Mastering Floor Leveling: Effective Techniques for Leveling Concrete Slabs

When you’re installing new flooring in a commercial space, the foundation matters. If the concrete slab underneath isn’t level, you could run into big problems—tiles might crack, carpet could wrinkle, and floors may wear down faster than they should. Not to mention, an uneven floor can be a safety hazard. That’s why leveling concrete slab is one of the most important steps before any flooring goes in.

If you’re a contractor, business owner, or property manager, knowing the best floor leveling techniques can save you time, money, and frustration. In this guide, we’ll break down different ways to get a perfectly smooth concrete slab so your new floors last for years to come.

Why Floor Leveling Matters

A level floor isn’t just about looks—it’s about durability and safety. If a concrete slab is uneven, it can cause a lot of issues down the road, including:

• Flooring won’t stick properly. Materials like vinyl, tile, or hardwood need a flat surface to stay secure.
• Wear and tear happens faster. High and low spots can lead to cracking, shifting, and gaps in the flooring.
• Tripping hazards. A bumpy floor is dangerous, especially in high-traffic commercial areas.
• Drainage issues. In some buildings, an uneven floor can cause water to pool in the wrong places.

Making sure your concrete slab is level from the start helps avoid these headaches.

How to Tell If a Concrete Slab Is Uneven

Before fixing an uneven concrete slab, it’s important to assess the surface and determine the severity of the issue. Even slight variations in the slab’s height can cause major problems when installing flooring, so taking the time to check for unevenness will save time, money, and frustration later.

Here are some simple and effective ways to check if your concrete slab is level.

1. Walk Around and Visually Inspect the Floor

A basic first step is to do a walkthrough of the space and look for any obvious dips, bumps, or cracks.

• Are there noticeable high or low areas?
• Do you see cracks or gaps between sections of concrete?
• Does the floor look wavy or uneven under different lighting?

While this method won’t give you exact measurements, it can help you spot problem areas that may need a closer look.

2. Use a Straightedge or Level

One of the most reliable ways to check for unevenness is to use a straightedge, such as a long piece of wood, a metal ruler, or a contractor’s level.

How to do it:

1. Place the straightedge on the floor.
2. Look for gaps between the slab and the straightedge.
3. Measure the size of any gaps—anything over 1/8 of an inch may require leveling.
4. Move the straightedge to different areas of the floor to check for inconsistencies.

This method is great for detecting subtle dips that may not be noticeable with a simple visual inspection.

3. Try the Marble or Ball Test

This is a quick and easy way to check for sloping floors.

How to do it:

1. Place a marble, ball bearing, or small rubber ball on the floor.
2. Watch to see if it stays in place or rolls in a particular direction.
3. If it moves consistently toward one side, the floor has a slope.

While this method doesn’t give precise measurements, it’s an easy way to confirm whether a section of the floor is uneven.

4. Use a Laser Level for the Most Accurate Results

For a precise measurement of high and low points, a laser level is the best tool. This is especially useful for large commercial spaces where accuracy is critical.

How to do it:

1. Set the laser level on a stable surface.
2. Adjust it to project a level reference line across the floor.
3. Measure the distance from the laser line to the floor at different points.
4. Compare measurements to see where the floor is higher or lower.

A laser level provides exact data, making it the preferred choice for professional flooring contractors.

Common Signs of an Uneven Concrete Slab

Even without measuring tools, certain warning signs indicate a concrete slab may not be level.

• Doors that don’t close properly – If doors scrape against the floor or don’t latch, it could be due to an uneven foundation.
• Cracks in walls or flooring – Uneven slabs can cause visible cracks to form over time.
• Pooled water – If water collects in certain spots, the floor likely has dips or slopes.
• Gaps between baseboards and the floor – If baseboards aren’t sitting flush against the floor, there may be unevenness.
• Loose or lifting flooring materials – Tiles, vinyl planks, or hardwood that shift or don’t lay flat could indicate an uneven subfloor.

If you notice any of these issues, it’s a good idea to take measurements and determine how much leveling is needed before installing new flooring.

What Causes a Concrete Slab to Be Uneven?

