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Hi,
I’m planning to build a 490mm raised garden bed using 2-course 500x245x90 blocks (25kg each).
So far, I’ve compacted the Class A sandy soil and intend to add cracker dust for better stability. The bed will be 12m long and hold roughly 2m³ of soil. I’m setting the first block with 150mm of it into the trench.
Would concrete footings be necessary for this setup, or is there a way to build it securely without them?
Hi @Abhi_2691
It is always best practice to build a raised garden bed on a concrete foundation, as this provides the most stable and long-lasting base. A solid footing eliminates the risk of the wall shifting or sinking over time, particularly when it is holding a significant amount of soil as in your case. That being said, if the area has been compacted properly, you may be able to achieve a fairly stable base without going to the extent of pouring a full concrete foundation. However, it will never be quite as reliable as concrete. At the very least, I would recommend bedding your first course of blocks into a mortar mix laid over your compacted ground. This will create a semi-solid base that locks the blocks in and reduces movement. Building directly onto compacted soil alone leaves more room for settling and unevenness over time, especially with the weight of 2 cubic metres of soil pressing against the wall. A mortar bed is a good compromise if you want to avoid full concrete work, but a poured footing will always provide the strongest, most durable result.
Please let me know if you have any questions.
Mitchell
