The most common signs of foundation problems in a house are cracks in the foundation or brick, sinking or heaving floors, doors and windows that stick or won’t latch, gaps around frames, sloping floors, a damp crawl space or basement, and cabinets pulling away from the wall. One sign alone is often normal settling. Several signs together, or a sign that gets worse month to month, means the foundation is moving and you should have it checked.
Below are the eight signs we see most often, how to tell a minor issue from a serious one, what causes foundation movement, and what to do next.
What causes foundation problems?
Almost every foundation problem comes back to the soil under the house and the water in it.
- Expansive clay soil swells when wet and shrinks when dry. The house rises and drops with the seasons, and the foundation cracks where the movement is uneven.
- Poor drainage. Clogged gutters, short downspouts, and soil that slopes toward the house soak the ground next to the foundation.
- Poorly compacted fill. If the builder poured the footing on loose soil, it settles under the weight of the house.
- Frost heave. Water expands about 9 percent when it freezes. Wet soil that freezes around a shallow footing can lift it.
- Plumbing leaks under a slab wash out or swell the soil beneath the floor. An unexplained jump in your water bill is a clue.
- Hydrostatic pressure. Saturated soil pushes sideways on basement walls, which can crack and bow them.
Different foundation types show the damage differently. A slab-on-grade house shows it in floor cracks and doors. A pier and beam house shows it in sagging floors and the crawl space. A basement house shows it in wall cracks, bowing, and leaks.
The 8 most common signs of foundation problems
1. Foundation cracks, wall and floor cracks, and other fractures
Cracks are the sign people notice first, and they are also the sign most often misread. Most poured concrete foundations develop thin shrinkage cracks in the first year or two as the concrete cures. Those hairline cracks, about 1/16 inch wide or less, are usually not structural.
Cracks deserve a closer look when they are:
- Horizontal on a block or poured basement wall. A horizontal crack often means soil pressure is pushing the wall inward. If the wall also bows, call a structural engineer.
- Stair-step cracks that follow the mortar joints in block or brick, especially near corners.
- Wider than about 1/4 inch, or wider at one end than the other. A tapered crack shows one part of the foundation is moving more than the other.
- Growing. Mark the ends of a crack with a pencil and the date, and measure the width. Check again in a month. A crack that lengthens or widens is active.
- Leaking water, leaving white mineral crust, or letting in soil or insects.
Inside the house, watch for diagonal drywall cracks running up from the corners of doors and windows, cracked floor tile in a line across a room, and a cracked or leaning chimney.
2. Foundation settling or sinking
Settlement is when part of the foundation drops. You may see one corner of the house sitting lower than the rest, a gap where the porch or steps meet the house, or a slab that has dropped away from the wall. Settlement usually causes vertical or diagonal cracks that are wider at the top.
Every house settles a little. The concern is differential settlement, where one part drops more than another. A 1/2 inch dip at one corner can start a chain of cracked drywall and sticking doors. If the drop continues, the fix is usually steel or concrete piers driven under the footing to stable soil, which lift and hold the house. Sudden, fast sinking needs immediate attention.
3. Foundation upheaval
Upheaval is the opposite of settling: part of the slab moves up. It is most common at the perimeter of a slab foundation but can show up as a hump in a hallway or a doorway where the floor rises. Causes include clay soil swelling after heavy rain, frost heave in cold climates, and plumbing leaks under the slab. A slab can heave an inch or more, and much less than that is enough to crack floors and jam doors.
If you suspect a slab leak, turn off every faucet and appliance and watch the water meter for an hour. If it moves, call a plumber before you call a foundation contractor.
4. Doors that stick or don’t open and close properly
When a foundation shifts, door frames go out of square. Interior doors start to rub at the top corner, exterior doors drag at the threshold, and double or French doors no longer meet in the middle. Look at the gap between the door and the frame. If it is wider at one top corner than the other, the frame has racked.
Humidity also makes wood doors swell, especially in summer or after a flood. If a door sticks only in humid months and works fine in winter, the cause is more likely moisture than the foundation. If it sticks year round and there are cracks nearby, have the foundation checked.
5. Gaps around exterior doors or window frames
Look for gaps between the frame and the brick or siding, caulk that has torn open, and windows that are hard to lift or won’t lock. Brick that pulls away from a door or window frame is a strong sign of movement. These gaps also let in air and water, which raises energy bills and can rot the framing.
6. Sagging or uneven floors
Set a marble or a level on the floor in several rooms. A floor that slopes more than about 1 inch over 15 to 20 feet deserves an inspection. In a pier and beam house, sagging or bouncy floors often mean a pier has sunk or a beam or joist has rotted or been damaged by termites. In a slab house, an uneven floor usually means settlement or heave in the soil below.
Sloping floors are also a safety issue for small children and anyone who uses a walker or wheelchair.
