In the world of resilient flooring, the shift toward vinyl-backed products has led to a significant issue for many contractors and homeowners: dealing with old cutback adhesive residue. Cutback adhesives were commonly used for securing flooring materials like vinyl and asphalt to various substrates, especially concrete and wood underlayment. However, with the advent of newer flooring products and techniques, the presence of cutback adhesive can cause serious complications, particularly when trying to install new flooring on top.
What Is Cutback Adhesive?
Cutback adhesive refers to a type of adhesive that was used primarily in the 1950s through the 1980s to secure resilient flooring, like vinyl tiles, to subflooring surfaces. It’s typically a black, tar-like substance that has a distinct odor due to its chemical composition, which includes bitumen (a form of tar). The adhesive can be challenging to remove, especially when it’s adhered firmly to the subfloor.
While cutback adhesive was once considered an effective bonding agent, it has since become problematic due to its potential interaction with modern flooring materials. As vinyl-backed products become more common, the issue of dealing with this residue has become more pressing, especially since it can cause staining, adhesive bonding issues, and even health risks when not handled properly.
Why Is Cutback Adhesive Problematic?
The core issue with cutback adhesive is the plasticizers present in modern vinyl flooring. These plasticizers migrate downward through the vinyl and attack the cutback adhesive beneath, which softens it. Once this happens, the softened cutback adhesive begins to migrate upward, causing staining in the vinyl or vinyl-backed flooring. In some cases, the cutback adhesive may bleed through felt-backed products as well.
This problem doesn’t only manifest in staining; it can also create bonding issues when attempting to install new flooring on top of the existing cutback adhesive. When the adhesive residue remains, it becomes nearly impossible to achieve a stable and long-lasting bond, leading to potential floor failure in the future.
The Risks of Asbestos in Old Cutback Adhesive
Another serious issue with cutback adhesive is that older formulations often contain asbestos, a dangerous mineral that can cause respiratory issues and other serious health concerns if disturbed. Asbestos was commonly used in flooring adhesives until the 1980s, and while not all cutback adhesives contain asbestos, it’s important to test the material before attempting to remove or cover it.
When working with old cutback adhesive, it’s crucial to identify whether it contains asbestos before proceeding. If asbestos is present, specialized removal procedures should be followed to avoid inhalation of harmful fibers.
How to Deal with Cutback Adhesive
Now that we understand the challenges posed by cutback adhesive, the next question is: how do you properly address it? There are several approaches to managing cutback adhesive, depending on the situation and the type of flooring you’re installing.
1. Grinding and Shot Blasting
If the cutback adhesive does not contain asbestos, one of the most effective methods for removing it is grinding or shot blasting. Grinding involves using a floor grinder with diamond or carbide abrasives to remove the adhesive residue, while shot blasting employs high-velocity steel shots to blast the adhesive off the surface.
However, these methods can leave behind a rough and uneven surface, which may require additional preparation before new flooring can be installed. If you choose to grind or shot blast the adhesive, a self-leveling compound may be needed to smooth out the rough subfloor before continuing with the installation.
2. Self-Leveling Over Cutback Adhesive
In many cases, it’s not necessary to remove the entire adhesive layer. Instead, you can patch or self-level over the cutback adhesive using a cementitious compound. Some manufacturers recommend applying a minimum of 1/8” of this compound to prevent the adhesive from bleeding through.
Here’s a general guideline for self-leveling over cutback adhesive:
- Remove excessive adhesive: Scrape off as much of the cutback adhesive as possible, leaving only a thin, residual layer behind.
- Prime the surface: Use a primer specifically designed for this application, such as MAPEI’s Primer T.
- Apply self-leveling compound: Use a self-leveler like MAPEI’s Ultraplan Easy, which is designed for use on subfloors that haven’t been mechanically profiled.
This method effectively encapsulates the adhesive, preventing it from affecting the new flooring.
3. Triseal Adhesive Residue Encapsulator
For a less invasive solution, you may want to consider a product like Triseal Adhesive Residue Encapsulator, which is sold by companies like JJ Haines. Triseal is an acrylic polymer compound designed to isolate cutback adhesive and other types of old adhesive residues. This product creates a barrier that prevents the adhesive from affecting the bond of new flooring adhesives. It is a single-coat application that provides a protective layer over the existing adhesive.
While Triseal can be used with water-based adhesives, it is not recommended for urethane hardwood adhesives. When using this product, it’s crucial that the adhesive used is dry to the touch. If wet adhesive is applied over Triseal, the vinyl or rubber flooring may not dry properly, leading to indentations and potential adhesive bleeding.
Installing Different Flooring Types Over Cutback Adhesive
Depending on the type of flooring you are installing, different approaches may be required when dealing with cutback adhesive. Here are some common flooring types and the best practices for installing them over cutback adhesive:
1. Vinyl Composition Tile (VCT)
Vinyl Composition Tile (VCT) adhesives can be applied directly over cutback adhesive, provided the existing adhesive is smooth and thin. It’s important to ensure no ridges or puddles are left behind. In some cases, you may need to cover the adhesive with a primer like MAPEI Primer T before applying the new adhesive.
2. Luxury Vinyl Tile (LVT)
For glue-down LVT, the vinyl backing cannot come in direct contact with the cutback adhesive. The adhesive should be covered with a cementitious patch or self-leveler, or you can use Triseal before applying LVT adhesive. Floating LVT can be installed after covering the cutback adhesive with a cementitious patch, self-leveler, or Triseal.
3. Engineered Hardwood
Engineered hardwood adhesives will not adhere to cutback adhesive. To ensure a secure bond, you will need to cover the cutback adhesive with a cementitious patch or self-leveler. If using Triseal, only adhesives that can be used dry to the touch, such as DriTac 6200, should be used to avoid issues with cupping and moisture retention.
4. Vinyl and Linoleum Sheet or Tile
Both vinyl and linoleum sheet or tile adhesives require that the cutback adhesive be covered with a cementitious patch, self-leveler, or Triseal. The adhesive used must be dry to the touch for optimal performance.
5. Rubber Flooring and Carpet
For rubber flooring or carpet installations, the cutback adhesive must be covered with a cementitious patch or self-leveler, or Triseal should be applied to prevent any adverse effects on the new flooring.
Conclusion: How to Ensure Successful Flooring Installation
Dealing with cutback adhesive can be challenging, but with the right tools and techniques, it’s entirely possible to successfully install new flooring over existing adhesive residue. Whether you choose to grind, self-level, or use an encapsulation product like Triseal, it’s essential to follow the manufacturer’s recommendations and ensure that the subfloor is properly prepared.
Before starting any renovation project, it’s crucial to ask the right questions about the type of flooring previously installed and how it was removed. Adhesive removers may seem like a quick solution, but they can introduce long-term problems that affect the performance of your new flooring. By taking the time to properly address cutback adhesive, you’ll ensure a long-lasting, beautiful floor that will stand the test of time.