Residential landscape retaining walls can be constructed to improve the aesthetics of a property, to resolve structural landscaping issues, or both. There are a few options based on what you would like to achieve. The most economical is to use a single block system in which all the retaining wall units are the same size. A more advanced and expensive alternative is to install a multi-piece or even an aged or tumbled product. The correctly built segmental wall will last a lifetime.
The simplest of retaining walls is the gravity wall. Gravity walls rely on their own weight and setback to hold the soil behind them. Gravity walls are less than three feet tall and do not need any type of reinforcement grid for stability. To make this wall economical and simple to install, use a single block system, which will be the least costly.
Water infiltration will destroy retaining walls from the inside out. All segmental retaining walls must have drainage gravel directly behind the full height of the wall. A slotted drainage pipe needs to be installed behind the base course of block. This must be piped to daylight to help relieve any water pressure behind the wall. Drainage swales need to be constructed at the top of the wall to keep water directed away.
A segmental retaining wall needs a compacted gravel foundation. A concrete foundation is not necessary for a segmental retaining wall. Segmental walls are meant to flex with the seasonal cycles of the soil and a rigid concrete base only causes problems. If you know the area to have soft or wet soils, extra excavation is required.
Compaction is the key to a successful segmental retaining wall. The foundation must be compacted. The drainage gravel behind the wall must be compacted, and the soil behind the wall must be compacted. It is best if this is done with a mechanical plate compactor, but can be achieved with a hand tamper on small walls.