What is the best option for your drainage needs? Let’s compare Aluminium vs Polymer Concrete.
Aluminium vs Polymer Concrete
Aluminium and polymer concrete sit at opposite ends of the channel-drain spectrum. One’s light enough to carry under your arm. The other needs a forklift and a tile saw with a diamond blade.
Most of the time the choice is obvious from the load rating. Pedestrian plaza? Aluminium will do. Container yard? Don’t even price aluminium. Where it gets interesting is the middle — hotel forecourts, basement carparks, hospital ambulance bays — where either could technically work, and the deciding factor is something else. How it’ll be cut on site. What it sits next to. Whether the chemical resistance on the spec sheet is real or theoretical.
We fabricate stainless, so take this with the appropriate grain of salt. But aluminium and polymer concrete both have a place, and the comparison below is the one we’d give a specifier who rang us asking which to use.
Aluminium
The case for aluminium is weight. A 1-metre channel section weighs around 2–3 kg depending on profile, against 15–25 kg for the polymer concrete equivalent. On a multi-storey job where every kilo gets craned up, or a refurb where you’re carrying material down a corridor, that matters. One person can install it. You cut it with a standard drop saw and a metal blade — no wet cutting, no silica dust, no exclusion zone.
The case against aluminium is everything that happens after install.
It dents. A dropped scaffold pole or a pallet jack wheel will mark anodised aluminium permanently. Not a failure, just ugly, which on an architectural job is the same thing.
It corrodes when you put the wrong thing next to it. Galvanic corrosion is the one that bites people. Aluminium in contact with stainless fixings, copper flashings, or carbon steel in the presence of water sets up a small battery, and the aluminium is what dissolves. We’ve seen flanges eaten through in under a decade on coastal jobs where the original spec didn’t isolate the dissimilar metals. It’s avoidable — nylon washers, isolation tape — but it has to be specified, and on site, it often isn’t.
It doesn’t love strong acids or alkalis. Fine for stormwater. Not fine for a commercial kitchen washdown bay with caustic degreasers, or anywhere chlorinated pool water splashes regularly.
Load-wise, aluminium grates are realistically a Class A to Class C product (pedestrian through to slow-moving cars). You can find Class D aluminium systems but you’re usually paying stainless money for them by the time the frame is beefed up enough, and at that point the material choice stops making sense.
Pricing sits between galvanised steel and stainless. Anodising adds maybe 15–25% but is worth it — bare aluminium oxidises to a chalky finish within a couple of years outdoors, and once it’s chalked, there’s nothing you can do about it short of replacement.
Polymer Concrete
Polymer concrete is what you spec when the loads are serious and the chemistry is hostile. The material is aggregate (sand, gravel, sometimes recycled glass) bound with a polyester or vinyl ester resin instead of cement. The result is denser, stronger, and far more chemically resistant than ordinary concrete, with effectively zero water absorption.
What it’s genuinely good at:
Load rating. This is the headline. Polymer concrete channel systems go up to Class F (heavy industrial) and Class G (aircraft hardstand) when paired with the right grate. Nothing else in the precast world does that at the same price point.
Chemical resistance. The non-porous surface shrugs off acids, alkalis, fuels, and most solvents. In a food processing plant where the floor gets hosed down with sanitisers daily, or a chemical bunding application, this is the whole game.
Hydraulics. The cast surface is smooth and stays smooth. Flow rates hold up over decades because nothing’s eating into the channel walls.
What people underestimate:
Weight. A 1-metre Class E section can weigh 25–40 kg. You’re not carrying that down a stairwell. Lifting equipment, two-person handling, and proper site planning are non-negotiable on anything beyond a small run.
Silica dust when cut. This is the one that matters from a WHS perspective. Cutting polymer concrete dry releases respirable crystalline silica, which is now regulated hard in Australia — workplace exposure standard halved to 0.05 mg/m³ in 2020, and silicosis is a notifiable disease in every state. Wet cutting with a diamond blade is mandatory. P2 respirators, exclusion zones, and engineered dust controls. If your installer’s plan is “we’ll just cut it on the slab with an angle grinder,” walk away.
Joints and fixings. A polymer concrete channel run is precast sections joined on site. The joints are the weak point — bad sealing means water tracks behind the channel and undermines the bedding. Done properly, the system lasts decades. Done quickly to hit a Friday deadline, you’ll see settlement and joint failures within five years.
UV and fire. The resin binder is the soft part. Long-term UV exposure makes some resin systems chalky and brittle at the surface. Fire damages the resin matrix permanently — the channel doesn’t melt the way aluminium does, but it loses structural integrity. For most drainage applications neither matters, but worth knowing.
Pricing is the highest of the common channel materials at install, but the lifetime maths usually wins. A polymer concrete system in a heavy-duty environment is a 30-plus year asset. The same job in aluminium would be a replacement programme.
Side by Side
| Aluminium | Polymer Concrete | |
|---|---|---|
| Load rating | Class A–C realistically | Up to Class F, Class G with the right grate |
| Weight per metre | 2–3 kg | 15–40 kg depending on class |
| On-site cutting | Drop saw, metal blade, standard PPE | Wet diamond cutting, P2 respirator, exclusion zone |
| Install crew | One person | Two minimum, often with lifting gear |
| Chemical resistance | Poor against strong acids/alkalis, chlorinated water | Excellent across acids, alkalis, fuels, sanitisers |
| Galvanic corrosion risk | High — must isolate from dissimilar metals | None (non-conductive) |
| Impact and abrasion | Dents and scratches | Excellent |
| Aesthetic | Modern, metallic, can be anodised in colours | Utilitarian — looks driven by the grate choice |
| Recyclability | High (recycled aluminium uses ~5% of primary energy) | Low — thermoset resin can’t be remelted |
| Lifetime in tough conditions | 10–15 years | 30+ years |
| Upfront cost | Moderate | High |
| Best avoided when | Forklifts, aggressive chemistry, dissimilar metals nearby, long-life specs | Lightweight slab limits, tight stair access, small budgets, fine architectural finishes |
Where We’d Specify Each
Aluminium makes sense for light commercial, residential alfresco, retail fitouts, hotel pool decks on suspended slabs, and any job where weight on structure is the constraint and the loading is pedestrian to light vehicle. Anodise it. Isolate it from any dissimilar metal it touches. Don’t put it where chemistry will attack it.
Polymer concrete makes sense for loading docks, freight yards, food and beverage processing, chemical bunding, fuel forecourts, airports, and any external civil application carrying heavy vehicle traffic. Insist on wet cutting and proper joint sealing. Budget for two-person handling. The system will outlast the building it’s installed in.
Where we’d push you towards stainless instead: anywhere the finish is part of the architecture (hotels, hospitals, premium retail, public spaces); anywhere hygiene matters and the drain is visible (healthcare, aged care, commercial kitchens); curved runs, which neither aluminium nor polymer concrete handles; and any spec that wants both heavy load rating and a clean finish and chemical resistance. That combination is what stainless does and the others don’t.
If you’re weighing this up on a live project, ring us on +617 5499 1511. We’ll give you a straight answer about whether the job needs us or whether one of the other two will do the work.
