How to fix fenceline kickboard and retaining wall drainage?

Thanks for you help. The reserve next to my property is very wet during winter and ponds water in this area. Some run off is pushed towards my fence line. Down the back of property had issues with water channeling along brick of the house . ive graded it to fall to the fence instead.

I want to put like a kick board/ retaining wall on my side it will only raise the lawn by 100mm in the corner and will run drainage and plumb back into the storm water line.

Areas i have concerns.

1/ the kickboard/retaining wall cliose to the fence and notced around the posts where below the surface.

2/ back filling up to the kickbosard/retaining timber on the reserve side and my side ?

Any advice be greart thanks

Screenshot 2025-08-27 at 12.07.34 AM.png Screenshot 2025-08-27 at 12.04.12 AM.png Screenshot 2025-08-27 at 12.03.18 AM.png Screenshot 2025-08-27 at 1.28.30 AM.png

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Comments

MitchellMc

Welcome to the Bunnings Workshop community @Milliermatics. It's wonderful to have you join us, and many thanks for your question about retaining walls.

Your plan overall sounds quite reasonable, especially grading the yard to fall away from the house and installing proper drainage into your stormwater line. I can’t see any major issues with where you’re proposing to place the kickboard/retaining wall on your side of the fence or with backfilling against it on your own property. However, you likely won’t be able to backfill on the reserve side, both because it’s not your land and because there’s generally no need to – the retaining element is only there to support the extra 100mm of soil you’re adding on your side.

Could you tell us a little more about how the board will be notched around the posts and what your concerns are there? It appears that additional posts will be installed for the board. Bear in mind that if you are retaining soil, you need to build a retaining wall that is self-supported with its own posts. You can't use the plinth board of the fence to retain soil.

Please let me know if you have any questions.

Mitchell

Milliermatics

https://www.workshop.bunnings.com.au/discussion/comment/56399#Comment_56399

Thanks so much for replying.

you are correct i will be usin a 200x50 H4 board. I only needing to notch about an inch off the bottom off the board where the concrete are for the existing fence posts as it sits on top. its aboout an inch from the timber fence post and supported by the retaining wall 75x100 posts ive concreted in.

My concern is how i should run the drainage along there and back fill.

Having the perforated pipe running along there i dont want it to compromise the soil around the fence posts.

- Once my retaining board is in should i compact fill either side and re trench my french drain say 400mm inside that or

- Seal up sideof the 200x50 with polythene, Lay my geofabric and run my pipe along the board or

-I could use solid pipe along there and perfortated pipe coming off there into the lawn

*In my origional first post the thick red lines are so show where water is currently pooling/flooding

posts

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/90481#Comment_90481

I'd fix the board in position and then dig a 100mm-wide trench directly in front of it on your side of the fence, at least 500mm deep, @Milliermatics. You can line it with geo fabric, drop in the slotted agline, and backfill with drainage gravel up to 100mm below the surface. Finish off with soil for the last 100mm.

Adding drainage up against the retaining wall will not compromise its integrity and is the most common approach. This will work well, especially if water also passes through the retaining wall from the other side.

Mitchell

Milliermatics

https://www.workshop.bunnings.com.au/discussion/comment/111133#Comment_111133

digging the trench that close will expose the fence posts (concrete). The 200x50 board will only be max 150mm Screenshot 2025-08-27 at 3.20.26 PM.png Screenshot 2025-08-27 at 1.43.43 PM.png

digging the trench that deep and close will expose the fence posts (concrete). The 200x50 board will only be max 150mm soil level what would be the need to go 500mm deep if you dont mind me asking ? at about 400 its solid clay and i would be bto low to get enough fall to the stormwater im discharging into . Thanks for all you help

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/122964#Comment_122964

You want to have the drainage in the first immediate position after the retaining wall/board, so it captures the water transferring through @Milliermatics⁠;⁠⁠⁠⁠⁠⁠. So, taking into account the posts, position the trench directly after them. It also should be as deep as possible, which helps capture sub-surface water. There is no need to go deeper than the clay layer.

If the drain is placed close to the surface, it only captures water from the surface. Having a trench, say 300-400mm deep, helps collect all the water that is saturating the soil. Collecting that water allows room for any water sitting on the surface to seep in and be collected as well.

Mitchell

Milliermatics

https://www.workshop.bunnings.com.au/discussion/comment/130714#Comment_130714

Thanks Mitchel most appreciated !!

One last question . Where im plumbing it into it needs to angle towards the house . should this section (yellow) be solid pipe ? I read somewhere you dont want it releasing water near the house . and would you plumb into. the stormwater line with a connector or put a catch basin there where the downspout is ? Currently the Downspout pipe (80mm) goes inside a 110mm Screenshot 2025-08-28 at 9.20.18 AM.png

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/135486#Comment_135486

When transferring water @Milliermatics, you should be using solid PVC pipe or non-slotted agline. A pit at the downpipe would allow a convenient location to connect your drainage. However, remember that any connections need to be made by a plumber, and it is best to confirm with them whether a pit is required.

Mitchell

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