Q: Should block retaining walls be angled backwards or built vertically plumb?
A: A very short retaining wall built of only a couple of courses might work when installed plumb, but anything taller should be aligned so that each new course is aligned behind the preceding (lower) course. A typical setback distance is 3/4 inch from the front of the course beneath it. This setback causes the walls to cant backwards into the retained soil. Canted walls are structurally more stable than vertical walls because gravitational forces pull the wall into the retained soil.