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Hello @Zdenka
Welcome to the Bunnings workshop community. It's sensational to have you join us, and thanks for sharing your question about your Colorbond fence.
Yes, you can attach two lines of horizontal framing support to the fence posts and screw the panels on to the timber pieces. I suggest looking at the 70 x 35mm Outdoor Framing H3 Treated Pine - 2.4m as it will not be too heavy and will still be able to support the SpecRite 1800 x 902mm Pre-Oiled Merbau Alternating Slat Fence Panel. For the horizontal timber I suggest using the Zenith 10G x 40mm Galvanised Self Embedding Head Metal Screws Winged. Please note, since you are mounting timber to a Colorbond fence it's important that it be fixed onto the posts and top and bottom rails and not the fencing sheets as the screws will pose a hazard to those on the other side of the fence.
I suggest using the Zenith 8 - 10 x 60mm Galvanised Countersunk Rib Head Timber Screws for the Merbau panels. My best advice is to drill pilot holes for all the screws to prevent splitting the timber of the Merbau panels.
If you need further assistance, please let us know.
Eric
Can I please ask one more question. If we attach the horizontal support to the top, screwing it into to the vertical posts, it will create a small gap between the fence top and the wooden support due to the ridges (as in the photo attached). Do you think we need to attach it to the top as well and get longer screws (the danger of the fence flexing), or putting some washers between the fence and the wood? Or is it enough to attach it to the vertical posts only (2.4 m apart)? Thank you for your advice.
Hello @Zdenka
I propose rebating the ends of the timber so that it will sit snugly on the surface of the fence rail. It can easily be done with a hand saw and you won't have to bother with washers or spacers. I've placed a sample image below to give you an idea of what you'll need to do. It would be better to attach the support piece along the length of the fence as the Merbau panel does have a bit of weight to it.
If you need further assistance, please let us know.
Eric
Welcome to the Bunnings Workshop community @Bren2. It's terrific to have you join us, and many thanks for your question about installing a panel on a Colorbond fence.
You might like to jump up in size to 90 x 35mm timbers instead of the 70 x 35mm if you can't fix to the rails. The larger calibre timber will be more capable of spanning the gap between posts.
Please let me know if you have any questions.
Mitchell
Colorbond fences are designed and engineered to support their own weight and, in some cases, a small extension made from lightweight Colorbond material on top @Bren2. However, they are not built to carry additional loads such as timber panels attached to one side. Depending on the specific SpecRite panel you’re using, each one can weigh up to around 20 kilograms, so attaching five of them could add about 100 kilograms of extra weight to the fence.
If the fence posts were installed with slightly undersized footings, that additional weight could cause the fence to shift or lean under wind load, especially during strong gusts. For that reason, it’s generally not recommended to attach heavy panels directly to a Colorbond fence.
The safer option would be to build a freestanding frame that extends along the fence line, with posts anchored into the ground to bear the load of the panels. That way, the frame carries the weight rather than the fence.
It’s difficult to say exactly how much weight your specific fence can handle without knowing the size and depth of the footings, but if you were to check with Colorbond, they would likely confirm that their fences aren’t designed to support any extra weight attached to them. However, we have seen several members successfully use them to hang panels.
Please let me know if you have any questions.
Mitchell
