Types

• According to the website ConcreteNetwork, there are four main types of concrete retaining walls: gravity, semi-gravity, cantilever and counterfort. Gravity concrete retaining walls are massive, heavy structures that rely solely on their weight for holding back earth. Semi-gravity concrete retaining walls use steel tension reinforcing rods, which help minimize wall thickness. Cantilever concrete retaining walls, like semi-gravity walls, also utilize reinforcing rods. But these walls have the additional feature of a two-part base that includes an outward-reaching toe and a heel that reaches under the earth that the wall is retaining. Counterfort concrete retaining walls are the strongest. They have the same basic design as cantilever walls but also include webs of concrete, known as counterforts, which help tie the bases and main structures of counterfort walls together.
  
  

Height

• The specific height of a concrete retaining wall depends on the amount of earth you want to retain the type of wall you decide to use. A gravity retaining wall is typically sufficient and economical for heights of up to 10 feet. For a wall higher than 10 feet, you need a semi-gravity or cantilever design. A counterfort concrete retaining wall is your most economical choice for a wall higher than 25 feet, according to ConcreteNetwork. Before starting construction on any type of retaining wall, look over the building codes that apply to your area. Most states require that you have a licensed engineer design or approve the design of a concrete retaining wall that is more than 4 feet high.
  
  

Thickness

• As a general rule, a concrete retaining wall should be at least 12 inches thick, according to ConcreteNetwork. However, you might need a thicker wall in many instances, such as when using a gravity retaining wall or when working with highly reactive soils. With a cantilever or counterfort retaining wall, wall thickness is typically about 10 percent of the total wall height.
  
  

Length

• The length of a concrete retaining wall depends on the size of the area you are trying to retain. In most instances, length is approximately 50 percent to 70 percent of a retaining wall's height. So if your wall is 25 feet high, its length should be between 12.5 and 17.5 feet.