Signs of foundation problems

Which cracks are normal

Almost every house has some foundation cracks, from concrete shrinking as it cures and from minor settling, usually 1/8 inch wide or less (Colorado Geological Survey). Texas engineers note that most cracks don't compromise a structure (ASCE Texas Section).

Houston's Foundation Performance Association gives a rule of thumb by age: no wall cracks in a new house, no more than hairline cracks in a used house under 10 years old, and no more than 1/8 inch in a house older than that (Foundation Performance Association).

Direction matters too. Straight drywall cracks often come from taping or green lumber shrinking; diagonal cracks are more likely from swelling soil, settling or other foundation movement (Colorado Geological Survey). A floor that tilts more than 1% is usually noticeable (ASCE Texas Section).

Track it before you worry

Measure the width of a few cracks every month and note whether they hold steady, grow, or open and close with the seasons (Colorado Geological Survey). A crack that grows over months says more than one that appears once. An engineer's evaluation is the next step when it does: what that involves and costs.

Basements

Cracks in a basement wall can mean damage from soil pressing on the outside of the wall, and some older houses have unreinforced basement walls that can buckle or collapse (FEMA).

Where clay makes it likelier

USDA rates shrink-swell clay a limit for houses without basements where it expands and shrinks enough to move footings and slabs. Counties with 20,000 or more homes where it covers the most land:

Texas cities

Texas cities with 10,000 or more homes, measured inside city limits.