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Hello and thanks for providing this community portal.
I have an 18m long Colorbond fence in my front yard. I intend to plant a hedge along the fence but I have a drainage problem. We are in a low-lying suburb with wet soil and a high water table. To compound matters the neighbour over the fence has concrete surface which drains under the fence into our property creating pooling along the fence - up to 200mm deep after heavy rain.
My current plan:
- Add 200mm x 50mm sleepers along the base of the fence to keep soil from base of Colorbond to protect it from soil
- Add topsoil mix to entire area to level up to a gentle slope towards fence (it already slopes/drains that way)
- Install garden edging approx 400mm from fence to provide an area to plant in order to hide fence
- Add some additional soil to new garden bed against fence to raise new garden bed slightly (100mm?)
Drainage issue: the yard naturally slopes towards the fence and street. I can run ag pipe or possibly a french drain along the fence to transport water to outlet in gutter. My concern is root intrusion from new plants/hedge will invade any drain pipe I install.
I'm looking for any suggestions for what I can do here to allow planting new garden bed along fence without it turning into a muddy bog next time we get heavy rain.
My questions to the community please:
- If I run ag pipe directly under a garden bed with planted hedge or other plants - will it inevitably clog or is there something I do to prevent clogging with roots?
- Is it better to run ag pipe or perhaps a French drain outside the new garden bed, perhaps on the outside of the new garden edge away from the fence?
- Should I bury ag pipe along the fence directly collecting the water coming under the fence from the neighbour and create the new garden bed further away from the fence
Thanks for reading.
Welcome to the Bunnings Workshop community @philiptodd. It's brilliant to have you join us, and many thanks for your question about drainage.
Thanks so much for sharing the detailed plan and photos — it’s clear you’ve put a lot of thought into this already. The drainage and planting challenges you're facing are common in low-lying, water-retentive areas, especially where water is being pushed in from neighbouring properties.
In your situation, I think your instinct to install drainage along the fence line is spot-on. I'd suggest digging a trench directly in front of the Colorbond fence footings, around 600mm deep, and installing ag pipe at the base. Backfill the trench with coarse aggregate like blue metal to allow water to easily flow down to the ag pipe. This setup will capture water that’s entering from underneath the neighbour’s concrete slab and divert it before it can pool in your garden bed. Wrapping the ag pipe in filter fabric (or using a socked ag pipe) is highly recommended — this not only stops soil from entering the pipe but also helps to inhibit root intrusion from nearby hedge plantings.
If your yard remains boggy even without water coming from under the fence, I’d also recommend running a second ag pipe in front of your proposed garden bed, roughly where your new garden edge will be. This second line can catch any water coming from the rest of your property before it settles in the planting zone. With ag lines both behind and in front of the bed, you’ll effectively create a “dry pocket” for your plants, which is important because even moisture-tolerant hedge species can suffer from persistent root rot in saturated conditions.
Raising the soil level slightly and improving the slope toward the street is also a sound move. Just ensure the new topsoil is free-draining and that the bed itself isn’t too tightly compacted, as this could reduce the effectiveness of the drainage below. Plant selection is also key — opt for hedging species that tolerate periodic wetness, such as Callistemon, Lilly Pilly and Melaleuca.
With these layered strategies — deep trenching near the fence, ag lines both front and back, filter protection, and raised garden levels — you’ll have a far better chance of maintaining healthy soil conditions and a lush, long-lasting hedge without the risk of creating a waterlogged bog.
Please let me know if you have any questions.
Mitchell
