Grouted Cell

Not every cell in a block wall needs to be grouted; which cells carry reinforcement is set by wall height, soil load, and engineering requirements, and those are the ones filled solid while the rest stay hollow to keep the wall lighter and use less material overall. Grouting is done in lifts as the wall goes up so the grout consolidates fully around the rebar instead of bridging and leaving hidden voids inside the block, which is a common shortcut on rushed work. Pouring too much height in one lift is exactly how those hidden voids happen, since the grout can't settle and consolidate properly around the rebar before it starts to set. Cleanout openings at the base of the wall let us check that mortar droppings haven't blocked a cell before it gets grouted, which is another spot where a rushed job creates a problem that stays hidden for years.

A void or gap in a grouted cell is a weak point in the wall, and in a climate with hard freeze-thaw winters, any pocket where water can collect and freeze inside the block makes that weak point worse with every cold season. We consolidate grout as we pour it, rodding or vibrating it into the cell, so it fills completely around the steel rather than leaving air pockets we'd never see from the outside. It's slower than pouring straight through, but it's the difference between a cell that's actually solid and one that only looks solid from the top, and it's not a step we skip to save time.