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Sinking Concrete Slab

If you have started to notice sunken or uneven concrete slabs around your property, there could be many issues at work. Here are the problem signs that you should be aware of.

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Concrete slabs are incredibly important for many homes and structures across Missouri. That’s because of their strength, durability, and the cost-effective nature they offer as a construction material. Concrete is in everything, for very obvious reasons. Of course, like all things, they have certain weaknesses and drawbacks, the most prominent of which is the weight of even slim concrete slabs. 

The proportionally heavy weight of these slabs makes them very prone to sinking, settling, and cracking. This happens when they are put under too much pressure or they do not have enough support. Sinking concrete slabs around your home or property as a whole can be a sign of many different underlying issues that need to be addressed.

What Causes Concrete Slabs to Sink?

Sinking concrete slabs are a serious problem that you should not ignore for a number of reasons. You see, as well as causing a number of hazards on their own, inking concrete slabs are a warning sign for deeper issues that have the potential to affect the entirety of your property (including your home). The most common causes of a sinking concrete slab for homes in Missouri are:

Too Much Weight 

While concrete is a strong material, it does have a limit to the amount of weight that it can take, especially if the weight relies on its tensile strength rather than its compressive strength. If your exterior patio or driveway is overloaded, a sinking concrete slab is one of the most likely outcomes (as are spreading cracks). Examples of overloading could be the placement of too many cars on a driveway, putting heavy equipment or a full skip on a driveway, or leaving a heavy vehicle or piece of equipment in one place for too long. 

This can lead to cracks, sinking slabs, and generally unevenness, although it generally impacts driveways rather than exterior patios or sidewalks because of the immense weight required to cause this kind of damage. 

Concrete Defects

Though it is unlikely, defects and flaws in the concrete which is used to make up the slabs in your driveway or exterior patios can lead to cracking and sinking, both on an individual level and in a wider structural sense. Concrete defects can occur during the mixing or setting process and will undermine the concrete in a number of ways. 

The most common issues connected with concrete defects are large splits and cracks (caused by poor distribution of water and material) and cosmetic damage like pitting and spalling. Over time, this can also lead to sinking as the damaged slabs are less able to support weight being placed upon them.

Unstable or Weak Soil 

Expansive soils are the most notorious for causing damage to concrete structure and surfaces by shifting and moving. This is because of the way that they react to the presence or lack of moisture in the environment. When saturated, these kinds of soils swell and become soft. This can easily lead to the concrete slabs which make up your patio, sidewalk, or driveway sinking into the ground. 

When these soils become dry, however, they shrink and become brittle. This can lead to the formation of voids underneath concrete surfaces. This can easily cause the concrete slabs to crack and sag, or to sink into the ground entirely. 

Finally, very loose or light soils that are bad at holding themselves together (for example, sand-based soils) may shift as a result of extreme weather and cause instability in concrete surfaces. This kind of movement, too, can lead to concrete surfaces and slabs falling into voids left behind by moving earth.

Poor Drainage

Water is one of the most destructive forces that can go to work on your home, and your property as a whole. So, as you might imagine, it is not uncommon for poor drainage, soil saturation, or extreme rainfall and flooding to cause issues in even healthy and stable soil. 

When the ground becomes saturated, it can lead to concrete slabs slipping and moving laterally. This can lead to them cracking or sinking into particularly marshy spots of ground.

In most cases, the cause of a sinking concrete slab is complex and will involve more than one underlying issue. This is why it is so important for you to contact a professional to assess the situation and identify the best possible solution.

Problem Signs to Look For

As is the case with most issues, it is important to catch a sinking concrete slab early. If you do so, it will be much easier and cheaper to fix because the damage will be localized. This is why it is so important to know what the problem signs associated with concrete slab damage, sinking, and movement are. There are many different red flags which might arise, of course, but these are the most common:

Soil Deposits After Heavy Rain

If you noticed that there are deposits of dirt on your driveway, sidewalks, or concrete patios on a regular basis, you should seek advice. You see, this is a sign of soil wash out and will only become more serious over time. Soil washout and erosion are largely caused by high winds and water.

Whatever the cause of these soil deposits, however, they are signs that the earth around your property is on the move. If this has not yet caused some problems under your concrete slabs and your property, it will, because of the way in which the soil can open up and leave voids. This leaves a surface without support and can cause it to sink or crack under its own weight. 

Gaps Under Slabs

When the soil underneath a concrete slab or surface is being worn away, or washed away, one of the earliest signs is a gap underneath the concrete surface in question. Even a small gap, for example, the width of a finger, can be a sign of deeper issues out of sight. These small gaps may not seem like an issue, but you shouldn’t ignore them. 

