Roofing Sheet Profiles Explained: Corrugated, Trimdek and Klip-Lok

Every metal roof in Australia is built from sheet in one of a handful of profiles, and the profile matters far more than most buyers realise, because sheets of different profiles will not lap together, will not match visually, and often will not even take the same flashings. This guide explains the main families so you can identify what is already on a roof and buy the right thing to extend or repair it.

Why profile matching is non-negotiable

A roof is a system of overlapping sheets, and the rib spacing and shape of the overlap is specific to each profile. You cannot patch a Trimdek roof with corrugated sheet, or extend a Klip-Lok roof with Spandek, no matter how similar they look in a photo. If you are buying second-hand or surplus metal sheet to extend an existing roof, matching the exact profile name, not just "corrugated-looking", is the difference between a lap that sheds water and one that leaks from day one.

Corrugated (Custom Orb)

The classic wavy profile that most people picture when they think of an Australian tin roof. Corrugated sheet has been made since the 1800s and is still widely used on sheds, verandahs and heritage-style homes. It is forgiving to install on simple gable roofs and is the cheapest profile per square metre, but it has a shallower pitch tolerance than trapezoidal profiles and is less common on new architectural builds.

Trapezoidal (Trimdek, Monoclad)

Trapezoidal profiles, sold under names like Trimdek and Monoclad depending on the rollformer, have flat-topped, squared-off ribs rather than a smooth wave. They are the most common profile on modern Australian homes and sheds because they combine strength, a lower minimum roof pitch than corrugated, and a clean, contemporary look. Screw fixing is through the crest of the rib, which is visible on the finished roof, sitting between corrugated's low cost and concealed-fix's higher price.

Concealed-fix (Klip-Lok, Speed Deck)

Concealed-fix profiles like Klip-Lok clip into place with no visible fastener penetrating the sheet face, which means no exposed screw heads to fail over time and a cleaner architectural line. This is the profile of choice for low-pitch roofs (some concealed-fix systems handle pitches as low as 1 to 2 degrees) and for high-end residential and commercial work. It costs more than trapezoidal, both in material and in the specialist tools and training needed to install it correctly, which is why roofing tools and equipment like seamers and folders are a distinct part of the trade.

Standing seam and long-span decking

Standing seam is a step further again, a raised, mechanically-seamed joint running the full length of the sheet, used where a completely flat plane and minimal visible fixing is required. Long-span decking (also called roof decking) uses deeper, more widely spaced ribs to span greater distances between purlins with fewer supports, common on commercial and industrial buildings and large-span rural sheds.

Five-rib and Spandek

Sitting between corrugated and full trapezoidal in appearance, five-rib profiles like Spandek have a shallower, more closely spaced rib pattern than Trimdek and are common on both residential and rural sheds where a slightly stronger profile than corrugated is wanted without moving to a full concealed-fix system. Like corrugated, the fastener is visible on the crest of every rib, keeping installation straightforward and cost lower than concealed-fix options.

Insulated sandwich panel

Insulated roof panels combine an external and internal metal skin with a rigid foam core in a single factory-formed product, most common on commercial and cool-room style buildings and increasingly on patios and outdoor living areas where thermal performance matters without a separate sarking and batt installation. These are a different category of product to a single-skin sheet with separate insulation and sarking added afterward, and the two are not directly interchangeable in a repair.

Base metal thickness (BMT) matters as much as profile

Two sheets in the same profile can still be different products if the base metal thickness differs. Thicker BMT sheet spans further between purlins and resists denting and oil-canning (the visible waviness some low sheets develop), while thinner BMT is lighter and cheaper for shorter spans. When buying second-hand sheet, always check the BMT alongside the profile name; a listing with both is far more useful than one with a photo alone. This is also a large part of what drives re-roof cost, since heavier gauge sheet costs more per square metre.

Colour and coating

COLORBOND, COLORBOND Ultra and ZINCALUME are coating systems, not profiles, so any profile can come in any COLORBOND colour or as unpainted ZINCALUME or galvanised steel. If you are matching an existing roof for an extension or repair, get the colour name exactly right; see our COLORBOND colour matching guide for how colour runs change over time and what to do when the original name is discontinued.

Identifying what is on your roof now

If you do not know the profile on an existing roof, measure the rib-to-rib spacing (called the pitch of the corrugation, not to be confused with roof pitch) and photograph a close-up cross-section from underneath if you have roof space access. A licensed roofer can usually identify a profile from a single clear photo, and getting it right before you order is far cheaper than reordering after a mismatched delivery. Browse current metal roofing and sheeting listings for material by profile, or if you have offcuts or surplus sheet from a finished job, list it here for someone doing exactly the repair you just finished.