Concrete almost never fails on its own. A slab can sit flat and sound for forty years and then drop an inch in a season, and the concrete is the same concrete it always was. What changed is the dirt holding it up.
Everybody's concrete sinks for the same handful of reasons, so the cause is rarely worth arguing about. What's worth working out on your own property is which piece of concrete moved. The answer decides who you should be calling, and the two answers point to two completely different trades.
Concrete sinks when the ground underneath it settles or washes away and the slab drops into the space. A sunken driveway, sidewalk or patio is a concrete lifting job. Sunken steps, a stoop, a porch or the slab meeting your house is settlement, which Anglin's repairs with piers driven to firm ground.
Why does concrete sink in metro Atlanta?
Four things do most of the damage around here, and none of them are the thing you'll read about on every other page in this search.
Water gets under the slab and carries the dirt off
Water is the engine. A downspout dumping beside a walk, a driveway and a front walk shedding into the same few feet of dirt, a grade that tips back toward the house, a hard summer storm on ground that's already saturated. Each one moves a little soil, and the soil has nowhere to go but out from under your concrete. Asked what happens after a slab has been repaired on ground like that, the owner's description is blunt: "then we get these downpours that's happening, and then all that water seeps down back to that unstable soil, then that thing sinks."
The dirt under it was never packed to begin with
Most residential concrete goes down on fill, and fill is only as good as the machine time somebody spent on it. The industry benchmark is 95 percent compaction, reached in layers with a compactor. Crews under a schedule pack the top two or three feet and leave the rest loose, and the probe from the county only reaches the good part. Your slab then spends the next fifteen years finding the soft ground beneath the firm ground.
The footing was thin, shallow, or not there at all
Plenty of outdoor concrete has no footing at all, which is normal and fine for a patio. A structure is a different matter. In the owner's words, sometimes a settlement problem "couldn't be related to the soil at all. It could be the footing wasn't poured thick enough, or it was poured too thin."
The soil answer everybody else gives you is wrong here
Google's own AI Overview for this question lists expansive clay as one of three main causes, and nearly every concrete page in this SERP repeats it. The USDA soil survey doesn't support that for metro Atlanta. The dominant map units under most of the metro, Cecil, Appling and Pacolet, carry a linear extensibility of roughly 1.5 to 1.8 percent, which the USDA rates low for shrink-swell. Our red clay is dense and it holds water. Seasonal heaving is not what it does. Water, slope, fill and erosion explain nearly everything you're looking at, and knowing that changes what you should be fixing: the drainage, not the dirt chemistry.
Start by naming the concrete that moved
You can make this call yourself, standing where you are right now. Say out loud what the sunken concrete is attached to.
A driveway, a sidewalk, a patio or a pool deck
Flatwork poured on open ground carries nothing but itself and whatever parks on it. When the soil beneath washes out, the slab drops into the void, and putting it back means filling that space and floating the concrete up on the filler. Raising flatwork belongs to a concrete lifting specialist, a different trade from ours. Anglin's does not do concrete leveling, slabjacking or polyurethane foam injection, and we'd rather say so on this page than have you book a visit for an estimate we can't write.
None of that means the problem is serious. A sunken apron or a tipped front walk is a nuisance and a trip hazard, not a signal about your house, and a concrete lifting company can come out and tell you what it takes to put it back.
Steps, a stoop, a porch, or the slab tied to your house
Concrete attached to the building is a different animal. Entry steps, a stoop, a porch landing, a garage apron poured against the foundation, and a structural slab under living space are all carrying weight that belongs to the house. When the ground under those gives out, the word for it is settlement, and settlement is a foundation repair, not a leveling job. Steel piers go down beside the structure until they reach ground that holds, and the weight transfers off the fill and onto the steel.
Asked directly how his crews handle a set of steps that's gone down, the owner doesn't hedge: "we gotta go in there and completely tear it out, and go in and put the proper footings in it, and they're tied into the original foundation."
Is sinking concrete a foundation problem?
Only when the concrete is part of the house, and there are three free checks that settle it.
Walk the joint where the concrete meets the brick
Stand to the side of the entry and look at the seam. A gap that's opened between the stoop and the wall, widest at the outer edge, with square window frames and level brick courses above it, is a structure sitting on fill that let go. The house held its line.
Go inside and look at the same wall from the other side
Diagonal cracks at door and window corners, a door that's stopped latching, a floor that runs downhill toward that wall. Any of those on the same side of the house as the sunken concrete moves the problem off the slab and under the building, and that gets diagnosed before anything else happens.
