Metal roofing in Australian construction: profiles, coatings, and Colorbond selection

TL;DR

Australian metal roofing (used the same way across Class 1a houses, Class 2 low-rise apartments, and Class 3-9 commercial pitched and skillion roofs) is dominated by steel sheet (zincalume substrate with a baked Colorbond paint finish on the majority of jobs, plain zincalume on a minority) rolled into one of four common profiles: Custom Orb (corrugated, the heritage default), Trimdek (low-profile rib, the volume contemporary default), Klip-Lok (concealed-fix standing seam, premium), and Spandek (mid-rib, mid-tier). The dominant manufacturer is Lysaght (a BlueScope brand), with Stratco, Fielders, and Metroll providing alternates and regional alternatives. The Australian standard is AS 1562.1:2018 (design and installation). Profile selection is driven mainly by roof pitch (Custom Orb needs minimum 5°, Trimdek and Spandek down to 2°, Klip-Lok down to 1°), fixing visibility preference (pierce-fix screws visible on Custom Orb/Trimdek/Spandek; Klip-Lok hides the fix in a concealed clip), and architectural style (corrugated for heritage; standing seam for contemporary). The two job-killers: specifying a profile below its minimum pitch (water tracks back over the ribs and leaks at laps), and over-driving pierce-fix screws (the rubber washer is crushed and leaks form at every screw within months) (verified 2026-05-13, Lysaght technical).

What it is

Metal roofing is rolled or pressed steel (or aluminium, rare in residential) sheet, formed into a ribbed profile that gives the sheet enough stiffness to span between roof battens or purlins. The sheet is typically supplied in custom-cut lengths from the manufacturer’s coil, with one continuous sheet covering the eave-to-ridge run on most pitched roofs (no horizontal sheet joins). The standard sheet width is 762 mm cover or 820 mm sheet width across the rib pattern.

The base material is galvanised steel or zincalume steel (a zinc-aluminium-magnesium alloy coating on steel, more corrosion-resistant than plain galvanising). Both substrates are produced to AS 1397:2021. Most metal-sheet roofing today is zincalume base with a baked Colorbond paint finish on the visible side; plain Zincalume (no paint) is a less common alternative for budget jobs or industrial styling.

The Australian standard is AS 1562.1:2018 (Design and installation of sheet roof and wall cladding, Part 1: Metal). Wind pressure resistance testing sits under AS 4040.2:2018.

Common profiles

Profile	Manufacturer / brand	Rib height (approx)	Minimum pitch	Where used
Custom Orb (Lysaght); Corrugated (other brands)	All major brands	16-19 mm	5° (1:11.5)	Heritage, federation, traditional homes; the AU default for over 100 years
Trimdek (Lysaght); CGI / Trimsheet (others)	Lysaght, Stratco, Fielders, Metroll	29 mm	2° (1:30)	Contemporary residential; widely available and cost-effective
Spandek (Stratco); Multiclad (Fielders)	Stratco, Fielders	35 mm	2°	Mid-tier residential, light commercial
Klip-Lok 700 (Lysaght); Longspan (Fielders)	Lysaght, Fielders	41 mm	1° (1:60)	Concealed-fix premium residential, contemporary architectural
Standing seam (Snaplock, Quikslok)	Various	38-50 mm	1°	Low-pitch and architectural feature roofs
Spanrib (Stratco)	Stratco	25 mm	3°	Stratco-supply markets (WA, SA)

The minimum pitch is the manufacturer’s published limit. Going below it is a defect: water tracks back up the profile through capillary action at sheet laps and end terminations, and the roof leaks regardless of how well it’s installed.

Coatings

Coating	What it is	Service life (residential, inland)	Where used
Colorbond	Zincalume base + baked-on polyester paint top coat in 22 colours (2026 range)	30+ years exposed	The volume residential default; matched colour on flashings, gutters, downpipes
Colorbond Ultra	Zincalume base + higher-performance paint and primer for marine and severe-exposure conditions	30+ years even at coastal	Within 1 km of breaking surf
Zincalume (unpainted)	Zinc-aluminium-magnesium alloy coating, no paint	30+ years inland	Budget jobs, industrial aesthetic, plain finish
Galvanised (plain)	Zinc coating only, no zinc-aluminium upgrade	15-25 years exposed	Lower-cost markets, agricultural; less common residential
Stainless steel	Stainless 304 or 316	50+ years	Specialty architectural, marine-exposure

The colour range for Colorbond cycles every few years; some heritage colours (Cottage Green, Manor Red) sit alongside contemporary neutrals (Surfmist, Shale Grey, Monument). Confirm current colour availability before specifying.

Manufacturers and supply

Lysaght (BlueScope): the largest Australian manufacturer; Custom Orb, Trimdek, Klip-Lok, and an extensive accessory range. Available nationally.
Stratco: SA-based; Spandek, Spanrib, Heritage Corrugated. Strong in WA, SA, and regional Victoria.
Fielders: BlueScope subsidiary; Multiclad, Longspan, and architectural standing-seam profiles.
Metroll: QLD-based; Trimsheet (Trimdek equivalent), heritage corrugated, full residential range.
Other regional: Revolution Roofing (NSW), Stramit (national), Bluescope direct supply.

All major Australian metal roofing manufacturers comply with AS 1562.1 and AS 1397 substrate standards. Brand selection is mostly a function of local availability and the roofer’s habitual supplier; the profile patterns are largely cross-compatible with universal accessories.

