Concrete slabs are a perfect foundation for garages because they can bear a lot of weight and provide a flat surface ideal for parking. However, your concrete garage floor can crack, regardless of how well you take care of it.

One of the most significant mistakes homeowners make when repairing cracks in their garages is failing to determine what types of cracks they’re dealing with. It would help if you determined whether the cracks are active, shrinkage, structural, or dormant because understanding the different types of cracks and their causes will help you find the perfect methods and products for repairing them.

Failure to assess the type of crack you’re dealing with and what products you should use could result in unhappiness with the work you did or the repair work popping out. However, you can overcome these risks by taking a few minutes to evaluate the types of cracks you’re dealing with and choosing the right products to repair the cracks.

Why is My Garage Concrete Floor Cracking?

Cracks on your garage floor can be due to various reasons; however, the common causes for cracking include:

• Poor installation: You could blame poor construction if you notice many cracks in your garage floor. Builders might have poured a thin slab, created an insufficient gravel base or failed to add rebar reinforcement when needed.
• Shrinking: You shouldn’t worry about shrinkage cracks because they are pretty standard. However, natural shrinking happens during the curing process; therefore, it’s pretty common for concrete to have some cracks.
• Settlement: This refers to when the soil under your building or home moves and sinks over time. Settlement is expected over the years; however, it can pressure garage floors resulting in cracks.
• Drainage: Water not draining away from your home correctly could lead to the formation of garage floor cracks. The presence of heavy clay or other types of dense soils clings onto excess moisture. Water-heavy soil might freeze during the winter, making the soil expand and put some pressure against the garage slab leading to heaving and cracking.

Are Cracks in a Concrete Floor Normal?

When you see cracks in a concrete slab, your first assumption might be that something has been done wrong; however, that is not always the case. Concrete cracks are prevalent, and some are even inevitable.

Here are some of the most common types of concrete cracks:

Plastic Shrinkage Concrete Cracks

Concrete is usually full of water when still in its plastic state (before hardening). However, when the water eventually leaves the slab, it often leaves large spaces between the solid particles. These large, empty spaces make concrete weaker and more prone to cracking. This is the most common type of concrete crack known as plastic shrinkage cracking.

These types of cracks usually are very narrow and barely visible. Although they are almost invisible, it’s best to understand that these cracks only exist on the surface. They also extend throughout the slab’s entire thickness.

It’s also best to understand that an excessively wet mix is one of the top reasons for shrinkage in concrete. Water is a critical ingredient in every concrete blend; however, it’s not advisable to have too much water in the mix because the slab might shrink more than if you use the correct amount of water.

Thermal Cracking

When your concrete garage floor is exposed to large temperature differentials from summers to winters, it might expand or contract, leading to cracking. In addition, if the soil beneath the concrete freezes, it can also lead to cracking, especially if there’s moisture that migrates into the ground. If this happens every year and the slab cracks or move because of it, then the crack would be considered an active one.

Cracks Caused by Soil Movement

Soil movement can cause cracks in your concrete garage floor. The size of the cracks might vary from hairline to an inch or larger. Additionally, the cracks might be insignificant or cause significant issues. Most soil issues include one or more of the following:

• Moisture and drainage issues
• Settlement
• Slope creep
• Expansive soils

Most of all, the larger cracks in a slab relate to soil movement, especially when there isn’t proper reinforcement in the slab of concrete that is not structurally strong. For example, weak concrete in garage floors can be due to insufficient cement in the concrete mix or too much water was added when poured from the truck.

Crazing Cracks

Crazing cracks are a web of very fine hairline or smaller than hairline cracks. They are usually very shallow and less than ¹/₈ or ¼ of an inch deep, hardly visible unless the floor is wet. These cracks often form when the concrete’s surface dries faster than the rest of the slab when the floor is poured.

Most homeowners usually seal the cracks with a light sealant coating as part of their maintenance programs. However, it’s crucial to seal exterior crazing cracks than the interior ones. One of the disadvantages of sealing crazing cracks in a garage floor is that some sealing products might make them more prominent. On the other hand, sealing helps waterproof the garage floor and makes it easier to clean.

Structural Cracks

Engineers hardly consider cracks in a garage floor to be a structural issue requiring repairing them for structural purposes. However, the cracks might indicate some structural problems within the home.

Sometimes structural cracks might be a warning that there is a foundation concern, settlement of the structure itself, or slope creep. All these factors can cause structural damage to a home. Occasionally these signs might indicate poor drainage, a water table issue, or an indication that the compaction under the garage floor was poorly done.

However, there are few cases where cracks in a garage floor might become a structural concern. For example, if a house is built on a hillside and the garage floor has an open space or a living area under the garage floor, the garage slab sits on the soil.

If the cracks are a structural concern, you should consult an engineer and repair them per the engineer’s calculations and design. Additionally, you should obtain a permit for the repair works before performing them.

Best Way to Fill Small Cracks on Concrete Garage Floor

Repairing small cracks on your concrete garage floor doesn’t have to be as scary as it sounds. You can do many repairs easily without spending too much money on them. However, before you fix you start fixing the cracks on your concrete garage floor, you should diagnose whether the cracks are indicative of a structural problem that might require professional help to resolve.

