You may first notice that your garage floor is out of level when something begins to roll—a tennis ball, a baseball bat, a child’s wheeled toy. Or you’ll see spilled water that doesn’t pool up but instead develops long streaks as it makes its way downhill. But those are annoyances, more than anything.

An out-of-level garage floor may require levelling when any or all of three critical scenarios happen:

  • Gapped Garage Door: The garage floor may be so tilted that the garage floor does not meet the bottom edge of the door. When you’re inside the garage, especially when the garage is dark and it’s light outside, you’ll see that telltale crack underneath the door.
  • Garage Floor Tilts to the House: If the garage floor has begun to tilt toward the house, water from the driveway, often boosted by overflowing gutters and downspouts, may flow toward the house itself.
  • Critical Services Are Affected: Garages often contain three appliances to be level: the washer, dryer, and water heater. Washers and dryers may stop working when they are out of level. Water heaters may tip over, especially in the event of an earthquake.

In most cases, levelling a garage floor will require the services of a professional. We take a broad overview of these services here to help you make an informed decision on which route to take.

Slab Jacking With Slurry

Slab jacking is one method that can correct the tilt of an entire concrete slab floor. You cannot do this yourself, and it is expensive. But it is still cheaper than demolishing and re-building your garage. It utilises your existing concrete slab, with only minor touch-ups required if the slab jacking efforts succeed.

Also called mudjacking or concrete raising, a matrix of holes, each about 1-2 inches in diameter, is drilled into the concrete. Then a slurry of sand, gravel, ash, and water is ​injected into the holes. Technicians do not randomly inject slurry. 

By test and intuition, they have to make sure that the slab is supported in all areas. If one area gets too much push, it can crack the slab by forcing it upward too much. If one area gets too little slurry, it is left unsupported and can eventually crack and break.​

It takes about one day for the slurry to cure to its eventual strength of about 2,400 psi (however, this can be regulated by the technicians by adding different proportions of lime or sand). Slab jacking with slurry will be far less expensive than polyurethane-based jacking due to the lower cost of the source product and because it is a well-established method with many companies offering the service.

Slab Jacking With Polyurethane Foam

Foam injections are similar to slurry injections but are considered more effective because technicians can better predict the expansion of the polyurethane foam. The slurry injections require larger injection holes and more of them, plus more product needs to be injected under the slab.

Foam slab jacking requires holes that are slightly over 1/2-inch in diameter. After the hose is inserted into the hole, the foam is injected, and a calculated amount of time passes while the foam expands to its maximum size. After the injections are made, the holes are covered over with patching cement.

The foam product is far lighter than mud, too. About 3-4 pounds of polyurethane ​equals 100-150 pounds of slurry. Having a lighter base product would be to avoid overburdening the soil with yet more weight. Because of this, it is often used in weight-sensitive areas such as near bridges.

Poly-based slab jacking will cost about four times more than slurry-based jacking, mainly due to the cost of the source product.

Using Leveling Compound For Smaller Issues

Levelling compound or mortar can fix small areas of an uneven floor. This is regularly done for interior floors before the floor covering is installed.

But pouring out levelling compound or troweling down mortar across an entire garage floor. Masonry patch products tend to crack when applied thinly. Instead, apply levelling compound only as a spot fix if you might have a section that has cracked off and is now sloping down. Dips and sags are also great candidates for concrete levelling compounds, as they are fairly localised.

All areas that will receive the levelling compound must be thoroughly clean for this cement product to adhere properly. Since motor oil can be difficult and even impossible to clean from concrete, abrading the concrete may be necessary.

A similar option is to build platforms from plastic or wood sleepers underneath 3/4-inch plywood in select areas that need to be level.

FAQs About Garage Renovation

Can I Use Self-Levelling Concrete In A Garage?

Self-levelling concrete is perfect for basements or garages because it’s resistant to mould growth.

How Do You Raise A Sunken Garage Floor?

If your garage floor has a void underneath it, slab jacking is the best method for lifting the concrete back into position. Slabjacking means injecting a polyurethane foam through the concrete slab. As the filler is injected, it foams up and solidifies, raising the concrete as it does so.

What Is The Cheapest Way To Level A Concrete Floor?

The cheapest way to level a concrete floor is to use a specialised sand mix. This mix includes concrete and will easily spread across the floor for an even finish. To do this, spread the sand mix on the floor, spray it with water, and let it dry.

Why Is My Garage Floor Sinking?

There are three main causes for settling or sinking garage floors: poor construction, improper drainage systems, and displaced soil: Poor construction can cause cement floors to sink and settle more than normal as they age.

How Do You Fix Concrete Sinking?

You have three options: coat the hollow section with a sand-and-cement mixture to make the surface higher, raise the underwater section using mud jacking, or raise the sunken section using expanding polyurethane foam. Patching fixes the safety issue without costing much, but the patch is sure to show.

