Landscape Design forum: raised garden bed on a slope using 4x4x8 wood

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Aug 16, 2020 3:44 PM CST
My slope is not drastic. It has a slight drop on the north side, and the east side has the largest drop. This is going to be 4x8. The north side is about 9 inches approx 19% slope and the south side 8 inches approx 17%.

The 4ft sides will be running east to west. I found a picture that will give you an idea of what I am going to do. This does not appear to be a rectangle, and I probably won't build up the high side quite as much. Originally my plan was to remove the soil and build the rectangles from the bottom up. Living in Mobile, the less wood below the surface would be a much better idea with our humid and rainy conditions year round. I entertained the idea of using concrete blocks, but on a slope I decided I would will just live with the fact that the wood may only last a few years. This is strictly for vegetables not ornamentals.

I spoke to a longtime friend who is a professional landscaper who deals with irrigation & major landscaping work. He said there are many ways to build this using 4x4x8. He told me as a standard they usually will remove 2 inches and place the first level. So with using 4x4 it will leave approx 1 1/2 above the soil level. I could just place 1 or 2 on the high side and go from there. They talked about staggering the sides. I tried several times to find a you tube video and the majority build on top and use 2x6 up to 2x10. Here is a picture of what I would like to try to do, and keep in mind this is a square and I am building a rectangle. I don't intend on building it quite as high. Perhaps one less layer. I am just trying to figure how to go about this. I understand it has to be built level. Again my original plans was to lay it out & build from the bottom up using a preconstructed 1st layer get it level & build up from there by screwing in the other layers on top of one another & then drilling & using 1/2 rebar.

If you know of a video or illustration please post it. Any and all advice would be appreciated.

Thumb of 2020-08-16/tgolomb/bd8d37

Lockhart, Texas (Zone 8b)
Hydroponics Greenhouse Region: Texas
Aug 18, 2020 9:26 AM CST
I think your first instinct was correct. You could do all sorts of involve things, but the simplest is clearly to just remove soil to make a level rectangle and work as if you were setting a perconstructed bed border into that space. One virtue is that you get the selected raised bed soil depth the same throughout. And while it won't last forever, it will last a long time, and when the time comes, the "hole" is still there to be easily filled with a new bed.

And so what if the wood under ground starts to deteriorate. The soil bed is intact. It's not like the wood is going to vanish, or at least not for a very long time, and the end that breaks down is supported by the native soil and can't sag outward.

I think, given the reasonably small size of the project, I'd seriously look into doing it with natural stone blocks. For simplicity, I'll use 2 feet high and 4" thick. That's 36 cubic feet around,or about 5,400 pounds, 2.7 tons. Around here, chop limestone is about $160/ton, making stone cost $432. If you just want one foot tall, it's half that. You can play those number in all sort of ways, like one foot tall and 8" thick is still about $400 in stone. Certainly more than timbers and rebar, but permanent and beautiful.

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