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PolyRenewal injection for concrete repair

Soil Shrinkage, Compaction, and Settling

Wear and tear on old concrete is usually obvious, and it becomes more apparent as time passes. However, the greatest damage comes from what you can’t see.

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exterior cracks and sloping concrete

Whether it’s in your basement, foundation, patio, or your pool deck, concrete is a great material to use in homes. With that said, the soil underneath your concrete does not stay still, even if there’s a weighty house on top of it. Soil changes form, becomes looser, denser, and shifts around as moisture gets displaced.

With Colorado’s diverse climate, a homeowner’s soil is constantly going through changes. This causes concrete to sink and crack. Not only do these cracks ruin the look of the house, but they can also become a safety hazard if they get too big. If your home’s concrete flooring, your concrete driveway, or other parts of your property with concrete begin to show damage, then keep an eye out.

Here’s everything you need to know about the way changes in the soil will affect the concrete it supports.

The Causes of Soil Shrinkage, Compaction, and Settling

Soil can be classified as either cohesive or non-cohesive. Cohesive soil is soil that has the capacity to change in volume. Its malleability causes it to shrink, swell, and compact as the water content within the soil changes.

These changes cause concrete to break over time. Here are some of the reasons why soil would change in volume.

Dry Soil Causes Soil Shrinkage
drought dry soil

Soil shrinkage is defined as the change in soil volume relative to its moisture content. Soil that is rich in clay swells up when moisturized, but when the water evaporates, the soil shrinks. Once that happens, the soil gets denser as its volume increases. Cracks appear in the dried-up soil due to the pressures of shrinkage.

Because of the soil shrinkage, many gaps are formed and the concrete is no longer supported by the soil. Concrete may be tough to break, but it still needs to be held up by a proper foundation. The gap between the soil and the concrete eventually causes the concrete to break as it settles into the soil.

Complete loss of moisture does not need to occur in order for there to be shrinkage. Any concrete that has been exposed to water will go through a period of swelling and shrinkage. Complete loss of moisture rarely happens, especially in places like Denver and Colorado Springs, which have varied weather. Dry seasons are never long enough to fully dry out the soil, but there are never excessive amounts of rain either.

The moisture in soil can still evaporate even when it’s underneath concrete. This is why sidewalks, driveways, and uncovered patios deteriorate and crack a lot easier than indoor pavement like the floor of a garage. Exposure to the sun speeds up the shrinking process.

Heavy Weights Cause Compaction

All soil must be compacted before any concrete is poured over it. Compacted soil is soil that has had the air between the soil grains pushed out by firmly pressing the soil together. This is typically done when a massive amount of pressure or weight is applied to the soil. Before laying down concrete on a driveway, garage, or sidewalk, the soil must be compacted. Compacted soil becomes extremely firm and dense, which is why it makes for a much better foundation than loose soil.

Compaction is different from shrinkage and consolidation. Soil shrinking occurs when the soil’s water content dries up, while consolidation occurs when a heavy load presses soil so firmly together that all the water gets displaced, though it doesn’t evaporate or dry out. In the end, whether through shrinking, consolidation, or compacting, the soil grows denser.

Shrinking and Compaction Cause Settling

As the soil dries up and shrinks, so does the volume and surface of the soil. Because of the decreased surface of the soil, the concrete no longer has solid support. As homeowners continuously walk and drive their heavy cars on the concrete, it sinks and settles on top of the soil, which now sits lower than it did when it was placed.

As the heavy load weighs down on the concrete, it gives way and sinks further, and the crack on the concrete becomes even more significant. Soil compaction never occurs evenly, so the concrete never settles all at once. If it did, it wouldn’t break off and crack in different places.

How to Know If Concrete Settling Is Caused by Soil Shrinkage and Compaction

Concrete sinks and cracks for many different reasons, so how can you tell it’s happening because of soil shrinkage and not something else? It’s important to identify the cause so you can know what to do when it’s time to fix the issue or explain the situation properly when you call an expert. Here are some signs to look for.

uneven concrete
Sunken Edges and Corners

The edges and corners of concrete slabs are the most vulnerable to settling. They can’t withstand any extra weight without a solid foundation, but since there is a gap between the concrete and the shrunken soil, the slab sinks, and cracks. If your concrete has a lot of cracks, it doesn’t necessarily mean it was caused by settling. Though those cracks should definitely get fixed, until you see concrete sinking, the cracks were most likely caused by something else.

Tree Roots

Tree roots can grow underneath the concrete. They’re strong enough to lift and displace concrete slabs, and you don’t notice their growth until the concrete becomes uneven. However, if your sunken concrete is far away from any tree, there’s no way the breakage was caused by roots.

Most trees have roots that spread out about five times the radius of the whole tree. Before attempting to fix the concrete yourself or calling an expert, make sure there are no trees nearby. You’ll need to take care of the tree before trying to fix the concrete, or you’ll be running into the same problem in the near future.


