Foundation Problems: Cracks, Sloping Floors, Next Steps

01Severity table

Symptom, severity and next step

Symptom	Severity	Likely cause	Next step
Hairline vertical crack in concrete, stable	Monitor	Concrete shrinkage	Mark ends, date, photo; recheck
Stair-step crack in block or brick	Get an inspection	Differential settlement	Inspection
Crack wider than ~1/8", or one side offset	Get an inspection	Settlement or heave	Inspection, then a fix
Horizontal crack or bowing wall	Call an engineer now	Soil or water pressure	Engineer evaluation
Floors sloping or bouncy over a crawlspace	Get an inspection	Sagging girder, failed posts, rot	Leveling options
Doors and windows suddenly sticking	Get an inspection	Frame racking from movement	Inspection; note the date
Gaps at trim, cracked drywall at door corners	Monitor	Seasonal movement or settlement	Monitor; inspect if growing
Cracked chimney or chimney pulling away	Get an inspection	Settlement, quake damage	Inspection; chimney bracing
Porch or steps separating from the house	Monitor	Separate footing settling	Monitor; repair the steps
Cracks in the yard or slope, house on a hillside	Call an engineer now	Possible slope movement	Hillside engineer

Severity labels are general guidance, not a diagnosis. Only someone who has been in the crawlspace or under the slab can say what is causing a symptom.

02Heave vs settlement

Is the house sinking or being pushed up?

Settlement

Part of the foundation drops: soft or poorly compacted fill, soil drying out under a corner, leaking pipes washing soil away, or a downslope edge creeping. Cracks tend to be wider at the top; floors slope toward the low spot.

Heave

Clay soils swell when wet and push the foundation up, often in the middle of a slab or along a wet side of the house. Cracks can be wider at the bottom and close again in dry months. The fix starts with water, not piers.

Interior doorway with a hairline diagonal drywall crack from the door corner above a hardwood floor — A diagonal crack from a door corner is a common interior sign.

03Water

Water is behind most foundation movement

Roof runoff dumped at the foundation, yards that slope toward the house, and leaking pipes keep soil wet on one side and dry on another. Before paying for piers, ask whether gutters, downspouts and grading are part of the cause. For drainage fixes, see Walnut Creek Yard Drainage. More on soil in the soil and movement guide.

04Monitoring

How to document and monitor a crack

Pencil a short line across each end of the crack and write the date next to it.
Photograph it with a coin or tape measure for scale, from the same spot each time.
Check door and window operation and note which ones stick and when.
For sloping floors, roll a marble or use a long level in the same spots each season.
Recheck every two to three months and after heavy rain or an earthquake.
Keep the notes: an engineer or contractor can read a year of records much better than a single photo.

05Questions

Foundation problem questions

Should a foundation crack be repaired from the inside or the outside?

It depends on access and the foundation type. Raised-foundation stem walls are often repaired from the crawlspace side; slab cracks from above. Either way, sealing only makes sense once the movement behind the crack has stopped or been fixed.

What is the best time of year to look at foundation problems?

Watch cracks and doors through a full wet and dry season: many clay-soil cracks open in late summer and close in winter. Repairs are easiest in dry months, but fast-changing symptoms should be checked right away.

Are hairline cracks in a foundation normal?

Thin, straight shrinkage cracks in concrete are common and often harmless. Mark the ends with a pencil and date, photograph them, and recheck every few months. Widening, offset or new cracks call for an inspection.

Can I tell how serious it is from photos?

Photos help a contractor or engineer decide what to look at, but nobody can responsibly diagnose a foundation from photos alone. A site visit, crawlspace access and sometimes a floor-level survey are needed.

Sources · read October 4, 2026

Walnut Creek Yard Drainage