I'm wanting to build up a garden that currently drops off from my driveway pad. The wall needs to be about four foot high at highest point. The wall will not be visible, so I don't need a wall product that is decorative....it just needs to be sturdy.
Since you need a retaining wall there are two choices:
1. A rigid wall with a concrete footing at the appropriate depth for the frost and a reinforced wall to eliminate cracks.
2. A "flexible" wall that is built on a compacted soil base (about a foot or so below the surface) with a slight "batter" (3/4" per foot or so back into the slope) for stability. This type of wall allows the minor temperature and moisture movement without loss of stability. The wall is usually built using specially shaped concrete block or wood timbers. The are many different styles of block and generally have color or some sort of facial treatment because of the minimal difference in manufacturing cost.