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Soil Shrinkage, Compaction, and Settling

The same way your foundation supports your home, soil supports your concrete. Unfortunately, at the root of most concrete issues is weak soil. Here's why soils shrink, compact, and cause unwanted settlement.

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You may not think about it very often, but the soil is arguably the most essential component in home construction. This is because every single part of your property is supported by soil. Your foundation, your house, your garage, and your driveway all rest atop the dirt.

When soil undergoes changes caused by weather or weight, structures around your home can suffer damages, especially concrete structures. These soil changes include shrinkage and varying levels of compaction, which will eventually lead to settlement – and the various concrete issues associated with it.

Why is My Concrete Sinking or Cracking?

As mentioned before, concrete needs solid support from the soil below to stay strong. Being such a heavy material, concrete responds to even the smallest changes in soil strength. Essentially, if the soil becomes weak, the heavy concrete resting on it will begin to settle.

So why exactly does soil shrink or become poorly compacted? In Florida, hot days, rain, and humidity are common occurrences. Over time, these weather patterns cause soil to become loose and weak in its own ways. Poor compaction sometimes occurs during construction, or the soil type may simply not compact well. No matter the cause of weak soil, your concrete is guaranteed to sink and crack because of it.

Soil Shrinkage

Drought and The Sun

The most common cause of soil shrinkage is drought. In Florida, homeowners don’t have to worry much about droughts because of the State’s higher-than-average annual rainfall and humid environment. However, Florida experiences plenty of hot days that can dry out the soil and cause shrinking – especially with sandy soils that don’t retain very much water in the first place.

Tree and Plant Roots

Tree roots can also dry out soil as root systems absorb moisture and draw it away from the soil supporting your concrete. The ground surrounding plants will always be a little dryer because of their need for water. Lack of moisture causes the soil to shrink in volume, and a gap opens between your concrete and the ground.

Whether a lack of soil moisture is caused by the sun or plants, your concrete will eventually crumble into the empty space. You’ll be left with cracked and sinking concrete.

Poor Soil Compaction

During the initial construction of your home, the soil may have been transferred from a different area in order to level out the plot of land needed for the building. This soil is known as fill soil. Sometimes, fill soil can be improperly compacted during the construction process and cause concrete issues down the line.

Compaction is how tightly packed soil is. When more tightly packed, the soil is denser and can support more weight. So, poorly compacted soil becomes a problem when supporting heavy materials such as concrete. Besides unforeseen errors during initial construction, what else causes poor soil compaction?

Sometimes the soil type can drastically affect its compaction. Sandy soil is most common in Florida, and it happens to be one of the loosest soil types. Sandy soil can be compacted, but it is more susceptible to loosening over time and losing its tightly packed density. When soil becomes poorly compacted, more gaps and spaces occur within it, weakening the structural integrity of the soil. Again, heavy concrete will overpower the soil and begin to sink and crack.

Concrete Settlement is Inevitable

Concrete settlement is the term used when concrete begins to sink or crack because of soil issues. If shrinkage or poor compaction occurs on your property, it’s more than likely that your concrete structures will begin to settle. In Florida, concrete slab foundations are pretty common due to the State’s proximity to sea level, so entire homes can be put at risk when soil issues occur.

Unfortunately, soil shrinkage and poor compaction are quite hard to prevent for the average homeowner. You can’t control weather patterns or construction errors made before the house was built. Concrete settlement often occurs, however, and it is a solvable problem.

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    Solutions to Soil Issues and Concrete Settlement

    The best way to fix soil issues and concrete settlement is to take soil out of the equation entirely. Homeowners can’t control weather patterns, but they can control the material that supports their concrete. That’s because Alpha Foundations uses polyurethane injection to fill any gaps below your concrete with a durable and waterproof material.

    Advantages of Polyurethane Injection

    You may have heard of mud jacking, an outdated process used to lift sunken concrete. It was messy, tedious, and usually didn’t work. A modern solution called polyurethane injection is more effective and quicker to install. Alpha Foundations uses PolyRenewal™ to lift and stabilize your concrete. Polyurethane foam cures in just 15 minutes, which means you can use your concrete shortly after the job is completed. The material won’t be affected by heat or water and is strong enough to easily support concrete structures.

    Count on Alpha Foundations for Your Concrete Lifting Needs

    If you need to get your concrete lifted, Alpha Foundations is here to help. We’ve been servicing Florida and South Georgia for 20 years and have become the most trusted home repair experts in the region. Contact us today to schedule your free inspection and repair estimate with one of our experienced professionals.

    If you think that your property might be struggling with concrete settling, don’t hesitate to give us a call to learn more about polyurethane injection or other foundation repair options.


    Alpha crew member injecting polyurethane into concrete slab.

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