Foundation cracks — when it's serious
Thin vertical cracks in a poured foundation are common from curing and settling and are usually sealed against water, not structural. A horizontal crack, a wall that bows inward, stair-step cracks in block, cracks wider than about 1/4 inch or growing, or floors that slope point to structural movement — get a structural engineer before any repair or waterproofing sale. Use the safety check below.
First, a safety check — is any of this true right now?
No hazard flagged — the diagnostic steps below are appropriate. If any of the above changes, stop and follow the safety guidance.
Vertical vs horizontal is the key split
Vertical or slightly diagonal hairline cracks in poured concrete usually come from normal curing and settlement; they may let water seep but aren't typically structural. A horizontal crack — often mid-wall — suggests soil or water pressure pushing the wall in, which is structural and can worsen. Bowing or leaning walls are the same story and need prompt assessment.
Get the engineer before the salesperson
Waterproofing and foundation-repair companies inspect for free because they sell the fix. For anything that looks structural, an independent structural engineer's assessment (a few hundred dollars) tells you what's actually needed before you commit to a large repair. We don't publish a foundation-repair cost estimate because credible, sourced figures for it are highly site-specific — that's flagged as needs-more-evidence rather than guessed.
When to call a professional
- • Horizontal or bowing walls, stair-step block cracks, width over ~1/4 inch or growing, sloping floors — structural engineer.
- • Any doubt — an independent engineer's assessment beats a repair company's free inspection.
Common questions
- Is a vertical foundation crack dangerous?
- Usually not structurally — it's often a settling/curing crack that mainly needs sealing against water. Horizontal and bowing cracks are the ones to worry about.
- Should I get a free foundation inspection?
- It's fine for a first look, but the inspector sells the repair. For structural concerns, pay for an independent engineer's opinion first.