Raised planting beds made from brick have many advantages. They last practically forever and the stone does not react with the soil. Building one is not hard, but requires a lot of work. The materials involved are heavy.
The exact quantity depends on the size of your planting bed.
1) Begin by digging a trench along the foundation of the planting bed. The trench needs to be at least 15 inches deep and about a shovel width wide (10"). A bit more or less won't matter.
2) Fill the lower 5 inches of the trench with gravel. This layer will drain moisture away from the bed.
If you want to add a drain to your bed dig a trench for the pipe now. Later the concrete will get in the way. The pipe should exit under the gravel for best longevity.
3) Fill the trench with 4-5" of concrete. Install rebar in the corners and level the concrete all around. This layer is the foundation of your wall.
- iron rebar for all corners
The rebar is a good idea for any project that is built above the frost line. The foundation does not extend below the line, which makes it subject to frost jacking in the winter. The rebar reinforces the bed's foundation and keeps it from cracking during the winter.
4) Build your wall on top of the foundation; one brick at a time. Brick laying is not necessarily hard. It just takes time. The best advice I can give you is to layout your string lines properly. It is much easier to lay a brick on top of level one than it is to vary grout joints. Chances are your first wall won't be perfect, but it will be solid.
5) Fill the bed with soil and enjoy.
Before embarking on this project be very clear about the time required to build all but the most simple brick beds. Getting the materials from the home center to your building site alone will take all morning. Plan to spend two weekends on getting the project done.