Water pressure is the enemy
Saturated soil behind a wall is dramatically heavier and pushes far harder than drained soil. Drainage behind the wall is the structural element people cannot see and quotes often omit.
- Free-draining backfill
- Perforated drain at the base
- Outlets that actually discharge somewhere
Foundation and batter
A proper founding trench on undisturbed material, plus the correct lean back into the slope, do most of the remaining work.
Terracing beats one tall wall
Two shorter terraced walls are often cheaper, safer and better looking than one tall wall, and they create usable planting space.