Very few cracks are usually indicative of structural damage. It’s best to look out for these signs to diagnose a more significant problem and find professional help:

• Bulging
• One side of the crack is larger than the other
• Erosion

If the cracks on your garage floor are not structural, you can fix them yourself. But, first, get a sense of the crack’s length, width, and depth. Understanding these three things will help you determine the type of product you should use and how much of it you’ll need to repair the cracks.

Here is how you can fill small cracks on your concrete garage floor:

Clean Out the Crack

The first step in repairing a crack on your concrete garage floor is opening and cleaning out the crack with a cold chisel. This process is called “chasing the crack.” You can then clean out the crack using a vacuum cleaner and a wire brush. Be on the lookout and remove any easily crumbled or sandy concrete called laitance.

Laitance is a weak area in the original pour that you should remove because it doesn’t provide a stable surface for the repair to attach to and might cause your repair to fail. Clean the area with a vacuum cleaner and a wire brush until you’re confident that you’ve eradicated the crumbly concrete.

If you deal with longer cracks, you can use a small angle grinder with a crack chasing masonry wheel to create a nice, smooth groove that will save you a lot of time. Be sure to wear appropriate safety equipment such as gloves and goggles because angle grinders give off debris and sparks.

Fill the Crack

You can use two types of fillers for your cracks. If you’re dealing with more minor cracks, you can opt for a self-mixing concrete crack filler. However, if the cracks are longer and more extensive, you might find that it’s more economical and practical to mix the filler yourself.

Self-mixing crack fillers are great because they work without you having to mix several batches of filler. Several commercial products are available for this job, and you can choose one that best fits your area.

It can be unsettling to have large cracks on a concrete floor. However, you can fill and repair them yourself if you’ve ascertained that they don’t indicate a structural issue.

Can You Put Epoxy on Cracked Concrete?

Epoxy is an excellent way of repairing large cracks on a concrete floor. However, you can opt for a polymerized concrete mix if you don’t have epoxy. The polymer acts as a binder that helps adhere the filler to the rest of the original concrete.

Rust-Oleum’s EpoxyShield Concrete Patch & Repair is a great garage floor crack repair epoxy kit. It’s a two-part kit consisting of epoxy and sand, and the product has an excellent reputation and is easy to use. The product dries to a tough surface that seals the crack with a light gray finish.

You should clean the concrete crack thoroughly before mixing the product. After this, proceed to mix the epoxy and sand on a piece of cardboard. Next, proceed to fill the crack with the mixture; however, be keen not to mix too much because it might start curing before you are finished working. Be sure to only mix enough for what you’re using at the moment.

If you’re dealing with deeper cracks, ensure that you fill the crack two-thirds of the way using sand first. Then, ensure that you force the sand mixture into the crack to remove any air. Finally, if you want the best finish, consider adding sand to the top and then scrape it off after the mixture cures.

Some contractors might prefer polymerized concrete instead of epoxy-based solutions to patch large cracks because it’s easier to apply than epoxy. Using layers, you can fill any width crack with polymerized concrete.

You can mix polymerized concrete with water and then trowel it into the crack. Polymerized concrete also gives you more time to work with the slurry before applying it.

Will Cracks on the Concrete Garage Floor Keep On Spreading if left Unfixed?

The cracks on your concrete garage floor might keep on spreading if you don’t fix them. If you already have a cracked garage floor and drop a heavy piece of equipment or part on the floor, it can break further. Therefore, it’s best to fix the cracks to prevent them from spreading or prevent new ones from forming.

When Should I Be Concerned About Cracks in a Garage Floor?

It is pretty standard for your concrete garage floors to have cracks. Unless there is a structural defect in the floor, you don’t have to worry about the cracks because you can fix them quickly if you like.

However, when your garage floor has a significant number of cracks, wide cracks, or when a crack has one side that’s substantially higher than the other, then you should be concerned about the cracks. It is advisable to check the cracks further and check the entire home for possible soil and foundation movement signs.

Before you determine whether the cracks are a concern, you should look at other factors in the home. For example, the following signs might indicate that the cracks relate to foundational or other issues:

• Un-level floors: If the house’s floors are sloping, that might be an indication of structural movement.
• Doors or windows that are difficult to open or shut or inoperative.
• Cracked, leaning, or bowed foundation.
• If there are cracks in the siding or drywall
• If a crack across the garage floor continues up the garage wall.

If you note any or some of the issues above, you should be concerned about garage floor cracks. The cracks are then part of the overall picture of the home and might relate to foundation issues.

If your home is on a hillside lot and there is an open space or living area underneath the concrete garage floor, you should evaluate all cracks for safety purposes. It is best to consult a structural engineer for interior concrete floor crack repair if the cracks have rust stains, run extended lengths, or are getting worse.

Check this too: How Do You Get Scratches Out of Vinyl Flooring

It’s pretty common for your concrete garage floor to develop cracks, some of which might appear after the floor is poured. Other cracks might occur after the first year or so from the house settling slightly. Many reasons can lead to cracking of concrete slabs; however, most cracks do not usually indicate severe structural or foundation issues. Always analyze the cracks to determine the seriousness. After repairing all the cracks on your concrete garage floor, you can add an epoxy coating to protect it.