The nearest source of water many homeowners have is their backyard pool. Having a pool is a great convenience, especially during the summer, but it can also deteriorate the surrounding concrete over time. Water from the pool can leak out and affect the soil under and around it. The concrete pool deck can crack from the massive weight of the water, and the leaking can reach concrete pool decks or patios if the pool is close enough.

How to Prevent Soil Shrinkage, Compaction, and Settling

Soil shrinkage leads to compaction, which leads to settling. This can cause the concrete in and around your home to crack and become unleveled. Unfortunately, there is nothing anyone can do to prevent this from happening since soil will go through a cycle of getting wet and drying up no matter what.

However, there are a few things you can do to deter the effects of shrinking and compaction. These methods will keep your home’s concrete looking fresh for years to come.

Wet Your Concrete

July is Colorado’s hottest month of the year. During that time, homeowners can keep the soil under the concrete expanded and stable by wetting their concrete when the soil underneath is most likely to dry up. Soil shrinkage is a very slow process, and the surface of the soil won’t decrease significantly in a single month. However, the constant shrinking and swelling affect the concrete, especially the edges and corners, so keeping the concrete wet is a fast, simple prevention method that can go a long way.

Of course, you should only do this during July. A constant flow of water around concrete can end up eroding the soil if you’re not dealing with high temperatures.

Cover Your Driveway and Patio

Acquiring a cover for your driveway will prevent exposure to rain, snow, and heat. This reduces the frequency of shrink-swell and compaction in the soil under your driveway or patio. The cover also prevents heavy snow from adding extra weight to the concrete, which speeds up settling.

Alter Your Downspouts and Gutters

You can extend your downspouts and have them point away from your concrete. In doing so, you can prevent the soil from gathering too much moisture. Downspouts should be at least five feet away from the concrete slabs. Anything closer will affect the soil.

Don’t Plant Trees or Flowers Too Close

If you want your concrete to stay fresh and intact, don’t plant any trees or flowers near it. Trees, flowers, and bushes will absorb the moisture in the soil and cause it to dry up faster. The less moisture the soil has, the more it shrinks, and the more it shrinks, the bigger the gap between the soil and concrete will be. When the concrete eventually settles, the unevenness will be drastic. Sure, there’s a chance the concrete will eventually settle with or without plants near it, but small cracks appearing over time are better than a sunken piece of concrete. The latter is an absolute safety hazard.

Not to mention, tree roots are strong enough to destroy concrete, so you might want to keep them away regardless. If you want to decorate an area with concrete nearby, you’re better off putting those plants in pots.

Soil Shrinkage, Compaction, and Settling


Slightly uneven concrete might not bother you at all, but it’s something you should still look into fixing. Settling only gets worse as the years go by, and not only will your driveway and patio look aesthetically unpleasing, you won’t be able to use those areas properly if you let it get too bad. 
When Not to Worry 
Concrete is not invincible and will deteriorate over time. Cracks and breakage are to be expected, and not all of them are caused by settling. You shouldn’t worry about breakage if all you see are hairline cracks. Even if they are plentiful, as long as the concrete is even, settling won’t occur for a long time. 
If your garage, patio, driveway, or concrete pathway is still smooth and can be used without hassle, there is nothing to worry about. Hairline cracks are those that are small enough not to disrupt the functionality of the pavement. 
When to Worry 
You should worry about settling when parts of your concrete begin to crack unevenly. A sunken chunk of concrete, no matter how small, is the first sign of settlement. As the settlement gets worse, the gaps will get wider and the unevenness will become more apparent. 
If things go too far, you might have trouble using your pavement adequately. The concrete will sink farther into the ground to the point where it will be difficult to walk on. As soon as you see unevenness in your concrete, especially in the edges and corners, you should start to take action before it gets worse and becomes a serious safety hazard. 

Settling is an inevitable process that gets worse over time. This is why concrete sinking becomes more significant and noticeable the older the pavement is. But how long does it take for it to happen? Well, the question isn’t as straightforward as you’d expect. 
There are many steps you can take to prolong the settling process, but, for the most part, it’s nearly impossible to prevent it from happening completely. The soil we have underneath our houses, even if it was specially selected for foundation purposes, is unpredictable and uncontrollable. 
Internal Factors 
The kind of soil you have under your pavement is the biggest component when it comes to concrete settling. No matter what you do, it will either get wet and dry out or shift and erode with time. There are different types of soils with less clay in them that don’t have as much swell-shrink capacity, but most homeowners don’t get to choose which soils are used. 
Another big element is how the soil was placed. Soil that was poorly compacted or poorly placed has a higher chance of shrinking. If the soil is poorly placed, it won’t be dense enough to provide solid support. Moisture has an easier time passing through loose soil and reaching a much wider area of affect. But again, this is something most homeowners have zero control over. 
External Factors 
The weather plays a big role when it comes to the settling of concrete structures. Too much rain, and the soil swells and erodes. However, not enough moisture causes consolidation and eventual compaction. Too much snow places a heavy load on driveways and uncovered patios. Seasons of droughts and hot summers dry out the moisture from your soil a lot faster. 
Then there’s the stress that homeowners place on their concrete. How many cars or heavy boxes are in the garage? How much furniture is on the patio and how close are they to the edges of the concrete? How often do leaks occur and how quickly do they get fixed? All of these elements contribute to soil shrinkage. 

