Most foundation cracks in Southern California homes are normal: thin shrinkage cracks that formed as the concrete dried and have not changed since. A crack needs a professional’s eyes when one side has shifted out of line with the other, when it keeps getting longer or wider, when it runs horizontally along a wall that holds back soil, when it stair-steps through a block wall, or when it shows up together with sticking doors, sloping floors or new gaps outside. Those cracks are symptoms of movement, and the movement — usually water, expansive clay, poorly compacted fill or an earthquake — is what has to be diagnosed before anyone patches anything.
We are Green Design and Build, a licensed residential general contractor based in Van Nuys (CSLB #1110975), working across Los Angeles, Orange and Ventura counties and western Riverside and San Bernardino counties. This guide is how we read cracks on a first visit; it is general information, not an engineering evaluation of your house. The prices near the end come from our foundation repair cost guide and are budgeting ranges, not a quote.
Foundation cracks at a glance: normal, monitor, or call an engineer
Sort what you are looking at here; each crack type is explained below. If your concern is broader than cracks, start with our checklist of warning signs your foundation needs repair.
| Crack you see | What it usually means | What to do |
|---|---|---|
| Hairline crack, both sides flush, not changing | Drying shrinkage as the concrete cured | Normal. Photograph it once for your records |
| Vertical crack in a stem wall or slab edge, even width, no offset | Shrinkage or minor early settlement | Monitor through one wet season and one dry season |
| Vertical crack wider at the top than the bottom, or the reverse | Part of the footing settling or lifting more than the rest | Have it inspected |
| Diagonal crack from a foundation corner, or from the corners of doors and windows above | Differential movement: one part of the house moving more than another | Have it inspected, sooner if doors have started to stick |
| Stair-step crack in a block or brick wall | Mortar joints opening as the wall settles or rotates | Inspect; treat as urgent if the wall leans or bulges |
| Horizontal crack in a wall that holds back soil | Soil pressure pushing the wall inward | Call a structural engineer |
| Any crack where one side is higher or out of line with the other | The concrete has moved, not just cracked | Call a structural engineer |
| Random cracks in a garage or interior slab | Usually shrinkage; occasionally heave or a leak below | Usually normal; inspect if an edge is raised, tile keeps cracking, or the floor feels warm |
| New cracks right after an earthquake | Shaking damage; on raised houses, a sign to check bolting and cripple walls | Have it inspected |
Slab or raised foundation? Start here
Southern California houses sit on one of two foundation types, and they crack in different places. Very few have full basements, which is why so many crack guides, written for basement country, talk past what matters here.
Slab-on-grade
The ground floor is poured directly on the soil, with thickened edges or footings under the exterior walls. There are no vents low on the walls, and the floor sits a step or less above the yard. Many tract homes in Orange County, the Inland Empire and the newer parts of the San Fernando Valley are built this way. You see slab cracks in the garage floor, through floor tile and along the exposed slab edge outside.
Raised foundation (crawlspace)
The house sits on a continuous perimeter footing with a short concrete stem wall; the floor spans a crawlspace and is carried in the middle by wood posts on concrete pads. Many older homes add short wood cripple walls on top of the stem wall. Screened vents near the ground and an access hatch give it away. Look for cracks in the stem wall (outside below the stucco, and from the crawlspace), in the pier pads, and in the plaster above. Some older stem walls were poured with little or no reinforcing steel, so offset in an old stem wall matters more than the same crack in a modern one.
Hillside foundations
On a slope, footings are stepped, carried on caissons and grade beams, or partly hold back soil. The California Residential Code requires footings to bear on undisturbed natural soil or engineered fill (CRC R403.1), and hillside pads partly built up with fill are where we most often find settlement.
Why concrete cracks even when nothing is wrong
Concrete shrinks as it dries and moves with temperature. Wherever something restrains that movement — the soil beneath a slab, a footing, an inside corner — the shrinkage becomes tension, and concrete is weak in tension. The American Concrete Institute’s report on the subject, ACI PRC-224-01, Control of Cracking in Concrete Structures, reviews drying shrinkage and temperature change among the main causes of cracking, and its subject is controlling cracks, not preventing them entirely.
That is why builders cut control joints in slabs, so the shrinkage crack forms where it does no harm; cracks that wander anyway are common and not defects on their own. The presence of a crack tells you little. Its shape, whether the two sides still line up, and whether it changes tell you almost everything.
