What it is, how it works, and the questions to ask before you hire.
Last updated: October 2026
Not every crack means your foundation is failing — but every crack means something. Hairline vertical cracks are often just concrete shrinkage as it cured. Stair-step cracks following mortar joints, horizontal cracks, and any crack that's growing tell a different story: the foundation is moving. This guide covers how to read what a crack is telling you, which repair methods fit which cracks, and when a crack means it's time for a full inspection.
Stable, non-structural cracks — typically thin vertical hairlines that haven't changed — are candidates for epoxy or polyurethane injection, which bonds the concrete and blocks water. The key word is stable: if the crack is growing, sealing it without addressing the movement is cosmetic.
Stair-step cracks that follow mortar joints in brick or block walls are the classic signature of differential settlement — one part of the foundation dropping relative to another. They're the crack pattern most worth getting inspected promptly.
Horizontal cracking usually means lateral soil pressure — expansive clay or saturated soil pushing the wall inward. These deserve prompt professional attention, especially if the wall is bowing along with the crack. See our bowing basement wall guide for what comes next.