Understanding why a slab is uneven can help prevent future problems. Some of the most common reasons include:

• Poor installation – If the concrete wasn’t properly leveled when poured, it may develop dips and bumps as it sets.
• Soil shifting – Over time, the ground beneath the slab can shift due to erosion, moisture changes, or settling, leading to an uneven surface.
• Temperature changes – Extreme heat or cold can cause concrete to expand and contract, which may create cracks and warping.
• Water damage – Excess moisture can weaken the concrete, leading to sinking or crumbling areas.
• Heavy loads – Overloading a slab with weight beyond its capacity can cause sections to sink or crack.

By identifying the root cause of the unevenness, you can choose the best leveling solution and take steps to prevent future damage.

What to Do Once You Find an Uneven Floor

Once you’ve checked the slab and identified problem areas, the next step is deciding how to fix them. The best solution depends on the severity of the unevenness and the type of flooring that will be installed.

• For minor dips or small imperfections – A patching compound may be enough to fill in low spots.
• For widespread low areas – A self-leveling compound can create a smooth and even surface.
• For high spots – Grinding down raised sections will ensure the floor is flat.
• For sinking or structural issues – Mudjacking or slab lifting may be necessary to correct major unevenness.

By choosing the right method, you can ensure a level foundation that supports durable, long-lasting flooring.

Checking your concrete slab before installing flooring is a crucial step in any commercial flooring project. Taking the time to identify and fix uneven areas will prevent costly issues down the road, ensuring that your new floors look great and perform well for years to come.

Best Ways to Level a Concrete Slab

If you’ve discovered that your concrete slab is uneven, the next step is choosing the best way to fix it. The right method depends on how severe the unevenness is, the type of flooring that will be installed, and how much time and effort you’re willing to invest in the process.

For minor dips, a patching compound may be enough. If the entire floor has noticeable low spots, self-leveling concrete is the best solution. If there are high points that make the floor uneven, grinding them down can work well. And for slabs that have sunk over time, mudjacking may be the only option.

Here’s a detailed breakdown of the most effective ways to level a concrete slab.

Self-Leveling Concrete: The Easiest Fix

If your concrete slab has multiple dips or low areas, self-leveling concrete is one of the fastest and most effective solutions. This method involves using a special type of cement-based compound that spreads out evenly across the surface. As the name suggests, self-leveling concrete does much of the work on its own, filling in low spots and creating a smooth, even surface.

When to Use Self-Leveling Concrete

• The floor has widespread low areas but no major cracks or structural damage.
• A fast and efficient solution is needed before installing flooring.
• A smooth, even finish is required for tile, vinyl, or other flooring materials that need a stable base.

How to Apply Self-Leveling Concrete

1. Clean the floor – Sweep thoroughly and remove dust, dirt, and debris. Any loose particles can prevent proper adhesion.
2. Apply a primer – This helps the self-leveling compound bond to the concrete and prevents air bubbles from forming.
3. Mix the compound – Follow the manufacturer’s instructions to get the right consistency. The mixture should be fluid but not too runny.
4. Pour and spread – Pour the self-leveling compound onto the floor and use a squeegee or trowel to help spread it evenly.
5. Let it dry – Most self-leveling compounds dry within 24 hours, but check the product instructions for the recommended curing time.

Pros and Cons of Self-Leveling Concrete

Pros:

• Quick and easy to apply
• Creates a smooth, seamless surface
• Works well for large areas with minor unevenness

Cons:

• Requires proper surface preparation for the best results
• Can be costly compared to other options
• Not suitable for extremely uneven or damaged slabs

Self-leveling concrete is an excellent choice for commercial flooring projects that need a fast, durable fix with minimal downtime.

Grinding: The Best Way to Remove High Spots

If the problem isn’t dips but rather raised areas or bumps, grinding the concrete is an effective way to smooth things out. This method involves using a specialized concrete grinder with diamond-tipped blades to gradually wear down the high spots.

When to Use Concrete Grinding

• The slab is mostly level but has small areas that are slightly raised.
• The high spots are preventing flooring from being installed properly.
• The floor has surface imperfections that need to be smoothed out.

