The first step is to calculate the dimensions on the inside of the garden bed, which is the length and width that is actually usable for planting. If you bought your beds from a commercial source, then chances are, the interior dimensions are probably a little less than the advertised size.
Some of the other benefits of raised beds are: reachable - less bending and stretching gives the gardener easy access and makes maintaining and harvesting less of a task to perform; drainage - because the soil is above the ground it will not become compacted during heavy rains and will drain properly in preventing water-soaked soil;
A double skinned wall provides an air pocket of insulation that minimizes the temperature fluctuations and drying out of the soil in the garden bed. Sometimes raised bed gardens are covered with clear plastic to protect the crops from wind and strong rains.
our limitations will go as far as your imagination takes you and the area of space you have to work the garden. There are raised garden bed kits available for purchase at some nurseries, home and garden centers, or on-line.