It’s easy to take for granted the products and solutions we have today. Even something that seems as basic as adhesive has had years of research and technology poured into its development.
That’s what we’re going to dive into – how we got the adhesives we have today and practical tips for choosing the right one for a flooring project.
Where did flooring adhesives come from?
The first hardwood flooring adhesive used in the United States is generally credited to a product called “mastic.” It is difficult to know exactly what it was because many adhesive products at that time were classified as mastic. Centuries before, the earliest occurrence of mastic referred to products made from a gummy substance from mastic trees (Pistacia lentiscus), from the Mediterranean region. The term became synonymous with adhesives that derived from natural components like rubber, resins, casein (milk), and albumin (blood). These formulated glues were innovative, searching for the ideal for bonding wood products.
Mastics gained popularity due to their ability to provide a strong and durable bond, waterproofing, and their ease of use (especially true when asphalt entered the mix). Mastics significantly advanced hardwood installation by replacing previous methods of nailing or screwing flooring to the subfloor. Using mastic was so widespread that in 1936, the US Department of Labor included it in their description for “Floor-Layer Helper.”
Twenty-five years later in a 1961 publication, Wood Floors for Dwellings, experts were still questioning the exact classification of mastic adhesives. The difficulty stemmed from the amount of asphalt, rubber, and resin compounds composing these adhesives. Experts then attempted to classify known mastic adhesives at that time into these sub-categories:
- Asphalt base: hot-melt, cutback, and emulsion.
- Rubber base: reclaimed solvent-type, synthetic solvent-type, and emulsion.
- Asphalt-rubber base.
- Miscellaneous special type.
The Rise of Cutback Adhesives
Only one of these gained notable popularity, the asphalt-based adhesive often referred to as “cutback.” Its extensive use started in the 1930’s and consisted of asphalt mixed with solvents. This make-up allowed it to be spread easily and then evaporate, leaving behind a sticky residue that bonded the hardwood flooring to the subfloor. Cutback asphalt offered good adhesion and moisture protection. It was popular until the 1970s, when concerns about its environmental impact and health hazards (associated with the solvents and often added asbestos) led to its gradual phase-out.
Following the decline of cutback asphalt, other adhesive formulations and technologies were developed and used for hardwood flooring installation. These non-asphalt products offered various benefits such as improved performance, faster curing times, and enhanced environmental friendliness. These products included alcohol-base, acrylic, urethane and polyurethane, and modified silane to name a few. The newer adhesive formulations quickly became the viable alternative for the flooring installer.
Timeline of Adhesives for US Market
- Early 20th century: Mastic was a natural mostly rubber-based adhesive developed and introduced as the first hardwood flooring adhesive in the United States. It gained popularity for its strong and durable bond.
- Mid-20th century: Cutback asphalt adhesives (also called mastic), made from asphalt mixed with solvents, became widely used for hardwood flooring installation. Offered good adhesion but are phased out later due to environmental and health concerns.
- Late 20th century: Polyurethane adhesives emerge as a popular choice for hardwood flooring installation. These offer strong bonding, flexibility, and moisture resistance.
- Late 20th to early 21st century: Acrylic adhesives become widely used for various flooring applications, including hardwood flooring. They offer versatility, ease of use, and compatibility with different flooring materials.
- Early 21st century: Silane adhesives, such as Modified Silane adhesives, are developed and gain recognition. They combine the benefits of polyurethane and silicone adhesives, offering high initial tack, fast curing times, moisture proofing, and environmental friendliness.
Which brings us to today! There are numerous types of adhesives available for hardwood flooring installation, each with its own characteristics and suitability for specific job-site applications.
Let’s take a closer look!
Modern Day Flooring Adhesives
In the past 20 years, hardwood flooring adhesives have advanced significantly, with several options offering excellent performance. Here are a few types that have gained recognition for their quality and suitability for hardwood flooring installation:
- Polyurethane-based adhesives have become popular due to their exceptional bonding strength, flexibility, and moisture resistance. They provide a strong and durable bond, making them suitable for various hardwood flooring applications.
- Modified silane adhesives combine the benefits of polyurethane and silicone adhesives. They offer high initial tack, fast curing times, and good flexibility. Modified silane adhesives also have low VOC (volatile organic compound) emissions, making them more environmentally friendly. They also offer more moisture protection than other adhesive types.
- Acrylic adhesives are known for their versatility and ease of use with synthetic flooring. They offer good bonding strength, fast curing times, and compatibility with a wide range of materials like LVP. As a general rule, experts recommend to not use these in a hardwood flooring installation.
It’s important to note that the best adhesive for a particular hardwood flooring project can depend on factors such as the type of hardwood flooring, subfloor conditions, and environmental considerations. Always consult with flooring professionals or manufacturers to determine the most suitable adhesive for your specific needs.
