If you’re facing a cracked or uneven floor and want a quick, reliable fix, self-leveling concrete might be the perfect solution. Whether you’re renovating a basement, installing a radiant heating system, or simply updating old floors, this fast-setting, easy-to-pour material can save you time and money—while delivering professional-looking results.
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Self-leveling concrete can be a fast, cost-effective solution to the problem whenever you need to repair, smooth, or raise a floor.
Self-leveling concrete is a cementitious mixture, much like concrete. But unlike concrete, it flows easier and sets up much faster. The product is mixed with water, pumped or poured into place, and spread evenly with a gauge rake. Once it’s spread out, it continues to flow evenly and levels itself out.
Now that you know what self-leveling concrete is, in the article, we’ll discuss the following:
Depending on the product, it may be smooth and flat within 1-2 hours. In about 6 hours, it may be completely hardened and ready for use, depending on the flooring material being installed on top. Self-leveling concrete can be used as an underlayment for tile, carpet, or other floor coverings.
Now, let’s clarify some things concerning product names. Instead of “concrete,” you might see products called “self-leveling underlayment” or “concrete leveling compound.” This name means the same thing as “self-leveling concrete.”
They’re generally mixtures of Portland cement, polymer plasticizers, and other ingredients. They have the strength of concrete but flow more easily and are set up quickly.
Self-leveling concrete can be poured as thin as a quarter of an inch, just enough to smooth out small imperfections if that’s all you need. But if the concrete floor has low spots and needs to be smoothed even more, it can be poured as thick as an inch and a half without adding aggregate and 5 inches with the addition of aggregate (though make sure you follow all manufacturer’s guidelines).
Self-leveling concrete works especially well with radiant heating installations because it easily flows around the tubing. The thicker floor-leveling compounds that must be troweled to achieve a proper finish can’t do this.
If you find moisture is a problem in the slab, you need to get a professional to handle the moisture remediation. You can also visit the International Concrete Repair Institute (ICRI) for more information on next steps or to find an expert to help.
Let’s say you’re upgrading an old, damaged concrete floor that’s settled or cracked. Or maybe you’re installing a radiant heating system in a floor. Maybe you’re building an addition and must match the floor to the floor in an adjoining room. Maybe you’re finishing a basement where the floor is rough and uneven concrete.
Other concrete toppings applications include warehouse floors, light industrial applications, retail stores, and institutional facilities.
Concrete toppings can also receive pigmented color dyes, stains, saw cuts or mechanical polishing to produce a decorative concrete finished wear surface.
The cost of self-leveling concrete can vary depending on various factors such as the size of the area to be covered, the thickness required, and the brand of the product. On average, a 50-pound bag of self-leveling concrete flooring costs between $30 to $60, and it typically covers an area of about 20 to 30 square feet at a quarter-inch thickness.
Keep in mind that this is only the cost of the material itself. If you’re hiring a professional for the job, labor costs will also factor in. The labor cost usually depends on the complexity of the job and the contractor’s experience and can range from $3 to $5 per square foot.
When compared to traditional concrete leveling methods, self-leveling concrete often proves to be more cost-effective due to its ease of application and reduced labor cost, although the initial material cost might be higher.
Before installing your new floor, there’s an essential consideration you need to address: moisture in the existing concrete floor. All concrete contains moisture, and if the moisture level is too high, it may cause the leveling compound to degrade over time.
So you need to test the slab to ensure the moisture level is not too high.
This isn’t something you can do just by looking at the slab. No matter how the slab looks, moisture deep in the slab can migrate to the surface over time and cause serious problems.
If the moisture level deep in the slab is too high, you need to take steps to remediate it before you can pour your new concrete floor.
RH testing is the basis for the ASTM F standard. This standard governs the processes of obtaining results using in situ probes in concrete slabs. Despite the complex terminology, this test method is actually straightforward and much faster than you would think.
Once the L6 sensors are installed in the slab and equilibrated after the F requirement of 24 hours, there’s no need to move them from location to location and wait for them to equilibrate again.
Repeat readings can be taken without additional equilibration time. And unlike reusable probes, the L6 sensors never need calibration.
