cost of roof replacement now vs later:

• Replace iron with Zincalume corrugated (maintains character home aesthetic, longer lifespan) + solar = combined project
• Or proceed with solar now, accept ~$1,500–$3,000 remove-and-reinstall cost in 5–10 years

If iron sheeting has < 5 years remaining: Replace roof first. Installing solar on near-end-of-life iron creates an immediate remove-and-reinstall cycle that wastes installation cost.

Heritage considerations: Some Perth character homes in heritage precincts have restrictions on roof replacement materials. Heritage Council or local council planning approval may be required to replace iron with alternative roofing — and the replacement material may need to match the original. Check heritage constraints before committing to a roof replacement + solar project.

Zincalume corrugated: the modern equivalent

Zincalume (BlueScope's aluminium-zinc alloy coated steel) corrugated sheeting looks similar to traditional galvanised iron but has significantly better durability — typical service life of 30–40 years. If you're replacing worn corrugated iron and want to maintain the character home aesthetic, Zincalume is the appropriate modern equivalent. Solar mounts to Zincalume the same way as standard corrugated iron.

Caution: Standard galvanised fasteners and some aluminium racking components can cause galvanic corrosion when in contact with Zincalume in coastal environments. In Perth suburbs within 1km of the ocean (Fremantle, Cottesloe, North Beach, Trigg), specify stainless steel or compatible fasteners for all mounting hardware.

Corrugated iron and insurance

Some Perth insurers have specific conditions on older corrugated iron roofing regarding:

• Age-related exclusions for storm damage claims
• Requirements to report the roofing material and condition

Review your building insurance policy before proceeding with solar installation, and notify your insurer of the intended work. This is especially important for character homes in Fremantle and inner-suburban Perth, where building insurers are more familiar with older roofing materials.

Corrugated iron roofing in older Perth homes is a workable surface for solar installation, provided the iron is in serviceable condition with at least 10 years of remaining life. The key decisions are: professional roofing condition assessment before committing, quality sealing at all penetration points, and a clear plan for what happens when the roof eventually needs replacement. Character home owners in heritage precincts should also confirm any planning restrictions on roof replacement materials.