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How to install timber fence on concrete sleeper retaining wall?

Hi Team!

I'm looking to put a Timber fence on top of a concrete sleeper retaining wall. I understand using brackets like the photo at the bottom is the go, but I'm wondering from an aesthetic point of view, would it be ok to cut a slot in the base of the timber upright, and mount the post over the steel upright, so the steel upright is not visible? I've tried to draw what I'm looking at doing on the right.

Would there be a drawback to this, or a reason to not do it that way?? (Obviously the slot in the timber fence would only be enough for the steel upright. My drawing skills just make it look like it's 2 inches wide 🙂 )

Thanks in advance for any advise or feedback.

Screenshot 2025-01-21 171209.png

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Comments

EricL

Hello @Decker72

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about attaching a post on your concrete sleeper retaining wall.

If we are just talking about aesthetics, then it would look best with the steel in the center of the timber post.

However, I suggest engaging the services of a local builder who is familiar with concrete sleepers and foundation installations. The builder should be able to tell if your concrete retaining wall will be able to carry the fence you are about to install over it. If the foundation of your concrete sleepers is not deep enough the fence installed above it will cause it to lean forwards or backwards.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

Nailbag

Hi @Decker72

Though aesthetically the centre mounted bracket in the post may look better, it will definitely be the structural weaker option. Over time the slotted cut out will come back to haunt you by splitting up through the middle as the fence moves with the weather etc.

But all that aside, I would definitely follow @EricL recommendation to find out if in fact the wall you have can handle a fence being secured to it and if so what will be the requirements. A registered builder or probably a local engineer would be best to contact.

Nailbag

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/47730#Comment_47730

Good Evening @Decker72

I like the look of the fence attached at the top of the retaining wall posts, it looks professional but and its a big but, I have concerns about the long term effect of having the fence attached like that if it hasnt been factored into the depeth of the posts/foundations.

I agree with both @EricL and @Nailbag at getting some advice on if its structually sound to install the fence like so.

If you decide to go for the fence then I would also go for a solid post with bolts through it over no slit for long term lasting. I think it would be easier down the track to change if needed that way.

Dave

Decker72

https://www.workshop.bunnings.com.au/discussion/comment/47730#Comment_47730

Thanks @EricL, @Nailbag and @Dave-1. Appreciate your feedback and advice.

Makes sense to avoid centering the post if it's going to lead to splitting down the track. On the side it is 👍

As for the post depth, we will actually be building the wall as well, so will be able to ensure we make the posts deep enough to support both the wall and the fence. The wall will vary between only 1-3 sleepers high so we shouldn't have too much trouble getting the holes down to a good depth.

I'll start doing some homework about appropriate depths and then over engineer it 😊

Again, thanks for your help 👍

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/85904#Comment_85904

Hi @Decker72

It was only a few months ago that a neighbour wanted me to reinforce her fence that was leaning because the posts were installed in to split style brackets. 7/10 were rotting and split causing the issue. That aside thew rest of the fence was extremely well built and in good condition. But only 5yrs old.

Fence posts need to be a min1/3rd the height of the post. So, an 1800mm post will need to be 600mm in the ground.

Nailbag

Decker72

https://www.workshop.bunnings.com.au/discussion/comment/108232#Comment_108232

Thanks Nailbag,

Think we are a bit variable on some of these. The wall goes from between 200mm high to 600mm high, and the fence on top of the wall will only be 1200mm high.

I'm thinking it would probably make sense to say each post hole will be the same as the wall height at that point (same in the ground as out) and then add 1/2 of our fence height (600mm). So where the wall is 200mm high with a 1.2m high fence, the post will be 800mm deep. Where the wall is 600mm high with a 1.2m high fence, the hole will be 1.2m deep. It may be overkill, but it should be solid at those depths.

Brett.

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