Steps for Grinding Concrete

1. Use a floor grinder – An industrial-grade concrete grinder with a diamond blade attachment is ideal for this process.
2. Vacuum up the dust – Grinding creates a lot of dust, so using a vacuum attachment or cleaning frequently is important.
3. Check for evenness – Use a straightedge or level to ensure the floor is smooth before moving on.

Pros and Cons of Grinding

Pros:

• Removes raised areas effectively
• No need for additional materials
• Works well for small problem areas

Cons:

• Can be time-consuming for larger areas
• Creates dust and requires proper cleanup
• Not a solution for low spots

Grinding is a good choice when the floor is mostly even but has a few high points that need to be smoothed down before flooring installation.

Patching Small Dips with a Floor Compound

For small dips and surface imperfections, a patching compound is a simple and cost-effective way to even things out. This is a great option if only a few small areas need to be fixed, rather than the entire floor.

When to Use a Patching Compound

• The floor has only a few shallow dips or imperfections.
• A budget-friendly solution is needed.
• The dips are small enough that a full self-leveling compound isn’t necessary.

How to Patch Small Dips

1. Clean the area – Remove all dust, dirt, and debris to ensure proper adhesion.
2. Mix the patching compound – Follow the manufacturer’s instructions to get the right consistency.
3. Apply with a trowel – Spread the compound evenly over the low spots, smoothing it out as you go.
4. Let it dry – Give it enough time to fully cure before installing flooring.

Pros and Cons of Patching

Pros:

• Cost-effective and easy to use
• Good for minor surface repairs
• Requires minimal materials

Cons:

• Not a solution for large or deep dips
• May not provide a completely smooth surface
• Can take time to dry properly

If your concrete slab has only a few minor imperfections, patching is a quick and simple fix. However, if there are widespread low areas, self-leveling concrete is the better option.

Mudjacking: Fixing a Sunken Slab

If a section of the concrete slab has actually sunk, it may need to be lifted back into place. This is where mudjacking comes in. Also known as slab jacking, this method involves injecting a cement-based mixture under the slab to raise it.

When to Use Mudjacking

• A section of the concrete slab has visibly sunk.
• The unevenness is caused by shifting soil rather than surface imperfections.
• The floor is outside or in a large commercial space where lifting the slab is more practical than replacing it.

How Mudjacking Works

1. Drill small holes into the sunken concrete to create access points.
2. Pump in a leveling mixture made of cement, sand, and other materials.
3. Allow the slab to rise as the mixture fills in the empty space below.
4. Patch the holes and let the concrete set.

Pros and Cons of Mudjacking

Pros:

• Can fix major sinking issues
• More affordable than completely replacing the slab
• Works well for large commercial spaces

Cons:

• Requires professional expertise
• May not work if the underlying soil is still unstable
• Not ideal for minor surface unevenness

Mudjacking is best for exterior spaces, warehouses, or other commercial areas where sections of the slab have settled over time.

Choosing the Best Method for Leveling Your Concrete Slab

The right leveling method depends on the type of unevenness and the condition of the slab.

• For minor dips: A patching compound is a quick and affordable solution.
• For widespread low areas: Self-leveling concrete provides a smooth, seamless finish.
• For high spots: Grinding is the best way to remove raised areas.
• For sunken slabs: Mudjacking is the most effective way to lift the concrete.

Leveling concrete slabs is an important step in preparing a commercial space for flooring. By choosing the right method, you can create a stable foundation that ensures your flooring lasts for years to come.

Tips for a Successful Floor Leveling Project

No matter which method you choose to level a concrete slab, following the right steps will ensure the best results. A well-leveled floor provides a strong foundation for any type of flooring installation, reducing the risk of problems down the road. Here are some important tips to keep in mind before, during, and after your floor leveling project.

Preparing for Floor Leveling

A successful project starts with proper preparation. Before applying any leveling method, take the time to assess the floor and gather the necessary materials.

1. Check the Floor First

Before you start leveling, you need to understand the extent of the unevenness. Skipping this step can lead to wasted time and materials.

• Walk around the space and do a visual inspection.
• Use a straightedge, marble test, or laser level to identify high and low spots.
• Mark problem areas with chalk or tape so you don’t lose track of them.
• Consider the type of flooring that will be installed. Some materials, like tile and vinyl, require a nearly flawless surface, while carpet is more forgiving.

