Colorbond Fencing

Colorbond® fencing has become very popular for many reasons. It is low maintenance and comes in a wide range of colours and styles. Best of all, it is not affected by termites.

We believe that the most important thing to check when buying steel fencing is that it is a genuine Colorbond® product. That means it comes from BlueScope Steel (once part of BHP) so it has the best chance of being totally Australian made. The Colorbond® process uses zinc and aluminium coatings onto which the paint is baked. This process is generally regarded as far superior to simply painting galvanised steel.

For the purposes of this article (as in real life) we will refer to all roll-formed steel fencing as “Colorbond®”, even though some brands use cheaper imported alternatives.

Erecting a fence near – or on top of – a retaining wall has its own special set of problems

Structure & form

In its most basic form, Colorbond® fencing usually consists of vertical sections sometimes called ‘C-Posts’, horizontal sections called rails, and sheeting called infills. The rails slide inside the C-Posts, and the infills slide inside the rails. The rails are then screwed to the C-Posts in each corner.

When turning corners, a square steel post is usually added. These may also be added for high-wind situations to supplement the strength of the C-Posts. They are also required on both sides of any gates (sometimes called hinge post and latch post). The post size is dependant on how big and heavy the gates are. Where a fence is to be erected over a concrete slab, a ‘flange post’ will be required between every panel. This allows the post to be bolted to the slab rather than requiring a hole to be dug.

Infills come in several different ‘profiles’ including sawtooth (or zig-zag), trimdeck (originally a roofing sheet profile) and corrugated. There are also several proprietary profiles specific to particular manufacturers. And of course one of the main attractions of Colorbond® fencing is the range of colours that it comes in.

But Colorbond fencing is not as forgiving as traditional timber fencing. Accuracy is critical during design and construction.

Unusual situations

Colorbond® fences can be sculpted around obstacles and made to fit in most situations. It can be more challenging than with a timber fence, and may require a little ingenuity.

Sometimes thinking outside the box is required – we used hidden tabs and rivets to hold this one together

Occasionally, some comedian will want to put a fence in a really difficult location, like on the edge of a concrete slab.

Mounting a support post half-on and half-off a concrete slab requires some fabrication and forethought.

Curving a Colorbond® fence can be tricky and requires a slightly different technique to a straight fence. You can use a round steel post between panels, but it is also possible to provide an angle between panels by screwing the ‘C-Posts’ together down one side instead of in the middle.

As close as you can get to a curved Colorbond® fence – this one nearly sent us around the bend

These days there are plenty of options to dress up a Colorbond® fence. You can choose contrasting colours for framing and infills, or add lattice or slats along the top for airflow, among many others.

Fancy top panels on a sloping site will usually dictate a stepped, rather than raked, top profile.

Stepped or raked?

There is also the age-old question – stepped or raked? With a stepped profile, each panel is square and horizontal. As the fence progresses up or down a slope, ‘steps’ are used to maintain minimal ground clearance. The advantage of this type is that infill sheets won’t need to be cut to follow ground contours. But the disadvantages are many, including uneven ground clearance, reduced post footing depth and a somewhat amateur-looking result. Further, it can be more challenging to get the levels correct between panels during construction.

Sometimes you just have to step a Colorbond® fence – like when someone else has already done the other two boundaries and you need to match them.

Hence we usually recommend a ‘raked’ profile. This usually involves cutting the tops and bottoms of infill sheets to match the ground slope. It takes a little more time but the end result is much more pleasing to the eye. However, sometimes a stepped profile is required such as when a lattice or slat top panel is used, or there is an unusual ground feature to negotiate. Various combinations of rake and step can also be used.

A steeply raked fence can send you over the edge if you don’t know what you are doing

For steeper sites

Sometimes a steeply raked profile is required. This has its own set of problems to deal with. Sure, you will need one leg longer than the other to stand up while digging holes. But steep raking means that a great deal of thought and planning needs to go into the design and execution of the job.

For example, the angle of fall needs to be measured fairly accurately, and post-tops, rail ends and infill sheets cut to match this. There are several ways to do this including phone apps, string lines and bevel gauges, and builder’s levels with angle measuring capabilities.