While self-leveling concrete is designed to be easy to use, problems can sometimes occur. Here are a few common issues and their solutions:
If the compound doesn’t level as expected, it might be due to incorrect mixing or application. Ensure that you follow the manufacturer’s instructions for mixing and applying the product. Using a gauge rake can help to distribute the product evenly.
This can happen if the compound dries too quickly, which might be due to high temperatures or low humidity. Try to control the working environment as much as possible to avoid rapid drying.
This problem may occur if the old concrete smooth surface wasn’t prepared properly before application. Make sure the surface is clean, free of dust or oil, and primed if necessary before applying the self-leveling concrete.
As mentioned in the original article, high moisture levels can cause problems. Always check the moisture content of the slab before application and take necessary steps if the moisture level is too high.
Remember, when facing difficulties, it’s always beneficial to reach out to a professional or contact the product manufacturer’s customer service. They can provide you with specific advice and guidance based on your situation.
Whenever you need to repair, level, or raise a floor, self-leveling concrete can be a fast, cost-effective solution.
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Self-leveling cement can be used as an underlayment for tile, carpet, or other floor coverings.
For a successful self-leveling concrete installation, follow the seven tips in this article.
To ensure that your finished floor does not suffer from a concrete flooring failure, it’s essential to test the concrete subfloor for high moisture levels according to the ASTM F standard. It’s not that hard to do, and you’ve got a great product from Wagner Meters that can help.
The Rapid RH L6 system is the fastest, easiest, most cost-effective system for RH testing concrete slabs in compliance with ASTM F. It will get you accurate results in a fraction of the time versus other methods, and it’s digital, with convenient wireless communication to your smart device.
Learn more about if your concrete is ready for underlayment.
Yes, you can—as long as you properly prepare the surface. Self-leveling concrete requires thorough cleaning, priming, and sealing of any cracks or gaps before pouring. Skipping these steps can lead to poor adhesion and uneven results.
You should avoid using self-leveling concrete if:
Yes. In most cases, self-leveling concrete can be poured over existing slabs. However, the old concrete must be:
Coverage varies by product, but generally, a 50 lb bag covers about 20–30 square feet at ¼-inch thickness. Always consult the manufacturer’s guidelines for exact coverage, as mixing ratios and desired thickness can affect how far each bag goes.
Drying times vary by product and environmental conditions. In many cases, the surface is walkable within 2–4 hours, and you can install most floor coverings after 24 hours. Check your specific product’s instructions for exact curing times.
“Self-leveling underlayment” (SLU) is a bit of a misnomer. Although this type of product is incredibly useful, it does require a thoughtful installer to ensure the best results. Follow these guidelines to prevent issues in your self-leveling underlayment installation.
Select a product appropriate for the installation: Know your installation environment and familiarize yourself with the relevant ASTM standards for strength. A commercial floor subject to heavy rolling loads will require a higher-grade self-leveling underlayment (like TEC® Level Set 300 Self-Leveling Underlayment) than a floor in a single-family home.
Also, it is critical to understand your project timeline and choose a product that fits within the appropriate schedule. Some products may require 24-48 hours prior to installing floor coverings while other more premium products are ready to accept moisture-sensitive floor covering in 12 to 16 hours.
Consult product data sheets for information on tensile strength, compressive strength and flexural strength, as well as recommended cure times.
Generally speaking, there are two types of self-leveling underlayments – traditional and next generation technologies. The most noticeable difference between traditional and next generation SLUs are the flowability and the smooth surface profile of each product. Check out TEC's new high-flow SLU: Level Set 500 HF and for best practice tips for successful high flow SLU installations view our Technical Bulletin.
Some installers prefer the attributes of traditional SLUs because of the working properties. Others prefer the new technology for its high flow properties and extended working time.
The job scope will dictate which product technology should be used for installation. Traditional SLUs work best for deep fill applications greater than 3/16”. The newer technologies are ideal for thinner applications.
