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Tips About Self-Leveling Concrete
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.
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.” 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.
Installing Self-Leveling Concrete
7 Tips for a Better Concrete Installation:
- Read and follow the manufacturer’s instructions to the letter. Don’t skip or skimp on any step. And if any of these tips conflict with the instructions, go with the manufacturer’s process instead.
- Buy more product than you need. A difference of a fraction of an inch thickness can mean several bags of product. You have to finish the job in one pour so you can’t go back to the store for more.
- Have all your tools and supplies ready. Once you pour, you may only have about 10-20 minutes to work.
- Keep your leveler product dry – store the bags indoors and up off the ground.
- Do not mix product in extremes of heat or cold.
- Do not add water to the product while spreading it. The mix ratio is critical.
- Clean all tools and buckets immediately when you’re done. If you allow the product to set it will never come off.
- Be careful not to pour more product than you need. If you do, quickly and carefully scoop it up into a bucket and remove it.
Where Self-Leveling Concrete Is Used
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 you need to 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.
Preparing to Use Self-Leveling Compound
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.
This is a well-known problem with a well-known and scientifically proven solution. The way moisture moves in a concrete slab has been studied since the 1960s, and researchers have developed a scientifically proven test for measuring moisture levels deep inside a slab. That test is called “the relative humidity test using in situ probes.”
RH testing is the basis for the ASTM F2170 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 very easy and much faster than you would think.
The Rapid RH® L6 system uses single-use sensors for speed, economy, and ease of use (for example, they come calibrated from the factory and don’t require continual calibration checks and new documentation).
Once the L6 sensors are installed in the slab and equilibrated after the F2170 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.
The Rapid RH Total Reader® reads, displays, and transmits temperature and RH data via Bluetooth® to the DataMaster™ L6 app. The DataMaster L6 app stores, displays, and reports the data on your iOS or Android mobile device. You can email PDF format reports from your mobile device to your client and all interested parties.
Backup copies of your readings are stored in the cloud and in the sensors permanently installed in the slab. This unbroken digital path from the sensor to the final report, plus automatic data backup ensures the highest data integrity, accuracy, and peace of mind.
Here’s a list of what you’ll need to do the job:
- Shop vacuum, broom, and mop
- Mixing buckets or barrels, as large as you need (6-gallon minimum)
- Mixing drill and mixing head
- Gauge rake
- Cleats
- Kraft paper or plastic sheet
- Silicone caulk
- Leveling product and primer
Free Download – 4 Reasons Why Your Concrete Is Taking Forever to Dry
Takeaways for a Successful Self-Leveling Pour
Whenever you need to repair, level or raise a floor, self-leveling concrete can be a fast, cost-effective solution.
Self-leveling concrete 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 F2170 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 F2170. 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. This helps you cut down on the paperwork and give you greater confidence in the documentation of your test data.
Jason has 20+ years’ experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.
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Last updated on June 21st, 2022
800-634-9961
I need to self level the slab in my basement. The basement slab is painted, I don’t know if it’s oil or latex. Can I self level over the paint or does the floor have to be scarified
I will be tiling a very small bathroom floor (22 sq ft) which now has linoleum over concrete. Do you think self- leveling will be necessary on such a small floor? Or can I clean the concrete and proceed to installing the tile directly, using the proper adhesive?
Also, in a larger bathroom (80 sq ft) with linoleum over concrete , is underlayment a good idea?
Thanks, Jason.
Charles
Charles:
Thanks for the questions. For questions like this, my standard answer will always be to consult the manufacturer you are looking to install. It’s hard to say if leveling will be required because I don’t know how far out of the flat it is. At the end of the day, after consulting the install documents for the manufacturers, you should have a better idea of how to proceed. Good luck.
I have an outdoor kitchen where the wood countertops have aged because exposure to sun and rain.
Can I pour self-leveling concrete about 3/8 inch deep on top of the wood?
If so, will it be, a permanent fix?
Verne:
This is going to be a question for the self-leveling product manufacturer. Make sure, as you are evaluating and asking questions, that they understand your application is exterior. That will make a difference. Good luck.
