Why Is My Garage Floor Cracking?

Garage floor cracking is a very common occurrence. As a home inspection company, we get many concerned clients asking about these cracks. How can you decipher whether these are just minor cosmetic defects or serious structural issues? In this blog, we will get to the bottom of it!

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What Causes Garage Floor Cracking?

Improper Installation: When it comes to installing concrete slabs, it is crucial that the concrete is properly mixed and cured. Additionally, it must be correctly reinforced by the necessary amount of rebar and/or wire mesh. In the case that it is installed improperly, the concrete can end up shrinking as it dries, resulting in cracking.

Soil Movement: The soil under the concrete can also have a direct influence on its condition. If the soil underneath is not completely compact, it can start to shift and settle over time. This could cause portions of the slab to sink and crack. On the other hand, extreme temperature fluctuations can also cause the soil to expand, causing the slab to jut upward. This defect is also know as heaving.

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Heavy Loads: Garage floors are built to handle a predetermined amount of weight. If that weight is being consistently exceeded with heavy machinery or vehicles, it could lead to damage and cracking.

Moisture: Water is always a potential threat to any component of a home – and the garage floor is no exception. Moisture can make its ways into hairline cracks in the concrete. Then temperature fluctuations can cause the moisture to freeze and thaw, resulting in alternating expansion and contraction. This pattern can eventually worsen cracks over time. This will especially be an issue in garages that are not climate controlled in locations with extreme weather conditions.

Should I be Worried About Cracks in My Garage Floor?

If you do have cracking, when should you be concerned? The short answer is not that often…

Almost all garage slabs built within the last 80 years are called floating slabs. This means that they are not connected to the foundation wall of the home and can move freely up and down within their space. This is structurally good news and it means that garage slab cracks rarely indicate larger issues.

However, it’s important to know when there are other problems that may come from garage slabs. So when should you consider fixing things? It mainly depends on the size and location of the garage floor cracking.

Small cracks less than about 1/8″ are considered hairline cracks, and are generally due to shrinkage during the curing process. These should not raise too much concern, and should be monitored over time.

As cracks start to exceed 1/8″, they may require repair to prevent further damage. When two segments of a crack are uneven, with one side higher than the other, this could indicate that heaving or settling has occurred. This is more concerning because the slope of your garage floor is very important.

A garage floor typically slopes outward so excess moisture can drain out of the garage overhead door and not sit inside. Settling and cracking can alter this slope causing water to pool near a foundation wall, or within garage cracks. This can lead to real foundational problems and worsening cracks in your slab.

Also, if the cracks are significantly larger and extend up along the wall, there could be structural concerns. In any of these instances, evaluation from a structural engineer may be advisable.

How to Repair Garage Floor Cracking

Small Cracks: When it comes to small cracks (usually between 1/8″ and 1/4″ in thickness), repairs can often be performed by the DIY-savvy home owner. You must first clean out any debris from the crevice with a brush or compressed air. If the area is particularly dirty with oil, grease, etc, you may need to scrub the area with a degreasing solution and water.

After clearing the area completely and allowing it to dry thoroughly, you can then fill it with a strong concrete filler and sealant. Once the filler is applied, smooth it out with a wet trowel or putty knife. Allow it to dry for the manufacturer’s recommended amount of time.

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Large Cracks: For larger cracks (approximately larger than 1/4″), the process is similar to small cracks. However, it is recommended to instead use concrete patching compound or some type of mortar mix.

Apply the concrete compound into the crack using a trowel or putty knife, making sure to smooth it out and remove all air. If the crack is deeper than 1/2″, it is best to apply the compound in 1/4″ layers at a time, allowing each layer to dry before applying the next. This is to make sure the concrete compound sets and binds properly with the slab.

*Keep in mind these are only tasks you should undertake if you are comfortable with DIY projects. There are plenty of online resources that can guide you on how to make the necessary repairs. However, it is never a bad idea to hire a professional for the task!

Major Defects: If you are seeing any extra long or wide cracks, seriously damaged concrete, uneven portions of slab or signs that settlement or heaving has occurred, there is a possibility that there are serious structural issues at hand. In this case, it’s time to call in a pro.

Sometimes mud jacking (or slab jacking) may be necessary. This is a process that involves drilling holes in certain areas of the concrete slab. A mixture of water, soil and cement is then injected into the holes under the slab to create a base under it that will level its surface. This can help extend the life of the slab and help fix the slope of the garage.

If there are many cracks present, or the concrete itself is chipping-damaged, mud jacking won’t be possible and the damaged floor must be completely removed and a new one must be poured.

Inspecting Garage Floors

Inspecting the garage is one of the main portions of our standard inspection. Our inspectors make sure to evaluate the entire structure, including foundations,  slabs, and any attic spaces, if present.

We also observe the exterior and make note of any problematic items. Moisture is one of the biggest threats to any structure. Therefore, we are sure to evaluate items such as: grading, drainage, gutters and siding. Because taking preventative measures is one of the best ways to avoid future garage floor issues.

To learn more about the items we cover in our standard inspection, check out this article.

Scott Home Services has been a leading provider of home inspection services in the Colorado Front Range for over 18 years. If you are in need of home inspection services, we are here to help! To learn more about our inspection services, visit us online. Or contact us to book your home inspection now!