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Michelle’s townhome has limited garden space and this project should maximize her planting opportunities with an additional 24 square feet (2.2 square meters for international readers) of full-sun garden. Longtime readers may recall Michelle’s hanging gardens and deck planting boxes, earlier projects intended to support her healthy gardening habit. We also stabilized the planting area at the entrance to her townhome against erosion with a drainage project.

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Now we’re moving to the untamed plot outside her privacy fence.

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The soil, an abysmal mix of red clay intertwined with a variety of building scraps, is not usable without serious amendments. The sun bakes this spot from 10 a.m. onwards and plants will need deep roots to survive. I turned the plot last November and added organic material. Michelle added more organic material this spring and although the soil shows some improvement, we have a long way to go.

To jumpstart the garden we will move to a raised bed design and add workable soil above the clay. The bed’s dimensions will be 36” x 89” so that Michelle can reach any plants in the rear. She may also opt to install dwarf shrubs or other plants along the perimeter. I have several Japanese Maple sprouts in the 6” range and one of those may find a permanent home in this new bed.

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We opted for a simple mortise+tenon+peg design. I think raised bed kits similar these may be available commercially, but those arrive with a healthy price tag and without the satisfaction of DIY. The photo shows the simplicity of our design. Assembly is a cinch.

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Redwood, teak, cedar or cypress may be valid choices, but we opted for 2×8 pressure treated pine which is readily available and reasonably priced. The thickness of the wood allows the gardener to sit on the edges for planting without tipping the bed.

Materials list:

  • Three 2” x 8” x 8’ Pressure treated pine
  • One 1”x2”x 8’ Pressure treated pine (Lucky me. I had a scrap from a previous project!)

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Our building day was a balmy 98 degrees with matching humidity. Michelle completed all the measuring and marking, and we took turns with the cutting. In this photo she is working on the first tenon. (Note that next time there will be no dangling neck chains worn in the shop!)

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The mortises in a budget shop like ours are cut with a drill, jigsaw, chisel, or whatever it takes. Michelle discovered that the four corners offense provided quick access for the jigsaw.

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I shaved some material from the sharp edges of the tenons to ease the connection and prevent splintering. With a wood rasp and hand planer I smoother the edges of the mortise and tenon, working until the fit was snug but easily joined.

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We are ready to do a test assembly.

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Oops. A CME (careless math error) on my part. The two pieces join, but the holes for the pegs are hidden under the mortise piece. Mistakes happen in the shop and represent opportunities for brainstorming to find suitable workarounds. We simply lengthened the peg hole and shifted to 1×2 instead of 2×2 for the pegs. A few minutes with the table saw, and we were back on track.

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Our work yielded an easily-transported garden bed kit. We assembled and tested the fit. Note installing the pegs should require tapping not pounding.

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The truck is loaded with the bed pieces, three large trashcans filled with compost and soil donated from my garden, and all the necessary tools. We’re off to Michelle’s home. Access to her garden can be made through the townhome (not likely for this work), or I can wheel the materials around the building. Isn’t the wheelbarrow a great invention?

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The bed is in place and leveled. Now we add the soil. We will purchase 5 or 6 bags of planting soil to top off the fill and mix it in with a shovel.

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The happy gardener stands ready to create a masterpiece with her blank canvas.

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Now let me correct my CME. I worked through the dimensions on paper and triple-checked before making a test tenon.

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Use one of the cutout chunks to mark the width of the mortise piece.

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From that line create a rectangle large enough for the peg. Our pegs are 1×2, which being interpreted means 3/4 x 1 1/2.

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Cut the hole.

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Test the fit. And it’s perfect this time.

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See the difference.

Readers can follow this link for a PDF with diagrams of the project.

Raised Garden Bed Dimensions


Update 6/24/2019

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I modified this design for a new set of raised beds in my own garden. Take a look at the article: Cedar Raised Beds