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Wood Flooring Adhesives
Types of Wood Flooring Adhesives  ~ History of Wood Floor Adhesives





















Types of Wood Flooring Adhesives

FAST FACTS > > > Wood Floor Adhesives work by creating a bond between the substrate and the flooring through a chemical reaction. While all adhesives work on the same principle of changing from a liquid to a solid state, they differ by the carrying agent or catalyst that activates them. The most common types of wood flooring adhesives include:


Water based adhesives certified as "very low emission" are the first choice for health and environmental protection. They are free of solvents or VOCs and safe to install. However, their range of application concerning certain types of wood floor or sub floor is limited.

Solvent based adhesives are well proven for wood floor installation over several decades offer a large range of application but contain non-hazardous solvents which will evaporate during the first weeks after installation is completed.

Urethane based/ moisture-cure adhesives offer the largest range of application and highest installation security but are usually more expensive than other adhesives. The can be applied under almost any circumstances and have hardly any restrictions on type of wood floor or sub floor.

Powder adhesives work pretty much the same way as water based adhesives, except you add the water yourself and thus do not have to worry about freezing or transportation of extra weight. The cement that is in the powder will permanently bond most of the water resulting in a reduced wood swelling compared to water based adhesives.

Technical Overview

~ A general rule of thumb for any adhesive is not to spread more than you can cover in 15 to 20 minutes.
~ Many failed glue-down floors are caused by contractors not taking the time to properly check and prepare
the subfloor.
~ The adhesive’s spread rate is controlled by the shape and size of the trowel’s notches.
~ If you are familiar with one product and switch to another, don’t assume you can use the same trowel or
spread rate.
~Using adhesives in the correct wood flooring application is a key to success. Certain wood flooring products
and substrates work best with a glue-down method of installation. Adhesives are most commonly
used with engineered wood flooring installed over concrete, as well as parquet installed over a slab or plywood.
~Many adhesives have a recommended “flash time”— they must be down for a certain amount of time before the wood flooring is installed. Other adhesives are “wet-lay,” which don’t need flash time, and you can lay the wood flooring into them immediately. The technology and chemicals in each manufacturer’s adhesive vary, so always refer to the manufacturer’s guidelines for how much, if any, flash time is required. A general rule of thumb for any adhesive is not to spread more than you can cover in 15 to 20 minutes. This is your window of opportunity to bond the flooring to the adhesive. If the adhesive is exposed longer, it may start to dry out and not transfer to the flooring surface. Other factors such as relative humidity may also affect open times for some adhesives, so it’s a good idea to check job-site conditions and document all of your findings before you install. To ensure a proper bond between the adhesive and floor, some manufacturers recommend rolling the wood floor in all four directions with a 100-pound roller.
Many failed glue-down floors are caused by contractors not taking the time to properly check and prepare the subfloor. A concrete slab should be clean, dry and flat. If a slab isn’t clean, the adhesive will form a bond with the debris, not the slab. Contaminants such as paint overspray, plaster or adhesive
from an old floor covering may interfere with adhesion, so the slab may have to be abraded with a heavy-grit sandpaper and hard-disc plate. Thoroughly vacuum, and if necessary, wetmop the slab to remove all dirt and debris.
In new construction, the slab should have cured at least 60 to 90 days before testing and installation. Take several readings with a concrete moisture meter, or perform a calciumchloride test or a phenolphthalein test according to instructions. If necessary, use the recommended moisture barrier, such as 6-mil poly. A high pHlevel can also adversely affect the performance of an adhesive, so some manufacturers also
recommend performing an alkalinity test. Installing a floor over an uneven slab can cause the adhesive
to adhere to some spots in the flooring and not others. This creates a common customer callback of hollow spots in the floor that make a popping sound when walked on. For glue-down installations, a flat slab has a tolerance of 3⁄16 of an inch over a 10-foot span or 1⁄8 of an inch over a 6-foot span. To even out a slab, high spots can be ground down, or low spots can be filled with an approved leveling compound. The subfloor should be compatible with the adhesive and product you’re installing. Super-slick concrete slabs can interfere with the adhesive’s bonding ability, so the surface of the slab may need to be abraded. Other surfaces, such as lightweight concrete, may not be compatible with certain adhesives, so always double-check with the manufacturer before you install. For a glue-down installation, the plywood subfloor should be at least 5⁄8 inch thick in 4-by-8-foot sheets. Always check with the adhesive and flooring manufacturers for subfloor requirements.
(Acknowledgment: Parts of the above information is from Hardwood Floors, the official magazine of the National Wood Flooring Association 09/06 issue)


