Rebar Reinforcement

Concrete and CMU handle compression well, meaning they resist being pushed together, but they crack under tension or lateral force, which is exactly what a retaining wall or foundation wall faces from soil pressure. Rebar runs vertically through grouted cells and horizontally through bond beams to resist that bending, bowing, and lateral push. The size and spacing of that rebar depends on wall height, soil type, and what the wall is actually holding back, which is why a tall retaining wall needs more reinforcement than a short garden wall, and why we don't guess at spacing on anything load-bearing. Rebar also has to be positioned correctly within the cell, centered rather than pushed against one side, so it can resist force from either direction instead of just one. On a retaining wall, that vertical rebar works together with horizontal rebar in the bond beams to resist both the downward weight of the soil and the outward push against the face of the wall.

Steel rebar and freeze-thaw climates have to be handled carefully together: rebar needs to be fully encased in grout so water and repeated freezing cycles can't reach the steel and cause corrosion or cracking from the inside out. Exposed or poorly grouted rebar is a slow failure waiting to happen in a climate that freezes and thaws all winter, since rusting steel expands and pushes on the surrounding block from within. We grout every cell that has rebar in it completely solid, not just the cells that are easiest to reach, and we check placement before the pour, not after, because that's the point where a mistake is still cheap to fix.