Selection Guide · 11 min read
How to Choose a Roof Profile: Corrugated, Trimdek, Spandek and Klip-Lok
The profile you choose decides your minimum roof pitch, your purlin spacing, your fastener count and the look of the finished building. This guide walks through each major Australian steel roof profile and where it fits.
In short
Steel roof profiles differ in rib height, cover width and minimum pitch. Corrugated suits classic residential roofs at 5 degrees or steeper. Trimdek and Spandek handle low pitch down to 1 to 3 degrees. Klip-Lok concealed-fix systems are the choice for commercial and long-span roofs where no exposed fasteners are wanted.
This guide compares the five profiles CSA supplies, explains the trade-offs between exposed-fix and concealed-fix systems, and gives a simple decision framework so you can match the profile to your building, pitch and budget before you order.
1. Why profile choice matters
A roof profile is the shape that is roll-formed into a flat steel coil to give it strength and water-shedding capacity. The shape sets three things that matter on every job: the minimum roof pitch the sheet can drain reliably, the maximum distance it can span between purlins, and how the finished roof looks. Choosing the wrong profile means either a roof that leaks at low pitch, a roof that needs far more structural framing than it should, or a building that simply looks wrong for its setting.
There is no single best profile. A heritage Queenslander wants the classic corrugated wave. A near-flat commercial warehouse wants a concealed-fix standing seam that drains at 1 degree. A contemporary architect-designed home might specify the clean wide pans of Spandek. The right answer is always the profile that matches the building geometry, the pitch, and the look the owner wants.
2. The five profiles compared
| Profile | Rib height | Cover width | Min pitch | Best for |
|---|---|---|---|---|
| Corrugated | ~17 mm wave | 762 mm | 5 degrees | Classic residential, sheds, walling |
| Trimdek | 29 mm rib | 762 mm | 2 degrees | Residential and commercial, low pitch |
| Spandek | 24 mm rib | 700 mm | 2 degrees | Architectural cladding and facades |
| Klip-Lok 700 | 43 mm rib (concealed clip) | 700 mm | 1 degree (0.48 BMT) | Commercial, industrial, long span |
| Monoclad | 29 mm rib | 762 mm | 2 degrees | Industrial and commercial roofing and walling |
Common Australian steel roof profiles supplied by CSA
Corrugated is the most recognisable profile in Australia and still the default for residential re-roofing. Its rounded wave handles foot traffic well and re-rolls for curved verandah roofs, but it needs a minimum 5 degree pitch to drain reliably.
Trimdek has a trapezoidal hi-rib that spans further than corrugated, so it needs fewer purlins, and it drains down to 2 degrees subject to Lysaght design provisions. That combination of low pitch and long span makes it the workhorse profile for both modern homes and light commercial buildings.
Tip
If you are unsure between corrugated and Trimdek for a residential roof, Trimdek often works out cheaper to install because the deeper rib spans further, meaning fewer purlins on wide bays. Corrugated wins on appearance for heritage and traditional homes.
3. Exposed-fix versus concealed-fix
Corrugated, Trimdek, Spandek and Monoclad are exposed-fix profiles: they are fastened through the sheet into the purlin with roofing screws and sealing washers. Every screw is a small penetration of the roof skin. On a well-installed residential roof this is no problem for decades, but on a near-flat or very large commercial roof the sheer number of penetrations becomes a maintenance liability.
Klip-Lok is a concealed-fix system. The sheet snaps onto clips that are screwed to the purlin, so there are no fasteners through the weather face of the roof at all. This gives a clean look, eliminates screw-hole leaks, and lets the roof drain at pitches as low as 1 degree. It is the standard choice for warehouses, shopping centres, schools and any long-span commercial roof.
Note
Concealed-fix systems cost more per square metre than exposed-fix and need closer attention to thermal expansion detailing on long runs. For most homes, exposed-fix Trimdek or corrugated is the right balance of cost and performance.
4. Matching profile to pitch
The single most common roofing mistake is using a profile below its minimum pitch. Water that cannot drain fast enough will pond, find its way under laps and around fasteners, and the roof will leak no matter how well it was installed. Always check the manufacturer minimum pitch against your actual roof pitch before you order.
- Pitch 5 degrees or steeper: any profile works. Corrugated is fine.
- Pitch 3 to 5 degrees: use Trimdek or a concealed-fix system. Avoid corrugated.
- Pitch 1 to 3 degrees: use Klip-Lok concealed-fix, or Spandek with vertical-seam detailing.
- Below 1 degree: specialist membrane or fully welded systems only. Talk to an engineer.
5. A simple decision framework
Start with pitch, then building type, then appearance. If the pitch is below 3 degrees, you are choosing a concealed-fix system regardless of anything else. If the building is a large commercial roof, concealed-fix usually wins on whole-of-life cost. If it is a residential roof at normal pitch, choose between corrugated for traditional looks and Trimdek for the most economical install. For facades and feature walls, Spandek and Monoclad give the cleanest contemporary appearance.
When you have a shortlist, use the CSA roof and gutter takeoff tool to estimate sheet quantities, then send your measurements to our trade desk for a firm quote. For custom-cut, large-volume or commercial orders we will prepare a project-specific quote with full compliance documentation.