Wood Floor Adhesive History & General Information

Modern technology has developed wood flooring qualities and finishes that have never before been available. Never have there been more colors, patterns, styles, and types of wood floors. The technology that has emerged from the chemical and adhesives companies has contributed greatly to the use of wood flooring and expansion in commercial and residential construction. New adhesives today enable us to use wood floors products in applications that just a few short years ago would have been prohibitive. These new adhesives in turn have contributed greatly to the increased use of wood flooring in all types of new construction as well as in remodeling.

It has not always been this way. Limitations were placed on the use of wood flooring in many areas because of the lack of good installation systems. It has only been in the last 50 years that adhesive installed floors have become common. It is interesting to look back over these 50 years and see just how adhesives have played a role in the growth of the wood flooring industry and how the evolution of different adhesives occurred, each solving some problems of its predecessor but creating new problems of their own.

Let's examine this evolution by adhesive types. And examine the pros and cons of each adhesive type or system. We'll then take a crystal ball look into the future to see what may lie ahead of us in a world of modern technology that constantly faces government and political controls.

The very first installer of wood flooring with adhesives was probably an ex-roofer. He had an old smelly asphalt wagon that he practically set on fire to soften the asphalt into a workable consistency. While the application was not very pleasant, his mentality was exceptionally keen to have the foresight to experiment with these asphalts for installing wood flooring. The system was simple in a way but very difficult and definitely not the type installation that even the experienced flooring installer could easily master. Nevertheless it worked, by hot mopping asphalts on a substrate and then embedding wood flooring into the asphalt. Thus, adhesive installed wood flooring systems were born.

One can only be somewhat awe struck by the problems with this type of application. Without a doubt it was messy; results were inconsistent; it was smelly; it was somewhat hazardous; clean up of smears and slop overs was nearly impossible; mistakes and repairs were difficult to handle. About the only good thing was that for the first time someone had the idea for a new method of installing floors that would ultimately contribute greatly to the tremendous growth that the industry has experienced.

Without a doubt the old smelly asphalt furnace on a trailer had to go and be replaced by some type of system that was controllable and easier to apply. Since asphalts were already being used, then why not continue to use asphalts but devise a better application method. This thinking led to the development and use of "asphalt cut-backs". They were called "cut-backs" because the old solid blocks of asphalt were "cut-back" with a flammable solvent such as mineral spirits, to make them fluid. They were then filled with materials, sometimes asbestos, to provide a uniform viscosity or thickness. Now an adhesive was available that could be purchased in a container, actually troweled on a substrate, and then you install wood flooring in the asphalt mastic. The release of the solvent caused the asphalt to 64 set up" and provide a bond. This type material is still used today. It overcame many of the problems of the old hot-mopped asphalt but then it created some very important new problems.

  1. The most serious problem was that of flammability. It was not uncommon to trowel out very large areas before installing any flooring because the working times were extremely long. This saturated the surrounding areas with solvent vapors and carelessness on the part of the mechanics caused serious fires and explosions.

  2. The flammability resulted in greatly increased insurance premiums.

  3. The technology involved in the formulation was not very sophisticated and some very questionable compounders began formulating these materials.

  4. Asbestos, a common filler that was low in cost, was used but later found to be an extremely hazardous material for the compounders to handle and ultimately was banned. The result was formulation with different fillers that increased prices of an already questionable material.