You see, even a small void or gap underneath a concrete slab can lead to it struggling with the weight it is expected to hold, or even holding its own weight. Worse still, once a void has started to form, it will grow and fill with water at an alarming rate. This is bad enough in summer, but can be very serious in winter.

Spreading Cracks

A few small, hairline cracks in a concrete slab are not necessarily a huge problem. Hairline cracks are those which are too small to fit a credit card into and they tend to be stable. This means that they are not actively growing and spreading. Spreading cracks, by contrast, are larger and actively changing in size, depth, and width. 

These kinds of cracks are a sign that the slab or surface in question is struggling to deal with pressure or weight. This can be caused by excess load or a lack of support, but will result in the fragmentation of the slab in question. Once a slab has fragmented, it is far more likely to start sinking or moving. 


If you notice visible unevenness and sinking in your concrete slabs and surfaces, this is a serious sign that the slabs are being undermined in some way. Defective concrete will generally show signs of aesthetic or cosmetic damage as well as cracks and fragmentation, but a slab which is moving despite being fully intact is most likely to be struggling with external factors. 

How the slab has moved can help you to understand the kinds of issues at work. Lateral movement, for example, is most likely the result of loose soil moving in bad weather, while sinking is generally caused by expansive soil or soil washout. 

Pooling Water 

If the soil around your home is healthy and well-maintained, it should be able to deal with moisture and drain away even large amounts of rain fairly quickly. If you see water pooling around your yard, beside or on concrete surfaces, or around your property perimeter, however, this is a sign that you have serious problems in your soil. 

This can be a sign of unevenness in your sidewalk, driveway, or patio, of course, but when it happens in your yard, it can also be a sign that washout and erosion or even the formation of a sinkhole. As such, you should not ignore these instances. If you see water around your foundation, however, this is a serious issue that will have a much more serious outcome for your home as a whole. 

Each of these problem signs can also be connected to other issues, however. As such, you should not try to diagnose the cause of your sunken concrete alone. It is unlikely that you will identify the right cause, or mix of causes. As such, you will be unable to formulate and implement an effective solution. That is what concrete lifting and repair specialists are there for.

Why Worry About Sinking Concrete Slabs? 

We understand that sinking concrete slabs may not be the most pressing concern on your list right now. After all, keeping your home in good shape can feel like an uphill battle sometimes. A sunken concrete slab or slightly uneven driveway often seems less intimidating than, for example, a leaking water heater. However, there are a few good reasons you should be concerned. 

Sunken Slabs are a Tripping Hazard 

If concrete slabs around your home have started to sink or tilt, this is actually a risk to your health and well-being, as well as your home. These unstable surfaces pose serious tripping and falling hazards for you and anyone who visits your property. This will affect the elderly, very young, and those with mobility issues most of all, and could result in serious injury for them. After all, a fall onto a concrete surface is hard on anyone, but an elderly person could very well break bones. 

Sinking Concrete Slabs Affect Your Property’s Value 

If you are thinking about selling your property any time soon, sinking concrete slabs should be high on your list of things to fix. Even if the damage is purely cosmetic, it will have a huge impact on your home’s potential resale value. They may even put buyers off altogether, especially if they are in a sensitive area or immediately visible from the street. Curb appeal is a powerful thing, after all. 

This is a Degenerative Issue 

Once a concrete slab starts to sink, there is no chance that it will rectify itself. Likewise, there is very little chance it will stabilize without intervention. If it does, it will most likely be in a position that is entirely different from its intended placement. The longer issues like this are left alone, the more pronounced they become, and the more expensive they are to fix. Acting quickly will save you money in the long run. 

There are other things to consider, but these are the most pressing reasons. Thankfully, there are different repair options available if you want to return your home to optimum condition. All you need to do is find the right people to help you. 

Sinking Concrete Slab


Concrete is a fairly durable material, but that does not make it infallible. There are a few things that can cause staining, discoloration, and general cosmetic damage to concrete surfaces around your home. This cosmetic damage can also be a sign of more serious problems on the way, but this is not always the case. 


Defects in the concrete itself cause a huge number of issues for any structure. They can also originate in many places. In fact, issues with the fundamental makeup of the concrete can go all the way back to the cement mixing process. After all, concrete is really just a mix of water, sand, and aggregate. Having too much water, sand, or even a certain kind of mineral in the aggregate can cause cosmetic issues to form. Likewise, concrete that is disturbed after it has started to set or that is improperly cured is far weaker. 

