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Heritage Galvanised Roof Replacement Options

Heritage Galvanised Roofing: Z600 & Replacement Options

Owning a heritage home is literally living in a piece of history. Nothing compares to it! However, maintaining that old-fashioned architecture and aesthetic can be a real challenge. Unlike a traditional home, you can’t just call up the first company that pops up on Google.

Especially when it comes to replacing heritage galvanised roofing, you need a professional who doesn’t just know how to install the roof, but also has the expertise necessary to preserve as much of the existing structure and aesthetics as possible.

In this post, Vivify Roofing wants to share some of that expertise with you. If you know that your heritage metal roof needs restoration, you may have heard of lots of different options available. Z600, Zincalume, COLORBOND and more—but what’s the difference and what is best for you?

Read on and we’ll help answer your toughest questions about heritage galvanised roof replacement.




Heritage Galvanised Roofing Z600 Replacement Options 1


What is Z600 galvanised steel?

Z600 galvanised steel is steel that has been coated in a layer of zinc. It is an ideal roofing material because the zinc coating provides added protection (specifically against rust) and increases the lifespan of the roof.

Z600 is the best choice for replacing heritage metal roofs because it provides an authentic historical look with modern durability and performance. Metal roofs and walls started gaining popularity in Australia as early as the 1800s. The roof sheets were actually imported from England.

Back then, the base material was iron, not steel, and the 100% zinc coating was “hot dipped”, which led to a pretty uneven coat and poor performance (compared to modern standards). Luckily for heritage homeowners, methods and materials have evolved over the years. Z600 galvanised steel allows you to maintain your home’s historical aesthetic without suffering through leaky roofs and premature rusting.


Heritage Galvanised Roofing Z600 Replacement and Options 2


Galvanized steel is widely used in applications where corrosion resistance is needed without the cost of stainless steel, and is considered superior in terms of cost and life-cycle. – Wikipedia


How thick is Z600 coating?

The Z in the name stands for zinc, but what about the 600? That number actually indicates the number of grams per square metre. A higher number, therefore, indicates a thicker coating. In fact, heritage gal roofs are also available in Z275 and Z450. So Z600 is the thickest available option, coming in at 600 grams of zinc coating per square metre.

What does the difference in thickness mean to you, the homeowner? Well, when it comes to heritage steel roofing, the thicker the better. If you look at roofs that were made in the early 1900s, they mostly used the “double thick” Z600. The lighter options were introduced later (mostly to save money), but they proved to be more susceptible to rusting. While the thinner coatings do have their applications, they aren’t ideal for heritage roofs.



Heritage Galvanised Roofing Z600 Replacement and Options and explanation


How long do galvanised roof sheets last?

The answer all comes down to the thickness. As you may have guessed, thicker coatings make the roof last longer. This is because the zinc helps protect the steel underneath from corrosion and rust.

Z600 can last about 50 years, whereas Z275 has a lifetime closer to 30 years. These numbers assume that the roof is regularly and professionally maintained. There are a few other factors that might affect your expected metal roof lifespan:

  • Moist environments, such as those near the ocean, are harsher on the zinc. As the coating begins to wear away, a steel roof exposed to humidity is more likely to start rusting.
  • Fallen branches can scratch your coating, and gathering debris can promote unwanted growth. Both issues can be caught and prevented with routine inspection.
  • Zinc coated roofs are best in residential areas. The air in industrial zones is often filled with caustic particulates that can reduce the expected lifetime of your coating.


Heritage Galvanised Roofing Z600 Replacement and Options and explanation 2


How long does a galvanised iron roof last?

Iron roofs are actually a bit of a misnomer, at least today. When galvanised roofs were first introduced, they were often made of iron. However, modern roofs are made of steel.

It’s sort of like how we still talk about tin roofs. This is leftover language from when tin was a common roofing material. If your neighbor is talking about getting a tile to tin roof conversion, for example, they are actually referring to getting a new steel roof to replace their tile one.


Z600 Galvanised Steel Melbourne


You can make changes to your heritage property to improve, update or renovate it. You just need approval from Heritage Victoria fist. –


What is the difference between heritage galvanised and Zincalume?