You will need to start with much longer infill sheets than for a level fence, as you will be cutting large amounts of the top and bottom of these to form the shape required. Also when digging post holes, remember that a 2400 rail running down a slope will not reach the same horizontal distance as it would when on level ground. Once you know the angle of the slope, you can use a scale drawing (or trigonometry, if your are that clever) to work out the sizes you will need.


Occasionally the ‘rake’ angle changes in the middle of the fence – this requires a special type of string for the string line 🙂

Special Cases

We have even been called upon to create a Colorbond® fence that would allow floodwater to escape without damaging the fence. The solution was to provide a small section at the bottom of the fence separate to the main fence. That section could be easily removed if someone was around at the time. If nobody was around, the section would easily be pushed out by the water without harm to the rest of the fence. This was achieved by ‘slotting’ the infill sheets so they would more easily buckle under pressure, rather than pushing the whole fence over. The size of the lower section was determined using local historical rainfall data and catchment area. Using this we could predict the worst-case scenario for surface water build-up.

The bottom section of this fence can either be removed manually without tools or the infills will collapse under the weight of excessive flood water

Finally, a timber plinth can be used where the levels on each side of the fence are different. This may be used to retain gardens or to provide a solid edge for the whipper-snipper. It is also useful for preventing grass and weeds growing into (or out of) neighbouring properties. This is handy when your neighbours only mow their lawns once a year – whether they need it or not!

A timber plinth or integrated retaining wall is often a great solution – most 50mm sleepers fit neatly inside Colorbond ‘C-Posts’ (depending on the brand).

When things go wrong

Lots of things can go wrong with fencing – even when licenced ‘experts’ have done the job. Below is the before photo of a job where the fence started to lean badly after a couple of years. There were so many mistakes made during construction that it was quite comical. Except for the poor owner who had to pay to get it fixed because no-one could find the original contractors.

Firstly the fence was too high after the timber plinth/retaining wall was added underneath. It was just over the legal maximum height of 2 metres (without council approval). But the original builders had only used standard 2400 posts. With 1800 fence height plus up to 300 plinth height, that didn’t leave too much post in the ground. The usual minimum in-ground depth is 600, so they were up to 300 short, or half the required minimum depth. Then they had compounded the problem by ‘loading up’ the posts by backfilling behind the plinth with dirt and gravel.

The guys who put this fence up must have been from Pisa – or on the piss

Worse, in a couple of holes, they had forgotten to add the cement to the concrete blend (sand and gravel), so the mix never set. That made our job easy when removing the old posts. There were many other problems including nowhere near enough screws holding the various components together.

Lucky this time around

This job was a disaster waiting to happen, and they were lucky it did not collapse at the wrong time. In a storm it could do some real damage. In strong winds, flying fence infill sheets can act like a guillotine and cause catastrophic damage to life and property .

This clearly underlines the need to only use fencing contractors who have a proven track record and good reputation. Unfortunately, a licence does not guarantee either of these things.

The footing on the left was no longer than my boot, and I am not a clown with large feet. On the right is the finished repair.

One final stuff-up

Finally, here is another fence that was not built correctly, although the error was relatively minor. During a storm, several of the infill sheets blew out of the frame. Luckily they did not hit anything (or anyone) else or the damage could have been nasty. In fact, as luck would have it, all the old sheets were able to be refitted back into the fence.

Poor initial construction can make a fence quite dangerous when the wind blows

The problem was that the top and bottom rails were too far apart, and the infill sheets were not tightly supported in the frame. You can see from the inset photo above how much the top rail was able to slide down once we reassembled the panels. The simple solution (which should have been done in the first place) was to screw in the top rail level with the top line of the fence. Then we lifted the bottom rail and infill sheets until they were tight. Finally we re-screwed the bottom rail in the higher position.

2 thoughts on “Colorbond Fencing

  1. It’s great to know that Colorbond fencing offers a wide range of colors and styles. Since I’m planning to put up some fence around the house for privacy and security purposes, I’m glad that I came across this option while looking for materials. I like that you mentioned that this type does not require much maintenance. I guess I shall then find a manufacturer that offers installation services.

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