Cosmetic vs. Structural Cracks
A thin, straight, vertical hairline crack in a slab or wall, especially one that isn't growing, is usually just normal concrete shrinkage. What tends to point to a real structural issue is a crack wider than a quarter inch, a stair-step crack running through brick or block mortar joints, or a crack paired with sloping floors or sticking doors.
If you're not sure which kind you're looking at, our free checker above walks through the questions a contractor would ask first.
How Injection Repair Works
For a crack that's confirmed as cosmetic or stable, a contractor cleans it out and injects it with epoxy or polyurethane. Epoxy is a rigid filler that's often used on cracks that aren't expected to move again. Polyurethane stays flexible, which some contractors prefer for cracks in a slab that still sees some seasonal clay movement.
Injection repair doesn't fix the underlying cause of movement. It seals water out and restores the look and strength of that one spot. If the crack is a symptom of a bigger shift, piering is the fix, not injection.
Not sure how serious yours is? The free check takes about a minute.
Take the free crack checkWhen to Stop Watching and Call Someone
Measure the crack now, in writing or with a photo and a date. If it gets noticeably wider over a few weeks, or new cracks show up elsewhere in the house, that's the point to get someone out rather than keep watching it.
A Note on Horizontal Cracks
Most of the cracking discussion around here is about vertical or stair-step cracks, since those are what expansive clay typically produces. A horizontal crack running sideways across a foundation wall is a different and generally more serious pattern, often pointing to outside pressure pushing in on the wall rather than simple settling. If you see a horizontal crack, it's worth a professional opinion sooner rather than later, not a wait-and-watch situation.
Cracks Around Windows and Garage Doors
Diagonal cracks that start at the corner of a window, door, or garage opening and run up toward a roofline are common and worth noting separately from a straight vertical crack in a plain wall section. Openings are naturally a weak point in a wall, so stress from foundation movement tends to show up there first. A single short crack at one window corner is usually minor. The same pattern repeating at several openings around the house is a stronger signal that the whole foundation has shifted, not just one spot.
Matching the Repair to the Surface
A crack in a painted interior wall, a brick exterior, and a bare concrete slab all get repaired a little differently, since the injection material needs to bond with and finish out looking right on each surface. A contractor repairing an exterior brick crack may also need to match mortar color, which is a cosmetic detail worth asking about up front if the look of the repair matters to you.
Questions
Can I fill a foundation crack myself?
A small, stable hairline crack can often be sealed with a basic concrete crack filler from a hardware store. If the crack is wider than a quarter inch, growing, or paired with other symptoms, it's worth having a contractor look before you seal over a bigger problem.
Does a sealed crack mean the problem is fixed?
Sealing stops water from getting in, but it doesn't address why the crack formed. If clay movement caused it, a sealed crack can still reopen or new ones can appear nearby.
How wide is too wide for a foundation crack?
As a general rule, cracks wider than about a quarter inch, or ones that step across brick or block in a staircase pattern, are the ones worth a professional look rather than a DIY fix.
Will a crack get worse in winter?
Oklahoma's freeze and thaw swings can widen an existing crack, especially if water gets into it and freezes. Sealing a stable crack before winter is a reasonable precaution.