Types of foundation cracks, one by one
Hairline shrinkage cracks
These are thin cracks with both faces flush: single vertical lines on a stem wall, or random and map-like patterns across a slab or garage floor. They are cosmetic. They do not mean the house is moving, and on their own they do not need a repair. What would change that verdict is a crack that keeps changing; if it looks the same in a year, it is finished.
Vertical foundation cracks
A vertical crack in a stem wall or at the edge of a slab, the same width from top to bottom and with no offset, is usually shrinkage or a small amount of early settlement. It is the most common crack we see on raised foundations, and most of them are harmless.
The vertical cracks worth an inspection are tapered — wider at the top or at the bottom — which points to one stretch of footing moving more than its neighbors. On a raised house, check from the crawlspace too: a crack through the full thickness of the stem wall that lines up with a sag in the floor above is a different finding from a surface line.
Diagonal cracks
Diagonal cracks run at an angle from a foundation corner, a step in the footing, or the corner of a door or window above. They signal differential movement: one part of the house dropping or rising more than its neighbor, such as a corner settling on loose fill or an edge lifting on wet clay.
Diagonal cracks at the corners of openings in stucco and drywall can come from framing shrinkage alone; they matter when they appear at several openings, line up with a foundation crack below, or arrive with doors that start to rub or stop latching. Once the cause is known, our guide to stucco repair, re-coating and re-stucco covers fixing the finish so the crack does not simply telegraph back through.
Stair-step cracks in block and brick
Block (CMU) and brick crack along their mortar joints, so movement shows up as a staircase — in property walls, retaining walls, chimneys and the occasional block stem wall. A stair-step crack in a freestanding wall that is still plumb usually means that wall’s own footing has settled at one end. A stair-step crack combined with a lean, a bulge, or blocks pushed out of line means the wall is rotating or being pushed by soil.
A retaining wall in that condition should be looked at before the rainy season. Our retaining wall service page explains how we rebuild failing walls, and retaining wall ideas for sloped and hillside lots covers the drainage and design choices that keep a new one from cracking the same way.
Horizontal cracks
A horizontal crack along a wall that holds soil back — a hillside stem wall, a lower floor dug into a slope, or a retaining wall — is the crack to take most seriously. It usually means soil pressure is pushing the wall inward, often with visible bowing. That is a call for a structural engineer, not a patch.
A single straight line where a stem wall meets its footing may be a construction joint between two pours rather than a crack, but a joint that has opened or slid is a problem too, so have it identified.
Cracks with displacement
Displacement means one side of the crack is higher than the other, or the two sides have slid out of line. It tells you the concrete has moved, not merely cracked. Lay a straightedge or level across the crack: if it rocks on one side, there is vertical offset.
Offset is the clearest single reason on this page to bring in a structural engineer. Width alone can mislead; a crack whose sides no longer line up rarely does.
Cracks in a slab foundation or garage floor
Garage floors and interior slabs crack almost universally, often at re-entrant corners where the slab turns a corner. Flat, stable slab cracks are normal. Have these looked at:
- A raised edge or a hump along a crack, possible heave on expansive soil.
- Tile that cracks again along the same line after replacement.
- Moisture or white mineral deposits seeping from the crack.
- A warm patch in the floor or running-water sounds with every fixture off, possible signs of an under-slab leak that call for leak detection and plumbing repair before the leak becomes a soil problem.
- Perimeter cracks that open and close with the seasons, typical of a slab on clay.
One caution: some slabs, mostly in newer tract homes, are post-tensioned, with steel tendons inside the concrete that were stressed after the pour. Before anyone drills, cores or saw-cuts a slab to investigate a crack, confirm whether it is post-tensioned and locate the tendons.
Driveway and patio cracks follow the same rules but are not foundation problems; if yours are breaking up, see our guides to concrete driveway cost and concrete patio cost.
Cracks after an earthquake
After real shaking, walk the house: stem walls, chimney, stucco, the joint with the porch or patio. On a raised house the bigger question is whether the house is bolted to its foundation and its cripple walls braced. Our seismic retrofit page explains what that work involves, and our guide to the Earthquake Brace + Bolt grant covers who qualifies for help paying for it.
What makes Southern California foundations crack
Frost heave, the usual villain in colder states, rarely figures in the low-elevation areas we serve. Water, clay, fill and earthquakes do.
