People use “tin roof”, “Colorbond” and “metal roof” as if they’re all the same thing. They’re not. There are three quite different products sitting under the “metal roofing” umbrella, and knowing which is which matters when you’re getting a roof quoted on the Darling Downs — because the price difference and the long-run difference between them is real. Here’s the plain-English version of what each one actually is, where it suits, and why most Downs homes end up with Colorbond.
The three products, in order of age
It helps to understand these in the order they came along, because each one built on the last.
Plain galvanised (old “galv”) steel is the original. It’s steel sheet coated in zinc to stop it rusting. For decades this was the standard tin roof, and you’ll still find it on plenty of older sheds, Queenslanders and farm buildings across the Downs. It works — until the zinc coating wears thin, and then it rusts, often starting at the cut edges, the laps and around the fixings.
Zincalume is the upgrade to galv. Instead of plain zinc, the steel is coated in an aluminium-zinc alloy (roughly half aluminium, half zinc, with a touch of silicon). That alloy holds up far better against corrosion than the old zinc-only coating — it’s the reason Zincalume lasts considerably longer than the galv it replaced. Zincalume is the bare, unpainted silver metal you see on a lot of newer sheds. It’s a genuinely good roofing steel in its own right.
Colorbond is Zincalume with a baked-on colour coating. Underneath the colour, a Colorbond sheet is an aluminium-zinc coated steel base — then it gets a layer of primer and a tough oven-baked paint finish on top. So Colorbond isn’t a different metal from Zincalume; it’s Zincalume with extra protection and a colour. That’s the single most useful thing to understand here: Colorbond is the painted version of the same coated steel.
Plain galvanised steel: where it still fits
We’re not going to tell you galv is rubbish, because it isn’t — it’s just old technology, and it has a narrower place now.
Where it suits: matching repairs on an existing old galv roof or shed, and budget farm structures where looks don’t matter and the building isn’t precious. If you’ve got a galv shed that’s mostly sound and one sheet’s gone, replacing like with like can make sense.
The catch: plain galv corrodes faster than the newer coatings, especially at edges and fixings, and out on the exposed, dusty plains around Oakey, Pittsworth and Dalby it can rust through sooner than you’d hope. It also can’t be left bare and pretty — it dulls and streaks. On any home roof, galv is the past, not the choice you’d make new today.
If your old steel roof is at this stage, it’s usually a re-roofing or roof replacement conversation rather than a patch-up one.
Zincalume: the quiet workhorse
Zincalume is a real step up and a perfectly sound roof. The aluminium-zinc coating resists corrosion far better than plain galv, which is why it’s the standard bare-metal roofing steel now.
Where it suits: sheds, workshops, carports, patios and outbuildings where you want a long-lasting metal roof but don’t care about colour. Plenty of rural properties roof their big machinery sheds in bare Zincalume and it’s a sensible call — it’s durable and it’s usually a touch cheaper than the painted equivalent because you’re not paying for the colour coating.
The catches:
- No colour, no heat control. Bare Zincalume is bright silver and stays silver. You can’t pick a light heat-reflective colour because there’s no colour at all — and a bare metal roof can run hot. On a house, that matters in our summers.
- Glare. That bright silver finish reflects sunlight hard, which neighbours and councils don’t always love on a home in town.
- It can’t be repainted as easily as people think. Bare Zincalume needs proper preparation before it’ll hold paint, so “I’ll just paint it later” isn’t the simple job it sounds.
For a shed, none of that matters and Zincalume is great value. For a house, the lack of colour and heat control is exactly the gap Colorbond fills.
Colorbond: why it’s usually the pick for Downs homes
Colorbond takes that good Zincalume base and adds the two things a home roof actually needs here: a tough protective paint finish and a colour you choose.
Why it wins on the Downs specifically:
- Heat. This is the big one in our climate. Colorbond comes in 20-plus colours and the lighter ones reflect a lot more summer heat than bare silver metal or dark tile. Many Colorbond colours also carry Thermatech solar-reflectance technology in the paint. On a Toowoomba summer, the colour you pick does real work keeping the house cooler — we go into that in our guide to the best roof colour for a hot QLD climate.