I had water damage in my RV that caused the particle board to sag in one area. I have been able to remove a tile. I have made sure there is no moisture and the particle board is not waterlogged or rotten. Can I pour self leveling cement in to build up the low spot about ½”.
Brian:
Thanks for the question. When the particleboard has sagged, the strength of the product has more than likely been compromised. In my opinion, adding more weight to it would not be recommended and most levelers would not be recommended over particleboard anyway.
Hi There
I have an old slab garage floor that has sikaflex put into the expansion joint and i do know that the moisture level is high when it rains heavy, is there a product i can put down before self leveller to seal in the moisture? and can i put the leveller over the top of the sikaflex?
Cheers
Theo:
Thanks for the question. “Typically”, any type of moisture mitigation product is applied to the bare concrete, then expansion joints filled, and leveler applied. That being said, I would reach to Sika and see what solutions they have to take care of the situation you currently have.
We had to jackhammer up a trench (approximately 6″ across x 3 ” deep x 22′) in a concrete slab to lay down plumbing drain lines in the basement level of my home. My contractor filled them concrete and then used Dap Concrete Floor Leveler for a smoother finish. He did not use any bonding liquid with it. It seems solid currently. I will be laying floating LPV over the top of it. Is it likely that we will run into problems with the subfloor coming up? Would using a sealer over the floor before laying the LPV be helpful or recommended? Is there any way to remedy the situation other than jacking it back out and starting over. If the later, we will just take our chances and hope for the best.
Thanks for your input.
Vicky:
Thanks for the questions. I am not familiar with the leveling product you have mentioned, but typically, prior to any leveling product going down on a floor, a moisture test should be performed on the concrete to see if there is a moisture issue. If there is then some type of moisture remediation product would be applied to the concrete prior to the leveler. Doing the moisture testing allows you to identify what type of moisture remediation product to use. Here is the product we offer http://www.rapidrh.com Good luck.
I have outdoor concrete patio 13’x20’ that needs to be leveled. I intend to use the pad for a spa. What leveling agent do you recommend knowing it will get wet from time to time?
Is it safe to use a self-leveling flooring compound on a cement basement floor that gets wet from leaking rainwater or floods?
If it does get flooded would the self-leveling compound break apart?
I have water pumps for floods which happens about twice a year.
Luann:
Thanks for the question. Most companies that produce products of this nature have various products for various conditions. I would reach out to some of the more prominent companies such as Ardex, Mapei, and Uzin to see what they have to offer for your application. Good luck.
Jason, great stuff. I have a room that is 9 x 6 and is concrete [old garage converted to living space]from left to right [9 foot run] the floor drops 2.5 inches and I want to level it to my current kitchen floor. Kitchen door is center room [so 1.25 inches at the door]. Basically I need to raise the right side 2.5, middle 1.25, and left side skim coat. Seems all products say 1″ max pour. I am looking to do this all in one pour rather than 3-4 separate pours. What says you? Can I pour all in one event?
Tom:
Thanks for the question. I will always defer to the manufacturer’s recommendations, but I believe there are products out there that will do 1 ¼ – 1 ½ per lift. Good luck.
Is this something I could use in my garage if the existing floor is asphalt. The asphalt is old and uneven in places and we would like to overlay with concrete but do not want to add too much elevation to prevent large lips at the doorways.
Sarah:
Thanks for the question. So first it would depend on how thick the concrete is that you would be pouring. From what you are saying, it doesn’t sound like it would be that much. Second, are you going to put a finish on the concrete after it is poured? I think the bigger concern in my mind is, based on your description, whether the asphalt is thick enough and in good enough shape to act as an appropriate base. Good luck.
Hi there, im thinking of using a RH test for my basement. Im curious, what are the standard parameters for RH value in concrete slabs that would be considered safe for using floor leveler? I have a house built in 1940, obviously no vapor barrier and very little thought in how to keep out water. Im planning on finishing the basement even though we have a high water table. I’ve already taken steps including replacing the entire drainage system, rerouting the septic line, removed 5 massive trees to stop our gutters from constantly clogging, added a dry well 30′ away from the house to stop water from cycling back in, etc, and those damp spots (not puddles, just damp and discolored, a few of them roughly a foot in diameter) in my slab have still not disappeared. I plan on leveling the floor within the next few months, using an epoxy coating to seal it, and using a flooring system with drain tile built into it. Do you think that would be sufficient to keep water out permanently?