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Facts About Garage Floor Sinking And Repair

Cracked and sunken garage floors are more than just an eyesore. They can become a trip hazard and deteriorate over time if not addressed. Many homeowners will ignore an open or cracked garage floor, assuming it’s a cosmetic issue only, and most of the time, out of sight and out of mind. 

However, this condition can be caused by an issue that could ultimately impact the rest of the home and should be addressed.

Water Drainage

A cracked garage floor may indicate a water drainage problem between the garage and the house. Left unchecked, this could impact the foundation of the home itself. If this is the problem, the water issue needs to be fixed, and the water redirected from the house to prevent future damage. Mudjacking can lift the floor back to where it’s supposed to be without requiring any demolition.

Soil Displacement

If the soil beneath your garage floor has become displaced or was not compacted correctly, to begin with, that soil needs to be stabilised and replaced before future repairs can be done. 

If you don’t fill that void, you will continue to experience sinking of your garage floor, so this needs to be addressed. If you’re unsure how best to stabilise the soil beneath your garage floor, contact a concrete lifting professional for recommendations.

Settling With Age

Even with the most well-compacted foundation, there is some settling of floors over time. Typically, this will result in small cosmetic cracks only and don’t necessarily need to be repaired. However, if you see the cracks worsening over time, or you start to see sinking or buckling of your garage floor, you may need to contact a mudjacking specialist to come in and do repairs. 

Mud jacking is helpful in areas that don’t require a lot of load on the surface. In the case of a garage floor where there is the potential to have thousands of pounds resting on the floor, you want to ensure it’s done correctly. Also referred to as “slab jacking”, mudjacking is a specialty concrete repair technology. 

It attempts to lift a sunken concrete slab by pumping a grout through the concrete, effectively pushing it up from below. This process comprises drilling holes through the uneven cement slab to raise it. Grout is pumped through the access holes to raise the slab. The holes are then patched with a quick setting cement.

A Cost-Effective Alternative To Concrete Replacement

Concrete garage floor settlement will typically happen over time if placed on top of poor or non-compacted base preparation. Erosion and other factors contribute to the garage floor degradation and settlement of concrete’s solid base, supporting it. 

However, many times simply repairing the concrete is more cost-effective than replacement. Mudjacking is typically an ideal alternative to costly concrete replacement! You can noninvasively repair the damage over time with this technique, and it is an ideal solution for open garage floors.

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Problems Of Settled Concrete Garage Floors

The effects of settling are not just cosmetic. Settling often results in unsightly cracks, unevenness that may cause your garage to lean, and tripping hazards when the slab is uneven with adjacent concrete.

Settling can cause even more problems. Your garage door is designed to go up and down on a parallel track; when one side of your garage is lower than the other, the door may not operate correctly or may perform erratically. Doors that lead to the outside or even into your home can be unlevel, which means that they will not fit correctly into the door jam; this can pose security risks and let extra air into your home, raising your energy bills.

Your first thought might be to replace the slab, but the solution is costly. Depending on where you are in the country, your garage was either built on top of the slab or set in a slab with a thick edge. In either case, replacing the floor would require moving or removing the garage to do the job. If the sloping occurred due to underlying problems beneath the slab, new concrete would be a short-term fix at best.

Why Slabs Sink

The slab beneath your garage may sink for several reasons:

  • The concrete may have been laid on top of base material that was not properly compacted.
  • The soil under the slab settled unevenly.
  • The slab was not properly reinforced, which leads to cracking and “differential settling,” where one part of the slab sinks lower than the other.
  • Drainage from downspouts or grading around the building eroded the soil.

Even if you lay new cement, problems are likely to emerge again unless the soil problems underneath the slab are corrected. The best solution to fixing garage floor settlement is through concrete lifting. By drilling small holes in your floor and pumping in organic or foam material to stabilise the soil, the slab is lifted and made level once again.

Why Concrete Lifting Works

There are several advantages to this approach:

  • Slabjacking costs less than half what it would replacing the concrete
  • The process can be completed without removing the contents of your garage
  • You can use the floor almost immediately
  • The process fixes the root of the problem, reducing the likelihood of future settling

Once the floor is even again, you will find that your doors shut properly and concrete joints are level, making your property both safer and more attractive.