Clearly, the days of asphalt cut-backs were numbered and something had to be done to replace these materials for the installation of wood flooring. Mastic application of wood parquet floors was firmly in place in the industry. The market had become sizable and new flooring products were being developed by the manufacturers that required a quality mastic without the inherent problems of the asphalt cut-backs. Thus the modern day chlorinated solvent mastics and some emulsions for special applications of finger block were developed.

To many, this sudden evolution from asphalt cut-backs into chlorinated solvent and emulsion formulations came as a shock. All of a sudden the price per gallon of adhesive sky rocketed and the days of $1.00 per gallon asphalts were gone forever. From an industry point of view however, this was not all bad because for the first time a technology was spawned that was instrumental in the rapid growth of the wood flooring industry. The technology created some very important situations and advantages.

  1. For the first time the burden of performance was placed on the manufacturers of the adhesives. Heretofore, this responsibility rested almost entirely with the installer and he was at the mercy of the quality level of the cut-backs. The installer was also liable for the hazardous characteristics of the adhesive.

  2. The ease of application and use of these new mastics opened up new horizons for installers that previously would not have attempted to install wood floors in mastics.

  3. For the wood flooring manufacturers, it presented new opportunities for research and development of different patterns and flooring types, thereby expanding the market.

  4. Eliminated were the hazards associated with flammable products which resulted in reduced insurance rates and liability.

  5. The technology involved in the formulation and manufacture of these new mastics is provided by manufacturers who are far more sophisticated in their research, development, and production than the manufacturers of the past. No longer is it possible to set up a "garage operation with a cement mixer" to produce these formulations. You are for the most part supported by reputable and quality oriented manufacturers.

Just what is it about these chlorinated mastics that is so good? Why is it they have become so widely used in spite of their higher cost? What characteristics do they possess that are not totally desirable and may make them questionable in the future?

  1. First and foremost they are non-flammable. With today's government constraints, you just cannot use the hazardous, flammable products of yesteryear on flooring installations.

  2. Because of their non-flammability, your exposure to liability is far less.

  3. The elastomeric chlorinated systems possess most of the key application requirements such as ease of application, high green grab (tack), long working time and high strength. They really have most of the good application characteristics of the cut-backs plus some added benefits and few of the negatives.

  4. They are easier and cleaner to use.

  5. They have excellent long term aging characteristics if properly formulated.

They are not, however, free from negatives.

  1. Chlorinated solvents as a class have some pretty bad actors among them. Although most of the chlorinated solvents used in adhesive formulations are relatively safe to use and are not generally considered a carcinogen by the EPA or OSHA, there are some blends of 1, 1, I trichloroethane that may be questionable. To be on the safe side, be sure that your manufacturer uses pure 1, 1, I trichloroethane rather than blends in his formulation.

  2. Prices continue to escalate on chlorinated solvents that could eventually limit the market.

  3. The odor is extremely pungent and you must use adequate ventilation and air circulation while in use.

  4. Under certain conditions, without adequate ventilation, air circulation, and the extinguishing of all flames in the area, they can create an atmosphere that will be corrosive to metallic surfaces throughout a home or structure.

  5. When used over existing vinyl floors, they can cause a migration of plasticizers between the vinyl floor and the mastic, that will not permit the mastic to set up. This problem is avoided by using primers designed to provide a barrier between the mastic and the vinyl floor, as well as an improved bonding surface. Incidentally, this is not peculiar to only chlorinated mastics. Migration can also occur with emulsion formulations over vinyl.

At the present time, chlorinated mastics are the most widely used in the industry and will continue to be for the immediate future.

What will replace the elastomeric chlorinated systems and be the product of the future? The basic technology is already in place and being used. It is similar to that used in the emulsion polyvinyl acetate (PVA) systems. The future may be in the development of emulsion polymers that can be adapted to wood flooring applications of all types, even though they are water based. After all, we are already doing this with the PVA emulsion products on finger block installations.

Hey! Wait a minute! Are we getting too technical, or what?

What does this wood floor industry of ours want from a mastic, and how must it work? We want mastics that are:

  • Safe to work with.