Find the hollow beside it
Probe the dirt right against the sunken edge with a piece of rebar or a stick. A void that runs back a few feet under the concrete is the fill that used to be holding it up, and that same void will keep eating whatever gets poured or pumped into it if the water feeding it isn't dealt with first.
There's a version of this where both are true at once. Ground that undermined a front walk can run under the corner of the house it's sitting next to. Two repairs happening to be neighbors is worth knowing about before the estimate lands, and it isn't cause for alarm.
What honest sorting looks like from the customer's side
Anglin's has been repairing Atlanta foundations and masonry since 1930, and the company used to offer foam lifting for flatwork, which is why so many old articles on this site talk about it. That changed. Piers are the whole business now, and the owner puts it plainly: "we don't do no more foam, pumping, or nothing. We do it strictly by foundation piers."
So a free look here sometimes ends with nobody selling you anything. One homeowner wrote about exactly that:
I would highly recommend Anglin. They are professional and helpful. They came to my home to give us a quote but fortunately our issue didnt require their services. Even though it did not, the Anglin rep was extremely thorough and gave us a full synposis of all the work we would need to have the concrete contractor complete. If I ever did need foundation or masonary services, I would call them again.
Elle Kerris, 5 stars
On the work that is ours, the approach is the same one described across every settlement job: "We try to be honest with them, and tell them what we see." What a pier repair involves on a settled structure, what it costs and what it's warranted for all live on the foundation repair page. If the sunken concrete at your house is the front entry specifically, why are my front steps sinking goes deeper on how entryways get built and why they move first.
Five things to check on your own concrete
Each of these is free, and they're the same things you'll be asked about on the phone:
- Name what the concrete is attached to. Touching the house means settlement. Standing alone in the yard means flatwork. That single answer routes the whole job.
- Watch where the water goes during the next hard rain. Downspouts, the driveway apron, the low corner of the yard. Water pooling in the sunken spot is feeding the void that made it.
- Check the fall away from the house. Concrete that's dropped often now slopes back toward the foundation, so the repair has to restore the drainage, not just the level.
- Look at the joint against anything fixed. A pool deck separating from the coping, a walk parting from a stoop, a garage apron dropping off the slab edge. Those gaps measure how far it has actually moved.
- Photograph it for yourself and write the date on it. In a month you'll know whether it's still moving, which tells you more than any single measurement.
Frequently asked questions about sinking concrete
Does Anglin's do concrete leveling?
Anglin's does not do concrete leveling, mudjacking or foam lifting of any kind, and hasn't for years. Each of those methods works by filling the space under a slab and floating it back up, which is a different trade with its own specialists. What we do is settlement repair: steel piers driven to load-bearing ground under structures that are part of your house, such as steps, stoops, porches, garage aprons and structural slabs.
Can a sunken concrete slab be repaired without replacing it?
Usually yes, and replacement is the most expensive route by a wide margin. A slab that's still sound in one piece can be brought back up, either by a lifting specialist on flatwork or on steel piers when it's carrying part of the house. The exception is concrete that's broken into several pieces, crumbling, or spalling apart, because raising a broken slab just gives you a broken slab at a new height.
Why did my concrete sink again years after it was fixed?
Because the earlier repair was carried by the same loose fill that failed the first time. Anything that sits on soft ground adds weight to soft ground, so a few dry years pass and then a run of heavy rain finds the void again. A repair that lands on bearing soil behaves differently, which is why what the support reaches matters more than what the surface looked like the week after.
Is a sunken slab a safety problem?
A lip between two slabs is a trip hazard well before it's anything structural, and the people who find it are the ones who don't live there. Delivery drivers, guests and kids running to the pool all move across a surface they haven't memorized. The sunken area also collects standing water, which keeps working on the same soil that caused the drop.
How do I know if the slab under my house has settled?
The tells are inside rather than outside. Look for diagonal cracks running from door and window corners, interior doors that stick or swing open on their own, a floor that feels like it runs downhill, and cracks in a basement or garage slab that have a lip you can feel with a shoe. Any of those in a pattern on one side of the house is worth having looked at.
How fast does sinking concrete get worse?
Nobody can tell you that honestly, and the owner says as much: movement can stop for good, creep along slowly, or accelerate. What is predictable is the water. A low spot that ponds after every storm is still feeding the void underneath it, so fixing the drainage is the one thing that changes the odds regardless of which repair you end up needing.
Find out which problem you actually have
You shouldn't have to guess which trade to call from your own driveway. Somebody can look at what the concrete is attached to, check whether anything inside the house moved with it, and tell you plainly whether this is settlement or flatwork, including when the answer is that it isn't ours.
Call 770-422-2924 for a free look.