Know your substrate: Most SLUs require that all surfaces are fully stable and structurally sound prior to the application of a self-leveling underlayment. For example, understanding your existing substrate porosity is critical to choosing the proper primer. (A simple water droplet test will determine the surface porosity per ASTM F). Equally important is to know the make-up of the existing substrate. For example: typically, sound concrete requires a single coat of primer. Unsealed Gypcrete may require additional steps, including multiple coats of primer prior to the application of cement-based self-leveling underlayment.
Prepare your substrate: Make sure to plug all floor openings, gaps and cracks and install termination dams to prevent any seepage. Consult with product manufacturers to determine moisture limitations of the floor covering, self-leveler, and adhesives to determine if moisture mitigation is needed.
If moisture mitigation is required, this must be done prior to installation of the self-leveling underlayment.
Self-leveling underlayments require the use of a primer prior to installation (like the TEC Multipurpose Primer). Failure to use product recommended primer may result in installation failure. Primer retains the moisture within the self-leveling underlayment to allow proper curing. Secondarily, it acts as a bonding agent to ensure the SLU bonds properly to the substrate. Refer to the primer label for information regarding application methods and dilution per ASTM F.
Beyond priming, most self-leveling underlayments require that the substrate is free from any contaminants that may inhibit bond, including adhesive residue, sealers/curing compounds, oil, grease, loose or peeling paint, or other contaminants. Polished underlayments will require epoxy primers and/or a specific Concrete Surface Profile (CSP), and in these cases, mechanical abrasion (shot-blasting), is required.
Proper water demand: Mix your self-leveling underlayment within the water range specified on the bag. Overwatering will lower the strength of the underlayment and may cause cracking and disbonding. Additionally, a white film may form on the surface of the cured underlayment if the product is overwatered. Failure to properly mix the SLU may make it difficult to work with and lead to improper flow, cracking, or an irregular surface. Mix a minimum of two bags at a time when barrel mixing to ensure optimum efficiencies during the application process. In addition, some SLUs can be pumped. If pumping, special attention is needed to maintain proper water ratios and prevent overwatering. Follow equipment and product manufacturer’s recommendations when pumping self-leveler.
Product and ambient temperature: Make sure that the temperature of the room is within the manufacturer’s acceptable range. A climate that is too cold or too hot can affect the product, such as increased set time in cool temperatures or reduction in heal time in hot environments. Temperature and humidity will affect flow, working time and set time of the SLU.
Additionally, the temperature of the powder and the water is crucial. Leaving product in the sun, or in a hot environment may lead to flash setting. In situations where warm product is unavoidable, mixing with cold water may help combat installation issues. To maintain cold water temperatures in hot conditions, use blocked or bagged ice in your water barrel.
Whether the environment is warm or cool, acclimating the product prior to mixing is always a best practice.
Use as recommended: Manufacturers will specify the maximum thickness of their product. Some products allow for the addition of aggregate (pea gravel) to increase the depth of the pour, while others only allow their product to be used neat. Be sure to use the appropriate aggregate size and amount when extending a self-leveling underlayment in a single pour. Two separate pours or multiple lifts will achieve the target thickness without the use of additional aggregate. Once the SLU from the first pour becomes a walkable surface, you may proceed to apply the proper primer coat for the additional pour or lift. If a surface is extremely uneven in isolated areas with depressions greater than ½” deep (bird bath), you may treat these areas independent to the final pour. This will assist with the application process by using a consistent amount of self-leveling underlayment throughout the application. Always consult with manufacturers to determine the most suitable product for your application.
Protect your freshly poured underlayment: All self-leveling underlayments should be protected from direct air movement (drafts) during the initial curing process (2-6 hours) as they may cure prematurely which leads to cracking. Generally, most underlayments are not considered final wear layer surfaces. During the final curing process (2-24 hours) they should be protected from excessive construction. Traffic without protection can lead to gouging and irregular surfaces. Allow to cure completely to prevent any unnecessary surface damage, prior to the floor covering installation.
A common theme connects these successful self-leveling underlayment application guidelines: noting and adhering to the manufacturer’s instructions. You must read labels and product data sheets carefully to ensure products perform as desired.
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