Retaining walls restrain tons of soil that would otherwise damage foundations or landscapes. They increase usable yard space and are carefully engineered to counteract gravity and soil pressures. Ideal locations include sloped landscapes prone to erosion, below soil fault lines, or where soil is sliding near foundations. Common retaining wall types are timber, interlocking blocks, stacked stone/brick/block, and concrete. Even small walls contain enormous soil loads, so taller walls require stronger engineering to prevent bulging, cracking, or leaning over time.