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How to add fence frame on top of existing retaining wall?

Hey,

Currently I have an existing retaining wall sitting about 100mm from the main boundary fence. This is due to the plinths breaking and the neighbour being much higher without a retaining wall.

Regardless, we are wanting to install the Ekodeck Batten Screen Castellated Panel along this section of the fence for the length of the retaining wall. I beleive we would need some sort of frame to support this.

I currently plan to use something like the Galvenised Steel Fence Bracket or Galintel Outdoors 6mm Steel Fence Bracket. these will both attach fine to my steel posts for the retaining wall. Ideally I would want to install a Steel Posts onto the bracket and then 3 steel rails roughly 600 apart.

Question is, can these posts be attatched to these brackets. And how would you attach rails between the posts? Ideally want the rails between the posts and not accross to keep in line with existing retaining wall.

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EricL

Hello @JesseS6

Thanks for sharing your question about installing a fence frame on top of your retaining wall.

We've had a similar question asked before about installing a fence above an existing retaining wall. I suggest having a look at this discussion - How to build a fence on a retaining wall? by @mitchcasey. As mentioned in the discussion - When it comes to building a fence on or near a retaining wall, it’s important to understand that once the two structures are connected or closely interact, it’s no longer a simple standalone fence job. Attaching a fence directly to a retaining wall, or placing it right behind the wall where it might affect stability, typically requires assessment by a qualified professional. This is because the combined structure can behave differently under load, especially in softer soil or if the wall is retaining a significant height.

In regards to the rail, if you are using RHS steel, I recommend having it professionally welded to the post and then re-sprayed with galv paint to protect it from the elements. If you are using timber on the other hand, I suggest having a steel "U" bracket welded onto the posts. These brackets can be drilled through to hold the weight of the rails and panels securely.

In order to give our members a better idea of your retaining walls structure and position. Would it be possible for you to share a photo with the community? It will give us a better idea of its configuration. We can then offer recommendations on how to proceed.

If you need further assistance, please let us know.

Eric

JesseS6

@EricL attached is a phot of the retaining wall. The steel H section posts are concreted in 500mm and 600mm out.

The idea being to bolt the fence extension brackets to the steel H sections, then attach a to a fence post. I believe this is what these brackets are for.

I can use either timber or steel posts. Would doing this create any issues, given this is close to the existing fence, the forces applied to the screening would be reduced.

EricL

Hello @JesseS6

Thank you for sharing that photo of your retaining wall. The Ridgi 50 x 3mm 0.58m Galvanised Steel Fence Bracket is the right part to use when adding extension pieces to a retaining wall. However, in this instance, I'm not sure it will take the weight of the frame and panels. I don't know how deep the "H" channels have been driven to and I'm not sure how much weight the "H" channels can take. Anchoring it to the timber fence is also a question mark as it is hard to tell if the timber fence can handle the added weight of the frame and panels.

If you still wish to install it on top of the retaining wall, I propose engaging the services of a builder or an engineer to determine the best way to install your frame and panel without compromising your retaining wall or fence. One other option comes to mind and that is to install it in front of your retaining wall.

I suggest having a look at this discussion - How to install Ekodeck castellated panels onto retaining wall? by @Neil1984. They more or less had the same issue, but they eventually installed the post onto their concrete slab. It would be possible to recreate this by putting in cement footings for your post.

Let me call on our experienced members @Dave-1, @Nailbag and @Remarka6le for their recommendations.

If you need further assistance, please let us know.

Eric

Remarka6le

Hey @JesseS6,

Those galvanised extension brackets will physically bolt onto your steel H posts just fine, and yes, you can mount a post onto them. The bigger question isn’t whether it can be done, it’s whether it will be rigid enough once you’ve got the battens and wind load on there. The Ekodeck castellated panels catch more wind than people expect, so the frame needs to be very solid or you’ll get flex and movement over time.

If you do go ahead with brackets on the H posts, I’d personally lean toward steel posts rather than timber. A 50 x 50 or 65 x 65 galvanised steel post bolted through the bracket with high tensile bolts will give you far less movement than timber ever will.

One thing I’d avoid is relying on the timber boundary fence for any support. Treat this as a completely independent structure. That fence won’t be designed to take extra load and you don’t want movement transferring between the two.

If it were mine, the most bombproof option would actually be installing new steel posts in small concrete footings just inside your retaining wall line, then building the screen frame off those. That’s actually the route we went with at our place, steel posts and concrete sleepers, simply because it’s far sturdier, lasts much longer and comfortably holds more weight without any flex or long-term movement. It adds a bit more work upfront, but you end up with something that feels completely solid and maintenance free.

Nailbag

Hi @JesseS6

My concerns are 1. That the ground supporting the existing Gal posts may overtime give way to the overall weight of the feature wall. Remember, these were installed based on the current application. 2. The framework to support the feature panels will sit directly on the top of the sleepers resulting in the the panels not being supported underneath as they will sit proud of the sleepers. So, I would factor in adding more support in the plan. 3. Ensure there is no plan to using the boundary fence in anyway to support the new wall.

All that said, I agree with @Remarka6le comment in considering a fully independent structure in front of the retaining wall. This will provide a purpose built solution and is exactly how I recently helped a builder mate build a taller feature wall in front of a pretty ugly boundary fence.

Nailbag

Dave-1

Good morning @JesseS6

I am very hesitant to attach fence extension to a retaining wall. The H posts are only into the ground 500-600mm deep and doing a great job by themselves in retaining the soil behindthem. Add in a fence extension and it will change all tyhe dynamics, It will add an overally pivot weight, so a small force at the top such as wind blowing, being leaned on, stormy wet weather will be amplified and the fence/retaining wall will lean towards your yard. I agree with all the rest of the crew that a seperate fence would be a preffered option.

I am currently adding a privacy beside my fence, the fence is already high and I did not want to add potential issues to it so I am building a seperate fence next to the boundary fence. Factoring in a retaining wall as I am raising the soil level for paving (looks very similar to what you have done) That is also not connected to the posts or fence. :) Fun puzzel but I am half way through it. I just need to kick my butt to continue it.

The H frame posts also dont look strong enough for holding a fence up long term (just a feeling by looking at the thickness of the metal)

Dave

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