Another modern evolution of metal roofing was the invention of Zincalume in the 60s. Zincalume is a metal roof coating consisting of about 43.5% zinc and 55% aluminum. This is compared to standard heritage galvanised steel roof coating, which is 100% zinc.

Zincalume is praised for applications in heritage roofing because it has a longer lifetime than traditional zinc roofs. In tests, Zincalume steel stands up to corrosion for about four times longer than galvanised steel.

This is, of course, due to the addition of aluminum. While zinc resists corrosion, aluminum slows its spread. So if a Zincalume roof gets a scratch that exposes the steel to humidity, it might rust just as fast as a traditional zinc roof. However, the rust won’t spread as quickly or as far.


Z600 Galvanised Steel Melbourne 2


COLORBOND vs Zincalume

There is some confusion between COLORBOND and Zincalume, and this probably arises from the fact that they are both manufactured by the same company: BlueScope Steel. BlueScope is an Australian-based business that specialises in durable, high quality steel products, such as roofing and gutters.

The confusion is further compounded by the fact that these two products are very similar. Both consist of a solid steel base, and COLORBOND roofing is actually coated in the same zinc/aluminum protective coating that Zincalume relies on. The main difference is that COLORBOND relies on unique 5 layer protection technology, which makes it a bit more resistant to scratches and other damage. Furthermore, COLORBOND comes in a wide range of colours, while Zincalume is only available in one. However, when it comes to heritage homes, restrictions on colour choice may make it a moot point anyway.



Colorbond vs Zincalume Heritage Roofs


What if you want 100% zinc roof coating?

There is actually only one company in Australia that still produces 100% double thickness Z600 roofing from BlueScope Steel: Fielders. Although the process and materials may have changed a bit over the century (or two) since the original roof was constructed, Fielders’ heritage gal is going to be the closest that most homeowners can get to authentic heritage roofing.

The good news is that even though Zincalume is more durable, a 100% zinc roof is still pretty darn long lasting. As we mentioned earlier, lighter weight coatings will have shorter lifespans, but Z600 should last you around 50 years.


100% Zinc Roof Coating


For a deeper, bolder look CorroMax 35® has the added benefits of an even greater rainwater carrying capacity and added strength, making it the perfect choice for heritage, residential and commercial projects alike. – Fielders


4 Challenges of Heritage Roof Replacement

Now that you have a better understanding of your options when it comes to heritage roof replacement, here are a few of the challenges you should be aware of:

Construction Standards

While the basics of roof construction might not have changed much over the centuries, technology certainly has evolved. For this reason, hiring a roofer who is only experienced with modern roofs may be a cause for concern. Someone who is skilled with heritage roof restoration and gutter repair will be able to remove the old roofing and restore it without damaging the original construction—all while still maintaining modern safety standards.


Speaking of older construction standards, one of the biggest problems with historical roofing was insulation. Technology has just advanced so much that heritage homes can benefit a lot from using newer methods to make up for old problems. We often recommend the addition of blanket insulation during heritage roof replacement. It can drastically reduce energy bills and improve interior comfort. Plus, since you’ve already got the roof opened up, it’s the perfect time to make the upgrade.


Challenges of Heritage Roof Replacement

Local Regulations

If your house has been designated as a heritage home, there are probably regional guidelines that dictate how repairs or restorations need to be conducted. They might dictate rules about materials, colour and style, for example. This is to ensure that the historical nature of the area is preserved. A qualified heritage roofer will be aware of the regulations in your region and be equipped to work within them.


One of the reasons that you (and your neighbors) bought a heritage home is for the old-fashioned architectural aesthetics of bygone times. The last thing you want is to “modernize” your home during repairs. A professional heritage roofer will focus on restoring the roof in a manner that looks as close to the original as possible. This is one reason to choose Z600, since it is the closest roofing option to the original galvanised iron of the 1800s.


Challenges of Heritage Roof Replacement 2


Trust Vivify Roofing with your heritage roof replacement!

Vivify Roofing has been repairing, restoring and replacing the roofs of Melbourne for over 15 years. We are well-versed in the complexity of heritage roof work and equipped to install galvanised Z600, COLORBOND, Zincalume or any other heritage roof material you might require.

Entrust your heritage roof to a professional who can give it the tender loving care it deserves. Entrust it to Vivify!

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