According to "This Old House," a raised bed is just a very large container garden. The raised bed is typically set above the soil line, and filled with topsoil or container soil. Raised beds may be constructed to raise the level of soil and make cultivating and weeding easier. A raised bed may have better drainage than soil in the ground. Raised beds also make attractive additions for landscaping and planting. Constructing a raised bed can be labor intensive, but if you can construct a box, you can build a raised bed.
Mark the bed's location by laying out landscaping timbers in the correct area.
Mark the ground by cutting the sod with a spade on the inside and outside of the timbers.
Remove all sod and dig a trench around the area where the landscaping timbers will rest.
Drill ½-inch holes into the base timbers every 2 feet.
Place the 4 timbers in the ground with the drilled holes facing upward.
Check that timbers are level from corner-to corner by laying a spare timber from corner to corner and measuring with a carpenter's level.
Pound rebar into the drill holes and 1 foot into the ground with a sledgehammer.
Saw the tops of the rebar level with the boards using a hacksaw.
Arrange the next level of timbers counterclockwise over the first course so that the corners overlap.
Drill timber screws through this row of timbers and into the bottom course.
Drill drainage holes in the second course of boards every 4 feet.
Slip copper pipe into drainage holes to protect the wood from rotting.
Repeat steps 9 and 10 for as many courses of timber as you require for your planter.
Cut the board ends at a 45-degree angle with a miter saw.
Line each board up along the inside top of the planter and attach to raised bed wall with decking screws every 1 foot.
Glue at corners with carpenter's glue.
Cover the bottom of the raised bed with gravel to a depth of 3 inches for drainage.
Fill the raised bed with topsoil up to 3 inches from the lip of the raised bed.