2. Choose the Right Leveling Method

The best method for leveling depends on how uneven the slab is.

• For minor dips – Use a patching compound to fill small low spots.
• For widespread low areas – Self-leveling concrete is the most efficient solution.
• For high spots – Grinding the surface down will help create a smooth finish.
• For sunken slabs – Mudjacking may be necessary if the concrete has settled unevenly.

Assess the severity of the issue and select the appropriate method for the best results.

3. Gather the Right Tools and Materials

Using the correct tools can make the leveling process easier and ensure a smooth, even result. Depending on the method you choose, you may need:

• A straightedge or level to check for unevenness
• A concrete grinder if you need to remove high spots
• A mixing bucket and drill for self-leveling concrete or patching compound
• A squeegee, trowel, or float to spread leveling materials evenly
• A vacuum or broom to clean the surface before applying leveling compounds
• A primer to help self-leveling concrete adhere to the slab

Making sure you have everything on hand before starting will help prevent delays and mistakes.

Best Practices for Leveling Concrete Slab

Once you’re ready to start the leveling process, follow these best practices to ensure a durable and professional-looking result.

1. Clean the Surface Thoroughly

Any dust, dirt, or debris on the slab can prevent leveling compounds from properly bonding.

• Sweep or vacuum the entire area.
• Remove any loose or crumbling concrete.
• If there are grease or oil stains, clean them with a degreaser before proceeding.

2. Follow Mixing Instructions Carefully

If you’re using a self-leveling compound or patching material, make sure to mix it correctly.

• Always follow the manufacturer’s instructions on water-to-mix ratio.
• Use a drill with a mixing paddle for a smooth consistency.
• Avoid overmixing, which can introduce air bubbles and weaken the compound.

3. Apply the Material Evenly

Whether you’re using self-leveling concrete, patching compound, or mudjacking, proper application is key.

• For self-leveling concrete, pour it slowly and use a squeegee to help it spread evenly.
• For patching compound, use a trowel to press it into low spots and smooth it out.
• For grinding, move the grinder in even passes to avoid creating dips.
• For mudjacking, allow professionals to pump the mixture evenly under the slab to lift it gradually.

4. Allow Proper Drying Time

Rushing the drying or curing process can lead to weak spots, cracks, or adhesion issues with the final flooring.

• Most self-leveling concrete needs at least 24 hours to cure before flooring can be installed.
• Patching compounds may need several hours before they’re fully set.
• Grinding does not require drying time, but the floor should be cleaned thoroughly before installing flooring.
• Mudjacking requires a few days for the slab to fully stabilize before heavy weight is applied.

Always check the manufacturer’s recommendations for drying times to ensure the best results.

5. Test for Levelness Before Installing Flooring

Once the leveling process is complete, double-check that the floor is as smooth and even as possible.

• Use a straightedge or level to check for any remaining dips or high spots.
• Walk across the surface to feel for any uneven areas.
• If necessary, do a final touch-up with a patching compound or additional grinding.

When to Hire a Professional

While smaller leveling jobs can often be done with DIY methods, large commercial projects or severely uneven floors may require professional help.

Consider hiring a professional if:

• The slab has major structural issues or large cracks.
• The unevenness is too severe for self-leveling concrete alone.
• The job requires mudjacking or other specialized equipment.
• The space is large and needs to be leveled quickly and efficiently.

A flooring expert can ensure the job is done correctly and prevent costly mistakes.

Choosing the Right Floor Leveling Method

If you’re still unsure which method is best for your project, here’s a comparison to help you decide:

The method you choose will depend on the condition of your concrete slab and the type of flooring you plan to install.

Conclusion

Getting a level concrete slab is an important step before installing commercial flooring. Whether you use self-leveling concrete, grinding, patching, or mudjacking, the right approach depends on the floor’s condition and the type of flooring you’re installing.

At East Coast Flooring & Interiors, we specialize in commercial floor leveling and high-quality flooring solutions. If you need expert help getting your concrete slab ready for a new floor, contact us today.

By using the right techniques, you can make sure your leveling concrete slab project goes smoothly—literally.

This article was originally published on 10/10/2022 and has been updated on 02/24/2025 to provide the most accurate and relevant information.