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The home page in this series on building raised bed gardens is Raised Beds Jim’s Way.
For my example, throughout these pages, I’ll be “building” two side-by-side beds 3′ 6″ (3 feet 6 inches) by 12′ (inside dimensions). I’ll have a single 3′ walking path between them. There will be a 4′ walking path around the outside as well. Finally, we will make the beds out of 2″x12″ treated lumber1. So, the length of the garden will be the length of the planks plus 8′. The garden’s width will be the total width of the beds (7′) plus 4′ for each of the two outside walkways, and another 3′ between each bed. That adds up to 7′ + 8′ + 3′ = 18′ for our width. The garden’s length is 12′ plus the two 4′ paths around the outside, or 20′ total.
For setting up precise locations in your chosen area, we’re going to have to use a little trigonometry. But, I’ll show how to do it without requiring any actual math to be performed.
The first step is to choose an object to which you want to align your beds. This can be a fence, the side of a building, or any number of other possibilities. I’ll refer to it as the “yard object” in these steps.
If you’re using a building as your guide to setting these up in your yard, add some clearance between the side of the garden and that building, to prevent the building’s shadow from falling on the garden. In my location, that’s about 7′. In my example, the long side of the beds is closest to the building. So, add 7′ to the other direction (the 16′ side), making the total 23′ by 18′. However, the gap between the bed and the yard object can include the walking path around the outside, so this can be 20′ instead of 23′. I’ll use 20′.
We will be marking six locations using my example dimensions. Two stakes will be placed at the edge of the yard object we’re aligning with. Two optional stakes are placed the width of the gap between the wall of the yard object and the start of the garden (7′). Two final stakes will be placed the width of the garden from the second pair of stakes (16′).
Pick a spot on your yard object closest to one corner of the garden area. Put a stake #1 in the ground. With the tape measure, measure off the distance along the yard object at the length of the garden (18′). Put stake #2 here. If the building or fence is not long enough, put stake #2 in the ground along a line extended from the object.
Stakes #3 and #4 are optional, used only if you have a gap between your yard object and the garden itself. In our case, they would go at 7′ from the first two stakes.
Stakes #5 and #6 go the width of the bed from the last two stakes you placed (#1/2 or #3/4). In our case, these would be 16′. Also, measure to the yard object as well as to the other stakes. This can let you know if there’s a problem with the other measurements.
Unless you are lucky or really good at eyeballing straight lines, the corners of the box you just made with stakes are not going to be square. To fix that, we will use a math trick to get the plot corners square. Measure from stake #1 to stake #6 (diagonally across the bed area). Then measure from stake #2 to stake #5. (The measuring lines will make an X across the garden area.)
To make the garden actually have square corners, move stakes #5 and #6 until these two diagonal distances are the same. Always maintain the same distance from the yard object (20′) and the distance between the two stakes you are moving (18′). So, you basically have to move both stakes #5 and #6 at the same time, in the same direction, and the same amount. The amount you should move them is about half of the difference between the two diagonal measurements.
Measure again, and move the stakes accordingly. Once the diagonals are the same size, your garden area is now measured. Leave the stakes in the ground.
If you used all six stakes, repeat the above process for stakes 3, 4, 5, and 6. This time measure from statke #3 to stake #6, and again between stake #4 and stake #5. Move stakes #3 and #4, leaving #5 and #6 in place. When done, you should be able to eyeball a line through stakes #1 to #2 and #3 (and 4, 5, & 6).
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