Retaining walls are excellent for increasing the usability of a steep area or to provide separation from a planting bed to a lawn. Proper construction is important for a retaining wall, many fail due to improper reinforcement and drainage.
Smaller walls are commonly used for around planting beds around the house to add height to the landscape. These can be an inexpensive way to add a new look to your property. Smaller walls are not recommended around large trees unless a root barrier is used. Over time the roots would push the wall up leaving it unsightly and reducing its structural stability. To avoid this a root barrier can be installed, this stops root growth in the areas where they touch the barrier. This is a simple way to avoid problems many years into the future.
Larger walls are used to level portions of a yard, provide a terraced area, or to support a patio. With these walls, the method of construction becomes very important. The more the wall retains the more reinforcement behind the wall is needed. A product called geogrid is installed in between the layers of wall block and extended behind the wall. The purpose of this is to spread out the weight on the top of the wall downwards over a larger area. Different methods of construction are used based on soil types and what the area above the wall will be used for.
Concrete walls can be more aesthetically appealing than timber walls. When properly built concrete block walls will last much longer than timber walls. Over time the wood will rot and lose its structure, when this happens the wall would need to be removed or replaced which could negate any savings of going with wood in the first place. When concrete block retaining walls are installed with the correct drainage, base, and reinforced backfill they will outlast timber walls many times over.