As a rule of thumb, cracks under 1/8 inch are usually cosmetic, 1/8 to 1/4 inch are worth monitoring, and anything over 1/4 inch — or any crack that is growing or offset — should be evaluated. Width matters, but growth, offset and whether doors and floors are affected matter more.
Foundation Repair Baton Rouge measures cracks on every evaluation. Here’s the framework we use.
Crack width guide
| Width | What it usually means | What to do |
|---|---|---|
| Hairline to 1/16 in | Concrete shrinkage or minor seasonal movement | Note it; usually no action |
| 1/16 to 1/8 in | Minor movement | Mark and monitor |
| 1/8 to 1/4 in | Moderate movement | Monitor closely; evaluate if growing |
| Over 1/4 in | Significant movement | Get it evaluated |
| Any width with offset | One side has moved relative to the other | Get it evaluated |
These are general guidelines used widely in the industry, not code limits; context matters.
Direction tells you more than width
- Diagonal cracks from door and window corners — differential settlement.
- Stair-step cracks in brick — the beam under that wall is dropping.
- Vertical cracks in a slab or stem wall — often shrinkage; check for offset.
- Cracks aligned across the slab, driveway and street — in a few Baton Rouge neighborhoods, a possible fault signature. See the Baton Rouge fault guide.
How to monitor a crack
- Measure the width at its widest point and write it down with the date.
- Pencil a line across each end of the crack with the date.
- Photograph it with a ruler for scale.
- Re-check every month or two through a wet season and a dry one.
Growth past your pencil marks, or width changes of more than a hairline, mean the crack is active. We also install calibrated crack monitors that read to fractions of a millimeter.
When sealing is the right fix
Stable cosmetic cracks can be sealed to keep moisture and insects out. Cracks from active settlement shouldn’t be sealed until the settlement is fixed — the patch just cracks again. See foundation crack repair.
Bottom line
Under 1/8 inch and stable: watch it. Over 1/4 inch, growing or offset: get it measured. For a free evaluation, call Foundation Repair Baton Rouge.