Self-leveling underlayments, also known as self-leveling compounds or floor levelers, are used to level out shallow dips and humps in a subfloor, prior to installing a finished floor covering. Because these products are very thin, they can be troweled out to make small adjustments to a floor without adding an additional layer of subflooring. 

What makes one self-leveling underlayment (SLU) better than the one next to it? How can it help your workflow be more efficient? What are the benefits of one SLU compared to another? These might be some of the questions you’ve found yourself asking when trying to decide which SLU product to go with. Here, we asked some of the industry’s leading SLU producers to weigh in. 

Elvis Torres, product manager, Laticrete.

Laticrete

NXT Level Plus Lite
Elvis Torres, Product Manager 

Benefits: 

NXT Level Plus Lite is a highly versatile SLU that’s compatible with projects that have load-bearing concerns and multiple substrates in residential and commercial spaces. It’s also 50% lighter in packaging weight, making it safer and easier to carry by reducing the physical strain on installers. The lighter weight also enhances jobsite efficiency by allowing the product to be moved more easily, as well as eliminating the need for staggered applications due to its high pour depth. It is fiber-reinforced and can be used on concrete, gypsum, plywood, and OSB without the additional need of metal lath. 

The product is UL Greenguard-certified for low VOCs and does not contain respirable crystalline levels that exceed the OSHA action level, promoting healthier conditions for contractors and end-users. Lastly, its quick drying time allows for walkability within three to four hours and the application of moisture-sensitive coverings after 24 hours.  

How It Stacks Up:

With its packaging weight now 50% lighter, NXT Level Plus Lite is not only easier to carry but is free-flowing, pump-friendly and can be poured up to four inches thick—substantially more than the one to two inches typical of other self-levelers. This streamlines project timelines by eliminating the need for staggered applications and reduces physical strain on workers, contributing to a safer and more efficient work environment. With a high compressive strength of 4,400 psi, this strong lightweight SLU is also extremely durable. From enhancing the installer experience to supporting diverse project requirements, NXT Level Plus Lite reflects our focus on developing versatile products that directly address the needs of our customers.   

NXT Level Plus Lite is free-flowing, pump-friendly and can be poured up to four inches thick—substantially more than the one to two inches typical of other self-levelers. With its packaging weight now 50% lighter, NXT Level Plus Lite is easier to carry. Photo: Latictrete.

Brett Mauny, national technical director, Merkrete.

Merkrete

Underlay SLU
Brett Mauney, National Technical Manager

Benefits:

Self-levelling underlayments, or SLUs, are great products for flattening out and levelling large horizontal areas before installing finished flooring. Without a flat substrate to install on top of, the finished flooring surface will be faulty, unsafe and highly susceptible to damage.  It’s for these reasons that the industry outlines the flatness threshold in ANSI specification A108.02-4.1.4.3.1, Subfloor Surfaces.

Another benefit of using SLUs is that your underlayment will be monolithic, meaning there will be no seams that need to be addressed and mitigated. You get a flat floor that can be installed on as soon as the SLU has cured.

How It Stacks Up:

Merkrete’s Underlay SLU is a popular product due to its workability and acceptability with all floor coverings. Our customers find its high-flow aspects and ability to go from featheredge to ¾” depth valuable to creating lasting flooring installations in a timely manner. Underlay SLU can be applied by a screed rake, or it can be pushed to areas needing leveling or flattening. Lastly, Underlay SLU dries quickly, allowing for flooring installation in just a few hours. 

Merkrete’s Underlay SLU is a popular product due to its workability and acceptability with all floor coverings. Merkete Underlay SLU dries quickly, allowing for flooring installation in just a few hours. Photo: Merkrete.

John Lio, director of marketing, Sika.

Sika

SikaLevel 050 Slope Rapid
John Lio, Director of Marketing

Benefits:

SikaLevel-050 Slope Rapid is a quick-setting polymer modified cement-based skim coating and ramping compound for the repairing and smoothing of interior concrete and plywood floor substrates. It fills voids, holes, cracks and plywood seams from a feather edge to 2” thick. SikaLevel-050 Slope Rapid smooths and finishes substrates in under one hour, prior to the installation of resilient, carpet, ceramic tile and stone tiles. Moreover, properly prepared well bonded cutback adhesives and existing ceramic tile installations can be skim coated. 

How It Stacks Up: 

SikaLevel-050 Slope Rapid offers an initial set time of thirty minutes, dry time of under one hour and has no MVER limitations, making for the ultimate user-friendliness and workability. Installers can rely on it for interior and exterior applications alike, in residential or commercial settings. This innovative repairing and smoothing compound speeds up installations while maintaining the highest degree of performance and reliability. In keeping with Sika’s commitment to environmental responsibility, SikaLevel-050 Slope Rapid also contributes up to two points toward LEED certification.

SikaLevel-050 Slope Rapid smooths and finishes substrates in under one hour, prior to the installation of resilient, carpet, ceramic tile and stone tiles. SikaLevel-050 Slope Rapid offers an initial set time of thirty minutes, dry time of under one hour and has no MVER limitations, making for the ultimate user-friendliness and workability. Photo: Sika.

Courtney Korselt, regional business director, Bostik. Photo: Bostik.

XL Brands

PrepStar
Courtney Korselt, Regional Business Director

Benefits:

XL Brands PrepStar offers abundant coverage per-pound due to having an extremely lightweight filler. Its moisture-insensitive formula has been approved for usage under all Bostik and XL adhesives. PrepStar will adhere to virtually any clean, dry, and bondable surface without the need for a primer. It also offers variable water tolerance engineered to meet installers’ requirements and has a superior working time. Furthermore, PrepStar can be wiped repeatedly to reduce waste, provides self-hydrating/drying to reduce down-time on the jobsite, and sands smoothly for even the trickiest of installations. And lastly, it meets ASTM F710 standards.

How It Stacks Up

The cement-based, rapid-drying, trowelable skimcoat is used to smooth interior subfloors prior to the installation of the finished floor covering. Many common coverings can be installed in as little as 15 minutes. PrepStar technology allows application over a wide variety of properly prepared substrates without priming or the use of an additive, including concrete, wood, ceramic, quarry tile, VCT, cutback residue, non-water-soluble adhesive residue and sheet vinyl (when used as an embossing filler). It is available in 10lb. bags. 

XL Brands PrepStar offers abundant coverage per-pound due to having an extremely lightweight filler. Photo: Bostik.