Water and expansive clay
Clay soils swell when wet and shrink when dry, and a foundation on them rises and falls with the seasons. Under California Building Code section 1803.5.3, soil with an expansion index greater than 20 (or that meets the plasticity and fine-particle tests in the same section) is expansive, and the Residential Code (R403.1.8) requires foundations on it to be designed under CBC 1808.6. On an existing house the pattern is cracks that open in late summer and close after winter rain, and doors that stick in one season but not the other.
Water drives that movement, and most of it is self-inflicted: downspouts emptying at the stem wall, planters against the house, paving that slopes back toward it. CRC R401.3 requires the ground to fall at least 6 inches within the first 10 feet from the foundation, and paved surfaces within 10 feet to slope at least 2 percent away. Correcting drainage is frequently the first repair and sometimes the only one; our El Niño home preparation guide walks through gutters, grading and downspouts.
Fill, hillsides, earthquakes and leaks
Hillside pads were often made by cutting one part of a slope and filling another; where the fill was poorly compacted the house settles over it, and the cracks concentrate on the downhill side. Earthquakes crack stucco, plaster and chimneys first, and the structural risk on older raised houses is a house that is not bolted down. And a pipe leaking under a slab saturates the soil in one spot, so a crack sitting over a bathroom or kitchen run is worth a leak test before anything else.
Check the mapped hazards for your lot
Two free tools show, by address, whether your lot carries a mapped risk that changes how a crack should be read.
- California Geological Survey EQ Zapp. The state’s earthquake hazard zone app shows whether a property lies in a mapped fault-rupture, liquefaction or earthquake-induced landslide zone, and whether the area has been evaluated at all.
- ZIMAS and the LADBS parcel profile (City of Los Angeles). Look up a parcel in ZIMAS or the LADBS parcel profile to see whether it is flagged as an earthquake-induced liquefaction or landslide area, an Alquist-Priolo fault zone, a hillside grading area, or compacted filled ground.
A map is not a diagnosis. It does tell the engineer what to look for, and it is a good predictor of whether any repair will need a soils report first.
How to monitor a foundation crack yourself
Whether a crack is changing is the most useful evidence there is, and you can collect it yourself:
- Photograph each crack straight on with a tape measure beside it, and keep the dated photos together.
- Mark both ends with a pencil line and the date, so you can see whether it grows in length.
- Re-check at the end of the rainy season and at the end of summer, the cycle clay moves on. A crack monitor glued across the crack makes small changes easy to read.
- Check for offset with a straightedge or level laid across the crack.
- List doors and windows that start to stick and gaps that open at trim or the patio, and where they are relative to the crack.
- Walk outside during or after rain. Note where downspouts discharge and whether water ponds against the wall.
- On a raised house, look into the crawlspace from the hatch with a flashlight: damp soil or standing water, cracked pier pads, posts that lean or no longer touch the beam above.
Do not caulk, patch or paint over cracks before someone qualified has seen them. Patching destroys the evidence — the direction, the offset and the history of the crack — that the diagnosis depends on.
Engineer, contractor or nobody: who to call about a crack
- Nobody, for now: hairline cracks with flush faces, no offset, nothing sticking, and no change across a full year of photos.
- A licensed general contractor: a first look at the whole house, the crawlspace and the drainage, sealing stable cracks once the cause is fixed, and coordinating the engineer when one is needed. Check the license first: see our guide on how to verify a contractor’s license in California.
- A structural engineer: offset cracks, horizontal cracking or bowing in a wall that holds soil, tapered cracks with sticking doors and sloping floors, visible earthquake damage, and any repair that changes how the house is supported.
- A geotechnical (soils) engineer: hillside lots, mapped liquefaction or landslide areas, suspected expansive clay, and underpinning design.
Permits follow the same line. In the City of Los Angeles, the exemption for small jobs valued at $2,500 or less does not apply to work that impacts the structural stability of a building (LAMC 91.106.2, item 1), so structural foundation repairs are permitted work. Other cities and the counties run their own building departments; check with yours.
