Self-Leveling Compound Not Flat (Causes & How to Fix?)

If you need to smoothen, repair, or raise a surface, a self-leveling compound is an excellent choice. The self-leveling compound is an easy-flowing polymer-modified cement often used to create a level and smooth surface.

When poured on a surface, you only need to spread it with a gauge rake, and it will flow and level itself. It is a suitable solution for dipped floors or those that need to be filled.

Even though a self-leveling compound is a pretty useful product, there are times when it may not cure into a flat and smooth surface. So, what should you do when the self-leveling compound is not flat? Keep on reading to find out.

Floor leveling. Filling the floor with a self-leveling compound

What Causes Self-Leveling Compound Not to Be Flat?

• Not Pouring Enough Product

A common mistake most first-time users of self-leveling compounds usually make is not pouring enough product. As you shop for a self-leveling compound, you need to know how much product you need to pour on your floors.

If you use too little, there is a good chance that certain areas will not get enough amounts of the self-leveling compound, and it may not cure with an even surface.

• Having a Massive Dip on Your Floor

A self-leveling compound can be used to fill in dips on a hole. But if the dip is too big, it may not dry into a flat surface. Before pouring the self-leveling compound, you need to measure how deep your floor dips are.

• Failure to Use String Lines During Installation

A step most people often overlook is the use of string lines during installation. String lines allow you to measure deviations or slopes on a floor. Failure to use string lines can often lead to the self-leveling compound not curing into a flat surface.

• Improper Mixture of the Self-Leveling Compound

Self-leveling compound can’t dry into a smooth, flat surface if the product is not correctly mixed. The best way to mix a self-leveling compound is by using a drill.

You should also make sure that you use the correct water ratio. Too much or too little water can affect the flow of the self-leveling compound, thus creating bumps and dips.

• The Presence of Holes and Seams on the Floor

When you pour the self-leveling compound, and there are seams or holes on the floor, a significant amount of the compound will spread into other areas, and it may dry into an uneven surface.

What Should You Do If Self-Leveling Compound is Not Flat?

There are a couple of methods on how you can fix the uneven self-leveling compound. We will go through all the methods, and you can choose which seems ideal for your scenario.

1. Pour More Self Leveling Compound

If you notice that the self-leveling compound is not flat after it dries, perhaps it has a few dips. The easiest and quickest solution is to pour more product on the floor.

The unevenness may have been caused by a massive dip on your floor or using an insufficient amount of product.

Whichever the case, when you pour more self-leveling compound, it should fill up any dips left behind with the previous application.

During this second attempt, make sure that you spread it evenly. Also, don’t forget to check what the manufacturer recommends about pouring another layer of self-leveling compound.

The likes of self-leveling products made by Mapei require you to wait for 24 hours, prime and then pour another layer of self-leveling compound. This is very important.

2. Sand It Down

If your self-leveling compound is not flat and has a couple of bumps, you don’t need to add more product. The best solution here is to sand the bumps until they are flat.

To do so, you will need a chisel, scraper, and an orbital sander. Don’t forget a mask, goggles, and gloves because this project can produce a lot of dust.

For bumps that are too big, you may want to pry them off the floor using a chisel. You can follow up with an orbital sander to create a smoother finish.

You don’t have to be very keen when sanding because even if you create a few dips, you can always refill them with a more self-leveling compound.

Should I Hire an Expert Contractor If Self-Leveling Compound is Not Flat?

These days, there isn’t a single construction project you can’t pull off by yourself. You only need some guidance and the appropriate tools.

However, if you have attempted to install a self-leveling compound several times and it’s not flat, don’t hesitate to call in the experts.

Pouring self-leveling compound is easy. But it has a learning curve. The more you do it, the more you learn how to avoid mistakes.

Therefore, if you are having trouble with installing a self-leveling compound, you can hire a professional contractor to help you out. It’s not expensive, and the best part is that you are assured of a smooth and flat finish.

Can You Flatten Self-Leveling Compound with Thinset?

Assuming that you plan on tiling your floor after the self-leveling compound dries, then you can use a thinset to flatten it out. But there is a limitation.

When a self-leveling compound dries into an uneven surface, and you have plans to tile over it, you can play around with the thinset during tile installation to get a level finish.

Please note that you can’t use excess thinset because it may create some hollowness beneath the tiles, eventually leading to cracking.

Though doable, flattening self-leveling compound with a thinset is a project that requires meticulous precision and expertise.

If you don’t have enough experience, I would advise you to pour more self-leveling compound on the dips until you get a flat surface.

Can You Flatten Self-Leveling Compound with Another Product?

Not at all. Never mix two different self-leveling compounds because the formulas may be incompatible, which can lead to catastrophic results.

If you were using Ardex, Bostik, or Mapei, please stick to that brand when re-pouring another layer of self-leveling compound.

Even though all self-leveling compounds are formulated to do the same job, they have varying formulas and water-mixing ratios.

Therefore, if you pour Ardex over Bostik’s self-leveling compound, the two layers may not merge, which can result in many problems later on. To be safe, stick to the product you started with.

Can I Add More Water to Self-Leveling Compound If It’s Not Flat?

As the self-leveling compound dries and you notice that it’s not even, you may assume that adding more water can level it out. But that’s not true.

When you add more water, you will weaken the mix. Therefore, the self-leveling compound may not be as durable as it was initially. And as it dries, it may crack or break.

When you notice self-leveling compound drying unevenly, let it cure fully. This should happen within a few hours, depending on the brand you are currently working with.

Once it dries, identify if the unevenness is in the form of dips or bumps and follow the methods I have shared with you earlier.

Does Feathering Help Prevent Unevenness of Self-Levelers?

Feathering goes a long way in ensuring that your self-lever dries into a smooth and flat surface. Self-levelers are formulated to flow and level on their own.

However, from experience, this isn’t usually the case unless you use more water than recommended. And we have already mentioned the risks associated with this.

It’s a good idea when pouring self-leveling compound to always spread it out gently with a rake. And you can finish up by feathering it, so it spreads more evenly. You will be surprised at how much difference feathering makes in creating a flatter finish.

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