20 Causes and Fixes of Cracking Garage Floors

Concrete is the primary material used in making garage floors. Generally, concrete floors are resistant to wear and tear, scraping, scouring, and pounding. But, as tough as concrete floors may be, it is not unusual for them to develop some cracks or chips. It will help if you know the reasons these cracks happen and how to fix them. 

Concrete garage floors can be beautiful, economical, and functional. Their only downside is when they get cracks, it is not usually appealing to the eyes. Cracks in a concrete garage floor can be annoying, especially after spending resources to put your garage floor in place. Here, we will discuss why garage floors crack and simple fixes you can use for them.

Some reasons your garage floor crack include:

  • Overloading
  • Porous Concrete
  • Poor Craftsmanship or Substandard Concrete Mix
  • Damage in Foundation 
  • Root of trees
  • Faulty Drainage System
  • It is Concrete’s Nature to Crack
  • Ageing Floors

Why Garage Floors Crack 

Crack on garage floors are caused by several reasons. It can be due to shrinkage, settlement, and many more. Here are some of the common reasons why garage floors crack.

It is Concrete’s Nature to Crack

Concrete is a great building material because it is sturdy and can resist compression. However, it is non-ductile and lacks flexibility. Garage floors made of concrete can carry a massive weight and are durable. Concrete cracks occur when it tries to twist or stretch. 

Expansion and Contraction

Changes in temperature cause concrete to expand and contract. A rise in temperature on a hot day makes the concrete expand, and a contraction occurs when the temperature falls on a cold day. This temperature pressure causes a crack on the concrete.

Porous Concrete

Concrete floors should have a moisture barrier between the floor and the soil. This moisture barrier will help to prevent the concrete from pulling moisture out of the ground. A little amount of water poured on your garage floor should disappear in half an hour, but a garage floor prone to moisture may lead to cracking.

Foundation Shift

Some garage floor cracks could be due to foundation-shift. It is the process whereby your building continues to settle on its foundation after it is constructed. This foundation shift takes years, and it is a normal process.

Soil Saturation

Soil saturation can happen when too much water from places like clogged gutters or heavy rain saturates the soil around the garage area. This soil saturation makes the soil move and cracks the garage floor.

Roots of Trees

The roots of trees planted around your compound or your environment can cause cracks in concrete floors. Trees’ origins are so deep that they put pressure on the underside of your foundation. It is this push that causes floor cracks.

Soil Movement

A lot of homes are built on expansive soils. Rainwater saturates the ground underneath and around such homes, causing expansion. It pushes against the foundation of the house, resulting in a crack on the garage floor.

Poor Craftsmanship or Substandard Concrete Mix

A concrete mix can be substandard if the proportion of cement and water is not right. Water is needed when mixing concrete; this water evaporates later and makes the concrete shrink. This shrinkage builds forces that pull the concrete apart, and concrete mixed with more water will have a higher degree of shrinkage.

Poor craftsmanship includes:

  • Bad Construction and Installation: Most times, poor construction results in cracked garage floors. Some mistakes like skimping on gravel and using uneven soil lead to cracks in garage floors. Care must be taken when pouring the garage floor slab. It must be done gently and away from the house to enable proper drainage.

More so, pouring the garage slab at an incorrect level will cause water to flow from the garage into the home. Some common mistakes made by builders include:

  • Too low MPA of concrete
  • Insufficient gravel
  • Improper base, uneven or disturbed soil.
  • Poor Subgrade Compaction: Sub-grade preparation involves compacting the sub-grade base, consisting of gravel and sand. This sub-grade is prepared before pouring a concrete slab. 

Compacting of sub-layers must be done before concrete is poured on them. The concrete’s heaviness will cause a slight drop down of these sub-layers and will lead to cracks in your garage floors if not done well.

Freezing and Thawing

The ground freezes sometimes. When it does, it may lift some inches off your floor before it thaws and settles back. This freezing and thawing movement of a concrete floor can lead to the cracking of a garage floor. The crack happens as the concrete floor of the garage is trying to move with the ground.

Ground Settling

Another cause of garage floor cracks is settling beneath the garage concrete floor. This kind of damage occurs when there is a void in the ground beneath the garage’s surface concrete floor. For instance, a hole could form when a company digs a trench for pipes and refills it but does not compact the soil.


