Most raised beds tend to be at least six inches deep. In many cases the soil is sloped toward the border of the bed. Some raise beds use stone or other material to provide a short wall effect to hold the soil in. Using Living Earth soil mixes will give your plants a good start before their roots reach the soil level below. For larger shrubs, a deeper raise bed will be necessary. You will find that after plants have established and watering the beds that they subside. This is when you add additional soil or mulch.