How to build a fence on a retaining wall?

[mitchcasey]

Hey everyone! I've purchased a prefab steel rapidfence from Bunnings and am wanting to install it just behind the edge of this retaining wall. The posts require a 200mm diameter hole, can anyone tell me how far from the edge these holes need to be.

The wall has timber sleepers and the soil is on thr softer side.

Thanks!

 

[EricL]

Hello @mitchcasey 

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

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.

Local councils often have specific rules around this, particularly if the wall is over 600mm high for example or the fence adds structural pressure. While it’s absolutely possible that some simple installations can be DIY-friendly, in this case it would be best to check in with your local council or planning authority to understand what applies to your property. If in doubt, consulting a professional fencing installer or structural professional will ensure everything is done safely and within the right guidelines.

If you need further assistance, please let us know.

Eric

[mitchcasey]

Thanks so much for the insight, Eric! Our other option was to build a farm style post and rail fence with mesh wiring on top of the timber sleeper directly. I'm guessing your answer to this question would be the same as your answer to the last question?

Thanks 

 

[JacobZ]

Hi @mitchcasey,

The main point I think @EricL was trying to get across is that any additions to a retaining wall have implications on the structure. Considering your retaining wall appears to back onto a council stormwater channel and looks to be around 1m high, which is often the height limit where engineering plans and council approval are required, it is best that any alterations, regardless of how minor they may be, should be checked with your local council. 

If you were building a fence on top of the retaining wall, a wire fence would be a good option because it would allow wind to pass through it, meaning there would be much less of a wind load on the structure and therefore much less force transferred into the retaining wall.

Ultimately, I don't think you would have too many issues if you concreted in some posts as long as they were at least around 900mm behind the retaining wall, but it should still be checked with your local council to ensure you are in line with their regulations.

Let me know if you have any further questions.

Jacob