Is galvanised expanded metal compliant with Australian building code AS 1657 for walkways?
Walkways don’t get second chances. Whether they cross a factory floor, climb around a water treatment plant, or hug the side of a mezzanine, the people on them assume — rightly — that someone has done the engineering homework. In Australia, that homework is spelt out in AS 1657:2018 – Fixed Platforms, Walkways, Stairways and Ladders – Design, Construction and Maintenance. Among the materials engineers reach for, galvanised expanded metal (GEM) keeps coming up, and for good reason: it’s light, strong, grippy, and the zinc coating shrugs off weather. But popularity isn’t compliance. So let’s answer the question properly — does GEM actually satisfy what AS 1657 demands?
What AS 1657 Actually Requires
AS 1657 exists to make sure fixed access structures are safe to use, safe to maintain, and safe to build around. Rather than wading through the whole standard, the parts that matter for walkway flooring come down to four things:
| Requirement | What the standard expects |
|---|---|
| Design load | Walkways designed for a minimum imposed load of 5 kN/m² |
| Load-carrying capacity | No permanent deformation under at least 3 kN/m² |
| Edge protection | Edges safeguarded against falls and dropped objects |
| Surface finish | Smooth, clean, free of slip or contamination hazards |
On top of that, the standard expects walkways to be inspected regularly — at least annually — and kept in a safe condition throughout their service life.
Why GEM Keeps Winning Walkway Work
Expanded metal starts life as a solid steel sheet that gets slit and stretched into a lattice of diamond-shaped openings. Nothing is welded, nothing is woven — the sheet simply becomes stronger than it looks. Add a hot-dip galvanised coating and you get a flooring material that offers:
- High strength-to-weight ratio — heavy-duty performance without dead load
- Natural traction — the raised strands grip boots in both dry and wet conditions
- Open area — water, dust, and debris fall through instead of pooling
- Full 360° zinc protection — far more robust than painted finishes outdoors
- Self-draining, quick-drying surfaces — a genuine safety feature outdoors
Walking Through the Compliance Checklist
Here’s where GEM stands against each of AS 1657’s core requirements:
Load-carrying capacity. The raised diamond geometry gives GEM exceptional stiffness for its weight. Standard industrial gauges comfortably support the 3 kN/m² no-deformation threshold, and heavier profiles exceed the 5 kN/m² design load with margin to spare. The key is matching the gauge and strand dimensions to the span — which is where your engineer comes in.
Edge protection. The standard wants edges detailed so people and tools can’t tumble off. GEM contributes here too: its patterned surface creates small ledges and recesses that catch rolling objects far better than smooth plate, and kick plates can be added where the risk justifies them.
Surface finishes. AS 1657 calls for surfaces that are smooth, clean, and hazard-free. A quality hot-dip galvanised finish delivers exactly that — uniform, corrosion-resistant, and free of the flaking or blistering that turns painted mesh into a trip hazard. The anti-slip profile of expanded metal is a bonus the standard welcomes rather than penalises.
Maintenance and inspection. This is where galvanising quietly earns its keep. Because the zinc coating resists corrosion even in harsh environments, GEM walkways stay within specification longer between inspections — though the annual inspection AS 1657 requires is still non-negotiable.
The Compliance Verification Process, Step by Step
Compliance isn’t a claim — it’s a sequence of verified decisions. From first specification through to sign-off, a GEM walkway project moves through a small number of checkpoints, each with a clear pass/fail outcome:
Common Mistakes That Undermine Compliance
Even a compliant material fails if it’s mishandled. Watch for these:
- Undersized spans — running a light-duty mesh across an unsupported span it was never rated for
- Cut edges left unsealed — every cut breaks the galvanised layer; zinc-rich paint must restore it
- Mixing components — GEM flooring on a frame it wasn’t detailed with invalidates the whole assembly
- Skipping the paperwork — designers and certifiers want evidence, not assumptions
Frequently Asked Questions
Does AS 1657 apply to all walkways? It applies to fixed platforms, walkways, stairways, and ladders in workplaces. Temporary or domestic structures fall under different requirements.
Is galvanised or stainless expanded metal better for walkways? Galvanised suits most industrial and outdoor settings at far lower cost. Stainless earns its premium in food processing, marine, or highly corrosive environments.
Can GEM walkways be used outdoors in coastal areas? Yes — hot-dip galvanising handles coastal exposure well, though inspection intervals should shorten in aggressive marine atmospheres.
The Bottom Line
Galvanised expanded metal isn’t just compatible with AS 1657 — done properly, it’s one of the most practical ways to meet it. The material’s inherent strength covers the load requirements, its geometry contributes to edge safety, its finish satisfies surface standards, and its corrosion resistance simplifies the maintenance obligations. Specify the right gauge, detail the edges, protect every cut, document everything, and GEM will carry foot traffic safely for decades.