What are the benefits of modern adhesives?
The advantages of modern urethane, urethane hybrid, and silane-based flooring adhesives over petroleum and alcohol-based adhesives are numerous. The following list highlights the most important differences:
Urethane and Silane-Based Hybrid Adhesives:
- Provide stronger tensile strength and durable bond of hardwood to substrate, reducing the risk of floorboards coming loose over time.
- Greater flexibility to accommodate wood movement caused by changes in temperature and humidity, preventing gaps and cracks between floorboards.
- Exhibit higher moisture resistance, making them suitable for humid areas like bathrooms and kitchens.
- Have lower or no VOC emissions, improving indoor air quality and making them safer for installers and homeowners.
- Modified versions address specific flooring installation challenges. They also offer enhanced performance with added sound reduction and versatility over a variety of surfaces.
- Silane-based adhesives form strong chemical bonds with various substrates, providing excellent adhesion for hardwood flooring.
- In contrast, the solvent and alcohol-based adhesives used in the past have a higher VOC content, lack flexibility, and offer inferior moisture protection compared to advanced modern flooring adhesives.
RW Supply + Design Partners
The most innovative adhesive manufacturers offer products that are guaranteed to set you up for success. The following is a tried-and-true list of various adhesive brands we stand behind.
|Bona Quantum R851||Silane-based adhesive||No VOC, No Fatigue application, fast dry-cure time, No etch on prefinished floors|
|WAKOL MS232||Hybrid polyurethane/silane||No VOC, use directly over PU280 Moisture Barrier, easy-to-use tube size|
|Pallmann P5 Grip||Hybrid-polymer-based adhesive||Moisture cured, excellent bond strength|
|Pallmann P7||Urethane-based adhesive||2-in-1 Moisture Barrier, superior green-grab, hollow-spot reduction|
|Mapei Ultrabond ECO 985||Hybrid-polymer-based adhesive||2-in-1 Moisture Barrier, sound reduction. Click here to see our guide to this adhesive!|
|Mapei Ultrabond ECO 995||Urethane-based adhesive||2-in-1 Moisture Barrier, sound reduction. Click here to see our guide to this adhesive!|
|Real Wood Floors Adhesive||Urethane-based adhesive||Strong bond, economical choice|
|Real Wood Floors Cohesive||Urethane-based adhesive||2-in-1 Moisture Barrier|
|Wakol MS290||Silane-polymer adhesive||No VOC, long working time, no limitation on solid width glue-down, no etch on prefinished floors|
|Wakol MS260||Silane-polymer adhesive||No VOC, long working time, use directly over PU280 Moisture Barrier, up to 8″ solid glue-down|
|Wakol MS230||Silane-polymer adhesive||No VOC, No etching prefinished surface, easy cleanup, up to 4″ solid glue-down|
Are there some adhesives you should not use?
For hardwood flooring, do not use any glue or construction adhesive not specifically designed and tested for use with wood flooring.
One example of this is latex adhesives, which are generally not recommended for hardwood flooring. While latex adhesives commonly are used for various applications, such as bonding carpet or vinyl flooring, they are not ideal for hardwood flooring. A few reasons include:
- Lack of strength: Latex adhesives typically do not provide the same level of bonding strength as other adhesives specifically designed for hardwood flooring. Hardwood flooring requires a strong and durable bond to ensure its stability and longevity.
- Moisture sensitivity: Latex adhesives can be susceptible to moisture. Hardwood flooring installations often require moisture-resistant adhesives to prevent issues such as warping, cupping, or adhesive failure. Latex adhesives do not offer sufficient moisture resistance for this purpose.
- Flexibility: Hardwood flooring expands and contracts with changes in temperature and humidity. Adhesives used for hardwood flooring need to be flexible enough to accommodate these movements without compromising the bond. Latex and construction adhesives are generally not as flexible as other adhesives formulated specifically for hardwood flooring.
For hardwood flooring installations, experts recommend using adhesives specifically designed and labeled for hardwood flooring applications. When possible, use adhesives that are tested and recommended by the flooring manufacturer. Equally important is to remember that it is the adhesive manufacturer that guarantees their products to work under certain conditions and in specific applications. Always read, understand, and follow their installation guidelines for what is and is not acceptable use for your flooring project.
Looking for adhesives for your next flooring project?
Drop by any of our Pro Shop or Design Centers to learn more about the right adhesive for your next project.
What if I need to glue and nail a floor?
For some wood flooring applications, it’s recommended to both nail and glue the flooring, a method called “glue assist”, to avoid problems down the road. We suggest a glue assist method when installing hardwood floors that are thin, or solid and over 5″ wide, or being installed in environments with high moisture fluctuation.