The short answer
A foundation may be moving if several signs show up together, in the places where a moving house would show them. The ASCE Geo-Institute guide says more indicators = higher probability. A single sticking door on a humid day is not that.
Signs and their lookalikes
| What you see | Why it may be the foundation | What else can cause it |
|---|---|---|
| Doors that bind or won’t latch | doors that bind or don't latch are on Texas inspectors’ lists | a loose or undersized hinge, or a strike plate out of alignment |
| Stair-step cracks in brick | diagonal (stair-stepping) cracks in brick follow mortar joints as the wall shifts | Brick and mortar flex with heat and cold; the FPA names thermal expansion and contraction of the brick for vertical cracks |
| Cracks above doors and windows | cracks above doors or windows are on ASCE Geo-Institute’s list | an undersized or overloaded lintel can crack the brick above an opening |
| Sloping floors | sloping floors are on TREC’s list | A house built out of level from day one |
| Gaps where walls meet ceilings or floors | walls separating from ceilings or floors | Drywall settling and seasonal wood movement |
| Frieze board or trim separation | frieze board separations | Moisture swelling in the trim |
| Cracks in tile | They can follow a crack in the slab below | flaws in the tile itself |
| Cracks in a new house | Fresh slabs also shift | The FPA suggests waiting approximately two years before judging a new house |
Call to schedule an inspection
Inside, outside and under the house
Outside, walk the perimeter. Look at the brick, the corners of windows, the top of the slab edge and the gap around garage doors. Water pooling against one side, downspouts that end at the wall and a big tree on the sunny side all matter more than any one crack.
Inside, stand at the end of a hall. Doors that don’t clear the frame, trim pulling away and a visible slope are easier to see by eye than to measure.
Under a pier and beam house, a dry crawl space shows leaning piers, gaps between shims and beams, and soft or stained wood. San Antonio has many of these houses; see the pier and beam page.
Why signs come and go with the seasons
San Antonio’s clay shrinks in dry spells and swells in wet ones. The Texas Department of Licensing and Regulation says expansive soils heave when wet, settle when dry. The city’s record includes a year with 10.11 inches of rain and one with 52.28 inches, so movement between seasons is not a surprise. The TREC guide for inspectors adds that some movement is normal.
Call to schedule an inspection
Track it yourself
- Date and photograph each crack with a coin or tape in the frame.
- Mark the ends with a pencil and a date. A crack that grows past the mark is worth a call.
- Note which doors stick, and the weather that week.
- Check with a long level or a marble on the floor.
- Repeat in a different season.
ASCE’s Texas Section says that in some situations may be a prudent approach before any structural repair. A record of dated photos makes that monitoring real.
When to call
Call to schedule an inspection when cracks widen, doors stop closing, you see a visible slope, or a plumbing leak was found under the slab. If the problem is minor, you’ll hear that too: some visits end with advice to fix drainage and monitor.