Most channels and trims on the UK market are folded or roll-formed from aluminium sheet. Ours are extruded. This guide sets out what that difference means in practice, backs the carbon claim with our verified EPD data, and — to be fair about it — sets out where folded sections are perfectly acceptable.
How each is made
Folding starts with flat aluminium sheet, typically 0.9–2.0mm gauge, bent to shape in a press brake or roll-former. The geometry depends on the machine setup and the operator, and every bend carries a radius — sheet cannot fold around a sharp corner without cracking.
Extrusion pushes heated aluminium billet through a machined steel die. The profile emerges as a continuous solid section in exactly the shape of the die, at whatever wall thickness the design calls for — our channels run 2–2.5mm. The die does not have good days and bad days. Every metre off it is the same metre.
That single difference — formed by a die versus formed by bending — drives everything below.
Tolerance
A folded channel is only as accurate as its press setup, and accuracy drifts across a production run. Widths vary, legs sit slightly out of square, and twist creeps into longer lengths. Individually the deviations are small. Over a 30-metre ceiling run butted end to end, they accumulate into visible steps and wandering lines.
An extruded channel holds its dimensions along its full length and from batch to batch, because the die defines them. When you set out a ceiling from the channel line — which is how pre-coordinated installation works — that consistency is what keeps every downstream trade off the critical path.
The arris
The arris — the edge where two faces meet — is where the two processes are furthest apart.
A fold always has a radius. On thin sheet it can be tightened, but never eliminated, and on a shadow gap or flush junction that rounded edge softens the whole detail. The line reads slightly out of focus. An extruded arris is sharp because the die cuts it sharp. On details that are nothing but line and shadow — recessed channels, flush junctions, perimeter gaps — the difference is visible from the floor. It is the difference between a drawn line and a sketched one.
Site handling and snagging
Thin-gauge folded sections are vulnerable at every stage after they leave the factory: they dent in transit, twist in handling, and deform when an installer leans a board against them. Damage often isn't caught until decoration, when replacing the section means opening up a finished ceiling.
A 2–2.5mm extruded wall resists all of that. Sections arrive straight, survive normal site handling, and hold their geometry through fixing. The practical effect is fewer snags at handover — and snags on ceiling lines are the expensive kind, because everything above them is already closed up.
Carbon per metre — the evidence
Manufacturing route drives embodied carbon too, and here the gap is large. Our channels are extruded in the UK from 100% recycled aluminium billet. Recycling aluminium uses roughly 95% less energy than smelting primary metal, so a recycled-billet channel starts from a far lower carbon base than folded sheet made from imported primary aluminium — before you add the shipping.
lower CO₂ than European folded sheet, like-for-like SEAM size
lower CO₂ than imported Chinese folded sheet
less energy to recycle aluminium vs. smelt primary
Manufacturing CO₂ by process route — SEAM 150
kg CO₂e per linear metre. A&L figure net of Module D; folded & virgin routes cradle-to-gate. Lower is better.
The chart above takes one size — SEAM 150 — and shows every route side by side. The pattern holds across the range. Extruded recycled billet sits at the bottom; folded sheet is roughly double; virgin billet and imported routes climb steeply from there.
Extruded recycled vs folded sheet — across every SEAM width
kg CO₂e per linear metre, 100–300mm. The carbon gap widens as sections get larger.
Because carbon scales with the metal in the section, the saving grows with width. On a 300mm run the difference between our recycled extrusion and European folded sheet is over 8kg CO₂e per metre — multiplied across a full ceiling, that is a material line in a project carbon model.
Full SEAM comparison table
| Route | 100mm | 125mm | 150mm | 200mm | 300mm |
|---|---|---|---|---|---|
| A&L recycled billet (UK) — net Module D | 2.79 | 3.14 | 3.49 | 4.18 | 5.58 |
| European sheet (folded) | 6.83 | 7.68 | 8.54 | 10.24 | 13.66 |
| Middle East sheet (folded, est.) | 7.19 | 8.09 | 8.99 | 10.79 | 14.39 |
| Europe virgin billet | 10.30 | 11.59 | 12.88 | 15.45 | 20.60 |
| China sheet (folded, est.) | 17.24 | 19.40 | 21.56 | 25.87 | 34.49 |
| China virgin billet | 26.72 | 30.06 | 33.40 | 40.08 | 53.44 |
A&L figures are net of Module D (end-of-life recycling credit), based on the verified Cortizo Infinity® billet EPD. Other routes are cradle-to-gate (manufacturing only), as no comparable Module D data exists for them — so they are not on an identical basis. Figures include powder coating; they exclude installation and use. Full assumptions and sources on request. See the sustainability page for the complete dataset and REVEAL figures.
When folded is acceptable
Folded and roll-formed sections are the right answer more often than a manufacturer of extrusions might like to admit:
- Short, simple perimeter trims where the run is a few metres and the detail isn't a feature.
- Concealed sections that will never be seen — carriers, closers, backing pieces.
- One-off non-standard shapes needed faster than a die can be cut, where geometry isn't critical.
- Genuinely cost-driven work where the detail is secondary and the programme can absorb snagging risk.
Where folded sections stop being acceptable is predictable: long runs, feature details, service-carrying channels, and any junction the client will photograph. That is extrusion territory.
The specification test
One question sorts most cases: will the line be seen, and is it longer than a few metres?
If yes to both, specify extruded. The premium over folded sheet is modest at supply stage and is usually recovered before practical completion in reduced snagging and zero replacement sections — with a lower carbon figure on the certificate as well.
Specifying a ceiling channel?
SEAM flush and REVEAL recessed channels — UK-extruded from 100% recycled billet, five widths, 5-day despatch.
Frequently asked questions
What is the difference between extruded and folded aluminium?
Extruded aluminium is pushed through a machined die as a solid continuous section, giving consistent geometry and sharp edges. Folded aluminium is sheet bent to shape, which always carries a fold radius and greater dimensional variation.
Is extruded aluminium stronger than folded?
For channel sections, yes in practice. Extrusion allows thicker walls (2–2.5mm versus typical 0.9–2.0mm sheet) and one-piece geometry, so extruded channels resist denting, twist and site damage far better than folded equivalents.
Does extruded aluminium have a lower carbon footprint than folded?
It can, and ours does — but the driver is the metal, not only the process. A&L channels are extruded from 100% recycled billet, which carries far lower embodied carbon than the imported primary sheet most folded sections use. Like-for-like, our SEAM sizes are around 59% lower than European folded sheet and up to 84% lower than imported Chinese folded sheet.
Are folded aluminium trims ever the right choice?
Yes — short perimeter runs, concealed sections and non-critical details where geometry doesn't drive the finish. For feature details and long runs, extrusion holds the line.