How to build raised garden bed on top of artificial turf?

pikesh

Hi Team, I have an existing artificial turf with pebbles alongside the walls. I want to create a raised garden bed alongside the wall by removing the pebbles and adding retaining wall blocks. Is it okay to put the wall blocks on top of the existing turf?

Or do I have to cut the turf and make sure to put the wall blocks on the soil?

Also should I consider anything for drainage solution? Or the water will just get soaked by soil?

Please see the images attached.

MitchellMc

Hi @pikesh,

For any type of block retaining wall, it’s really important to start with a properly compacted base. Leaving the artificial grass in place would make it very hard to achieve the kind of firm, stable footing you need for the blocks to stay put over time. I’d recommend removing the turf underneath where the blocks will go, digging down a little, and compacting the soil properly before you start building.

The other thing to bear in mind is that depending on how high you want this raised garden bed to be, blocks might not be the best solution. For a small raised bed, simple stackable garden blocks might be fine, but if you're planning to go higher or hold back a lot of soil, you'd generally want the blocks to be laid on a concrete footing for stability. You might also need to install some reo-bar (reinforcing steel) through the blocks and into the footing to strengthen the wall and prevent movement over time. Unlike sleeper-style raised beds, block walls don't have corner posts or frames to help hold them together, so it's the base and the way the blocks interlock that give them their strength.

As for drainage, it’s definitely something to plan for. Even though garden soil does soak up some water, when you’re building against a solid wall and using blocks, you’ll want to make sure excess water can escape properly. Usually, this is managed by adding drainage gravel behind the wall and a drainage pipe (ag pipe) at the base that can direct water away. Without it, you can end up with soggy soil or pressure building up behind the wall.

It would be helpful to know what type of blocks you're thinking of using, and how high you’re planning to build, as that will really determine how much prep work is needed.

Please let me know if you have any questions.

Mitchell