This can lead to many cosmetic defects and issues, but the most common are spalling, flaking, pitting, and staining. Spalling is a process by which large, ovular chunks of concrete break away from the rest of the surface. It’s also the issue most likely to cause structural damage in the long run. By and large, however, these issues are unlikely to result in more serious problems, like sinking. 


The weather and climate around your home are very important and can have a huge impact on the health of concrete surfaces. In areas like Missouri, where the summers can be humid but the winters are fairly harsh, concrete will start to suffer fairly quickly, especially when there is a particularly hard winter or a changeable spring season. 

Repeated freeze/thaw cycles are by far the most damaging influence on a concrete slab. This is largely because of the porous nature of concrete. It absorbs water that expands during a sudden cold snap and shrinks when it thaws. Most concrete can cope with this happening once or twice, but when it happens a few times in rapid succession, the chances of damage increase dramatically. 

Concrete that has suffered cosmetic damage is not always likely to sink, but it is certainly more exposed to further damage. As such, it is a good idea to take particular care of damaged concrete. Here are a few basic things that you can do to protect concrete slabs around your home from sinking. 

Manage Soil Saturation 

That said, most sinking concrete slabs are caused by issues in the soil rather than defects in the slab itself. As such, managing the health and texture of your soil will go a long way toward preventing sinking concrete slabs (and protecting your property as a whole). 

First and foremost, you should make sure you have appropriate foundation drainage systems in place to handle the amount of water and rain your home usually has to deal with. This covers drains, both inside and outside, and appliances like sump pumps. Secondly, you should make sure all your drainage options direct water away from your property. Finally, consider how you plant your yard. The right mix of flowers, bushes, and other plants can seriously increase the stability of your soil. 

Conduct Yearly Checks and Maintenance 

As well as making sure that you have all the appropriate drainage systems in place, you should take the time to check and maintain them. Scheduling annual checks and maintenance appointments will go a long way toward preventing foundation flooding and soil saturation. This will not only prevent sinking concrete slabs but will protect the entire structure of your property. 

You can also carry out seasonal tasks and cleaning to further protect your drainage systems from avoidable clogs and damage. Cleaning out your window wells, gutters, and drains in fall and spring can help prevent debris from clogging your drainage systems and causing runoff, overspill, and flooding around your property. By making these simple changes to your routine, you could prevent huge amounts of avoidable damage and save yourself a lot of money in the long run. 

Once a concrete slab has started to sink, it is time to call in a professional. DIY concrete lifting rarely gives the desired result, and it can often cause more damage in the long run. Two options include mudjacking or polyurethane foam injection. 


Mudjacking is somewhat of a heritage solution to sinking concrete slabs around a home. It involves pumping cement slurry underneath the damaged concrete slab. The pressure created by this process hold the slab in place once set. This provides a strong and stable surface but has a few drawbacks. 

This is a slightly less efficient process. First and foremost, the process is quite messy, making it unsuitable for interior use. Secondly, the cement slurry is very heavy and takes a long time to fully set. As such, this process is unsuitable for weaker soil and inconvenient for surfaces that see regular use. 

PolyRenewal™ Polyurethane Foam 

PolyRenewal™ polyurethane foam is a far more up-to-date method of concrete lifting that uses less material and sets far more quickly. This process sees a professional creating a tailored blend from the two-part foam to give just the right amount of expansion and force. The foam is then injected into the space beneath the sunken concrete slab. 

This foam expands quickly and sets to 90% rigidity in under an hour. It is also very lightweight and moisture resistant. As such, PolyRenewal™ is a far more efficient and long-lasting solution that does not overburden already weak soil. This more than outweighs the extra cost, in our opinion, because it minimizes the risk of recurrence. 

Concrete Lifting with Foundation Recovery Systems 

If you have noticed sinking concrete slabs in or around your home, it’s time to call in Foundation Recovery Systems. Operating throughout Kansas City, Moberly, St. Louis, and Springfield, we are one of the most reputable foundation, basement, and concrete repair specialists in the state. Since opening our doors in 1992, we have helped thousands of homeowners just like you. 

If you are ready to start the repair process, all you have to do is contact us to schedule a free inspection appointment. One of our experts will then complete a thorough evaluation of your home and its problematic concrete and provide you with a free written estimate for all suggested repair costs that day. 

Let our Concrete Lifting Experts help you

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Lee's Summit, MO 64082
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Moberly, MO 65270
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Springfield, MO 65803
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Fenton, MO 63026
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