I recently went to a buddy’s house to see how he was doing with his latest project. He told me that he was planning to change the look of the flooring in his garage. He had some large foam mats that he wanted to throw away so he could add sealant and epoxy to the concrete for a nice finish. As we worked together to pull up the decaying mats, he discovered a large crack in the concrete underneath them. He was surprised at first, and I could see it on his face – this threw a wrench in his plan. We got to talking about if the epoxy was still an option or if he should simply replace the mats with new ones. I did some research for my friend and this is what I discovered about cracks in the garage floor. 

To fix cracks in concrete in your garage, you first need to assess the state of your slab and follow through with larger repairs as needed. Then make sure the crack and the surrounding area are properly cleaned from debris, dirt, oil, and grease. For smaller cracks, use an epoxy concrete crack filler. Once the filler is applied, use a trowel to work the filler into the crack and to level it to the surface. For larger cracks, remove any broken concrete, then with a cold chisel, undercut the edges of the crack. Using a sand mix with an adhesive additive, use a trowel to level the surface and allow to dry. Once dry, use a grinder to level the surface to the rest of the concrete floor. 

Why Do I Have Cracks in My Garage Floor? 

So, before we begin, you may have some questions about where this floor damage even comes from. (I know my friend with the floor mats certainly did!) A lot of what you see has to do with how the slab was originally poured. Things like quality of materials, how the base was prepared, or if there was underground moisture, could have all played their part in what you are currently looking at under your feet. If you live in a colder climate, the soil under your garage can also freeze, causing the expansion and contraction of the concrete with the changes in moisture and temperature. Cracks can also be caused by shifting soil. Improper water drainage can also begin to erode the soil underneath the slab and cause cracking. Settling of any house is normal and it may cause cracks in the floor. However, it is a good idea to look at your grading and drainage to ensure other damage isn’t caused to your home from water pooling somewhere it shouldn’t. 

Assess the Cracks in Your Floor 

Before you dive in and become the garage floor fixing warrior that you see in the mirror, there are some things you need to check to make sure you do not need to tag in a professional. As previously mentioned, check the grading and drainage around your home to ensure that water flowing away from your house, instead of under it. This may need to be adjusted before you tackle the cracks themselves.  

Next, assess what you want to fix by determining if the two sides of the crack are level. If they are, you are in the clear and are ready to get to work. If the two sides of the concrete are not level, you will need to contact a professional for a more thorough assessment. There may be other problems with your slab, and more extensive work may be required, such as re-leveling, or slab replacement. It is important to make sure you are not masking a larger, underlying problem, or your crack fixes will be temporary at best.  

Next, determine the size of the crack or cracks you are looking to fill. You will use different products and methods for filling different sizes in your floor. For smaller cracks (up to ½ inch in width), you should be able to use an epoxy concrete crack filler (Amazon link). For larger cracks, you will need a mortar mix, something like this (Amazon link). Once your materials have been collected, you are ready to get into the process. 

Prep the Garage for Working othe Floor Cracks 

As with any kind of patch or replacement, you will want to take some time to clean up the area first. This will ensure that the material bonds correctly inside the cracks, and that dust from other areas of the floor isn’t being blown into your project. While you are at it, you might as well just clean the floor so once the crack(s) are filled, you are done, and the garage is on point. Here is an article if you need assistance “How to Clean a Garage Floor”, 

How to Prep Cracks in Your Garage Floor 

To prep the crack itself, take the time to vacuum it out and make sure that you removed all the gravel, dirt, and debris. You may want to run a bristle brush down the crack to make sure you removed all the chipped concrete. If you are experiencing a lot of concrete dust, pressure wash the crack and the surrounding area. Make sure you allow ample time for the floor and crack to dry before you continue with the project. 

Fixing Small Cracks in Your Garage Floor 

Fixing small cracks is an easy job. Using epoxy concrete crack filler, run a bead of filler down the crack in the concrete. Use a small trowel to work the concrete filler into the crack and allow a few minutes for it to settle. If some areas are looking a little thin, and you think the crack can hold some more, apply some additional filler and use a trowel to level. Allow at least 24 hours for the filler to dry before walking over it or replacing any shelving or tools that may have occupied the floor space before then. Allow longer drying time if you live in a moist climate. 

How to Further Prep Large Cracks in Your Garage Floor 

For larger cracks in concrete, there are additional steps that you might need to take, depending on the depth and length of the crack. With larger cracks, you will need to undercut the crack in the floor using a cold chisel (Amazon link). The undercut will help hold the patch in place and should limit further damage to your floor. Make sure you take precaution and wear proper personal protective equipment (PPE) so you do not hurt yourself. 

For troublesome areas, you might need to use a circular saw with a concrete blade to cut away the broken concrete area. Cut all the damaged concrete out and remove the rubble. If it feels like you just created a ravine in your garage, you sorta kinda just did. Once you have the ravine…I mean… crack in the garage floor cleared out, now we can start repairing the damage. 

Concrete Bonding Adhesive  

Concrete does not bond overly well to itself, so an adhesive will be needed to help the sand mix patch adhere to the rest of the garage floor slab. Before you use the adhesive, make sure to thoroughly clean the area so that the adhesive can bond directly to the slab. Lingering concrete dust can weaken the patch, causing future problems and further aggravation.  

Applying the adhesive can be done in two ways. You can either brush in on to the sides of the crack before the filler is added, allowing time to dry in between or mix it with the concrete filler itself. As ever, follow the directions given on the product you choose. For the concrete adhesive itself, I would suggest using Quickcrete bonding adhesive (Amazon link)

Mix and Apply Sand Mixture to the Crack in the Concrete Floor  

For the actual sand mix, I would suggest this Quikcrete product (Amazon link). Mix the product according to the directions. This is where depending on the bonding adhesive that you decided to go with, if it is an additive, mix it thoroughly into the sand mix. Once mixed, use a trowel and work the material into the crack. Smooth it over with your trowel until it is even with your floor. The filler may take so much time to fully set. If you plan to epoxy your floor, you may also want to wait a certain amount of time.  

Project Complete!  

So, getting back to my friend. He was concerned at first about the task of trying to repair that large crack in his concrete floor. We took the time to research his options and determined that it was something he thought we could tackle. We prepped the floor, cleaned off some oil and other gunk buildup he had near the edge of one of his mats. He undercut and recleaned the crack and then we pressure washed the garage floor and allowed it time to dry. The next morning, he used some sand mix and some concrete adhesive and started troweling I the filler. The next weekend, I swung by to see how the progress was coming. By that time, the crack was filled and dried, and he had used a paint epoxy on the garage floor. It looked fantastic!  

There are some steps involved but taking the weekend to spruce up your garage floor has definite advantages. Not only will your floors look great but sealing the cracks can also help make your garage easier to maintain. It makes it so cleaning is easier, and spills are not the end of the world.