Save Your Back: U-shaped Cedar Raised Garden

I just made a raised vegetable garden for my wife. I used red cedar for the parts that touch the soil to prevent contaminating it with treated wood, which I used only for the bottom. It took me about 40 hours to design and build this; the supplies cost me about 700 USD. I used common hand tools and an electric miter saw. I showed the results to a few friends who requested that I share plans and instructions, so here.

This is my first instructable and English is a second language, so my sincere apologies for any mistakes I made and please feel free to let me know how to improve on all this. Thanks!

Marc

Supplies

Plywood 4’ X 8’ treated wood : 2

4X4 8’ treated wood : 3

2X4 8’ treated wood : 13

2X4 8’ cedar : 9

Cedar deck boards, sold as 2X6 (really 1 X 5½”) 16’ (can be cut into 16 8’ for transport) : 8

Galvanized wood screws 3” X 8 : 300

Galvanized wood screws 1½ X 8 : 300

Galvanized assembly plates 2 X 6 (screwed or hammered) : 16

Spruce strapping 1X2 (really ½ X 1½”) 8’ : 8

Galvanized welded ¼ mesh 36” X 25’

Geotextile 40” 20’

Optional : 1X styrofoam 2’X8’X1”, plastic film to wrap the cedar pieces exposed to earth

Optional : Ground layout : 50’ geotextile, 3 80L bags of colored cedar mulch, plastic border

Step 1: Site Preparation

Cleanup a 11X11’ area in your yard for a 18” clearance around the raised garden
If so desired, cover cleared ground with geotextile and cedar mulch, surround with plastic border.

Step 2: Base

Cut sixteen 4X4 trapeze-shaped 45° braces with 9” long side

Cut eight 4X4 legs of 16” length

Assemble the eight legs with braces on two adjacent sides; use lots of screws on this.

Cut 2X4 treated wood in the following dimensions; the 45° cuts are made on the 3½” side

Three pieces of trapeze-shaped 45° with 94” long side
Two pieces of trapezes-shaped 45° with 34” long side
One piece of trapeze-shaped 45° with 31” long side
Two pieces of parallelogram-shaped 45°, both sides same length: 60”

Assemble and screw the base 2X4's and legs

Step 3: Frame

Cut pieces of 2X4 treated wood in the following dimensions:

92” : 2 pieces
89” : 2 pieces
59” : 2 pieces
30” : 6 pieces

Cut twenty-four 6” pieces of 2X4 cedar

Assemble the bottom part of the frame as shown in the figure

Cut both plywood pieces using the dimensions shown in the second figure; cut-out openings (dotted lines) for the vertical 6” pieces.

Screw the floor to the bottom frame.

Cut pieces of 2X4 cedar in the same dimensions as for the bottom part of the frame:

92” : 2 pieces
89” : 2 pieces
59” : 2 pieces
30” : 6 pieces

Assemble the top frame (cedar) and join it with the bottom frame.

Turn the frame upside-down; put the upside-down base on top and assemble, then flip the assembly back up. NB : I had to screw a beam between the legs on each side to prevent them from bending/ripping out during the flip.

Step 4: Walls

Cut 1x5½ cedar boards to the following dimensions:

Three boards at 94” (rear)
Six boards at 92” (exterior sides)
Six boards at 35” (front left and right)
Six boards at 58” (interior sides of center alley)
Three boards at 26” (end of center alley)

Screw boards to frame.

Step 5: Weather-proofing (optional)

Insert 6”-high pieces of 1” styrofoam between the bottom and top framing.

Cover earth-exposed cedar with plastic film to slow-down rot.

Step 6: Floor

Drill ¾” holes every 8 inches or so along whole plywood floor for drainage.

Screw the 1X2 strapping strips every 8” or so.

Screw or staple the mesh to the strapping.

Cover with geotextile and staple in place.

Step 7: Optional 'gunwale'

This part is optional. I think it looks better with it, plus it keeps the earth in when the wind and rain pounce.

Rip three 1X5½”X8’ cedar boards in half along their length.

Round-out the cuts using a sander or router.

Measure the length at of each top wall board in the center; make the 45° cuts so the length along the center of the gunwale matches the wall board's.

Flatten the rounded top wall board using a sander or plane to ensure a solid gunwale assembly. Screw gunwale pieces centered on walls.

Step 8: Finish

Fill with earth, plants... I plan to add a drip irrigation system with timer (that's what the piece of black ABS pipe sticking out on the left side is for), but otherwise I'm pleased with the results and so is Nancy!