Outdoor guide
Foundation cracks: how to tell a normal crack from a structural problem
By the Home Doctor team · Reviewed
Quick answer
Most foundation cracks are thin, vertical hairline cracks in poured concrete, left by the concrete shrinking as it cured. They're usually cosmetic and only need sealing if they leak, typically $300 to $1,000 for a pro to inject one crack. Horizontal cracks, bowing walls, stair-step cracks that keep widening, and cracks wider than about 1/4 inch or offset point to soil pressure or settlement. Get a structural engineer's evaluation before you call a repair company. Mark the crack's ends in pencil with the date to see if it grows.
- How urgent
- Fix soon
A hairline vertical crack usually just needs watching, or sealing if it leaks. It's urgent if a crack is horizontal, wider than about 1/4 inch, offset or growing, or the wall bows. Water against the foundation and freeze-thaw cycles make cracks worse.
- DIY or pro
- DIY if handy
Measuring and monitoring cracks, fixing gutters and grading, and sealing a hairline crack with a DIY injection kit are homeowner jobs. Diagnosing anything wider, horizontal or bowing is for a structural engineer, and the repair is for a foundation contractor.
Stop and call a pro now if
- A horizontal crack, or a basement wall that bows, leans or bulges inward: have a structural engineer look at it soon, before you hire a repair contractor.
- New cracks come with doors or windows that suddenly stick, gaps around frames, or sloping floors: call a structural engineer. Engineers diagnose the problem and don't sell repairs.
- A crack is widening quickly, or you hear cracking or see the wall moving: keep people away from that wall and call a structural engineer or foundation contractor right away.
Common causes and how to tell them apart
1. Shrinkage (poured concrete)
- How to tell
- Thin vertical or slightly diagonal hairline cracks, narrower than about 1/8 inch, often near the middle of a wall or at the corner of a basement window. Both sides are flush, and they usually appear in the first year or two.
- What fixes it
- Usually cosmetic. Mark it and watch it. If it leaks, seal it with a polyurethane or epoxy injection.
2. Water leaking through a crack
- How to tell
- Damp streaks, drips, or white chalky deposits (efflorescence) along the crack after rain or snowmelt.
- What fixes it
- Fix the water first: clean the gutters, extend downspouts 4 to 6 feet out, and slope the soil away from the house. Then seal the crack with a flexible polyurethane injection. A leaking block wall may need exterior waterproofing or an interior drain.
3. Settlement (diagonal or stair-step cracks)
- How to tell
- A crack that zigzags up the mortar joints of a block wall, or a diagonal crack in poured concrete that's wider at one end, often near a corner or where a downspout dumps water.
- What fixes it
- A small, stable crack can be repointed or sealed. If it's widening or wider than about 1/4 inch, an engineer should check for ongoing settlement, which may need piers.
4. Soil pressure (horizontal cracks)
- How to tell
- A crack running sideways along a basement wall, often partway down, or along a mortar joint in block. Sometimes the wall above or below it leans inward.
- What fixes it
- A red flag. Wet or frozen soil is pushing the wall in. Get a structural engineer's evaluation, then a repair such as wall anchors, carbon fiber straps or steel braces.
5. Active movement (wide or offset cracks)
- How to tell
- Wider than about 1/4 inch, or one side of the crack sits farther in or out, or higher or lower, than the other. You can feel a step when you run your hand across it.
- What fixes it
- Something has moved. An engineer should find out why before anyone patches it.
6. Bowing or leaning wall
- How to tell
- A long level or a string pulled tight along the wall shows it bulging inward, usually with horizontal or stair-step cracks at the worst spot.
- What fixes it
- Needs an engineer. Moderate bowing can often be stabilized with wall anchors, carbon fiber straps or steel braces. Severe bowing may mean excavating and rebuilding the wall.
Not sure which one you have?
Snap a photo. Home Doctor narrows it down, tells you how urgent it is, and prices the fix.
