I am looking at using old corrugated sheets to make a raised garden bed. But looking at around 10m in length. Due to the size, what is recommended to make sure the front wall doesn't start to collapse forward due to weight of soil pushing on it? Due to raised bed going against the concrete retaining wall, I was thinking of only building bed with three sides, i.e. no back.
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Raised garden beds are certainly very popular at the moment. What kind of height were you looking at for the bed? You are right in that there's going to be a lot of force from the weight of the soil. Let me tag one of our resident garden gurus @Adam_W who might like to kick off this discussion for you with his thoughts.
Hi @Phil_70 & welcome on-board!
Easiest and most cost effective way is to use treated pine sleepers (or recycled railway sleepers) as uprights. You'd just run a row of them then drop your sheet in behind & use roofing tek-screws to fix the sheets to the posts.
You'd likely want your posts at about 1200mm spacings, maybe a little less. Not sure of the load that the sheets would take so maybe even consider 1m centres.
Like any retaining wall, because that's basically what you are building, you'll want to make sure that the uprights are well fixed off to resist tipping. So say your bed wall will be 900mm high I'd be sinking posts into the ground around 500mm and then concreting them in place. Different soils change this though. If you've a heavy clay you don't need to go as deep.
I've two videos that may have some useful information for you. They don't use tin but show you some of the principles to consider.
Hope this helps!