Are Foundation Cracks Normal? When to Worry

Usually normal: hairline vertical cracks

Thin, vertical or near-vertical cracks (often less than 1/8 inch wide) in poured concrete or block foundations are extremely common and usually result from normal concrete curing and shrinkage. These typically don't need structural repair, though sealing them can help prevent water intrusion.

Worth monitoring: cracks that are widening

A crack that's stable is a different situation than one that's actively growing. A simple way to track this: mark the ends of the crack with a pencil and the date, and check back in a few months. Measurable growth over time is worth a professional assessment even if the crack itself still looks small.

Worth taking seriously: horizontal cracks

Horizontal cracks, especially in basement walls, are a different category from vertical ones — they can indicate lateral pressure from soil or water outside the wall pushing inward, which is a structural concern rather than normal settling. This pattern generally warrants a structural engineer's assessment, not just a sealant fix.

Worth taking seriously: stair-step cracks

In block or brick foundations, cracks that follow a diagonal, stair-step pattern along the mortar joints can indicate uneven settling. A small stair-step crack isn't automatically an emergency, but it's worth having assessed, particularly if doors and windows nearby have also become harder to operate.

Other signs worth pairing with any crack you find

• Doors or windows that have become difficult to open or close
• Visible gaps between walls and ceilings or floors
• Uneven or sloping floors

A crack alongside any of these is worth a professional opinion sooner rather than later. A crack alone, thin and stable, usually isn't cause for alarm.