Concretes are strong materials used for building, but it has its strength limit. Concretes have a strength limit of 3000, 4000, 5000 PSI. The maximum PSI tells you the amount of weight it can carry. Concrete could get damaged when such the specified value is exceeded.

When the ground below the garage concrete floor is overloaded, the risk of cracking increases. The ground below concrete becomes wet and soft after snow or rainfall. The excess weight on the concrete floor then weighs down on the concrete and cause cracks.

Premature Drying 

Cracks can occur when a garage floor dries out too fast, due to overexposure to sun or wind. There are two types of cracks that can happen due to premature drying: Crazing cracks and Crusting cracks.

Crazing cracks are smooth, surface cracks look like webs or broken glasses. They come up when a concrete top dries out too fast. Though they may not be pleasing to the eye, they are not structural problems. 

Crusting cracks occur during stamping when adding a pattern or texture to the surface of the concrete. The top of the concrete dries out too fast and becomes crusty on windy or sunny days. The stamps or pattern pulls the concrete surface and results in small cracks on the floor edges. Crusty cracks are not a structural issue and cause no bother.

Concrete Shrinkage

As the concrete move from liquid to a solid-state, it shrinks. This transition process is called curing, and hairline cracking occurs during curing. This concrete shrinkage can last for years.

Soil Settlement 

Settling occurs when the soil beneath a property moves with time. Its effect may not be visible when it happens. As settlement advances, it can lead to cracking in the garage floor. 

Settlement cracks should be taken seriously and need to be addressed. It could have adverse effects, such as flooding and other structural issues. Settlement can also happen because of vehicles’ weight, which puts extra pressure on the garage floors. 

Damage in Foundation

Cracking can sometimes indicate a form of damage to the foundation of your property. Issues in the foundation could arise because of 

  • Unstable soil
  • Invading roots
  • Heavy wet soil after a storm. 

These factors cause slabs to move and results in a crack.

Faulty Drainage System

Water contributes a lot to garage floor cracks. Cracks are more likely to occur in a place where excess water that is to be drained away is retained. High-density soils like clay retain a lot of moisture. This pressure can cause cracks on the garage walls.

Improper Troweling and Concrete Placement

Cracks can happen when troweling and concrete placement is not done correctly. Such cracks look like thin hairline in random hexagonal patterns. They are usually shallow, not deep even up to 1/8 of an inch.

Such cracks are called crazing cracks and are found on garage floors with troweled surfaces that are hard and smooth. Garage floors with broom finish surfaces do not have this feature.

Aging Floors

Cracks can also be a sign that your concrete garage floor is aging. You will notice small cracks that keep spreading if not corrected immediately. Older concrete floors tend to have more gaps as they age.

How to Fix Garage Floors Cracks

We have seen that cracking garage floors is not a strange occurrence and many reasons could be behind it. When you notice a crack on your garage floors, you must carry out maintenance to fix the cracks on the garage concrete floor.

Fixing cracks as soon as you notice them will save you time, resources and stop further damage from happening. 

To fix cracking garage floors, you need to evaluate the type of crack and check the possible causes. Then it would be best if you got the necessary tools that you will need. The tools to bring include:

  • A trowel
  • Wire brush
  • A broom or vacuum cleaner
  • Paintbrush
  • Concrete bonding adhesives
  • Cold chisel
  • Sand mix
  • Crack sealant (polyurethane)
  • Safety glasses 

Now that you have the tools ready, follow the steps below to fix a cracking concrete garage floor.

  • Use the wire brush to scrub the cracks and remove debris because the crack’s edge must be stable for the repair filler to stay firm.
  • Vacuum the crack and clean it carefully to remove grease or oil. If crazing cracks usually cover all the garage floor, you will have to clean the entire garage floor. But, if the cracks are large, you will have to clean only the cracks.
  • Ensure that the floor is dry because many crack repair products do not bond well if the crack area is wet. Depending on the temperature, you might have to leave the concrete set for a day or more. This allows for proper drying, and then you can begin the repair work. 
  • With your safety glasses on, use a big hammer to undercut the sides of the cracks. Doing this will give the sealant a base to sit hard.
  • Use the paintbrush to apply a coat of the concrete bonding adhesive on the crack. Then, allow it to dry.
  • Following the manufacturer’s instruction, mix the right amount of the sand mix.
  • With the help of a smooth trowel, fill the crack, smoothen it, and level the surface.
  • Let the patch filler cure for the length of time specified by the manufacturer.
  • Examine the patch when it dries to see if any more filling is required.
  • Seal the Patches

The next thing to do after the process above is to seal the patches using the crack sealant. Both the stain and water-resistance of the concrete are retained after sealing the patches. Use a brush or a roller to apply the polyurethane and ensure the coat gets deep into the rough patch. 

