Skip to Main Content

Sinking Concrete Slab

Keeping your concrete slabs even is all about spotting the problem signs early and preventing severe damage. Here’s everything you need to know.

Schedule Free Inspection

Looking at the concrete areas around their property, you might notice that some of the slabs are a little more uneven than they used to be a few years ago. This is a sign that they are settling. When you first notice sinking concrete slabs, it might not seem like a big deal. The signs are subtle and no major change has visually impacted your property.

However, as settling progresses, you will begin to notice a change in the way your home looks, how you maneuver yourself around your own property, and how safe you feel walking around. These changes can have a detrimental impact on your day-to-day life, which is why you should consider familiarizing yourself with the signs of concrete settling. This way, you’ll know when to take action before things get severe.

What Is Concrete Settling?

Concrete settling is a term used to describe the way concrete slabs settle against a gap in the soil beneath them. When the soil under a slab erodes and the particles become displaced, it can no longer support the slab. Because the slab now rests against an uneven foundation, it settles and sinks against the uneven soil.

What Causes Concrete Settling?

Even when seemingly undisturbed and under a slab, soil does not stay in the exact same spot forever. It shifts about and moves as the weather cycles make their rounds and human tampering displaces the particles slowly over time.

Soil Washout 

Soil washout refers to the displacement of soil due to a stream of water. Washout mostly affects sandy soils, since they are a lot looser than other kinds of soil. Clay soils, for example, become denser as the particles compact together. Water has a lot more trouble displacing the particles on densely packed layers of topsoil. Sandy soils cannot compact as well, meaning they wash away easily whenever there’s a stream of water.

Mid-Atlantic cities like Appomattox, Virginia, and Charleston, West Virginia, have sandy soils. Due to the high elevation of the area thanks to the Appalachian Mountains, soil washout is a common cause for slab settling because of all the steep inclines. Surface runoff is much more severe when there’s a slope.

The Freeze-Thaw Effect

When water freezes, it expands by around nine percent. As your soil gets saturated with moisture during the winter, that moisture expands when the temperature reaches below freezing. As it expands, the ice pushes the soil particles aside and displaces them. This displacement is what eventually causes the soil under your slabs to form gaps.


The sandy soils around Mid-Atlantic states are loose and move around easily whenever the earth shakes. While the east coast isn’t known for devastating earthquakes like the west coast is, you have to remember that West Virginia, Maryland, Washington, D.C., and Virginia are all near the East Coast Fault Line.

The severity of the earthquakes may not be anything to write home about, but they do still occur and the states near the fault line are in the yellow zone. The tremors are enough to cause significant soil displacement.

Heavy Loads 

Another downside to sandy soils is how they behave when under pressure. Because sandy soils are so loose, they break apart easily when having to endure a lot of pressure. The soil under your driveway has to withstand the weight of the slab, but the weight of any cars you have as well. Over time, all this weight contributes to settling.

Concrete Settling Problem Signs

As settling gets worse, the problems that come with it become unavoidable. Slab settling may have been a low-priority issue at the start, but, when left on its own, it can change a lot about your day-to-day life. At its worst, slab settling can put you and your family at risk of injury, which is why it’s so important to recognize the signs and do something about them as quickly as possible.


Even if the slab itself isn’t sinking, if it feels flimsy every time you step on it, it’s settling. There’s a gap left behind where soil is supposed to be, so the slab will wobble a bit and feel unstable. This is part of what makes settling so dangerous. An unsuspecting family member or guest can trip over the wobbling slab and hurt themselves.

When a concrete slab is flimsy, do not place any weight on it. If it’s flimsy, the soil is already unstable, so placing extra weight will only displace the soil further and accelerate the settling process.

cracks in concrete

Watch for cracks on the slab itself. There’s a very specific kind of crack that’s indicative of concrete settling. When the soil underneath erodes, it rarely does so evenly. This means there’s going to be a side of the concrete that is lower than the other. When settling, the cracks usually appear from where the concrete begins to slope down and settle against the gap.

This is because a slab that does not have an even foundation cannot withstand a lot of pressure. Because slabs often settle around the edges, most cracks that indicate settling can be found there.


The clearest sign of settling is an uneven slab. Concrete settling is something that usually progresses slowly. You won’t be able to notice unevenness at first until the problem has advanced significantly. Unless a harsh storm or flood has completely ravaged your yard, the settling won’t be noticeable until much later.

Strange Smells 

Besides the structural damage, slab settling can cause issues with insect infestations. If the gap under the slab is significant, insects and animals will make their way in and either find a way into your home or simply make a nest under the slab. This can lead to some strange smells as the insects die and shed their exoskeletons under the slab.

It may not be noticeable if you live in a suburban area, but for those of you in a more rural part of town, you might catch wind of an awful aroma near your concrete. If you can’t find the source of it, it’s probably because it’s under your slab.

