The answer to 'average cost of retaining wall' is that the cost can vary widely depending on several factors. Typical ranges for a basic retaining wall can be anywhere from $15 to $50 per square foot installed, but more complex or larger walls can cost significantly more.
The main factors that influence the cost of a retaining wall include the size and height of the wall, the materials used (such as concrete, stone, or wood), the complexity of the design, the site conditions, and the labor costs in your local area. Taller walls, walls with curves or corners, and walls that require extensive excavation or foundation work will generally be more expensive.