Concrete is an excellent material to use as flooring – it is strong and durable, it can withstand a lot of regular force, and it is cheap to make and install. For that reason, almost every home in the United States has some concrete flooring within it. However, the big issue for concrete is subsiding. If concrete starts to subside or sink it can crack and undermine the structural integrity of the floor, the room, or even the entire home. This is where concrete leveling comes in.
Concrete leveling is the act of adding material on top of the concrete floor in order to create a level surface. This is different from mudjacking (for more information see our guide on mudjacking. Mudjacking involves pumping material underneath the concrete to raise it up and provide support. Leveling, by contrast, involves placing material on top of the concrete to flatten it and allow you to create a flat surface to lay a carpet or tile on.
Such is the importance of concrete leveling that there is a wide variety of products available – the self-leveling concrete market is estimated to be worth $6.2 billion by 2022. If you decide concrete leveling is the right option for you, the below guide will walk you through the different options available.
WHAT IS CONCRETE LEVELING?
Despite concrete’s strength, over time it can become cracked. Alternatively, it may simply not have been poured correctly in the first place. Eventually, you are left with uneven ground on your flooring. In most cases, the unevenness of the concrete is not easily noticeable.
One test you can do is the ‘marble test’.
Take a marble and place it on the concrete floor. If the surface is level, the marble should remain exactly where it is. If, however, the surface is uneven, the marble will move to the lower point of the floor. In basements, you can run a similar test by pouring a bucket of water onto the concrete floor (except if you have a floor drain in your basement, floors are often intended to have a slight slope toward the drain).
In many cases, cracks in the concrete cause further cracking, and are very much only the beginning of the process. Water and moisture get into the cracks, which can place lateral pressure on the concrete, increasing cracks and creating new ones.
Concrete leveling involves not only leveling off the surface of the concrete but also sealing the surface so that no further water can get in. There is a wide variety of concrete leveling products available in hardware stores. For most of these, you mix the material yourself and then pour it onto the concrete floor, making it an extremely easy process. There is even self-leveling concrete to make the process easier. This is a project you can complete yourself at home over a day or a weekend.
The key question to determine how you go about leveling your concrete is what you are planning on placing on top of the concrete. If you are intending to keep it bare (perhaps with a finish or a stain), or place tiles on top, you will use a different approach than if you are intending to place carpet on top.
THE COST OF CONCRETE LEVELING
The average cost of concrete leveling a damaged concrete slab is around $900. This price can be as low as $350 and as high as $2,000 depending on your specific circumstances and labor costs in your area.
LEVELING A CONCRETE FLOOR FOR DIFFERENT SURFACES
Leveling a concrete floor for carpeting, wood, or vinyl
If you are placing a surface on top of your concrete such as carpeting, vinyl, or a more forgiving type of wood (such as subfloor grade), a professional will have tools for precise methods of leveling. However, your goal with DIY leveling of concrete for these types of coverings is to ensure that there are no noticeable peaks in the concrete.
To level the concrete yourself, you can rent a concrete grinder from your local hardware store. These work like sanders, in that you run it over the surface of the concrete, and it grinds down any small rises in the concrete. Once you’ve done this, you’ll need to mix a small amount of concrete and fill in any dips or depressions.
Once you’ve done this and the concrete has dried, you’re ready to lay your carpet, vinyl, or wood on top, safe in the knowledge that the surface underneath will provide a level base.
Leveling a concrete floor for tile
Tiles require an absolutely level surface underneath or they will not work effectively. This becomes even more true the larger the tiles. For very small tiles (think mosaic) you can potentially get away with a slightly uneven surface. However, for the most common tiles (1 or 2-foot tiles) you need the concrete underneath to be absolutely level. To give numbers to support this: for small tiles, the maximum grade for a concrete floor can be ¼ inch per 10 feet. For the larger tiles, the maximum grade is ⅛ inch per 10 feet. Both of these grades are effectively not visible to the naked eye, meaning you need to strive for perfection.
Luckily, there are a number of products on the market that can help. Despite the precision required, the development of self-leveling concrete technologies can make the process of laying a perfectly even floor much easier. Although self-leveling concrete products are available from hardware stores, one product to look out for is Quikrete Self-Leveling Floor Resurfacer. This product comes as a powder and a fortifying agent that you mix with water at home.
Once you’ve mixed the solution, all you need to do is to pour it over your floor, give it a brief push with a broom, and then gravity does the bulk of the work. You wait for it to dry and it gives you a level floor (or, to be more accurate, a floor that is level enough to lay tiles on it). The liquid flows into the cracks and follows the depressions to give you a smooth finish. There is some skill involved in actually mixing and applying the solution, but the section below will tell you how you can do this to get the best results.
MIXING AND APPLYING SELF-LEVELING COMPOUND
The leveling process is a straightforward process, but it can be difficult and messy. In particular, you need to do a little preparation in advance to make sure that the outcome is as perfect as it needs to be. Here is how you mix and apply self-leveling concrete compound to your floor:
Clean the surface
Thoroughly clean the concrete floor, being sure to remove any flaking paint, loose bits of concrete, or other debris from the surface. This ensures that the solution doesn’t bind to anything it shouldn’t, undoing all your hard work.
Grind any bumps
If you have an especially uneven floor, rent a concrete grinder and grind down the peaks. This is not absolutely necessary but will save you from having to use an excess of self-leveling solution.
Seal the drain
If you have a drain on the floor, you’ll need to seal it very tightly – if the self-leveling concrete solution goes down the drain it will lead to blockages (since you will have effectively sealed it up with concrete).
Pour your self-leveling solution according to the instructions on the box or packet. Once you’ve poured it, use a coarse brush to push it around the floor. It will eventually settle and then begin to set.
Once it has set, you are free to install whatever you want on top. Alternatively, you can leave it bare, with only a stain or polish on top. Regardless of your stylistic choices, you will now have a nice level floor to use as your base.
If your concrete floor is sagging or severely cracked,
then no amount of concrete leveling solution will help; in fact, adding the solution on top may result in further cracking. Instead, if you notice major cracks, you should call in an expert.
This is particularly true if you start to notice cracks spreading to the walls of your home, as this is a sign that major structural work needs to take place. Instead, you should think of concrete leveling as the equivalent of sanding and polishing a piece of wood to make it smooth.