Pooling Water

You may not be able to see unevenness when the slabs first start to settle, but it becomes a lot easier to do so after it has rained. If you notice that there are some puddles of water, it could be because of the craters formed from the uneven slab. Pooling water can cause a lot of drainage problems and actually make settling worse, so make sure to thoroughly inspect your concrete well if you see this problem sign.

Void Under the Slab

When checking for signs of slab settling, be sure to look toward the edge where the slab meets the soil. A good indicator of settling is an opening that leads to the underside of the slab. It’s common for slabs to have an exposed opening like this because the soil that meets the slab washes away a lot faster than the soil under the slab, due to exposure. As the topsoil washes away, it leaves an indent right along the edge of the slab.

If you do find a void, do not try to lift the slab to see how deep the gap is. Concrete slabs are extremely heavy, and you could hurt yourself while trying to do this. You could also end up displacing the soil further and making the gap worse.


Potholes are a sign of advanced settling. When the gap under the soil forms right in the middle of the concrete, the slab can crack, break, and form a pothole. This is most likely to happen on driveways since the weight of the cars is what ends up breaking the slab and causing the pothole.

When faced with this kind of settling, homeowners try to fix it themselves by simply filling in the pothole. However, this method does not solve the true problem: the displaced soil. When there’s settling, it’s not a problem with the concrete itself. Unless you plan on providing the slab with a solid foundation, there’s no point in repairing the concrete or it will settle once more.

How To Fix Concrete Settling

While concrete settling is a big problem, it is one that has a simple solution. With the right tools and methods, your slab can be supported for years to come.

The best solution for concrete settling comes in the form of polyurethane foam injections. At JES, we have PolyRenewal™, a revolutionary method that changes the concrete lifting game. Here’s how it works:

Contractors drill small holes the size of a penny into the settled slab. The polyurethane foam is then injected through the holes so that it can expand and fill the gap. Contractors carefully monitor the foam levels to make sure that there’s enough to lift the slab back into place. Once the slab is even again, the holes are filled and covered and the foam is left to cure for 15 to 30 minutes.

Overall, the process is very simple. The machine used to inject the foam is handheld and small, making it perfect for lifting jobs on slabs that are a little harder to reach. The holes drilled into the slab are small, meaning that they don’t compromise slabs that are already incredibly structurally weak, unlike other lifting methods that require larger holes to be drilled.

However, the convenient installation isn’t the only thing that makes PolyRenewal™ such a great concrete lifting method. PolyRenewal™ works well because it prevents soil from experiencing further displacement. Polyurethane foam is waterproof and can act as a barrier so water does not seep through the soil.

It’s also lightweight and doesn’t place pressure on the soil. Other concrete lifting methods require cement mixtures that are too rough and heavy for the soft, sandy soils of the mid-Atlantic to handle. They only ever contribute to the settling, making them a short-term solution.

With PolyRenewal,™ you can enjoy the following advantages:

  • Fast curing time (15 to 30 minutes)
  • Waterproof
  • Does not erode
  • Doesn’t place pressure on the soil
  • Can be installed in tricky places
  • Protects the soil from water
  • Foam expands evenly throughout the gap
  • Great tensile strength

Sinking Concrete Slab


Homes can often be difficult to keep up with. Just when you’ve gotten one thing fixed, something else breaks. It’s understandable if you want to put a repair job on the back burner while you try to solve other problems around your home.

You might be wondering just how long you can wait to get that settled slab of yours fixed. However, you might want to bump concrete lifting up your priority list, because it can go from insignificant to consequential in only a matter of days.

  • How Concrete Settling Damages Your Property

Nothing breaks a settling concrete slab faster than a heavy car going over it. Your car can create a pothole in the middle of the slab, effectively ruining it and making repairs very difficult. Not only does having to replace your slab more expensive, but it can also damage the wheels of your car as it goes over the potholes every time you use your driveway.

The more a slab settles, the more damaged your property is. The more damaged a property, the lower its value. Even if you’re looking to sell your home and aren’t interested in repairs because of it, you might want to consider lifting your slab to raise the property value. The longer you wait for the repairs the more expensive it will be.

  • How Concrete Settling Can Be Dangerous 

Part of the reason a property’s value goes down when there’s concrete settling is that it’s a safety hazard. Walking on a settling slab is a risky affair. If it’s not already sunken into the ground, your step can be the straw that breaks the camel’s back and brings down the slab as you’re walking on it. There’s nothing scarier than feeling the ground suddenly give out under you, so even if you don’t trip, you’ll get a little scare.

It’s especially dangerous for children and the elderly, as they aren’t able to balance themselves as well to avoid falling. If you want to protect yourself and your family members, you need to contact an expert for concrete lifting solutions as soon as you spot the problem signs.

