Brick and Block Movement
Brick and block move. Mortar shrinks. Units expand and contract with heat and moisture. A step crack in veneer is often that system talking — not a footing that just failed.
This page separates masonry behavior from foundation movement.
Why the crack follows the mortar, not the brick
Mortar is weaker and more brittle than the brick or block units it holds together. When the wall is under stress — from thermal movement, minor settlement, or normal curing shrinkage — the mortar joint is where it gives, not the masonry unit itself. That is why a step crack tracks in a staircase pattern along the joints instead of cutting straight through brick.
Brick and block also expand and contract at different rates than the wood framing or concrete behind them, which adds ordinary thermal stress on top of whatever else is happening.
What masonry does on a stable house
- Hairline cracks at openings and corners
- Step cracks that follow mortar and do not offset
- A crack that appeared in year one and has not changed
What it does not automatically mean
- The foundation dropped
- The wall is coming off the house
- Piers are required
When masonry is pointing at support
- The crack is offset, not just open
- It keeps growing after the first seasons
- It lines up with floors, doors, or a foundation crack that is also changing
How MFRC suggests homeowners think about it
Instead of asking "is a step crack serious," ask "is it still just a step — a clean line along the mortar — or has it started to offset, where one side sits higher than the other?" A clean step that has stopped growing is describing normal mortar behavior. An offset that keeps widening is describing something underneath it.
Related dictionary terms
(Each of these terms is explained in the MFRC Foundation Dictionary.)
A final note
This page is educational, not diagnostic. Masonry records stress. Time tells you whether the stress is finished.