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Soil Shrinkage, Compaction, and Settling

Soil shrinkage, compaction, and settling can be an issue for any home anywhere in the country. But what causes this effect, and how can you protect your concrete from it?

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Many homeowners are unaware of the dangers that soil shrinkage, compaction, and settling can present. However, you will quickly notice the problem when it takes a toll on your driveway, sidewalks, and other concrete surfaces around the property. Once it has, it can escalate to cause serious damage and even health issues. If left unattended, it can require heavy repairs or even the full replacement of your concrete. 

By understanding what causes soil shrinkage, compaction, and settling, you can prevent it from negatively affecting your home. Here are the warning signs to look for and the factors around your property that may make your soil more vulnerable to it. 

What Causes Soil to Shrink, Compact, and Settle? 

Soil shrinkage occurs after a dry period, where moisture is drawn from the soil and that results in the earth tightening up. By contrast, soil compaction and settling arise from rainy weather. Because saturated soil is vulnerable to feeling the immense pressure from the concrete above it, water can lead to it settling into a new position or packing tighter at a bad angle. 

Some homes stand for years without ever experiencing issues with their soil. Others are newly built and find the ground is quickly working against them, their concrete surfaces, and even their foundations. Because of this, it’s important to understand what factors make your property more vulnerable to soil issues. Here are the popular culprits:  

  • Clay Soil  

Clay soil is one of the most common types found in Raleigh and Winston-Salem, NC. It is so widely spread that the official state soil is Cecil soil, a type of red clay. With that in mind, there’s a high chance that any concrete around your property is relying on this expansive soil to support its weight. 

Unfortunately, clay soil has a high shrink-swell capacity. What this means is that clay soil expands dramatically when saturated with water but shrinks to tiny particles when dried out. As these particles shrink, the concrete slabs on top lose their support and then crack. 

Of course, clay soil is not as efficient in absorbing water, so if you have clay soil, you may find that water is puddling on the ground. This can be one of your earliest warning signs. 

Clay soil is also very prone to soil compaction. This is because clay soil is rather heavy and dense. When it begins to absorb any amount of water, it will become even denser. This weight bears down on the soil underneath it and forces it to pack together. Once it has, it’s less likely to absorb water or let it harmlessly seep between. 

This is an escalating problem because when clay soil becomes compacted, it is more likely to settle. The weight forces it to sink and try to find a steady resting place. As it does this, it moves down and away from your concrete slabs and leaves them unsupported. 

  • Repeated Soil Expansion  

To some extent, all types of earth will expand and contract when exposed to water or severe temperatures. For example, in the summer, the heat will result in your soil shrinking as all the moisture in it dries out, and in the cold reason, the frozen moisture may cause it to expand. If this happens multiple times in a row, the freeze-thaw cycle and the water exposure may put your clay soil under a considerable amount of stress. It will shift around as a result of the expansion-contraction and thus shrink more, compact, and then settle. 

Overall, this weakens the soil. Weak soil will compact under the heavy weight of the concrete it is meant to support. This may cause voids to form under the concrete slabs, and then result in damage you can see.   

  • Soil Washout  

Soil washout happens when the earth erodes from underneath your concrete slabs. This can occur due to either weakened soil or moistened soil. Although soil washout can happen no matter where you are, it’s more likely to happen in sandy soil, which is another common type present in North Carolina. 

Wind, water, and other factors can result in your soil beginning to wash out. As it does, hollow spots may develop under the concrete. The slabs will then put additional pressure on your earth and cause it to compact or settle, making the problem worse. 

  • Excessive Weight  

The driving force behind soil compaction is excessive weight. Excessive weight can manifest in a variety of ways. These can be cars parked in the driveway, wooden decks on top of concrete foundations, or even heavy décor in the yard, such as fountains, statues, and large potted plants. If your soil is already weak or your concrete was badly poured, you may find the weight of simple foot traffic causing issues. 

Depending on what items are weighing down your soil, they may be exacerbating the issue in other ways. For example, consider a large potted plant. If that pot is draining a lot of water onto the concrete and through the slab, the soil underneath will absorb it, resulting in soil expansion. During periods without water drainage from the pot, the soil will shrink. 

Of course, this potted plant will be watered often, so the soil will experience repeated expansion and shrinkage. With this repeated shrinkage, the soil will become weak and vulnerable to soil compaction and soil settlement under the weight of the potted plant. 

  • Weather  

Homeowners that reside in Raleigh and Winston-Salem, NC, are no stranger to wet and rainy winters, as well as hot and dry summers. Unfortunately, both the moisture from the rainy season and the aridness of the dry season can cause soil shrinkage, compaction, and settling. 

