One limitation of the recycled auto tire bed design is that, at 8 inches high, it is too low to work while in a seated position. Consequently, recent efforts have focused on the development of a relatively inexpensive high profile raised bed.
After evaluating several materials and construction techniques, we settled on a corrugated sheet metal-lined bed supported by a frame made of sucker rod and 2-inch by 4-inch treated lumber.
Of all the different high profile bed designs we've evaluated, the corrugated sheet metal design is the quickest and easist to construct.
The material cost to construct a corrugated sheet metal bed, excluding soil mix, is approximately $1.70 per sq. ft.
Refer to Table 1 for a list of building materials to construct one 40-inch by 30-foot corrugated sheet metal bed.
Refer to Table 2 for a list of components required to assemble one 40-inch by 30-foot corrugated sheet metal raised bed.
Carpenter's square, drill press or hand drill, chop saw or cutting torch, circular saw, tin snips, power grinder, 11/16-inch wood drill bit, eye and ear protection
Begin by preparing the wood component of the frame. Cut to size the following 2-inch by 4-inch lumber: two 10 1/2-foot-long boards; two 10-foot-long boards; two 9 1/2-foot-long boards; two 37-inch-long boards.
Using the schematic in Figure 1, mark the location for the stake holes on the narrow side of each board. Be sure to center the mark on the board. Use an 11/16-inch bit to drill the holes. Be sure to keep the bit vertical in order to accurately drill through the center of the board. For speed and accuracy, consider using a drill press for this job.
Next, prepare the stakes. Use a cutting torch or chop saw to prepare 70 5/8-inch by 36-inch long sucker rod stakes. If you're building more than one bed, consider using a cutting torch to make the job quicker. Use a grinder to remove the burrs from the ends of the stakes. A stand-mounted grinding wheel works best for this task. (Note: If sucker rod is not available, rebar can be used as a substitute. An 11/16-inch hole will not readily accept a 5/8-inch diameter rebar so you will need to use a ¾-inch bit. Because drilling larger diameter holes further compromises the strength of the lumber, it is imperative that the holes be drilled accurately).
Use tin snips to prepare four 12-inch-long pieces of angled metal flashing. The flashing is used to seal the bed corners.
To prepare the bed liner, cut the corrugated sheet metal in half lengthwise using a circular saw. Do not attempt to cut the sheet metal without reversing the blades. Hot fillings are ejected as the metal is being cut, so be sure to wear safety glasses. Cutting the metal is also very noisy, so be sure to wear earplugs.
Complete the fabrication of the liner by cutting a 3-foot-long section off of two of the sheets. When finished, you should have four 13-inch by 12-foot sheets, two 13-inch by 9-foot sheets and two 13-inch by 3-foot sheets.