One significant advantage of water-based sealants is that they dry fast and have no irritating smell. When the first coat dries, it is vital to apply another coat or even a third coat for high traffic areas.

For those attempting a DIY, the Corner Crack Repair Kit – RCF-CNR Repair Kit For Foundation, Wall, Basement, Pool, Concrete & Crack Repair is available on Amazon. This kit has some cool benefits and features; this includes:

  • It is made out of carbon fiber, which is the strongest man-made material.
  • It is inexpensive when compared to other repair options.
  • It is effective and can be used for foundation repair, wall repair, crack, and concrete repair.
  • It reinforces a cracking corner.
  • The end product is a beautiful finish that is smooth and flat and almost invisible to detect. 

Benefits of Fixing Garage Floor Cracks 

  • It increases your home’s value: A lovely looking garage floor adds to your home’s value and makes the garage look good. Fixing your garage floor extends the life of the garage floor and extends its use too. 
  • Fixing cracks prevents further cracks and helps to maintain the floor’s integrity.
  • It keeps out unwanted pests: It helps to solve the problems encountered with ants coming up through cracks. When the cracks are repaired, ants and other insects no longer have access to the garage and your home.
  • Fixing the cracks on a garage floor ensures that no dirt or debris can settle in them. In the absence of both cleaning the garage and its floor becomes very easy.
  • Mold and bacteria can hide unnoticed in the cracks found in garage floors. We may not see these bacteria, but they are harmful to everyone’s health that comes to the garage. Repairing the cracks will seal the breeding sites of these bacteria and mold.
  • Fixing cracks in the garage floor prevent moisture from reaching any rebar reinforcement. The concrete gets damaged if excess moisture passes through the cracks and gets to the rebar. When this happens, it will lead to more cracking and affect the floor structure. You can prevent this by carrying out timely repairs.
  • Sealing cracks in a garage floor will reduce the water that creeps up into the garage through the cracks. It is important to check the water source that comes up into the garage through the cracks. It might be a drainage issue, a leaking line, or a high-water table problem that needs repairs.
  • Repairing the cracks in the garage floor may help you to discover a hidden issue. Such problems can only be found while assessing the crack to know its cause. It helps to save cost before the fault becomes big, expensive or uncontrollable.

How Much Does It Cost To fix A Cracked Concrete Garage Floor?

Many concrete floorings like that in the garages get a significant amount of heavy wear and foot traffic. They are susceptible to cracking after a period of time. An epoxy floor coating, for example, can be used to repair the cracks, chipping, and wear and tear.

Repairing your garage floors may not be as costly as it seems, thanks to factors that help reduce the cost involved in coating a concrete floor. An experienced installer will fix your floor and cracks that make it look unappealing. Aside from that, the concrete garage floor will function well and last long in the coming years.

Here is an average cost to Epoxy Garage Floors:

  • A one-car garage of about 250-square-foot costs $750 to $3,000 to epoxy. 
  • A two-car garage of about 400 to 500 square feet on the average will cost between $1,200 and $6,000. 
  • Garages with more extensive and older surfaces that need more coats may cost more.

Garage Floor Resurfacing & Refinishing Costs:

  • Concrete resurfacing per square foot costs between $3 to $10
  • For a 500-square-foot garage, the cost is from $1,500 to $5,000
  • Residential project cost between $500 to $1,000 

Read more: “Is It Worth Painting or Epoxy Coating Your Garage Floor?

How to Prevent Random Cracks in Concrete 

Cracks in concrete floors happen. There are measures that we can take to prevent and reduce accidental damages. These measures are meant to be used from the time the concrete is mixed to the time it is set in place. 

Contraction Joints

Incorporating contraction joints is a way to control where a crack can occur in concrete. Contraction joints are easy to maintain and are formed with hardboard strip, saw cuts, or plastic.

Where the joints are placed and how deep they are is essential for it to prevent random cracks in the concrete. The joints spacing is 18 feet, and for the pattern, its ration of length to width should not be more than 1.5.