For example, consider how dry weather can shrink your soil. When moisture is drawn and evaporated from the earth, the particles shrink in size. This causes the entire area to contract, pulling away from your concrete structures. 

During the humid, wet season, soil can easily become compacted and eventually settle. This is because when water saturates the soil, the soil compresses together more easily. This can be further exacerbated by weight above the soil. Once soil compaction has happened, it is very likely that settling will follow. 

Problem Signs of Soil Shrinkage, Compaction, and Settling 

Of course, you can’t easily peek under your concrete slabs and check on how the soil is doing. If you wait until the problem is obvious, however, you could be faced with hefty repair costs. 

The good news is, shrinking, compaction, and settling is a slow process that will leave behind subtle warning signs. Look for these red flags that your soil and the concrete it holds need help. 

  • Cracked Concrete  

You may think that concrete cracks such as in your porch, driveway, or sidewalk are normal. While this is true in some cases, if the crack is actively growing, then it should be a reason for alarm. It is most likely a sign of soil shrinkage, compaction, or settling in progress. 

That’s because weather, water, or soil type are affecting the ground. As the earth is forced to shift underneath the concrete, the concrete is unable to stretch. Since it doesn’t have a stable base, it has no choice but to reach its breaking point and develop fissures all throughout its structure. 

  • Uneven Concrete Slabs  

If the soil is in flux, you may find that cracks aren’t your only problem. Heavy shifts in the earth will lead to the concrete slabs themselves moving, collapsing, sinking, or even bulging upward. That leaves an uneven surface that’s not only ugly—it’s dangerous.   

This is one of the worst problem signs. Do not attempt to step on or apply an immense amount of pressure to these uneven slabs. You may worsen the problem and the soil underneath. You also risk hurting yourself if the concrete slab collapses in on itself, depending on how severe the soil problem is. 

  • Hollow Sounds Under Concrete Slabs  

This is one of the more subtle problem signs of soil shrinkage, compacting, and settling. It typically accompanies uneven concrete slabs, but it does not always have to. 

If you gently tap on the concrete slab and hear a somewhat hollow sound, as if there is space underneath the concrete slab, then there is a high likelihood that your soil has shrunk, compacted, or settled. Much like uneven concrete slabs, you should not attempt to apply too much pressure on these concrete slabs. You risk breaking the concrete and injuring yourself.  

  • More Frequent Water Puddles 

Soil that has shrunk, compacted, or settled will have difficulty holding water. Because of that, moisture and standing water can puddle around the concrete or leave the earth surrounding that area damp. If you suspect that the earth at the top of your driveway is struggling, for example, look for standing water next to your slabs. If you step on concrete pavement and find water bubbling up between small cracks, it’s time to take action. 

Soil Shrinkage, Compaction, and Settling


When you first hear of soil shrinkage, compaction, and settling, you may think it’s a distant worry. Of course, the problem signs don’t show up right away, and it may take several months or years before your property sustains any damage. 

However, once you realize that your soil is having problems, it’s important to act fast. The longer you leave the soil to affect your concrete structures as it pleases, the more dangers you’ll encounter, and the more expensive repairs can be. 

Structural Damage 

One of the most common consequences of soil shrinkage, compaction, and settlement is damage to your property. This can mean both your landscape and the structure of your house. You may find plants struggling to grow, sheds or garages beginning to tilt, and concrete slabs forming cracks all throughout your yard. If the problem continues, it can eventually damage the foundation of your home, jeopardizing your living space.   

The damage won’t just be unsightly. It can be inconvenient and dangerous. Door and window frames can become misaligned, preventing you from closing them properly. Uneven concrete underneath your house can break up the flooring inside your house, letting in moisture and pests. If mold, dust, chemicals, and other elements seep up through these cracks, your health could be in danger.   

Water Intrusion 

Once cracks have formed throughout your driveway, garage, sidewalk, and even your foundation, water can gain access. That’s especially true if compaction and shrinkage have caused your soil to become weak. Once the soil is weakened, its ability to absorb water is disrupted, increasing the likelihood of water pooling up on top of it—and making its way right through any cracks. 

Surprisingly, there are a wide variety of soil contaminants that can be detrimental to human health. Carried in by the water, your home may be exposed to issues such as dust, pesticides, asbestos, petroleum hydrocarbons, and creosote. They can result in symptoms and illnesses such as: 

  • Nervous system damage 
  • Blistering, peeling, reddened skin 
  • Irritation of nose, throat, lungs 
  • Headache or dizziness 
  • Drowsiness 
  • Loss of coordination 
  • Nausea 
  • Skin irritation 
  • Labored breathing 
  • Pneumonia 
  • Increased risk of cancer 
  • Damage to nose, throat, lungs, and eyes 

The PolyRenewal™ system is more effective at targeting the source of the issue, while also working to prevent future problems down the road. In contrast, mudjacking can fix uneven and sinking concrete slabs, but it does not address the origin of the issue, which is soil shrinkage, compaction, and settling. 