- Corrosion protection. The baked-on coating sits over the aluminium-zinc base, so a Colorbond sheet is better protected than bare Zincalume and far better than old galv. That’s why it lasts so well — see how long a Colorbond roof lasts for the detail.
- Looks. It’s a clean, modern finish that suits new builds, Queenslanders and brick-and-tile homes alike, with no glare problem.
- Low maintenance. No re-bedding, no re-pointing, no painting for many years — an occasional rinse and a check is about it.
For the vast majority of homes we re-roof across Toowoomba and the wider Downs, Colorbond is the obvious choice. Our Colorbond roofing page covers the install side.
Cost vs longevity: the honest trade-off
Here’s roughly how they stack up, cheapest to dearest on the day, as indicative ranges only — your quote depends on roof size, pitch, access and what’s underneath:
- Plain galv: cheapest sheet, shortest life. You save a little now and spend it back in corrosion sooner. Only really sensible for matching old work or rough farm sheds.
- Zincalume: mid-priced, long life, no colour. Excellent value for sheds and outbuildings.
- Colorbond: dearest of the three on the day — you’re paying for the colour coating and the heat performance — but it gives you the longest comfortable life on a home, plus the heat and looks benefits Zincalume can’t.
The gap between Zincalume and Colorbond on a house is usually modest in the scheme of a whole re-roof, and the colour, heat control and finish you get for it are worth it on a home you’ll live in for years. On a shed, the gap is harder to justify, which is why bare Zincalume rules the shed world.
If you’re weighing metal against tile while you’re at it, our metal vs tile comparison covers that side of the decision.
A quick way to decide
Work through it like this:
- Roofing a house in town or near town? Colorbond, almost every time — for the heat control, the look and the no-glare finish.
- Roofing a shed, carport or workshop where looks don’t matter? Bare Zincalume is great value and plenty durable.
- Patching or matching an existing old galv roof? Like-for-like galv can make sense for the repair — but if the roof’s near the end, price a full re-roof in Colorbond or Zincalume instead of chasing rust around.
- On an exposed, dusty block out on the plains? Lean toward the better-protected coatings (Colorbond or Zincalume) and away from old galv, which corrodes faster out there.
Common questions
Is Colorbond just painted Zincalume? Essentially, yes — Colorbond is built on an aluminium-zinc (Zincalume-type) coated steel base, with primer and a baked-on colour finish added over it. That extra coating is what gives Colorbond its colour, its heat performance and its extra protection.
Can I paint a bare Zincalume roof to make it look like Colorbond? You can have a bare metal roof painted, but it needs proper surface preparation first and it’s not as durable as the factory-baked Colorbond finish. If colour matters to you from the start, it’s usually better to buy Colorbond than to paint Zincalume later.
Is bare Zincalume bad for a house? Not bad — just not ideal. It’s durable and long-lasting, but it has no colour to control heat and it can glare. For a shed it’s perfect; for a home most people are happier with Colorbond.
My old shed roof is rusting — what is it? Almost certainly old galvanised steel. Once galv starts rusting at the edges and fixings it tends to keep going. Patching can buy time, but a re-roof in Zincalume (for a shed) or Colorbond (for anything you want to look good) is usually the better long-term spend.
Does the type of metal change how long my roof lasts? Yes. In rough order, old galv has the shortest life, Zincalume considerably longer, and Colorbond gives you that same long-lived coated-steel base with an added protective finish on top. Workmanship and the local conditions matter too, but the product genuinely does set the baseline.
The bottom line
All three are “metal roofs”, but they’re not interchangeable. Old galv is yesterday’s roof, fine for matching repairs and rough sheds. Zincalume is a great-value, long-life bare steel that’s hard to beat for sheds and outbuildings. Colorbond takes that same coated-steel base, adds a tough painted finish and a colour you choose, and that’s exactly what a home on the Darling Downs wants — heat control, a clean look and a long, low-maintenance life.
Not sure which suits your home or shed? Get a free quote and we’ll tell you straight which product makes sense for your roof and your budget — whether that’s a full Colorbond re-roof or a sensible Zincalume shed roof.