Self Leveling Underlayment: A Solution for a Flawless Floor

When it comes to achieving a smooth and level subfloor, self-leveling underlayment, also known as self-leveling compound or floor leveler, is a go-to solution. Whether you’re preparing for tile, hardwood, or another finished flooring material, self-leveling underlayment can help you eliminate shallow dips and humps in your subfloor, creating a perfect canvas for your flooring project. In this article, we’ll delve into what self-leveling underlayment is, how it works, and provide some valuable tips from the pros.

What is Self-Leveling Underlayment Made Of?

Self-leveling underlayment consists of a mixture of very thin cement, polymers, and other additives. This combination allows the material to behave like a liquid, spreading out evenly and seeking its own level when poured onto the subfloor. Additionally, special chemical binders in the mix enable the underlayment to bond effectively to various subfloor materials, including wood and concrete. The fine texture of self-leveling underlayment, when mixed correctly as per the manufacturer’s instructions, creates a slurry that can be poured directly onto the subfloor.

Ease of Use

The good news is that most homeowners can work with self-leveling underlayment without much difficulty, especially if they have prior experience with mixing mortar or concrete. The mixing process is similar to that of Portland cement, and the same tools can be used for application. Another advantage is that you can apply self-leveling underlayment in layers if necessary to address deeper subfloor imperfections. However, it’s essential to exercise caution when adding multiple layers, as the added weight can potentially lead to floor support issues in wood-framed systems.

Using Self-Leveling Underlayment

Professionals often begin by assessing the subfloor’s flatness using a long level or straightedge. If there are humps exceeding ⅛”, they may choose to remove them using an appropriate sander. Afterward, the level or straightedge is once again placed on the subfloor to identify low spots by observing any light passing beneath it. Marking these low areas with a pencil, they proceed to apply the underlayment, spreading it evenly to be screeded. Screeding involves using a straightedge to eliminate any excess underlayment above ⅛” while ensuring an even distribution across low areas. The primary goal is to fill in the dips without overapplying underlayment. Once screeded, the underlayment can be troweled as needed and left to cure.

Compatible Finished Flooring

Self-leveling underlayment can accommodate a wide range of finished flooring materials. Its thin consistency makes it suitable for use under carpet, sheet flooring, vinyl, tile, laminates, and most other flooring options. Additionally, it can be applied beneath vapor barriers, carpet padding, and laminate foam underlayments.

How Self-Leveling Underlayment Works

Self-leveling underlayment comes in bags similar to Portland cement, mortar, and concrete. When mixed with water, it chemically reacts and begins to harden, seeking its own level when poured onto a surface. The correct mixing consistency ensures that the underlayment flows effortlessly. However, it’s not just watered-down cement; self-leveling underlayment contains additives like polymers that allow it to flex slightly without breaking. Other ingredients improve its bonding properties and maintain its thin consistency. Additionally, self-leveling underlayment can enhance the adhesion of various adhesives, such as carpet glue and engineered flooring adhesive.

Steps to Use Self-Leveling Underlayment

The application process may vary slightly among different manufacturers, but the following steps generally apply:

  1. Inspect the floor closely for defects, including protruding fasteners or adhesives that should be removed.
  2. Use a straightedge to identify any humps or dips in the subfloor.
  3. Correct high spots by sanding.
  4. Mix the self-leveling underlayment following the manufacturer’s instructions.
  5. Pour the slurry onto the subfloor and lightly screen it to facilitate even distribution.
  6. As the underlayment starts to solidify, use a long trowel in broad, arching movements to ensure low areas are filled.
  7. Allow the underlayment to cure, and if necessary, sand the surface for a perfectly flat finish.
  8. Saving Time and Money

Using self-leveling underlayment can be a cost-effective solution for uneven floors compared to installing an additional layer of subflooring, such as 5/32″ plywood sheets. It eliminates the need for additional materials, fasteners, and tools, saving both time and money. In many situations, self-leveling underlayment proves to be the most efficient and economical choice for achieving a flawless and level subfloor.