Perhaps the most important tips for building a retaining wall are to ensure that water can escape from behind the wall to prevent a collapse, and to make sure the materials used for backfill between the wall and the slope are compacted properly to avoid excess settling that can lead to a collapse. The processes for building the retaining wall will differ depending on the type of materials used and the size and shape of the wall, but the big ideas remain the same: ensure water can escape, and make sure materials are solidly compacted to prevent shifting.
The function of a retaining wall is to support the materials that press against it on the uphill or heavy side. This means the wall must not only become a solid structure that holds itself up, but also a strong structure that can bear the weight of the materials it is retaining. Building a retaining wall without a solid design or with subpar materials can lead to significant hassle and even a full rebuild not too far down the road. Choose materials carefully, and consult with a professional to find out what materials will work best for the materials the particular wall will have to support.
To prevent frost heaves from damage, the builder should be sure to backfill the wall with a material such as gravel or crushed stone when building a retaining wall. This will prevent excessively moist material such as soil from directly pressing against the wall during cold weather, and it allows for expansion of other, moister materials without damaging the wall. A retaining wall that is relatively short will also help prevent damage or failure. Taller walls are more at risk of failure since such walls are supporting more material. Smaller walls support less material, which means there will be less weight placed on the wall and less movement due to gravity or frost heaving.
The base of the wall should be built beneath the surface of the soil. Soil can move when wet or dry, which means building a retaining wall on top of this loose soil may allow the wall itself to move. Build the first layer of stone or wood of the wall several inches down beneath the surface of the soil for added stability. The builder may also consider building the wall at a slight angle toward the weight it is designed to support; this adds a bit of extra strength and stability as well.