Foundation cracks: which ones matter?
Updated 2026-11-02
Thin, vertical hairline cracks in poured concrete are common and often cosmetic, while cracks that are widening, horizontal, stair-stepped in block, or paired with sticking doors and water usually deserve an inspection by a foundation contractor or structural engineer.
How can you tell if a crack is getting worse?
- Photograph the crack with a ruler or coin for scale and note the date
- Mark both ends with a pencil and check again after a few weeks and after a wet spring
- Note any new signs: doors or windows sticking, gaps at trim, water at the crack
Which signs are more serious?
- Horizontal cracks or inward bowing in basement walls (see bowing walls)
- Cracks wider at one end, or offset so one side sticks out
- Water seeping through cracks during spring or after heavy rain
- Sloping floors upstairs
Where can you read an independent guide?
HUD's Rehab Guide on foundations covers shoring, crack repair, waterproofing and drainage for homeowners and contractors. It's dated (1997) but not written by a company selling repairs (HUD).