What fixing a foundation crack usually involves
The repair follows the diagnosis: a stable crack is sealed, a crack caused by water gets the water fixed first, and a crack caused by settlement gets the support fixed. These are the published budgeting ranges from our foundation repair cost guide for the repairs cracks most often lead to:
| Repair | When a crack leads to it | Budgeting range (not a quote) |
|---|---|---|
| Crack injection (epoxy or polyurethane) | The crack is stable and the cause has been dealt with | $500–$3,000 per area |
| Drainage correction | Water against the foundation is driving seasonal movement | $3,000–$15,000 |
| House leveling and pier-and-beam repair | A raised floor has dropped on sunken posts, cracked pads or sagging girders | $5,000–$25,000 |
| Underpinning | Part of the footing is still settling into soil that cannot carry it | $10,000–$40,000 |
These are budgeting ranges, not a quote; the only real number is a written proposal after a site visit. Injecting a crack that is still moving wastes money, because it reopens beside the repair. If settlement is ongoing, our guide to foundation underpinning methods compares the pier types and explains how to tell whether a house is still moving. See also our foundation design ideas, our foundation repair and retrofit services, and financing options for larger repairs.
Foundation Cracks FAQs
Are foundation cracks normal?
Yes, most are. Concrete shrinks as it dries, so thin cracks with flush faces appear in most foundations and garage slabs without meaning the house is moving. A crack stops being normal when one side is offset, when it keeps growing, when it runs horizontally along a wall holding back soil, or when it comes with sticking doors, sloping floors or new gaps around the house.
What kind of foundation crack is serious?
Cracks with displacement, horizontal cracks or bowing in a wall that retains soil, stair-step cracks in a leaning or bulging block wall, tapered cracks, and any crack that keeps lengthening or widening from season to season. Each points to movement in the soil or structure and deserves a look from a structural engineer or an experienced foundation contractor.
Are vertical cracks in a foundation bad?
Usually not. A vertical crack of even width with no offset is most often shrinkage or minor early settlement and only needs monitoring. One that is clearly wider at the top or bottom, runs through the full thickness of a stem wall, or lines up with a sag in the floor above should be inspected.
What do stair-step cracks in a foundation or block wall mean?
They follow the mortar joints and show that the wall has moved. If the wall is still plumb, one end of its footing has usually settled. If it also leans, bulges or has blocks pushed out of line, soil is pushing or rotating it, and a retaining wall in that state should be evaluated before the rainy season.
Should I worry about cracks in my slab foundation or garage floor?
Flat, stable slab cracks are normal shrinkage. Have the slab looked at if one side of a crack is raised, tile keeps cracking along the same line, moisture or white deposits seep out, part of the floor feels warm, or cracks near the edge open and close with the seasons.
Can I seal a foundation crack myself?
A hairline crack that has not changed in a year can be sealed with a concrete crack filler to keep water out. Do not seal a crack that is new, growing or offset, and do not patch anything before it is inspected: the sealant hides the evidence, and a moving crack reopens beside the patch.
Who should I call about a foundation crack: an engineer or a contractor?
A licensed general contractor with foundation experience is a sensible first call to read the crack in context and tell you whether it needs an engineer. Go straight to a structural engineer for offset cracks, horizontal cracking or bowing in a retaining or hillside wall, or visible earthquake damage; hillside lots and underpinning also need a geotechnical engineer.
Does homeowners insurance cover foundation cracks in California?
It depends on the cause and the policy. The California Department of Insurance says a standard homeowners policy does not cover earthquake damage, apart from fire following an earthquake, and that insurers must offer earthquake coverage separately. For shrinkage, settlement or soil movement, coverage depends on your policy wording, so check the exclusions or ask your agent. This is general information, not insurance advice.
Sources
- ACI PRC-224-01, Control of Cracking in Concrete Structures (American Concrete Institute)
- 2025 California Residential Code, Chapter 4 — R401.3, R403.1, R403.1.8 (the 2025 codes took effect 1 January 2026)
- 2025 California Building Code, Chapter 18 — section 1803.5.3, expansive soil
- California Geological Survey, EQ Zapp
- City of Los Angeles, ZIMAS
- Los Angeles Municipal Code section 91.106 — permits and the small-job exemption
- California Department of Insurance, earthquake insurance guide
Not sure what your crack means? Have it looked at
Send us photos of the cracks and anything else you have noticed — a sticking door, a sloping floor, water that pools. We reply within one business day, and a site visit takes about two hours: we walk the outside, check the drainage, go into the crawlspace or look over the slab, and tell you plainly if you are looking at something to ignore, something to monitor, or something that needs an engineer. In Los Angeles and Orange counties, ask about our free roof and foundation inspection before the El Niño rains, or contact our Van Nuys office to book a visit anywhere in our service area.