Short answer
A dormant crack formed during curing or past settlement and has stopped moving. An active crack keeps changing—widening, shifting, or leaking—because of ongoing hydrostatic pressure, soil movement, or settlement. Active cracks need engineered stabilization and water diversion, not a cosmetic surface patch.
Dive deep
The deciding signals are continuous movement and active water intrusion: crack-gauge change over time, sharp unweathered edges, or moisture and efflorescence bleeding through in rain. On site we read pattern and orientation (horizontal often means lateral soil/hydrostatic load; vertical/diagonal often differential settlement; stair-step often masonry unit movement), width and shear offset, dampness and mineral deposits, monitoring marks over weeks, and exterior drainage that may be stacking pressure behind the wall.
“Just fill it with hydraulic cement or foam” fails on active cracks. If the wall is still moving or under hydrostatic head, the fill shears open or water breaks out nearby. Movement and water load must be controlled first; injection or patching is a helper after the structure is stable—not a substitute for drainage or repair.
When it applies
- Vertical, horizontal, diagonal, or stair-step cracks in poured concrete or masonry foundation walls
- Before finishing a basement, covering walls, or authorizing crack injection
- Any crack that wets, widens, or shows offset
When it does not
- Non-structural hairline crazing on floor slabs
- Micro-cracks in non-load-bearing interior partitions
- Cosmetic plaster cracks above window frames unrelated to the foundation shell
What we do next
If fractures are widening, displaced, or leaking, skip cosmetic fill-only fixes. Schedule an evaluation and review engineered repair paths on our foundation repair hub (city pages such as Seattle crack repair when the job is local).
