You have two quotes for a new metal roof. One says Zincalume, the other says Colorbond, and the Colorbond one costs more. Both are steel. Both come from the same manufacturer. So what are you actually paying for, and does it matter when you live a few streets back from the beach?
This is the zincalume vs colorbond question we get asked most often in Shellharbour, and the honest answer is that it depends less on the product brochure and more on where your house sits, what the roof is covering and how much you care about how it looks in ten years. Here is how we explain it on site.
Same steel underneath, different coat on top
Start with the part that surprises people. Colorbond is not a different metal. It is Zincalume steel with paint baked on at the factory.
Zincalume is steel sheet coated in an alloy of aluminium and zinc. That coating is what stops the steel rusting. Left as it is, it has a bright silver finish that slowly dulls to a softer grey over the years.
Colorbond takes that same coated sheet and adds a pretreatment layer, a primer and a coloured topcoat, all applied and cured in the factory. So a Colorbond roof has every bit of protection a Zincalume roof has, plus a layer of paint that shields the metal coating from the weather.
That extra layer is the whole difference. Everything else in this post flows from it.
Salt air is what really decides it on the coast
In a dry inland town, plain Zincalume can last a very long time with almost no fuss. Shellharbour is not that town. Onshore winds carry fine salt spray well inland, and it settles on everything: roofs, gutters, flashings, the underside of the eaves.
Salt is hard on bare metal coatings. On an unpainted Zincalume roof close to the water, it sits directly on the alloy and works away at it. On Colorbond, the paint takes that first hit instead. That does not make Colorbond immune, but it does give the steel an extra line of defence.
For homes very close to breaking surf, the manufacturer makes heavier duty grades of both products, sold as Colorbond Ultra and Zincalume Ultra, with a thicker protective coating built for severe marine air. Whether your street needs an Ultra grade comes down to how close you are to the surf and how exposed the site is, so it is something we check at the quote stage rather than guess. The point is that on the coast, the grade of steel can matter as much as the choice between painted and unpainted.
The parts the rain never reaches
Here is the detail most people miss. Rain is good for a metal roof by the coast because it rinses the salt off. The trouble spots are the bits that stay dry: under the eaves, the back of the gutters, sheltered sections of a verandah roof. Salt builds up there with nothing to wash it away.
On an older metal roof, it is common for the open sheets to look fine while the sheltered edges and flashings have started to break down. Whichever product you choose, hosing those protected areas down every so often makes a real difference to how long they last.
Zincalume is cheaper to buy, but the gap shrinks on a full job
Zincalume sheet costs less than Colorbond sheet. No argument there. But on a full re-roof, the sheeting is only one line on the quote.
Taking off the old roof, checking and repairing the battens, new flashings, ridge capping, sarking (the foil layer that sits under the sheets), gutters, downpipes and the labour to put it all together cost much the same whichever finish you pick. So the price gap between the two products is smaller as a share of the whole job than it looks when you compare sheet prices alone.
If you are working out the full budget for a new roof, our guide to what sets the price of a roof replacement in Shellharbour goes through each of those items. For a small shed or carport, on the other hand, the sheeting is most of the cost, and Zincalume’s saving is much more noticeable.
Heat and glare are where Colorbond pulls ahead
A brand new Zincalume roof is shiny. On a sunny Illawarra afternoon it reflects a lot of light, which is great for keeping heat out, but it can also throw glare into a neighbour’s windows or a second storey next door. The shine fades as the coating weathers, though not overnight.
Colorbond has a flat, low sheen finish, so glare is rarely an issue. The paint is also designed to reflect a good share of the sun’s heat, and lighter colours do this better than dark ones. A pale grey or off white Colorbond roof will keep the ceiling space noticeably cooler than a dark charcoal one in summer.
Some councils and newer housing estates have rules or design guidelines covering roof colour and reflectivity. If you are building or re-roofing in a newer estate, check those before you settle on a finish. It is a lot easier than changing it afterwards.
You can mix the two, but keep copper and lead away from both
A Colorbond house roof with a Zincalume shed or patio next to it is completely fine. The two sit happily side by side because they share the same base coating.
The real problems come from other metals. Water running off copper pipes, copper flashings or old lead flashings onto Zincalume or Colorbond will eat into the coating over time. Wet treated timber and fresh concrete or mortar touching the sheets can cause similar damage. When we replace an old roof, swapping out incompatible flashings is part of the job, because one bad flashing can undo a brand new roof.
Where each one makes sense
Zincalume is a good fit for sheds, garages, carports and rear patios, especially further back from the coast or where budget matters most. Some people also choose it for the look: the silver finish suits industrial style homes and older farmhouse character.
Colorbond is usually the better pick for the main roof of a home close to the water, for any roof that faces the street, and for anyone who wants control over colour and summer heat.
When we quote a metal roof for a Shellharbour home, we look at how exposed the site is, what is underneath the roof, the flashings that need replacing and what you want the place to look like. Then we lay out the options side by side so you can choose. We would rather you understood the trade-off than took our word for it.
If you are still deciding whether to go metal at all, our comparison of Colorbond and tile roofs covers that bigger choice.
Straight answers on Zincalume and Colorbond
Which is better, Zincalume or Colorbond?
Neither is better everywhere. Colorbond gives you colour choice, less glare and an extra layer of protection from the paint, which is why it suits most coastal homes. Zincalume costs less and does a solid job on sheds, carports and buildings where looks and salt exposure matter less.
Is Zincalume cheaper than Colorbond?
Yes, the sheeting itself costs less. On a full house re-roof the difference is diluted, because removal, flashings, gutters, sarking and labour cost about the same either way. On a small shed or carport, where the sheets are most of the bill, the saving is easier to see.
Can you mix Zincalume and Colorbond?
Yes. They share the same base coating, so a Colorbond house with a Zincalume shed or patio roof is fine. What you need to avoid is water running onto either one from copper or lead, and direct contact with wet treated timber or fresh concrete.
How long does a Colorbond roof last near the beach?
A well installed Colorbond roof can last for decades, but salt air shortens the life of any metal roof, and exposure varies a lot from one street to the next. Choosing the right grade for your distance from the surf, fixing incompatible flashings and rinsing the sheltered areas the rain does not reach all help it go the distance.
What is the cheapest roofing material in Australia?
Of the options for a house roof, unpainted metal like Zincalume is usually the cheapest to supply. The cheapest material is not always the cheapest roof over its life, though. On the coast, a finish that holds up better against salt can save you money in repairs and an earlier replacement.
What is the best roofing material in Australia?
There is no single best. Metal and tile are the two main choices here, and each suits different homes, budgets and looks. Close to the water, the right grade of metal or a well maintained tile roof will both do the job when they are installed properly.
Get the choice right before the sheets go up
Roofing Shellharbour is led by Ryan Bruce, who has more than 10 years of experience on tile and metal roofs. If you are weighing up a new metal roof, we will look at your site, explain which finish and grade suits it and give you a free quote. Learn more about our metal roofing work or call us on (02) 4215 8188.