Diagnose it from a photoFirst diagnosis free. No account needed.
What you can safely try first
- 1Measure the crack at its widest point with an inexpensive crack gauge or crack-width card.
- 2Mark each end with a pencil line and the date, and draw a short line across the crack so you can see if the sides shift.
- 3Photograph it with a ruler or tape measure held against it, from the same spot each time. Repeat monthly and after heavy rain or a freeze-thaw season.
- 4Note the direction (vertical, stair-step or horizontal) and hold a 4-foot level or a tight string against the wall to check for bowing.
- 5Walk the house: check that doors and windows open normally, and look for new drywall cracks or sloping floors.
- 6Outside, clean the gutters, extend downspouts so water lands 4 to 6 feet out, and make sure the soil slopes away from the foundation.
When to call a pro
- A crack is horizontal, or a wall bows, leans or bulges.
- It's wider than about 1/4 inch, or one side is offset from the other.
- It grows over a few months of monitoring.
- Doors or windows start sticking, floors slope, or new drywall cracks appear at the same time.
- Water keeps coming through after you've fixed the gutters and grading.
What it costs
| Job | DIY parts | Pro, installed |
|---|---|---|
| Epoxy or polyurethane crack injection (one crack) | $50–$150 | $300–$1,000 |
| Structural engineer evaluation | — | $300–$1,000 |
| Extend downspouts and regrade soil at the foundation | $50–$300 | $500–$3,000 |
| Wall anchors or carbon fiber straps (one wall) | Not recommended | $3,000–$12,000 |
| Foundation piers (per pier; most jobs need several) | Not recommended | $1,000–$3,000 |
Ballpark US ranges as of September 28, 2026. Your region, access and the specifics of your home can move these a lot. Get two or three quotes for anything over a few hundred dollars.
What to tell the pro
I have a crack in my [poured concrete / concrete block] foundation wall, about [length] long and [width] wide, running [vertically / in a stair-step / horizontally]. One side [is / isn't] offset from the other, and the wall [is flat / bows inward about (amount)]. Since I marked it on [date], it has [stayed the same / grown]. It [does / doesn't] leak after rain, and doors and windows [work normally / have started sticking]. The house was built around [year]. Will I get a written report with the cause and a recommended repair, and are you independent of any repair company?
Questions people ask
Are cracks in a foundation normal?
Hairline vertical cracks in poured concrete are very common and usually come from the concrete shrinking as it cured. They're mostly cosmetic, though they can let water in. Horizontal cracks, stair-step cracks that keep widening, and cracks wider than about 1/4 inch or offset aren't normal and need a structural engineer's evaluation.
When should I worry about a foundation crack?
When it's horizontal, wider than about 1/4 inch, offset so one side sticks out, or growing, or when a wall bows or doors and windows suddenly start sticking. Any of those can mean the foundation is moving. Have a structural engineer look before you get repair quotes.
How much does it cost to fix a foundation crack?
Sealing one non-structural crack with epoxy or polyurethane injection typically costs $300 to $1,000 from a pro, or $50 to $150 for a DIY kit. Stabilizing a bowing wall with anchors or carbon fiber straps usually runs $3,000 to $12,000, and piers for settlement often cost $1,000 to $3,000 each, with several needed. An engineer's evaluation, typically $300 to $1,000, tells you which one you actually need.
Should I call a structural engineer or a foundation repair company?
Start with a structural engineer for anything beyond a hairline crack. An engineer finds the cause and recommends a fix but doesn't sell repairs, so there's no reason to oversell. Take the report to two or three foundation contractors for quotes.
Get an answer for your house
Every house is different. A photo gets you the likely cause, how urgent it is, and a fair price, in about 30 seconds.
Diagnose it from a photoFirst diagnosis free. No account needed.
General guidance, not a substitute for a licensed professional who can see the problem in person. If you smell gas, see sparks or smoke, or anyone is hurt, leave the area and call 911.