Building a retaining wall costs between $20 and $50 per square foot, on average, but some materials can cost a bit less, especially when building a straightforward, simple design. Complex designs and premium materials can increase costs dramatically such as steel or metal walls that can reach $150 per square foot.
Some inexpensive retaining wall ideas include using wood which costs $10 to $40 per square foot installed. Wood gives you a warm, rustic appearance that looks great in a garden area. Gabion is another affordable material. The wire mesh cages are filled with stones to create a unique and eye-catching wall that is also affordable, costing about the same as wood but will have better durability.