Raised beds, or raised gardens, are a godsend for gardeners with creaky joints, bad backs and knees or who live in areas with unsuitable soil for gardening. Raised gardens use frames to corral soil and make planting easier. You will most likely have to buy topsoil to fill your frames but you can minimize the expense of new topsoil buy mixing in compost or rotted manure to extend the soil and add nutrients. The secret to making a raised garden is the width of the frame. Too wide and you won't be able to reach the plants in the middle; too narrow, and you won't have room for all the plants you want to grow. Raised beds can be any length you like but should be 6 to 12 inches deep to allow for optimum root growth.
Choose a site that receives at least 5 to 8 hours of direct sun a day. The more sun your beds receive the more vegetables your plants will produce. Ideally the site will be close to a water tap to minimize the number of hoses you must use.
Make beds that are 3 to 4 feet wide and 5 to 6 feet long as these are the easiest to use (and you'll often find raised garden kits with these dimensions) and you won't have to use additional supports on the long sides to prevent bowing from the weight of the soil. Space your beds 3 to 4 feet apart, or wide enough that you can comfortable walk between the beds with a wheelbarrow.Orient your beds so they line up (the short side points) North to South to maximize the sunlight plants receive.
Use whatever material you are comfortable with. Wood is usually used to make the sides of raised beds but plastic kits are quite affordable or you can use concrete blocks or bricks. Use whatever material is handy and inexpensive in your region that can be securely stacked at least a foot high.
Stack the material so the bed is at least 6 inches deep. 12 to 16 inches is best if want to grow root vegetables. Use nails to secure the wood together. You do not have to use mortar to secure concrete blocks or bricks. Just stack them lengthwise (with the finished sides horizontal), one atop the other making sure to butt (gently tap with a hammer) the edges tightly together. You can use a quick setting mortar if you want to. Assemble plastic raised bed kits according to package instructions.
Mix topsoil with compost or well rotted manure until you have a 60/40 mix of soil and compost. Fill your raised bed to within 3 to 4 inches of the top. If you choose to make a shallow raised bed (6 inches or less) mix enough compost or rotted manure into the top 6 to 10 inches of soil (the soil inside the frame of the raised bed) to bring the level of the soil 1/2 the way up the sides of the frame. As you garden, adding compost or rotted manure to increase fertility, the depth of soil inside the frame will increase.