Downsides of Mudjacking 

Mudjacking is one of the traditional ways to level out concrete. This is performed by contractors, who begin first by drilling a soda can-sized hole into the concrete. A mortar-based mixture, also known as mud or slurry, is then funneled through this hole into the ground. After a few days, this slurry will be cured and your concrete will be as good as new. 

Or so you think. Remember that soil compaction can result from excessive weight. This can eventually lead to soil settlement. With that in mind, consider the fact that the mudjacking slurry is quite heavy. While it can level out your concrete, it will weigh on your soil even more, causing more cracks and slabs to become uneven. 

Benefits of the PolyRenewal™ 

The PolyRenewal™ system is extremely versatile. Because it’s lightweight and can set up in under an hour, it does not bear down on already weak soil. Instead, it works to lift and support your concrete, giving it the structure it needs without disrupting the compacted, shrunken, or settled earth more than necessary. 

This foam does not require large holes to be funneled through and is therefore less invasive. Because it is waterproof, it will not be affected by any pooling water from the compacted soil, nor will it make the problem worse by expanding or cracking itself. It has an impressive lifespan, making it a one-time solution rather than a temporary fix that needs updates or maintenance. 

Of course, it may feel like you’re avoiding the root problem if you just repair the concrete around your property. Why not fix the soil itself? 

Soil Will Always Shrink, Compact, or Settle 

Unfortunately, all soil will shrink, compact, and settle to some degree. The real issue is that some types of earth are more vulnerable to it than others, and those soils are very common in North Carolina. There is no way to completely stop this from happening to the ground around your property, and there are no treatments that can magically cause your earth to act like concrete and stay perfectly in place. 

Instead, the best solution is to fortify any structures around your property that are subjected to this flux. You can use PolyRenewal™ to repair damage, level out your slabs, and protect them against future damage. 

Changing Your Soil 

Technically speaking, you could lift up your slabs, excavate the soil underneath them, replace it with new soil that’s less prone to these issues, and lay the slab back down. However, just because it’s technically possible doesn’t mean it’s a valid solution. It would take an impressive amount of money to do this, even if you could find a local team willing to undertake the job. If it was done incorrectly, it would also subject your soil to even more compaction and settling. That’s not to mention how invasive the process would be. You’d have to tear up your landscaping, and it may even require you to redo your foundation, depending on where you replaced the soil. It would be far better to try and safeguard the concrete structures around your property, instead of trying to redo the very earth your property is made of. The good news is, by using the right solutions, these can be one-time fixes that keep your home and its concrete in prime condition for decades to come.

PolyRenewal™ For Soil Shrinkage, Compaction, and Settling 

Soil problems can be an eyesore, especially if they’ve caused the pavement or sidewalks around your home to crack or become uneven. This can be quite hazardous, and the problems will only escalate if the soil issues are allowed to persist. For example, cracks can grow and make their way inside your home or the concrete may pose a tripping hazard. 

Luckily, there are ways to repair the damage with PolyRenewal™. This solution works to stabilize the damaged concrete and repair any unevenness. As a plus, its quick setup time allows it to strengthen the slabs against excessive weight. 

The PolyRenewal™ Injection Foam is lightweight, stable, and robust. This allows it to work against the effects of soil compaction and settlement. It cures in as little as 15 minutes, and it’s waterproof, so homeowners don’t have to worry about this solution falling victim to the same factors that upset their soil. 

Of course, some professionals recommend mudjacking as a solution for issues with soil shrinkage, compaction, and settlement. While it is a traditional method, it has been found to serve only as a temporary solution and can worsen the problem more so than fixing it. 

The mixture used in mudjacking is mortar-based. Compared to the structural grade geopolymer foam used in the PolyRenewal™ system, this cement mixture can add additional weight onto the soil, actually increasing the chances of soil compaction and settling. Therefore, you are better off getting the PolyRenewal™ Injection Foam into your concrete, as it is long-lasting and more versatile. 

Rely On the Experts for Your Soil Problems 

Soil shrinkage, compaction, and settling are far more common than you’d imagine. While there is no way to completely fix the soil your property rests on, there are ways to fortify your structures against the negative effects that soil changes can have. By reaching out to local experts, you can benefit from their knowledge, gear, and expertise to apply the right solutions.  

Our team will be more than happy to serve you and your family to ensure a safer home. Contact us today to schedule a free inspection and repair quote. We can assess the problem signs you’ve found, discover the root cause, and apply the long-term fix you need. 

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