7. A damp crawl space or basement
Water and foundation problems feed each other. Water in the soil moves the foundation, and a moving foundation opens cracks that let in more water. Signs of a wet crawl space or basement include:
- standing water or mud in a crawl space
- a musty smell, mold, or mildew (see how to get rid of black mold in a basement)
- white, chalky efflorescence on concrete or block, which is salt left behind as water passes through
- peeling or bubbling paint on basement walls
- rotting wood on sill plates, joists, beams, or piers
- insects and pests, which follow moisture and come in through cracks
In a crawl space, a polyethylene vapor barrier over the soil and good drainage around the house reduce moisture. Some homeowners also pour a thin concrete rat slab over the crawl space floor. In a basement, find out where the water comes from before you choose a fix. Our post on what causes leaky basements covers the common sources.
8. Countertops and cabinets separating from the wall
Kitchen cabinets and countertops are installed level and tight to the wall. When the floor or wall moves, a gap opens: first 1/8 inch, then 1/4, then more. Cabinet doors may also swing open or shut by themselves. A gap that grows over time points to foundation movement.
Other warning signs to look for
- Drywall nail pops across several rooms
- A leaning or cracked chimney, or a chimney pulling away from the house
- Walls pulling away from the house or from the ceiling, which needs prompt attention
- Separated expansion joints in slabs, patios, and walks next to the house
- Cracked driveways and sidewalks near the house after a hard winter, which can point to freeze-thaw damage and soil movement (see how to repair a cracked concrete driveway)
Buying an older home? Check these first
Older homes often have foundation problems that are hard to see during a showing, especially homes on clay soil that have risen and settled for decades. Before you make an offer, look at the basement or crawl space for cracks, bowed walls, efflorescence, fresh paint covering stains, and a musty smell. Check whether the gutters and downspouts work and whether the yard slopes toward the house. Ask the seller about past water and pest problems, and hire a home inspector. If the inspector flags structural concerns, get a structural engineer’s report before closing.
What to do if you see signs of foundation issues
- Document it. Photograph each crack with a tape measure in the shot, and date it. Mark the ends of cracks. Recheck monthly.
- Fix the water outside. Clean the gutters, extend downspouts at least 6 feet from the house, and regrade soil so it slopes away from the foundation. See how to protect your home from exterior water damage.
- Get an independent opinion. A structural engineer’s report usually costs a few hundred dollars, and the engineer has nothing to sell you. Foundation contractors often inspect for free, but they also sell the repair.
- Get written estimates. If repair is needed, get at least two written bids with the method, the number of piers, and the warranty spelled out. Ask whether the warranty transfers to a new owner.
- Seal and waterproof once the structure is stable. Piers and wall anchors stop movement, but water can still come through the cracks the movement left behind. After the structure is repaired, seal the cracks and the walls so water stops coming through.
Foundation repair costs vary widely. National cost guides put many residential repairs in the range of a few thousand dollars to around $10,000, and jobs that need many piers or wall rebuilding run higher. Prices vary by region, soil, and access.
Seal foundation cracks and leaks with SANI-TRED
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The liquid rubber soaks into the concrete, bonds to it, and cures into a seamless rubber membrane. Cracks and the joint where the wall meets the floor are filled with a flexible rubber patching compound made by mixing LRB (Liquid Rubber Base) with TAV. The membrane stretches with small seasonal movement instead of cracking like cement-based patches. It also blocks 99 percent of radon gas. The DIY process is prep, prime, patch, and topcoat, and the basement system carries a lifetime warranty.
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Frequently asked questions
What are the first signs of foundation problems?
The earliest signs are usually small: a door that starts to stick, a new diagonal crack above a door frame, or a hairline crack in the basement wall that slowly widens. Track them with dated photos.
Are cracks in a foundation normal?
Thin vertical shrinkage cracks in poured concrete are common and usually not structural. Horizontal cracks, stair-step cracks, cracks wider than about 1/4 inch, and cracks that keep growing are not normal.
How do I know if my house has foundation issues or just normal settling?
Normal settling is minor and stops after the first few years. Foundation issues keep getting worse: cracks widen, doors that once worked start to stick, and gaps open around frames and cabinets.
Can foundation problems cause basement leaks?
Yes. Movement opens cracks in walls and floors, and saturated soil pushes water through them. Fix the drainage outside and any structural movement, then seal the cracks and walls from the inside.
Who should I call about foundation problems?
For a structural question, a licensed structural engineer gives an independent assessment. For the repair itself, a foundation repair contractor. For water coming through a stable wall, you can seal it yourself with a DIY system.
Does homeowners insurance cover foundation repair?
Most standard policies exclude settling, soil movement, and gradual water damage. Coverage is more likely when a covered event such as a burst pipe causes the damage. Check your own policy.
Sources: Cost ranges from national home improvement cost guides (Angi, HomeAdvisor); ranges vary by region. Water expansion when frozen: USGS Water Science School.