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How To Ensure a Successful Self-Leveling Underlayment


How To Ensure a Successful Self-Leveling Underlayment

As important to construction as an underlayment is, you would imagine that the products used to achieve a level one wouldn’t be so misleading. While many underlayment products tout themselves as being self-leveling, it’s important to know that whether or not you get a level underlayment is on your shoulders, not the product you’re using. A self-leveling underlayment (SLU) requires a certain amount of preparation and expertise from the user to make sure that it does what it says it will do. Given the immense usefulness of these products, we wanted to create a guide to help spread the knowledge about underlayment procedures. Let’s take a look at how to ensure a successful self-leveling underlayment.

The Planning Stage

Before anything can be poured, you’ll want to go into your underlayment with a solid plan ahead of time. There are a number of things that need to be known or addressed before you start getting ready to pour.


The substrate refers to the surface upon which you’ll be pouring your self-leveling underlayment. More of often than not, this substrate will be either wood or concrete. Knowing which substrate you’ll be using is crucial to choosing the right underlayment product. Concrete tends to be the more affordable option as your choices are much broader. Some self-leveling underlayment products that go over wood might need either a metal or plastic lath to reinforce the wood.

Product Speed

In addition to the substrate, you are going to want to know how quickly the product you’re choosing sets up. There are two main types, rapid setting and slow setting. Rapid setting self-leveling underlayment products are just that, as they only take a couple of hours to fully set up. This does, however, give you less working time once the product is poured. Slower setting SLU’s will give you more time to work, but often take more than a full day to finally cure.

Special Circumstances

There are a few extenuating circumstances that can make pouring an SLU more of a hassle. Be wary of pouring over an existing floor. Check your individual product to see if this can be done. Another possible hurdle is with older floors, as you’ll need to have them inspected for asbestos. If asbestos is found, you won’t be able to just rip that flooring up and may need to call an abatement company. Finally, you’ll need to be extra careful if you are working in an area of high moisture, as this can also affect the way the SLU works.

Preparing the Floor

Once you’ve got everything set up and planned out, it’s time to begin prepping the floor for the pour. Unfortunately, it’s not as easy as just giving it a quick sweep, although that is an important step as well. You’ll want the floor to be completely free of anything that could cause the SLU and the substrate to not bond well, including wax, grease, mud, dirt, and stones.

Grind the Floor for Best Results

No matter what your substrate is made of, the best way to prepare the floor for the SLU is to grind it beforehand. This not only removes extra bits that might get in the way, but it also prepares the substrate to more easily bond with the SLU being poured on top of it. Wooden substrates will also need to be sanded to ensure a flat surface.

Test the Floor After Grinding

There is a very simple test you can do to check if the floor is ready to have the SLU poured over it. Simply take a few small droplets of water and drip them over the part of the floor you have already ground. If the water absorbs into the substrate very quickly, in under a minute or so, then you are ready to get to work. Otherwise, you’ll need to continue grinding until the water gets absorbed much quicker.

Fix Cracks and Seams

Another of the many preparation steps is to fill any cracks or crevices in the floor with a floor patch product before you begin. Having these cracks can completely ruin the self-leveling properties of the SLU. This also applies to holes in the floor. These could be around heating vents or toilets and you’ll need to plan out a way to not allow the SLU to drip down these holes. A spray foam barrier can do the trick if you do it correctly. If there are holes, cracks, or seams in your substrate before you pour, the SLU will find these problems and make them a headache for you.

Getting Ready To Pour

The time has come to finally pour the SLU on your prepared floor, but you didn’t think it would be that easy, did you? Since most common SLU’s are rapid setting, you need to have everything ready to go before you start. Once you begin the process, there’s no time to slow down and no time to take a break.

Prepare Your Mixing Station and Pathway

You’ll want to have a completely plastic covered area that is just for your mixing and moving around. Make sure there is also a covered pathway to the room you are leveling because you will probably make a mess at some point in the process.

Ready Your Water

For smaller jobs, you will want to have all the water needed premeasured out and ready to go. For larger-scale jobs, it’s recommended to have something large like a garbage can full of water and then a designated bucket to take water out of it so you know how much you’re pulling at a time.

Pouring the SLU

Finally, you can pour your SLU onto your floor. Be sure to have your leveling tools ready to go, such as a smoothing tool and a spiked roller. You’ll need these to make sure the SLU reaches the entire area of the floor quickly before it begins to set. Make sure that you pour the SLU immediately after you mix it together with the water.

Pour starting at the back of the room and keep going until you reach the exit doorway, covering the wet edge of the SLU with a new mixture as you continue pouring. Always make sure that each pour meets up with the last pour’s edge so as not to allow the SLU to begin setting at different times. After a few times of going over the mixture with your smoothing tool and spiked roller, everything should be set up for success.

Now you know how to ensure a successful self-leveling underlayment. Bedrock Supplies is prepared to supply you with all of the concrete underlayment and overlay products you may need for whatever kind of project you’re working on.

Successful Self-Leveling Underlayment

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