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Foundation Floor Cracks

Sinking, cracked, and depressed concrete floors and slabs are not just unattractive, but they can be dangerous as well.

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Sinking, settled, and uneven concrete in your home are unsightly, dangerous, and indicative of deeper structural issues that require your intervention. Innovative Basement Authority is the leading foundation and structural repair expert serving Minnesota, North Dakota, and eastern Montana. We have invested many years in finding the best possible solutions for these problems. As a result, we have a portfolio of high-quality, cost-effective products designed to restore the look and stability of concrete slabs and flooring while also addressing the underlying issues.   

crack in basement floor

Understanding the Difference Between Hairline and Spreading Cracks 

Cracks spreading through your property’s concrete slab floor are a strong sign that you have structural damage in the affected areas. Stable cracks may have been caused by previous settling within the property, but ongoing structural instability will cause cracks to spread and grow. How can you know if a crack is a hairline crack or a spreading crack that indicates issues with the floor stability? 

Hairline cracks, in general, are stable, shallow, and slim. These cracks should be so small you can’t even fit a business card into them. These cracks are very common, forming during the natural process of settling that happens after construction. Hairline cracks are nothing to worry about, and you shouldn’t be concerned if you see them. 

On the other hand, spreading cracks are active, very unstable, and typically much larger than hairline cracks. Hairline cracks can turn into spreading cracks, but they’ll become larger, deeper, and much more noticeable in a very short period of time. Spreading cracks can even allow pests and water into your home. Keep an eye on any cracks you notice in your concrete, as even a very small crack can quickly become a problem.    

Additional Signs of Instability in Concrete Flooring  

A sinking or cracking concrete slab is a very strong sign that you have structural damage or instability to contend with. However, there are other, more subtle, signs that you can be on the lookout for. If you contact a foundation repair specialist upon seeing these early warning signs you might be able to reinforce the slabs in question before they sink. This will save you time and money.  

Less obvious signs of weakness or instability in concrete flooring and your property’s foundation include:  


Persistent dampness and humidity in your property can be a sign of structural damage, but this can also be a sign of many other issues. As such, you should investigate further when there is dampness with no clear cause.   


No one wants to deal with a pest infestation, but it’s something that may occur if you have extremely large cracks in your concrete. These large concrete cracks can allow pests in from the outside, making it possible to have pest infestations that seem to come “out of nowhere.”   

A Musty Smell   

A lingering, musty odor in your property is a sign that you have an issue with dampness which, in turn, can be one sign of low-level or hidden structural damage. Some people think that a musty smell is normal in a basement, but a musty smell anywhere in your home can indicate issues with the home’s overall structure.  

If you see one or two of these signs, you should contact a professional and schedule an inspection to get an idea of the overall health of your property and foundation. Understanding what can lead to these issues, and how they will impact your home if they are not dealt with, is also important.  

What Causes Concrete Slabs to Crack, Sink, or Settle? 

Floor cracks tend to be an indication of sinking concrete inside your property, and that means when you see them, it’s important to get professional help as soon as possible. While sinking concrete can sometimes come from relatively minor problems, it can also be a sign of foundational problems and incompetent soil around your home. There are many possible causes of issues with concrete slabs, including:  

  • Poor design, which can cause the foundation not to have enough stability on a design level.  
  • Substandard construction materials, which the construction company may have used to save money.  
  • Structural damage, which can come from a variety of sources, including hydrostatic pressure.  
  • Flooding, which can come from the inside or the outside.  
  • Incompetent soil, which can be a problem if the construction crew didn’t notice it or noticed and decided to continue building.  

While there are many technical causes of sunken concrete slabs, issues with the soil are almost always a factor. Concrete settlement, ironically, can also often come from issues with soil swelling. This is a problem called foundation heave, and it happens when the foundation of a home bulges upward due to swelling soil underneath it. However, when the soil contracts once again, it’s likely to contract even further than before it swelled. That push-pull process, where the soil swells, causes foundation damage, then contracts again, can cause even more damage than just a sinking foundation with no other problems.  

What Makes Soil Incompetent or Weak?   

Incompetent soil is soil that is incapable of bearing the weight of the structure it is supposed to support. This is determined by several factors including the type of soil, moisture levels, and the climate:   

  • Clay and Silt   

There are many types of soil, but a few broad categories can be formed: sandy soil, silt, loam, and clay-based soil. Soil can come in many different blends, but clay-based soils are the most expansive. This means that these are the most likely to move as a result of climate and weather changes, making them the most destructive for a property’s foundation.  

  • Extreme Weather   

Extremely heavy rainfall, snowfall, flooding, and drought can all affect your property’s foundation, both directly and through the soil under your home. All sorts of weather can have a negative impact on a home.  

  • Poor Drainage   

Poor drainage and extreme weather are connected, but the right drainage systems can prevent water and snow from gathering at your property’s perimeter when the weather is particularly bad.   

Why Worry About Floor Cracks? 

floor crack

It’s always a good idea,  to pay attention to floor cracks early on. There’s no such thing as a crack that “absolutely can’t” cause any problems because there are next to no ways to tell whether a crack is stable or cosmetic in nature without simply waiting to see if they spread. Once cracks start to spread they are likely to continue to do so, causing more and more damage, until a professional intervenes and deals with their underlying cause.  

Floor cracks that  spread are problematic in a number of ways for many reasons. They can present a tripping or accidental injury hazard to anyone in your home, but in particular to young children and those with mobility issues. Secondly, a floor crack which is actively growing can be a sign of structural movement and damage. As it grows, you will notice a number of other issues like sticking doors and windows.  

