As a homeowner, it is natural the sight of cracks in the basement floor of your home worries you. After all, you do not want the structural integrity of your home to be compromised. However, you may be relieved to know that not all cracks in your floor are signs of foundation damage or need immediate foundation repairs. 

On the other hand, other cracks need to be addressed immediately, as they could let dangerous soil gasses like radon into your living area. Others can weaken the foundation wall by letting water and excessive moisture seep inside.

Read on to learn more about recognizing the types of concrete slab cracks and knowing which ones actually require repairs.

The reason for the crack in your basement flooring

crack in floor

There are multiple reasons why you have cracks in the concrete floor in your basement.

For example, once your home is built, it settles slowly deeper into the soil beneath it over a period of years. This is called settling, and this causes minor cracks in the foundation.

Concrete shrinkage and curing could also cause minor cracks around the floor. Concrete shrinkage is a reaction that concrete and mortar molecules have with moisture. They expand when there is moisture, but as the concrete dries, they shrink. This reaction causes cracks to appear on the floor. 

A more serious cause for foundation problems is a poorly designed drainage system. Water tends to build up around the foundation if the drainage system is not properly designed or if the soil around the foundation is poorly graded. The pressure generated by this water build-up is called hydrostatic pressure and can cause slab cracks to appear.

However, this hydrostatic pressure can be easily relieved by following a few easy steps. For example, if the cause for the water building up is the way the soil is graded, simply make sure it is graded to prevent water from accumulating near the foundation. Instead, the grading should direct water away from the foundation.

It helps to always make sure your downspouts are directed to drain water as far away from your home’s foundation as possible.

Regular cleaning and maintenance of gutters and downspouts are other easy-to-practice solutions.

However,  it is important for you as a homeowner to be able to first recognize the type of cracks your basement has before you can fix it with the right remedy.

Read more: Basement support beams

Types of cracks and floor crack repair solutions

As we mentioned earlier, not all types of foundation cracks require repairs. Let’s take a look at how you can recognize signs of structural damage and what remedies you could employ.

Spalling or flaking

Spalling or flaking is caused when the mix for the concrete slab floor is too wet or hasn’t been cured properly. When the excess water evaporates, it loosens the top layer of concrete. This causes flaking, which looks undesirable.

However, spalling or flaking is not really hazardous to the foundation itself in any way and does not really require any remediation.

People often try to hide spalling by painting on top of it. This, however, is not really a solution at all, because the surface is likely to keep flaking and the paint will flake off with it. 

If you have to do anything about it, we’d advise you to consider either installing waterproof flooring on top of the concrete or concrete resurfacing to avoid future spalling.

Read more: Concrete foundation maintenance

Hairline cracks

Concrete shrinkage, which we discussed earlier, causes hairline cracks in the basement floor to appear even as long as a year after the floor has been finished.

However, don’t let these cracks bother you at all. They are unlikely to cause any lasting foundation damage.

That being said, if you do feel the need to address the cracks, simply cover the concrete with a basement flooring finish. 

Cracks measuring ⅛ inch or wider

In most cases, cracks that measure ⅛ inch or those slightly wider are caused by shrinkage, just like with hairline cracks. However, while they may not pose a direct risk to the structural integrity of the foundation immediately, these cracks are large enough to allow water and radon gas into your home. 

This means that the cracks need to be sealed at the earliest. However, these are repairs that you can handle by yourself as a DIY project. The best product for you to use for the job is an elastomeric caulking sealant that is designed just for the purpose of sealing cracks on concrete floors.

Cracks formed due to sinking

When your home settles, some parts of the floor may sink lower than others, forming large and uneven cracks to form. These cracks definitely need to be addressed at the earliest, since they are a tripping hazard waiting to happen. 

The best way to deal with these cracks is to use a high-density polyurethane formula, such as PolyLevel to bring the sinking portion of the floor to the same level as the rest of the slab. 

You will need to drill penny-sized holes into the slab and introduce the polymer into these holes. The polyurethane material then expands, causing the floor to rise to the same level as the rest of the slab.

Cracks caused by heaving

These are the most dangerous foundation issues you could get. Heaving is seen most often in places with clay soil. As the soil becomes wet, it begins to expand and lifts up, cracking the concrete floor.

These types of cracks require the attention of an experienced foundation repair contractor, make sure you contact multiple contractors and get free estimates from all of them, allowing you to make an educated decision on who to work with.

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Crack in foundation floor: Causes and remedies was last modified: October 14th, 2022 by Narayan Shrouthy
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God is my witness, men sometimes think they know everything. When my husband built our house, God bless him, he abused the weight of the main wing, a year later we saw how the first floor collapsed on top of our living room… You have to ask the experts in these things…