Mark:
Thanks for the questions. If there is no vapor retarder then you need to research some type of moisture mitigation product to put down on the basement floor before you do anything. Many floor levelers are not manufactured to withstand excessive amounts of moisture so if you put them on top of a constantly “wet” slab and then install a low permeable floor covering/coating, the excessive moisture will move up into the leveler and it may break down. Most levelers won’t have a maximum, because of this. It is a “system” maximum. So if the finished flooring maximum is 75%, then the same is true for the leveler. Good luck.
Dear Jason,
Hi from Australia!
I have just poured a slab to be used as a base for water tanks (roughly 4 tonnes of water each).
Unfortunately because I am an amateur, the base is not quite level and the tank company is now saying the warrantee will be voided if the slab is not absolutely flat.
A. will the fact that the slab was only poured two days ago mean that it will be too moist for the self-levelling concrete? If so, how long should I wait?
B. will the self-levelling concrete be strong enough to handle the weight of the tanks?
Malcolm:
Thanks for the questions. I would reach out to these guys directly to get the answers to your questions. This is a very large part of what they do. https://ardexaustralia.com/ Good luck.
This is a really helpful guide, I’m looking at leveling a concrete slab in my double garage. Would you advise mixing one bag at a time or multiple? I need 5mm thickness at the lowest point, how do you ensure you maintain the level when poaring out the compound? I.e. how to judge how much compound to poar/spread in each area – do you have any tips?
Gurj:
Thanks for the email. There are all types of products out there, but take a look at this video it gives you a good idea of the process https://www.youtube.com/watch?v=2YkoSFwBfow The question becomes are you trying to level or flatten the slab? Two very different things so keep that in mind. You will see in the video that this type of product is flowable so as you work it around, it finds those low spots. Good luck.
My home was built in 1976. The concrete flooring in the basement is very sandy and its impossible to paint as the paint roll will pickup fine pebbles during the painting process. Can I use the self leveling concrete to cover the sandy concrete only to then seal it with Drylok?
John:
Thanks for the question. Most leveling products will require some type of stability and structural strength of the base slab. With fines coming off like this, I am not sure how well the leveling product will work. Also, most leveling products aren’t intended as wear layers. That being said, I would reach out to the technical departments for companies such as Ardex, Sika, Mapei, and Uzin to see what they say. Good luck.
I had laminate wood flooring installed recently, after they finished I noticed walking into the mud room it felt like I stepped in a hole. They didn’t level the concrete so there is approximately a 2’ x 4 ‘ void under the floor approximately 1/2” . All the trim is in and cabinets built on top of the floor. My question is can I cut a small diameter (1”) hole in the middle of void with a hole saw and pot the leveler under flooring using a funnel or something then put the piece I cut out back in?
Allan:
Thanks for the question. I doubt that anyone would recommend this as a solution to your issue because you would be introducing something wet under the floor. There are ways to do board or floor section replacements. If it were my floor, I would probably get a hold of the original installer, especially if it is a recent install, and find out what they can do to fix it.
After a self-levelling product has been applied, can the floor be painted with COO-VAR Floor Paint?
Trevor:
Thanks for the question. This type of question is really best answered by the manufacturer of the self leveler or paint since they should know specifically how there products will react. Good luck.
Looking to level outside (under roof) porch. Is there a leveling product for outdoors?
Janice:
Thanks for the question. I would look at Ardex or Mapei (there are others) and if that fails I would seek out a concrete sundry specific distributor in your area and see what they have. Good luck.
Thanks for pointing out that cleats would be needed when it comes to concrete leveling projects. I’m thinking about getting a concrete leveling repair service soon because the steps leading to the gazebo in my garden are a bit crooked and uneven. I hope that making them look more symmetrical would elevate the aesthetic appeal of the gazebo.
This is fantastic detail! Thanks! I see you use the caulk in wooden joints. On a slab, would you also want to draw a line of caulk around the edges (like under the walls) so the self leveler doesn’t flow into the breathing room of the walls, or underneath old (and not straight) sills. My house is a 1960 slab with no basement and brick exterior.