Profile selection by application

Application	Profile choice
Heritage or federation home, pitched 15° to 30°	Custom Orb in matching colour (Manor Red, Cottage Green)
Contemporary single-storey, pitched 10° to 22°	Trimdek in Surfmist, Shale Grey, or Monument
Modern single-pitch (skillion) roof, 2° to 8° pitch	Klip-Lok or Trimdek (verify pitch against manufacturer table)
Low-pitch verandah / patio, 1° to 5° pitch	Klip-Lok 700 (concealed fix; pierce-fix profiles risk leaking at fixings on low pitch)
Architectural feature, exposed standing seam	Klip-Lok or proprietary Snaplock; matched fascia and wall cladding
Garage / outbuilding, budget	Trimdek Zincalume (no paint)
Pool or pool surround	Stainless steel (chlorine corrosion); avoid plain zincalume or Colorbond Classic

Bushfire (BAL) ratings

Metal roofing performs well in bushfire because the substrate is non-combustible. Under AS 3959:2018:

All major metal roofing profiles are acceptable up to BAL-40 without special detailing
BAL-FZ (Flame Zone) requires non-combustible roofing only; metal qualifies but detailing at penetrations, gutters, and eaves needs ember-protection compliance
Sarking under the metal at higher BAL ratings: the sarking and underlay must also be non-combustible-rated

This is one of the main reasons metal dominates residential roofing in bushfire-prone areas across NSW, Vic, ACT, and SA.

Fixing systems

Two distinct fixing approaches drive the visible appearance and install detail:

Pierce-fix (visible screw heads)

Applied on Custom Orb, Trimdek, Spandek, and similar profiles. A self-drilling Class 4 hex-head screw with a rubber EPDM washer passes through the sheet crest and into the timber batten or purlin. Spaced per the manufacturer’s nail pattern (typically every 2nd crest, every batten).

Screw type: 10g × 50 mm Class 4 corrosion-resistant for inland; Class 5 for coastal
Washer: EPDM rubber, must compress slightly without crushing
Driver speed: regulated; over-driving crushes the washer
Common defect: over-driven screws crush the washer flat, exposing the steel under the head. Water tracks down the screw threads and into the timber

Concealed clip (hidden fix)

Applied on Klip-Lok 700, Snaplock, Quikslok, and architectural standing-seam profiles. A clip is screwed to the batten; the sheet’s profile snaps over the clip. No visible fixings on the finished roof.

Clip spacing: every batten; clip stocked by the roof contractor as a separate item
Movement accommodation: the clip allows the sheet to expand and contract under thermal cycling (an important advantage on low-pitch roofs that get high solar gain)
Premium: 15 to 25% over pierce-fix on installed cost; the architectural appearance and movement accommodation justify it on contemporary architectural work

Common defects and on-site issues

Over-driven pierce-fix screws: crushed washer, exposed steel under screw head, leaks within months. The single most common metal-roof defect.
Lap detail at end joints (multiple sheets along the slope): any roof too long for a single sheet needs a lap. The lap detail is profile-specific; the manufacturer’s installation guide gives the lap depth and sealant requirement. Field-improvised laps fail.
Cutting on the roof: cutting sheet by abrasive disc on the roof showers swarf onto the surface. Hot swarf burns through the Colorbond paint and corrodes. Use cold-cut shears or pre-cut on the ground.
Galvanic corrosion with dissimilar metals: copper gutters draining onto zincalume sheet, or copper flashings on Colorbond, drive accelerated corrosion of the steel. Match metals at the roof boundary.
Wrong profile for the pitch: Custom Orb on a 3° pitch is a common defect. Even if the laps are sealed it leaks because the rib geometry doesn’t shed water at that angle.
Walking on the roof during install or maintenance: dents and deforms the sheet rib pattern. Always step on the screw line (over a batten), not the rib mid-span.
Inadequate sarking and underlay: builder spec missing the sarking + thermal blanket. The roof rains condensation from underside in cold conditions and the ceiling cavity becomes wet.
Mismatched flashings on retrofit roof: replacement sheet in Surfmist over flashings in Cottage Green. Order matched flashings at the same time as sheet.

Pricing (2026 indicative, ex-GST, supply only)

Profile / coating	Per square metre supply
Zincalume Trimdek (no paint)	$18-25
Colorbond Trimdek (standard colours)	$24-34
Colorbond Custom Orb (standard colours)	$26-38
Colorbond Klip-Lok 700	$34-48
Colorbond Ultra (coastal grade)	+$4-7 over standard
Premium architectural standing seam	$55-90
Matching flashings (per linear metre)	$14-32
Pierce-fix screws (per kg or per 100)	$8-18

Installed cost for a typical residential metal roof (supply + install, including underlay, sarking, flashings, gutters, downpipes) runs $130 to $220 per square metre in 2026 ex-GST, profile and complexity dependent.

Standards and references

Standards Australia, AS 1562.1:2018 Design and installation of sheet roof and wall cladding, Part 1: Metal. https://store.standards.org.au (verified 2026-05-13).
Standards Australia, AS 4040.2:2018 Methods of testing sheet roof and wall cladding. https://store.standards.org.au (verified 2026-05-13).
Standards Australia, AS 1397:2021 Continuous hot-dip metallic coated steel sheet and strip. https://store.standards.org.au (verified 2026-05-13).
Lysaght, Custom Orb product page. https://professionals.lysaght.com/products/lysaght-custom-orb/ (verified 2026-05-13).
Australian Building Codes Board, NCC 2022 ABCB Housing Provisions (roofing and bushfire references). https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions (verified 2026-05-13).