Depth of Joints

Joints for construction should be ¼ the thickness of the slab. Joining the concrete means that you are attempting to make a plane of weakness which controls where the concrete will crack. It is necessary to ensure that the hand tool you are using to create joints in the concrete will give the full depth needed. Also, make sure that the edges are placed right.

Timing of Jointing

Jointing of concrete should be timely done to prevent cracks. One of the benefits of using a preformed hardboard or plastic strip is that it can be placed in concrete’s liquid form. The strips should align well and must be done right to avoid random cracks.

Using a saw to cut the joints is excellent, but you should cut the concrete when it can withstand the sawing and not spoil the edges of the saw. 

Taking more time before cutting the joints means creating more opportunities for cracking to occur. If a crack already develops before sawing the concrete, the sawed joint will not have the expected effect.

The best time to cut a block of concrete is within the initial 6 to 18 hours and not longer than 24 hours if you want the sawed joint to be effective.

According to research, the depth of the saw cut is not as important as the timing. You may use a shallower depth, but you cannot miss the proper timing because the saw cut’s timing is essential.

Sealing Joints

Sealing of joints may not always be necessary, but it can protect the joints from the infiltration of incompressible materials and surface water. If the infiltration of surface water occurs, it leads to spalling and subgrade failure. It is best to delay the application of sealant to ensure a complete shrinkage of the concrete. The sealant materials will bond to the concrete and become firm enough to withstand expansion and contraction.

Proper Curing 

Proper curing is another way to avoid random cracking and ensure that concrete lasts long. The curing process is sustained by maintaining the moisture condition of new concrete. Moist curing usually lasts for about seven days, but you can let it last longer for a better result.

The most common method of moist curing is continuous spraying/fogging or wet covering. A soil-soaker or a lawn sprinkler can be used to achieve spraying/fogging. You can also use a moisture-retaining fabric with a cotton mat and burlap. 

Place the fabric on the concrete immediately; it has hardened enough so that you can prevent surface damage. Keep the covering moist and leave a stream of water on the concrete’s surface all through the curing period. 

Quality Subgrade Preparation

An exceptional subgrade operation is essential to build a good base for the concrete. The subgrade should be smooth, because a smooth subgrade preparation will ensure there is no restraint when the concrete is shrinking. This reduces the chances of concrete cracking.

Avoid using Excess Water 

One of the things that contribute to concrete cracking is excess water. Too much water in the concrete mix increases the chances of cracking. It is important to avoid this by not adding extra water to the concrete mix.

Consider the Temperature Changes

Massive difference in temperature between the concrete and the air and surfaces can lead to cracking. Do not place concrete on characters that are lower than 35® F (or 1.7® C). You should ensure that the difference in temperature between the concrete and the air should not be more than 20®F. 

For slab on grade construction, let the subgrade compact. Then slope the slab and subgrade for proper drainage. 


Make sure that the formwork is firm enough to take the pressure off the concrete without moving. Formwork generally has a design that can reduce cracking. That is, a thin form board between braces that are well spaced can make allowance for cracking.

Try Using Synthetic Microfibers 

Restraint caused by reinforcing steel can lead to settlement cracking. The use of microfibers can help support concrete to avoid such cracks. Microfiber distribution on concrete can improve crack control and impact resistance.

Cool Gradually 

It would be best if you allow concrete surfaces exposed to heat to cool down at the end of the preparation period. This cooling process will protect the concrete against surface cracking.

Fix your Floor Today 

Cracks on garage floors are typical. Some cracks show up almost after pouring the floor. Whereas others appear after a year or more because of the house settling. There are numerous reasons why concrete floors crack. 

Although, some of the cracks can be a warning sign indicating a foundational issue. In such cases, you should perform a thorough check to know how serious the problem may be. Make sure that repairs are properly done to fix the garage floor and restore its integrity.

Although the process of fixing your garage floor may be lengthy and take some hours of your time.  Ensure you follow the procedures carefully so that the work is done right.

It may be challenging to determine the exact cause of a crack because there are various reasons. You may want to reduce the appearance of cracks’ appearance by following these steps: 

  • Using the right site preparation
  • Using a quality mix 
  • A good concrete finishing. 

Doing so will reduce the number of cracks on your garage floor. The result is a beautiful concrete garage floor that is pleasing to the eyes.