¾" clean crushed stone is the standard drainage stone behind a retaining wall. It's large enough to leave open voids for water, angular enough to stay put under pressure, and free of the fines that choke a drainage zone.
The drainage recipe
- A 12"-wide column of clean stone directly behind the wall face
- Filter fabric between stone and soil so silt can't migrate in
- No stone dust, dense-graded blends, or anything with fines — they hold water instead of passing it
Skip small rounded stone on taller walls; round material drains well but shifts under load, while angular stone locks in place. Angular ¾" gray granite is the workhorse, and rounded 1.5" riverbed stone also drains freely where it doesn't need to grip a slope. Up to 6 yards per truckload, with multi-truck dispatch for long walls.
