Uneven concrete floors can cause problems for nearly every flooring installation. Whether installing tile, hardwood, luxury vinyl plank flooring, carpet, or polished concrete, many flooring projects require the slab to be completely flat before beginning work. Contractors typically have two methods to correct uneven slabs. They can choose to grind down high spots or pour self-leveling underlayment.
Many homeowners believe self-leveling products can fix any uneven floor. However, that is not always the case. Often, grinding high spots is the smarter option. It is usually the more time-efficient method and less costly than adding an additional layer of material across your entire floor.
Read on to learn when you should grind high spots rather than pour self-leveling underlayment.
Know Your High Spots
Just as the name suggests, high spots are any area of concrete on the floor that sits higher than the rest of the elevation. There are many reasons why parts of a floor can be higher than others.
If a slab was finished poorly or if there was settlement, inconsistent screeding, or slab movement after concrete was placed, high spots can occur. Sometimes these spots are raised only a small amount. Other times, multiple high spots can create extreme elevation changes across a room.
Not only are low spots unsightly, but high spots can cause many problems when installing finished flooring materials.
If one area of the floor is higher than another, it can cause the entire flooring system to not lay flat.
Floor Flatness Requirements
Flooring flatness is important to many manufacturers. Luxury vinyl plank flooring, hardwood floors, large format tile, and polished concrete all look and perform better when installed over the correct substrate.
High spots can cause:
- Lippage between pieces
- Hollow spots under finished flooring
- Flooring adhesive to fail
- Premature wear in high traffic areas
- Cracking in tile
The floor does not always need to be level. However, most flooring projects require a flat floor.
That is often when contractors decide to grind down high spots.
Grinding vs. Self-Leveling
If high spots are the only issue with the concrete slab, grinding is typically the best solution. But when do you grind high spots? Let’s say you have a concrete slab where most of the floor is flat. However, you do have some areas where the floor is higher than the rest.
By grinding down those high spots, you can often bring the entire floor back to a flat surface without adding any additional material.
Grinding high spots is typically the best option when:
- The majority of the floor is already flat
- The high spots are small
- There are not many high spots to grind
- You cannot change the height of the floor
- The flooring you are installing requires the floor to be flat
It is often quicker and cheaper to remove some concrete than to add an entire new layer to match the high spot.
Why You Should Avoid Pouring Over High Areas
Self-leveling underlayment does not raise floors up to the high spots. Self-leveling material flows to all areas of the floor that are below the original high spot. It pours into every crack, crevice, and low spot until it reaches the high spot.
This means three things:
1. You will use a lot more material and raise the cost of your project. Self-leveling products are not cheap. The more material you have to pour, the more it will cost you.
2. You are pouring your floor higher. If your floor was perfectly level before adding self-leveling underlayment, you now have just raised the height of your entire floor. That could cause issues with doors, cabinets, appliances, and more.
3. You will pay more to have that floor installed. More material plus more labor equals you spending more money.
Instead of pouring extra material to reach a ¼-inch-high spot, wouldn’t you rather just grind that area down?
When Self-Leveling Is the Answer
As you can see, there are times when grinding will be a better solution. But, there are also times when self-leveling underlayment is the right choice.
If your floor was perfectly level but you needed to raise it, you would need to use a self-leveling underlayment.
Self-leveling underlayment should be used when:
- Most of the floor is low
- You need to add height to the floor
- There are multiple dips in the floor
Flooring Contractors Use Both
Contractors installing flooring rarely use self-leveling underlayment because they have to grind or vice versa. Most of the time, they use both.
Professional contractors will often grind the high spots out of a floor and then self-level in low spots. Using self-leveling underlayment after grinding ensures they do not use excessive material and they do not have to bring the entire floor up to the height of the high spots.
By grinding first, contractors can often save time and money by avoiding the need to raise the entire floor.
Some Flooring Requires You to Grind First
The type of flooring also plays a significant role in the decision between grinding and self-leveling. Since large-format tile requires extremely flat floors, contractors must either grind down high spots or add self-leveling underlayment to get the floor flat enough to install the tile.
Many LVT flooring manufacturers also list flatness as a requirement. This often requires some grinding of the original concrete slab.
Since polished concrete does not add any additional layers to the floor, it must be ground first to achieve the proper level of flatness.
Hardwood floor contractors may need to grind high spots and fill low spots to meet the hardwood flooring manufacturer’s guidelines.
Tile, hardwood, LVT, and polished concrete all have different installation requirements. These installation guidelines often include flatness requirements. Always check with your flooring manufacturer before beginning any floor preparation.
Let the Professionals Help Decide
Deciding which method to use to fix your floor should not be based on looking at the floor yourself. At Custom Concrete Prep & Polish, we use specialized tools to identify high spots and measure the floor’s flatness.
Just because your floor looks like it needs to be self-leveled does not mean it does. You could be paying to have self-leveling poured over your entire floor when all it needed was a light grinding.
Not only could you be paying for unnecessary materials, but you may not even be fixing your problem. There could be low spots everywhere that you cannot see that will cause your new flooring to fail.
Contact our Concrete Preparation Pros Today
You should grind your high spots when the rest of your floor is already flat. Adding a layer of self-leveling underlayment to your floor will unnecessarily increase your project’s cost.
At Custom Concrete Prep & Polish, we want to make sure you get the best solution for your uneven concrete slab. We offer concrete preparation, grinding, leveling, and polishing services to help you prepare your floor for the next stage of your project.
Contact Custom Concrete Prep & Polish today to start your project. Let’s Talk About Your Flooring Project!
