If you’ve written or read a Sydney commercial concrete spec, you’ve seen “Class 2 finish to AS 3610.” Most of the time the spec writer means something specific. Sometimes they don’t. Here’s what each class actually requires.
What AS 3610 is
AS 3610 is the Australian Standard for formwork for concrete. It classifies the surface finish of off-form concrete (the finish achieved purely from contact with the formwork, before any patching or grinding) into five classes — Class 1 being the highest, Class 5 being effectively unspecified.
Class 1 — Architectural
The highest standard. Smooth, uniform, all formwork joints flush, no patching visible, no fins, no significant blemishes. Used where the concrete IS the finish — feature walls in lobbies, architectural off-form facades.
Class 1 requires bespoke formwork (often steel form panels, or phenolic-faced plywood replaced every few pours), specialist placement and finishing crews, and significantly more cost than standard structural concrete. Expect a 50–100% premium over Class 3.
Class 2 — High quality
Smooth uniform appearance from a reasonable distance (typically 6m+). Minor blemishes acceptable, small voids allowed, formwork joints visible but neat. The most common “premium architectural” spec.
Achievable with good quality plywood formwork, well-released, careful placement. Most experienced Sydney concrete crews can achieve Class 2 routinely.
Class 3 — General architectural
The standard for most commercial concrete that’s visible but not feature. Acceptable surface variation, some voids, formwork joints visible. Used where the concrete will be painted or coated, but you want a reasonable starting surface.
Class 4 — Structural
Functional finish — the spec doesn’t expect a polished result. Voids and surface defects up to specified limits, formwork joints not critical. Standard for concrete that will be hidden behind cladding, in lift shafts, in plant rooms.
Class 5 — Rough
Effectively unspecified — the concrete needs to exist and be structurally sound. Buried elements, footings, infrastructure.
What this means for your spec
The cost gap between Class 4 and Class 2 is significant. If your spec calls Class 2 everywhere, you’re paying for architectural quality on concrete nobody will ever see. If your spec calls Class 3 on the feature wall in the lobby, you’re going to be disappointed.
The right approach is class-by-element: Class 2 or 1 where the concrete is visible from close range, Class 3 where it’s visible but not feature, Class 4 where it’s hidden. We’re happy to advise on this at design stage — happy to look at a spec and flag where it doesn’t make economic sense.