Tips and techniques for working with floor self leveler

This post is all about how to get perfectly flat floors using floor self leveler aka self-leveling underlayment.

There a a few key things to consider before starting a project like this, such as, what type of floor is it? Is the subfloor plywood or concrete? These things matter as they will have different installation steps.

PRO TIP: Always check the manufacturer instructions for installation prior to starting a project like this. Each product will have slightly different steps and requirements depending on the surface you are installing to. Below is an example of what the data sheet looks like for the product I am using for this example. The product I am using is LATICRETE NXT PLUS.

The preparation steps for floor self leveler are all basically the same, besides some require wire lath over plywood, and require a minimum pour level. Keep that in mind when choosing a material to use. We specifically chose LATICRETE NXT PLUS because we don’t need wire lath over plywood and can pour as little as 1/4″ over plywood.

Preparation for floor self leveler over plywood

** We are using LATICRETE NXT LEVEL PLUS

Step1: Clean the subfloor to remove any dirt, dust, and debris

It is crucial when preparing for floor self leveler that you prep the surface of the existing floor. Leaving dried thin set, paint, and drywall will all cause poor bond between the subfloor and the self leveler. For this crucial step, we use a grinder and a diamond cup wheel to clean the surface of the wooden floor. This works really well for concrete subfloors as well. I prefer using a 7″ floor grinder with a diamond cup wheel, and a dust shroud, and vacuum to keep the dust to a minimum. If you don’t have a 7″ floor grinder, you can use a 4″ but it will take a little longer.

Step 2: Secure any plywood that is loose or squeaking with appropriate screws

As you walk on the floor, you may notice there will be some areas that squeak. This is because, over time the subfloor deflects (moves) and can cause the wood to become loose. It is best to make sure you secure these as to mitigate as much deflection as possible. You want the floor to be as solid as you can before installing a hard surface on top of it. If your subfloor is not solid, it can cause problems down the road with your tile installation such as cracked tiles.

Step 3: Fill any holes and gaps with caulking and underlayment tape

This is necessary as to not have your floor self leveler creep down to the floor below or leak out to adjacent rooms. I go around a fill any holes and seams between the plywood with caulking and go over the seams with an underlayment tape.

Step 4: Use a level to check the floors

I always recommend to check with a level where the high/low spots are before attempting to pour floor self leveler. Mainly because, despite the name “self-leveler” you can accidentally make your floors worse than when you started. For most floors you will need at least an 8ft level.

Step 5: Map out the floor according to depth requirements for flatness

I see this step skipped a lot with floor self leveler because everyone assumes it does the job for you. While that is partially true, there is also a thickness requirement for most of these products. Meaning, the minimum required pour will be 1/8,1/4, etc.

For the product I am using, LATICRETE NXT PLUS, according to the data sheet below, I am required to pour 1/4″ minimum over plywood. So over my highest spot in the room, I need to set my entire room 1/4″ over that high spot and level everything from there.

This method is called “mapping”. For a wooden subfloor, I use a laser, stick measure, and drywall screws to set my depth measurements. I create a grid. screw in the screws and start at the high spot to find the measurement. Using the stick measure and laser, I adjust all the screws to be level with the highest screw over the high spot on the stick measure. Check out the in depth tutorial on my YouTube channel.

This will give you a level floor, leveled to the 1/4″ requirement over your high spot.

Step 5: Prime the floor with approved primer

Always read the instructions for any product prior to using. Here I am using LATICRETE PRIME N BOND and a nap roller. You can also use LATICRETE NXT PRIMER. Make sure to apply an even coat and let dry before moving to the next step.

Step 6: Seal off the perimeter and the door with expanding foam

This step helps seal off the perimeter of the room and also allows room for expansion where the floor will meet the walls. This is extremely important and will save you a world of headache to not have your self leveler leaking to other areas of the house unexpectedly. Don’t forget to dam off the doorway.

Pouring floor self leveler

Step 7: Prepare, prepare, prepare..

This step is SO IMPORTANT! Self-leveling underlayment is so high maintenance, and you need to be ready with multiple buckets because it needs to be flowing always. The moment it stops flowing its already hardening. If you are not prepared, you can really cause so many issues.

Best way to prepare:

have multiple buckets ready
pre fill the buckets with required water amount (check instructions for the product you are using)
have an electric mixer
have a helping hand to mix while you pour
have your bags pre opened
always buy extra self leveler, just in case

Step 8: Time to pour

Preparing to pour self leveler is the lengthiest part of the job. Pouring it, depending on the size of the room, will take a fraction of the time. Make sure you have someone to help you mix while you pour and keep the operation moving. The screw pins you set will guide you on how much self leveler to pour in one area or another. Make sure the depth screws are not sticking out of the self leveler. Make sure to always pour from the inside of the room, out. Once you are done pouring, you can walk on the wet floor with spike shoes, and use a gauge rake to break the surface tension and allow the self leveler to move freely.

Once complete, check with the instructions on how long you should allow it to dry before setting tile over it.