Your concrete slab is a lot more likely to break once it begins settling. Concrete is a reliable building material that has excellent compression strength, meaning that it does not lose its volume when under a lot of pressure. Unfortunately, this compression strength comes at the cost of its tensile strength, which is the reason why concrete slabs break when settling.

  • Why It Breaks

Tensile strength refers to a material’s ability to handle pressure. It measures how much tension a structure is able to endure before breaking. If a concrete slab is able to evenly disperse the pressure throughout its body, it will have an easier time handling the weight. However, when slabs settle, they aren’t able to disperse the pressure evenly, causing them to crack.

This is more likely to occur in outdoor slabs that have to support heavy weights frequently. Your driveway is an obvious one, what with your heavy car putting pressure on the slabs whenever you drive in and out. The slabs on your patio are also likely to break if they have to bear the weight of heavy furniture and the people that use them.

  • How To Prevent Breaking Your Concrete 

The more cracks on the slab, the harder it is to repair. Replacing a concrete slab can be an expensive ordeal, and it’s not as convenient as polyurethane foam injection repairs. Because of this, it’s in your best interest to want to preserve your concrete and keep it as intact as you can.

The moment you notice the settling, make sure not to place any weight on the slab or the slabs that surround it. For your driveway, this might mean parking your car elsewhere until the slab can be fixed. For your patio, you might have to remove the furniture or simply avoid sitting on it. Avoid walking on any settled pathways, and make sure to inform your family members of the change so they don’t end up breaking the slab.

If your concrete is flaking off, it’s a sign that something is wrong with the concrete. Concrete doesn’t stay smooth forever, and some flaking is to be expected after a few years. However, you should inform yourself on the kind of flaking it is so that you can get a better understanding of what your concrete is going through and how it could potentially lead to settling.

There are two types of surface deterioration concrete structures go through: pitting and flaking. They are caused by different things though are very similar in terms of appearance. Pay close attention when inspecting your concrete, and you’ll be able to differentiate between the two.

  • Concrete Pitting 

Concrete pitting is caused by problems with the way the concrete was produced or poured. It’s a problem that only shows up after the concrete has finished curing. Concrete pitting means there’s a problem with the structural integrity of the concrete itself. It indicates that the concrete is weak and deteriorates incredibly easily, which means that you have to be careful if you see signs of pitting on a settled slab.

Concrete pitting is defined by small craters that form on the concrete structure. Although the craters are only visible on the surface, if you were to break the slab open, you would see that the craters run deep since the entire concrete is deteriorating. The craters can either appear sporadically across the concrete or, they can clump up and form one big crater that makes it look as if a piece of the concrete has broken off.

  • Concrete Flaking 

Concrete flaking is caused by an external force eroding the surface of the concrete. Freeze-thaw damage is a common cause of flaking since the ice creates micro-tears across the surface of the slab. If the micro-tears become too much, the piece will flake off. Concrete flaking can still happen on slabs that are strong, so it does not indicate that there was a problem with its production. You can tell it’s flaking and not pitting when a big chunk flakes off and you don’t see any craters, indicating that the damage was only surface-level.

Just because flaking can occur on slabs that are strong does not mean it doesn’t affect settling. By deteriorating the surface of the slab, it allows water to seep through to the soil a lot easier, accelerating settling. Plus, a flaking slab does not stay strong for long. As the surface breaks apart, the slab loses its soundness and is likely to break once it begins settling.

Call JES for Concrete Slab Repairs

If your concrete is settling and you need repairs, don’t hesitate to call JES. Since 1993, JES has been helping homeowners keep their homes intact, beautiful, and stable with the best repair solutions on the market. We service Baltimore, Massachusetts, Washington, D.C., Charleston, West Virginia, and Virginia (Appomattox, Richmond, Roanoke, Manassas, and Virginia Beach).

If you’re interested in PolyRenewal­™ for your settling slab, give us a call or use the online contact form on our website to set up a free inspection. One of our field agents will assess the damage and give you a rundown of what needs to be done as well as a repair quote. It’s that simple. JES is here to make things easy for homeowners like you.

Publish Date:

Last Modified Date:

Service Areas


8361 Town Center Ct
Nottingham, MD 21236


311 Central Rd.
Suite 2-02
Fredericksburg, VA 22401

Hampton Roads & NE NC

2569 Quality Ct
Virginia Beach, VA 23454

Northern VA & DC

7940 Gainsford Ct.
Bristow, VA 20136


309 Quarles Rd
Ashland, VA 23005

Southwest Virginia / Roanoke

2033 Cook Dr.
Salem, VA 24153

Western Virginia

456 Old Courthouse Rd
Appomattox, VA 24522


45 W Boscawen St,
Winchester, VA 22601