Cracks That Occur In The First Few Months Or Years

  • Shrinkage cracks: When a garage floor is first poured, the concrete begins to harden (contractors say cure), and when this process takes place, the concrete shrinks a little; a 20 foot square of freshly poured concrete will shrink about a 1/8 of an inch in each direction. As this happens, small shrinkage cracks appear in the concrete. These are normal and generally are not much of a concern. 
  • Cracks from a new home settling: In the first year or two, it is not uncommon for a new homes’ foundation to settle a bit. As this settling takes place, the slab will often develop a few cracks due to this setting, but in the overall picture, these likewise will normally not be of much concern.
  • Cracks during construction: Builders often say that “Time is money” and push the contractors and sub-contractors to get their work done sooner. In this haste, the framing contractor often wants to start framing the house as soon as the foundation and slab are poured. From a technical standpoint, the concrete needs some curing time before anything heavy can be placed on it; it needs to achieve a certain strength before heavy lumber and equipment get onto the concrete. Depending on the type of concrete, it usually takes 5 or 10 days and even up to 4 weeks before heavy equipment and loads can safely get onto a concrete slab; most concrete reaches full strength in approximately 28 days.

If a framing contractor drives a piece of heavy equipment loaded with lumber onto a 4-inch thick concrete slab, he may crack the green (not fully cured) concrete.

Fix Low Spots On A Garage Floor

Having an uneven, pitted, or dimpled concrete garage floor can be more than just a nuisance to look at. Low spots in a garage can indicate unsupported concrete slabs, something that often gets worse over time as the concrete continues to settle.

Also, low spots on a garage floor are the first place that liquids will run when the inevitable spill happens. This goes for motor oil and other lubricants, which are notoriously difficult to remove from concrete.

So, how can low spots on a garage floor be corrected? In this article, the concrete experts at AAA Concrete Raising are helping you with a few pointers related to doing this yourself, with some things to consider if you’re interested in hiring outside help to assist you.

Remember that the severity of any low spot on a garage floor will depend largely on how well the concrete slabs are supported. A lack of support beneath any concrete slab will invariably result in ongoing degradation. Therefore, the best approach to garage floor levelling will depend on the structural integrity of the concrete and how depressed each low spot is.

Garage Floor Levelling Compound Vs. Slab Jacking

It’s safe to say that there are two paths to success if you want to correct low spots on your concrete garage floor. These two strategies are both tried-and-true and work well in most cases. Let’s take a closer look at each one.

Using Leveling Compound

Using concrete levelling compound is a great idea for do-it-yourselfers, and it’s a great way to correct smaller, less severe low spots. For dips and sags that are fairly localised, using levelling compound can be a fantastic, low-cost solution.

Here’s a quick list of the steps required to complete a concrete levelling project using levelling compound found at most hardware stores:

  • Step 1: Clean the low area thoroughly. For low spots that have significant amounts of oil in them, rub the concrete first. Then, vacuum the entire area.
  • Step 2: Use a straightedge to gauge the depth of any concrete depression. A great tool for doing this is a long 2×4. Once you’ve located the depressions, mark them with a pencil.
  • Step 3: Use self-levelling concrete filler containing latex, epoxy, or some combination thereof. Pour the filler into the depression and use your straightedge to ensure uniform filling.
  • Step 4: Allow the garage floor levelling compound to cure. This often takes between 12 and 24 hours. Curing times are almost always listed on the packaging of any concrete levelling compound.

After the compound has fully cured, it will be safe to apply whatever paint or sealer you wish to use.

Slab Jacking

Unless you’re an experienced mason with a thorough understanding of mudjacking techniques, it’s highly advised that slab jacking be left to the professionals. This is because slab jacking involves modifying the underlying support system of the concrete slabs, something that can go very wrong if faulty materials, equipment, or techniques are used.

Garage floor levelling using a slab jacking process involves the following steps:

  • Step 1: The affected slab(s) are identified after a series of measurements are taken. The concrete raising technician will mark the ideal locations for drilling slurry or polyurethane injection holes.
  • Step 2: A matrix of 1-4 inch-wide holes is drilled directly into the concrete, going down as far as is necessary to reach the area below the concrete slab.
  • Step 3: A slurry mix or polyurethane foam compound is injected into the area below the affected slab(s).

[Note: Polyurethane foam injections offer slightly better results, as the expansion of the foam works harder to level the concrete. However, polyurethane slab jacking is often much more expensive than slurry-based slab jacking.]

  • Step 4: The holes drilled into the garage floor are patched with cement, and the entire floor can then be treated with whatever paint or sealer is desired.


It is common for garage floors to develop cracks, some of which appear right after the floor is poured (i.e. shrinkage cracks). Others appear over the first year or so from the house settling slightly.

Older homes and homes built on expansive soils tend to have more cracks, but even if they do, the question becomes if the cracks are significant or just normal for the age and geographic area.

Although there are many reasons for concrete slabs to crack, most do not lead to the serious foundation or structural issues; however, there are times that the cracks are a warning sign of foundational or other problems. In these cases, an owner or buyer should check several other things about the house to help determine the seriousness.

After you have fixed all of the cracks in the concrete, consider adding an epoxy coating to the garage floor.


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