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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 all the way around the outside as well. Finally, the beds will be made out of 2″x12″ treated lumber1. So, the length of the garden will be the length of the planks plus 8′. The width of the garden 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 length of the garden is 12′ plus the two 4′ paths around the outside, or 20′ total.
To build one 3′ 9″ by 12′ raised bed we need two 2×12 planks 12′ long, plus one 2×12 plank 8′ long. Cut the 8′ plank into two 3′ 9″ lengths, and throw the remaining few inches away. Many jurisdictions require that treated lumber is specially-handled when disposed of, so check your local regulations. Never burn treated lumber. Even though they’re no longer toxic, the gases given off by burning can be obnoxious.
The extra 3″ on each of the end pieces is because the planks are a little over 1-1/2″ thick. The 3′ 6″ section will overlap the 12′ plank, so the exterior dimensions will be 12′ 3″ by 3′ 9″.
To connect the pieces together, use the long self-tapping wood screws and a fender washer. For 12″ high planks, use four screw/washer pairs. Smaller sizes may require fewer screws. Note that the fender washers are so the screws don’t pull into the wood too far, which would reduce their holding ability.
You will probably need a second person to hold the pieces vertical so they can be screwed together.
Make sure the end pieces are flush with each other on the outside edges. If any of the planks are twisted, you may have to force the edge one direction or the other to make up for the twist. This should only be an issue on two corners at most, because the other end can be done no matter what shape the planks are in.
If any of the long boards are bowed, put the convex side towards the inside of the bed. The dirt will push out on the bow, making the board move towards being straight.
Once the four pieces of wood are connected together into a rectangle, it’s ready to put into place. This almost certainly will require two people or more, unless your bed is really small. Treated planks are heavy.
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