There are different types of soil used under foundations. Each has its own special properties and negative qualities. The kind of soil that is used is chosen based on the kind of property that is being built, what the weather is like in the area, and the site manager’s personal preference. 
Soil that has 10% or more clay content has the most shrinkage capacity. Organic matter can be mixed into clay soils to make them less malleable, and although this works in agriculture, in construction, mixing different types of clay increases the risk of an uneven foundation. Mixing is also very time-consuming, which is why engineers tend to stick with one soil type when it comes to construction projects. 
Clay Soils 
Clay soils are those that contain traces of clay in them. There’s the traditional expansive soil and loam. Expansive soil has the highest chance of shrinking and compacting because they are highly absorbent. Expansive soil is still used in construction, however, because it holds together extremely well, which saves time when compacting the soil. Its pliability makes it easy to manipulate, so it’s still used despite its swell-shrink capacity. 
Loam is considered to be the best kind of soil for under foundations. It’s a mix of silt, clay, and sand. It’s pliable enough to compact well, but it doesn’t have as much clay, so its swell-shrink capacity isn’t as significant as clay-rich soils. However, loam has clay content in it, so it’s still able to shrink. 
Sand and Gravel 

Sand contains very little clay content. Because of this, it doesn’t hold moisture very well and it doesn’t shrink when dried out, since compaction is very minimal. However, because it doesn’t compact well, it’s loose and has a higher chance of shifting. 
The same thing happens if the foundation is made of rock or gravel. The particles are too big, so water flows right through. If the water dries up, the gravel will still stay in place. However, the air between each individual rock leaves room for shifting. This is why sand and gravel are rarely used in places where earthquakes are frequent. 

If you have uneven concrete due to settling, your first instinct might be to level it yourself. Concrete leveling needs to be handled with extreme precision. If it’s not handled properly, the broken slab will sink again and possibly bring down even more concrete with it. You could end up making your situation worse. In order to truly fix the issue at hand, the concrete needs to be securely lifted in a reliable way. 
Calling an Expert is Your Best Bet 
Over the years, various means of concrete lifting have been used. However, some of these methods are outdated, time-consuming, and expensive. Not to mention, some of these methods simply don’t work for the specific type of pavement you have. An expert can also take a look at your situation and advise you on how to maintain your concrete properly to avoid damage in the future. There are certain things we do and have around the house that contribute to soil shrinking and settling, but we might never realize until we get a professional to take a look. 
Choosing which expert to call is just as important as choosing to call at all. If you’re going to call an expert to help you with your concrete lifting needs, you need to call one that’s going to save you time, save you money, and save you from having to go through all of this again in the near future. You can rely on your local expert to handle the concrete lifting with efficiency and expertise. 
What Solution an Expert Can Provide 
After the initial inspection, the expert will let you know what needs to be done. Different companies offer different solutions, and it’s important for you to know which ones are the best. For example, mudjacking is a common concrete lifting method. It involves a mixture of different types of cement that gets injected into the ground in order to lift the sunken concrete and even it out. A hole needs to be drilled for the mixture to reach underneath the concrete. It’s a widely used procedure known by many contractors, but it takes a long time to complete. Not to mention, the cement doesn’t always fill the gaps completely and the mixture is so heavy, it can cause further soil compression and make the concrete settle once more. 
The most effective solution is polyurethane injections with methods such as PolyRenewal™. It’s a faster method that involves lifting the sunken concrete slab with polyurethane foam. Because the foam is expansive, it’s able to completely fill the gap and avoid future settling. It’s also lighter than cement mixtures, so it doesn’t compress the soil any further than it already is. For the sake of your concrete’s integrity, it’s worth finding a local expert who uses polyurethane injections for concrete lifting. 

Call Complete Basement Systems for Quality Repair

Complete Basement Systems is one of the most reputable foundation and concrete specialists in Colorado Springs and Denver, CO. We’ve been around since 1999 and have the expertise to fix concrete that needs lifting in and around your property. Contact us today to schedule a free inspection and repair estimate detailing all costs of your recommended repairs.

If you think your property might be struggling with concrete settling, don’t hesitate to give us a call. We are always on hand to help.

Serving Greater Denver area, Colorado Springs, Eastern Colorado, and parts of Nebraska and Wyoming

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707 County Line Rd.
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Denver, CO

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Denver, CO 80216