Retaining walls need to be extremely strong and durable to be able to hold soil in place. Which type of retaining wall to build depends upon many factors, here is brief description of the 5 main types of retaining walls and when best to use them:
- Gravity. Gravity walls use their mass or weight to resist the pressure exerted by the earth behind them. These walls usually have an average height of three to four feet. They are made from mortar-less stone or masonry units. Gravity is able to hold back the earth or soil due to the walls construction. The weight or force of friction that is created by these materials is greater than the force exerted by the soil. The thickness of the wall at the base will exceed that of the top. This is a process known as 'battering' helps the walls to improve stability by leaning back into the retained soil. In this process, as the walls get taller they slant backwards. Battering is done to prolong the lifespan of gravity walls, which otherwise would tilt outward.
- Sheet piling. Sheet pile walls are usually used in soft soils and tight spaces. These walls are made out of steel, vinyl or wood planks which are driven into the ground. A cable or a rod is then used as a tie-back anchor to the walls.
- Concrete. These types of walls are common in gardens and other outdoor landscapes. They offer better support for vertically-slanting slopes. Concrete retaining walls are high-built and have deeper and heavier soil underneath them. These properties make them offer better resilience and solidity. Concrete retaining walls require a greater base depth so as to create a better foundation. Properly installed concrete retaining walls do not usually face problems such as tilting, bowing, or cracking. They are also not as susceptible to climate-induced degradation.
- Block. For enclosing an area in a garden, block retaining walls are the most suitable. These walls are of two types. Modular retaining walls and segmental retaining walls. They comprise of interlocking concrete units to hold back the load of the soil. Similar to gravity walls, they use the force of gravity to resist overturn and sliding. The nature of the walls prevents hydrostatic pressure as well.
- Rock. For leveling flower beds in gardens, you might consider the rock retaining walls. The rocks and stones that are used in the construction of these walls must fit with the landscape. When the rocks are stacked together, spaces are left between the rocks. These spaces or gaps are filled with the soil mix. If plants are allowed to grow in between the rocks, it will strengthen the walls. Growing roots will prevent soil from becoming loose, and control soil erosion.