using dividing brick fence as back wall of a slightly raised landscape

[rita4u]

There is a flat ground level landscape area in the front yard.  The shape is like a quarter of a cake with 2 straight lines and a curve line. 

One straight line is along the front fence.  Another straight line is along the dividing fence.  The cured line side is along pathway and on the same ground level.  I can walk freely on the landscape area to plant trees and water plants.

The landscape area is about 28 square meters in size with approx 10 meters adjacent the dividing fence.  

I intend to add more soil which will raise the landscape area by about 20 - 30 cm in height above the natural ground.  I will lay some landscape bricks along the curve line side so the soil will not spread to pathway.  I will also be able to walk on the landscape to water the trees and plants.

The dividing fence is made of brick and in good condition.  

Questions:

1. Can I pour soil directly and use the brick dividing fence as back wall for the slightly raised landscape area?

2. Do I need to build a retaining wall to protect the dividing fence? 

3. Is there a limit on how high a landscape area can be raised without needing to build a retaining wall?  

Thanks in advance for advice.

[MitchellMc]

Welcome to the Bunnings Workshop community @rita4u. It's fabulous to have you join us, and many thanks for your question about creating a raised garden bed.

You can generally use a brick dividing fence as the “back” of a slightly raised garden bed, but there are a few considerations to make sure you don’t cause problems for the fence or the soil structure. For a 20–30 cm rise, most well-built brick fences can handle the pressure without a formal retaining wall, so in your case, a separate wall isn’t strictly necessary. Brick fences are usually designed to resist lateral loads like soil, especially over short heights, and 20–30 cm is quite modest.

That said, you should avoid piling soil directly against the fence without some protection, because constant moisture from the soil can cause efflorescence, spalling, or, over time, mortar deterioration. To prevent this, it’s a good idea to add a moisture barrier, such as heavy-duty plastic sheeting, between the soil and the brick. This keeps the fence drier while still allowing drainage. Make sure the barrier doesn’t trap water against the brick; you want it to direct water down and away.

There isn’t a hard “maximum height” for raising a landscape before needing a retaining wall, but as a rule of thumb, anything over about 30–40 cm starts to create significant lateral pressure that could move or damage adjacent structures. Once you go above that, it’s safer to build a small retaining wall or use timber/stone edging along the fence line for support.

For your layout, raising 20–30 cm with a gentle slope away from the fence and containing the curved edge with your landscape bricks should be perfectly fine. Make sure the soil is well-compacted in layers, and keep heavier planting slightly back from the fence to reduce pressure on it.

Please let me know if you have any questions.

Mitchell
 

[rita4u]

Hi Mitchell,

Thank you very much for your prompt reply.

Really appreciate your advice.

Thumbs up!