We had flooring installed. They leveled the subfloor before laying the
floating floor down. The issue is 5 days later I went down in the basement
and realized the self leveling product they used leaked through the subfloor.
I now have it running down the walls and on the carpet. My question is
what did they do wrong did they miss a step? And how do you get off carpet and walls?
Thanks
Vicki,
Thanks for the question. Many subfloor/wall assemblies aren’t fully sealed in everyday life. When doing a self leveling product, the material will flow on the floor to the low spot of level and if there is any way for the material to flow out, it will. Many time, if they know there is a floor below, I have seen installers use something like a spray foam insulation to establish a perimeter around the area where the self leveler is to be poured. I would contact the installer or retailer and let them know what has happened.
I am planning to do a pour in our three-car garage – what is recommended to clean stains? I read that etching with muriatic acid is not advised. I really got a lot from your article, thanks for posting
Dusty,
Thanks for the question. I would look for a concrete sundry supply house in your area. A place that does finishing tools, stakes, curing compounds, etc. and give them the specifics to the stains. Are they rust, oil, etc. They should be able to give you guidance. Depending on the types and amount of staining you might just use white vinegar or you may find a more concentrated commercial cleaner. Good luck.
Can I use this product in a patio outside? Thanks.
Im laying 10mm layer of SLC to cover underfloor heating wires on a ply substrate. Do I need an expansion joint around the perimeter? The T&G 19mm ply should have a 5mm gap to the wall bottom plate for expansion so I either need to fill that with sealant or PEF rod first so the SLC doesn’t flow into the gaps. I assume I could use a neoprene sponge sticky back seal tape around the perimeter which I can get in 15mmx9mm for the SLC expansion joint? That gives me a 9mm expansion gap and 5mm, (15-10) above the finished SLC which is my drywall gap. Does that sound feasible? The pour area is about 4 sq metres. Thanks
I have a 40 x 40‘ pad that was poured poorly and very uneven so I would plan to use this leveling system along with a decorative system on top. And with the need of up to 1 inch of filler in a few areas. Can this product be poured twice if needed. Where could I buy the product for this application?
Rod,
Thanks for the questions. It sounds like products of this nature would be perfect for your needs. I would research companies like Ardex, Uzin, and Mapei to find the right product for your specific application. There are many others out there, so in your research make sure you reach out to each company specifically for your specific needs. Good luck.
I have 12″ by 12″ glazed floor tile. I would like to put a lock in place vinyl floor over this floor. Will this concrete pour product level the grout joints and more importantly will it adhere to the glazed tile? The grout lines are very shallow. Approx. what is the coverage per sq. ft. for a pour of this kind?
Gary,
Thanks for the question. Many times, you may be able to install over existing floors if the existing floor is sound and adhered thoroughly to the subfloor. Usually, a primer and some sort of leveling material would typically be the way to go, but I would consult some of the manufacturer’s like Ardex, Uzin, Mapei, Shonox, etc. (there are many others) to get their technical recommendations. Good luck.
What are you using the silicone caulk for? It’s not mentioned in the steps.
Is it for expansion gap?
Thanks!
Yes, it would be for expansion joints or any non-moving cracks. It’s labeled specifically as silicone, but more correctly it would any type of product that would set to a rigid hardness.
My floor has glue from old carpet. Do I need to remove all the old glue first?
Joan:
Thanks for the question. This is always going to be a question for the flooring adhesive and finished floor product manufacturer to give you direction on. I would recommend finding their number and asking them directly. Good luck.
I haven’t seen the finished product of this kind of leveling agent, but it does look very nice in these pictures. I plan to learn more about the product and start offering the service in my business. Thanks for the info.
Thanks for mentioning some of the equipment you’ll need to level concrete like a shop vacuum, broom, mop, mixing buckets, mixing drill, gauge rakes, and other things. My brother is thinking about hiring concrete leveling experts because he’s contemplating redoing his driveway next month. I think it’s a good investment that he hires a reputable company that has the necessary equipment for a concrete project if he decides to do the renovations.