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How to install fence extension? - Colorbond fence with exposed post and rail

Hi team!

I am after some advice on how to attach a 600mm timber fence extension to my colorbond fence which has exposed posts and rails on my side. The neighbour is about to remove the yukkas (good luck!!😂) so the extension will provide privacy. The landscaping is a work in progress, it will be a while before screening plants are doing their job.

All of the resources I have found so far only seem to discuss extensions for the ‘good neighbour’ type of colorbond fences or timber fences. I considered prefab timber extensions, but they have legs for both sides of a timber fence and would need to be modified to make them work - so thinking I would be better off just making a DIY slat version? I’m thinking along the lines of horizontal slats attached to vertical timber battens which would be tek screwed to the fence posts, with longer vertical battens mid way between the posts attached to top and bottom rails for extra support (not pretty, but plants will eventually hide the fence) .

I would be grateful for the brains trust’s thoughts on materials and fixings - or any other suggested solutions. Cheers!

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Comments

JacobZ

Hi @HandyishChick,

Welcome to the Bunnings Workshop community, it is fantastic to have you with us.

I think the idea of constructing your own slatted screen is a great idea and would be a fun project.

I'd be using 70x35 H3 framing as your vertical supports, and where possible, bolting it rather than screwing it. You'd likely struggle to do this on the midposts because of how the rails sit against the colorbond, but on the pieces attached to the metal posts, you should be able to. Using a bolt rather than a screw will give you a better transfer of load from the timber to the posts, so where possible, it is definitely worth it.

I'm guessing your posts are either 50x50mm or 60x60mm, so you'd need to use a bolt long enough to pass through the timber and the post. Depending on how you orient the timber and the size of the post, this could be either a 120mm or a 150mm bolt. Galvanised cup head bolts would be the way to go. Again, the orientation of the timber will change the length of the screw, but galvanised hex head metal screws would be the way to go.

Once you have your uprights in place, I'd use either 42 x 19mm Merbau Screening or 42 x 42mm Merbau Screening, or even a combination of the two for your horizontal battens. You could screw these to the framing using screws like these 50mm Galvanised Countersunk Rib Head Timber Screws.

I'd also paint the pine framing, so it closely resembles the colour of the merbau. For this, I'd use a quality exterior paint like Wattyl Solagard or Dulux Weathershield.

Allow me to tag our helpful members @Nailbag, @Dave-1 and @AlanM52 to see what ideas they have.

Let me know if you have any further questions.

Jacob

Dave-1

Good Afternoon @HandyishChick

I am always a little hesitant about adding weight to the top of an existing fence, mostly because the posts that carry the load are installed correctly for the existing load of the fence, raising it height brings a bunch of other factors into it.

As a work around you could install some new timber posts half way between the steel ones (no issues with compromnising the footings) and then you could install the extra 600mm height you want with no issues. You could then stay with the slats that you want.

I had the same issue with my fence, the old neighbours rmoved their bushes and bingo the area was nice and open 🙂 So I am going down the route of seperate post sto extend the height of my privacy screen.

02 20-03-2025.jpg

Existing fence

03 20-03-2025.jpg

New fence, have modified it mostly due to cost. And am only going to install horizontal slats the top 600mm ish with a narrow bench halfway up.

04 20-03-2025.jpg

I have minimal space to install footings, you have the space accesable so it should be easy to install some new posts next to your rails.

Dave

AlanM52

Hi @HandyishChick,

I am with @Dave-1 for a independent freestanding fence.

Rather than build another complete fence I and suggesting the fence trellis idea that you mentioned.

Timber Version

Mahogany Hardwood Lattice Panel.jpg

Turned on its side.

Plastic Version

Plastic Lattice Fence Extension.jpg

Choose your preferred design from the available choices.

Spray paint to match fence.

Cheers

Nailbag

Hi @HandyishChick

I guess the first thing that comes to mind is the significant weight you would be adding to a fence system not specifically designed to carry that additional weight. Plus the stress of the footings from high-winds against essentially thin posts albeit I assume are correctly concreted into the ground. Plus the flex on the fence sheets themselves. With all these concerns I am talking about the long term impact of the combined weight of very heavy timbers that will impact the integrity of the fence over time. If I was the neighbour I wouldn't permit the structure to our shared fence.

Sorry to sound so negative, but I see the results of just vines growing on fences which their weight alone eventually pull fences over. So, my advice would be to look for the lightest solution possible or build something free-string in front of the existing fence.

You could still consider one of the many light-weight fence topper pattens that you could spray paint to match. Replace the support legs on both sides with lightweight 25mm square aluminium tubing to just one side. The legs are easily pried off which is something I have done many times when cutting the panels to a custom length. Then use stainless or galvanised nuts, bolts and washers to secure them neatly on your site with the heads of the bolts on the neighbours with their permission of course.

Nailbag

AlanM52

https://www.workshop.bunnings.com.au/discussion/comment/59525#Comment_59525

CC: @HandyishChick

No need for words.

Cheers

HandyishChick

Thanks all for your ideas - plenty to consider here - maybe I’ll

just whack blinds on the verandah 😊

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