Every house moves a little. Concrete shrinks as it cures, wood framing dries out, and Los Angeles soil swells and shrinks with the seasons. Most small cracks are cosmetic. A few are early signs of a foundation problem that gets more expensive the longer it waits. Here is how to tell the difference.
1. Diagonal cracks at the corners of doors and windows
Thin vertical hairline cracks in drywall or stucco are common and usually come from shrinkage. Cracks that run diagonally out from the corners of door and window openings are different. They often mean one part of the house is moving more than another, which puts stress on the framing around openings.
2. Doors and windows that stick or will not latch
A door that rubs at the top corner, a gap that is wider on one side, or a window that suddenly will not close can all point to a frame that has shifted out of square. Humidity can cause some sticking, so watch whether the problem stays after the weather changes.
3. Sloping, bouncy, or uneven floors
Set a marble or a level on the floor in a few rooms. A gradual slope across a whole room, a soft spot, or a floor that feels springy can mean settling footings, rotted posts and beams in a crawl space, or deteriorated piers under a raised floor.
4. Stair step cracks in brick or block
Cracks that follow the mortar joints in a stair step pattern on a block wall, chimney, or brick veneer are a classic sign of differential settlement. Pay close attention if one side of the crack sits higher than the other.
5. Horizontal cracks in a foundation wall
Horizontal cracks in a concrete or block foundation wall can mean soil pressure is pushing the wall inward. This one deserves a professional look soon, even if the crack is narrow.
6. Gaps at trim, ceilings, and baseboards
Crown molding pulling away from the ceiling, baseboards separating from the floor, or caulk lines that keep reopening all suggest ongoing movement rather than a one time event.
7. Water, dampness, or musty smells under the house
Standing water in a crawl space, damp soil against the foundation, or a musty smell after rain points to a drainage problem. Water is the most common cause of foundation movement, and it also rots framing and invites termites.
8. A leaning chimney or a separating porch
Chimneys and porches often sit on their own footings. When they tilt or pull away from the house, their footings may be settling, which is also a safety concern during an earthquake.
A simple way to track a crack
Mark both ends of the crack in pencil with today's date and take a photo with a tape measure beside it. Check again in four to six weeks. A crack that grows longer or wider is active and should be evaluated.
When to call a professional
Get your foundation evaluated if you see any of the following:
- A crack wider than about 1/4 inch
- A crack where one side is higher than the other
- Horizontal cracks in a foundation wall
- Cracks that are growing over weeks or months
- Several of the signs above showing up at once
Structural foundation repairs usually need a design from a licensed structural engineer and a building permit. A general contractor can coordinate the inspection, the engineer, the permit, and the repair so you deal with one point of contact instead of several companies.
Common questions
Are hairline cracks in a concrete slab normal?
Usually, yes. Concrete shrinks as it cures, and thin hairline cracks in a slab or garage floor are very common. They become a concern when they widen, when one side rises above the other, or when they show up with sticking doors and sloping floors.
Does homeowners insurance cover foundation repair?
Many standard policies exclude settling, soil movement, and earthquake damage. Coverage depends on your policy and the cause of the damage, so check with your insurer before work starts.
How long can I wait before fixing a foundation problem?
It depends on the cause. Drainage problems and active cracks tend to get worse with each rainy season, and the repair usually gets larger. An early evaluation costs far less than waiting.
This guide is general information for homeowners. Every house is different, so an on site evaluation is the only way to know what your home needs.