So, waiting to deal with a floor crack increases the likelihood of deeper damage to your property and its wider structure exponentially. This means that waiting could lead to more costly repairs, accidents and injuries, or even localized collapse in your home (if the underlying cause of your floor crack is foundation damage). That is why it is best to act quickly and decisively when you first see signs of cracking. 

Foundation Floor Cracks


Damaged and cracking concrete slabs are caused by the fundamental inability of the soil underneath them to provide adequate support. This can be caused by excessive saturation or dehydration and usually starts with damage to your foundation.  

  • Subsidence  

Concrete slabs and a property’s foundation subside when the soil under them lacks the structural integrity to hold them up. The result is that they begin to sink into the soil and will continue to do so, usually in an uneven manner, until they find competent ground. This kind of damage generally causes irregular depressions and increased issues with dampness.  

If the foundation below a concrete slab is subsiding, the property may be experiencing larger issues as a result of the disproportionate pressure being placed on specific areas of the structure. It is important that you get a professional involved as quickly as possible; these issues only grow in scope and severity over time.  

  • Settlement  

Settlement usually occurs when the soil under a structure recedes or cracks as a result of dehydration. This shrinking leaves a void behind and removes support from the concrete slab or foundation section in question. As a result, they can ‘settle’ into the space left behind by the soil as it draws back. Unlike subsidence, this is likely to affect isolated areas of a property.  

While this issue is caused by dehydration, it can also lead to serious dampness in a home. This is because of the way that water will follow large cracks and gaps in the soil. In this case, choosing the path of least resistance will lead water directly to the damaged sections of your foundation and allow it to seep into your property.  

When you first notice concrete floor cracks, you might wonder how soil settlement and sinking could possibly cause problems with your concrete. There are many ways this can happen, but there are two main elements of concrete that tend to create this response to soil settlement.  

  • Concrete Doesn’t Bend  

The first thing to remember is that concrete just doesn’t bend. Whenever concrete appears to be bending, what’s really happening is that there are many little cracks opening along the surface of the concrete. These little cracks may make it look like the concrete is bending, but because concrete is such a rigid material, it’s actually just cracking.  

Whenever concrete is in a situation where there’s an uneven amount of pressure on one side of the concrete, you’re likely to start seeing cracking problems. Over a long period of time or when the concrete starts having to handle a significant amount of weight, you’re going to see more obvious cracks in the concrete.  

  • Concrete Is Very Heavy  

It’s also important to remember that on average, concrete is extremely heavy. A solid slab of concrete will weigh 150 pounds per cubic foot, which is a gigantic amount of weight. Your concrete almost certainly isn’t going to be a foot deep, but that means a four-inch slab across three feet will still weigh 150 pounds, and your concrete probably weighs even more than that.  

The heaviness of the concrete adds to the issues that can arise when concrete tries to bend. If the concrete were lighter, it might not end up with cracks so easily, but because of the weight of the concrete, it weighs on itself, causing it to crack a bit more easily. When the soil starts settling, especially if it starts settling unevenly, that weight is going to inevitably end up causing cracks.  

Secondary problems are one of the things to think about when you’re wondering why you need to fix floor cracks early on. There are a lot of reasons to fix your floor cracks as quickly as possible. Part of the reason is because if you don’t fix those problems, you can end up with these secondary concerns.  

  • Wet Basement Problems  

Probably the most prominent issue that can arise due to floor cracks, especially in foundation floors, is a wet basement. The soil around your basement has some amount of water in it at all times, and water is extremely good at finding its way through even very small cracks. When you have general basement problems, the source may just be cracks in your basement floor.  

Even if you don’t end up having standing water puddles in your basement, these cracks can be more than enough to have humidity travel through the basement and wreak all sorts of havoc. No matter how you end up looking at it, cracks in your basement floor will almost certainly lead to issues with water in your basement.  

  • Structural and Foundational Damage  

There are also serious structural and foundational issues that can arise if you don’t manage floor cracks. Because floor cracks aren’t just going to close with no interference, structural and foundational issues can arise if you let the floor cracks go for long enough. The problem will only get worse over time, and structural issues tend to be serious even from the beginning.  

Not all floor cracks will inevitably result in structural and foundational damage, but floor cracks do tend to result in these problems. Do you really want to take the risk that you’ll end up with the “best case scenario,” which can still cause issues with wet basement concerns? Avoid structural and foundational damage by managing floor cracks early.  

Contact Professional Foundation and Slab Repair Specialists for Assistance   

Innovative Basement Authority is the leading slab and foundation repair company throughout Minnesota, North Dakota, and eastern Montana. We provide tried and tested solutions to homeowners who want the very best for their property. Our team has worked for many years to bring the best possible products and services to homeowners across our service area.   

If you notice problems with cracking in your concrete slab floors, don’t hesitate to reach out to us as soon as possible as these issues will only worsen. Contact us today for a free foundation inspection and repair estimate! Our team will provide you with a written estimate for repairs that day. We want you to feel that you have made an informed decision to work with us.  

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Innovative Basement Authority Service Map

We service Minnesota, North Dakota, South Dakota and Eastern Montana for basement waterproofing and crawl space repair.

Fargo, ND

1330 41st St. N
Fargo, ND 58102

Minneapolis, MN

6265 Carmen Ave.
Inver Grove Heights, MN 55076

Rush City, MN

1325 S Frandsen Ave
Rush City, MN 55069

Sioux Falls, SD

101 S. Reid Street, Suite 307
Sioux Falls, SD 57103