  • Keep a floor down forever under normal conditions.

  • Less expensive.

  • Fast and easy to complete the jobs.

  • Compatible with a moisture barrier over concrete slabs.

  • Not going to overstress the substrate as the wood expands, yet return a shrinking floor. FREE Wood Flooring Quotes

Mastics must work by holding the floor with a dry, elastic, "stretchy" bond. The original roofer used asphalt that turned brittle, then as the wood changed dimension during season changes, the floor popped loose. The same is true for rigid/ stiff epoxies today. Even though extremely strong, as the wood moves the substrate fractures and there goes the floor. Cut-back asphalt holds the floor by suction and lets wood move or "float," but we've already covered the problems of this adhesive type. The mastic when spread must hold the bead of a notched trowel to insure positive contact with the wood when used over a less than perfect subfloor (all of 'em).

There are several other types of adhesives out there at this writing, namely:

  • Contacts that either are solvent-laden and dangerous, or water-laden and can destroy the wood. With both you must coat both surfaces, let them dry, then position the piece perfectly the first time!

  • Polyurethane's that are strong, elastic, age well and are water resistant, but are sometimes toxic, always costly, and difficult to use.

At this point in this study you can see how today's chlorinated solvent adhesive meets so many of our needs. The qualities of "strong," "dry," "elastic", "bead-holding" all apply and sound like rubber. Rubber sounds like "latex." Latex emulsion sounds like a mix of rubber with solvent or water. Solvents sound dangerous and expensive. Water sounds inexpensive and safe.

Thus we have come full circle, back to our crystal ball. The adhesive system of the future will be a water emulsion latex designed to eliminate warp and grain raise of wood floors. Needless to say, the adhesive and chemical manufacturers have a tough assignment! But realize that we no longer must set fire to an asphalt trailer -- and we have walked on the moon!

Another major consideration in the future will be waste disposal, particularly containers. The old fashioned trash man or garbage man will truly become a "waste engineer. As a matter of fact he already is one. Many of these waste collectors have been trained to keep their eye open for dumpster disposal of hazardous materials and they are notifying the EPA when they find them, resulting in some very costly situations for everyone involved.

Picture if you will the large volume of all types of adhesives used in just flooring applications on a high rise office building. Disposal of sometimes thousands of empty containers is getting to be a major problem. The problem is even greater when the mechanics fail to thoroughly wipe out the pails before disposal. We are about to see s o me major changes in packaging of all types of products in industry, particularly those containers that originally held products that even remotely might be considered hazardous waste.

New containers and new products will also generate new methods of application for adhesives of all types. Higher labor costs will also ultimately dictate that more mechanically applied systems be developed to accommodate all of these changes.

The 1990's brought many changes and innovative ideas to the wood floor industry. The installers of the future must remain open minded and be willing to participate in these new ideas. At the same time they must remain honest and practical, keeping in mind that they have an obligation to provide their customers with the best and highest quality installation possible. Always deal with well known, reputable suppliers and don't try to be penny wise and pound foolish by taking unnecessary risk with lesser quality or lower cost materials. Protect yourself and your customer by following the recommendations of the manufacturer. Be willing to try new ideas.

Today's technology has formulated parquet and engineered wood flooring adhesive that are Solvent-Free, VOC-Free, and non toxic. With fast setting formulas, no tack and flash time for the installer. The latest of these products include such characteristics that not only include solvent-free high-tack, premium pressure sensitive wood flooring adhesive specially designed for the installation of pre-finished engineered wood flooring and parquet. Some are acrylic-based adhesive specially designed for the installation of the new pre-finished engineered wood flooring and pre-finished wood parquet over approved interior substrates. Easy to spread. Excellent initial grab and high bond strength. There is also a solvent-free, two-component polyurethane adhesive specifically also designed for the installation of pre-finished engineered wood flooring and parquet over quality underlayment surfaces. Many product now have high solids, are of trowel grade, water-based synthetic adhesive developed specifically for installation of wood flooring. For use on, above or below grade. Allows for normal expansion and contraction of wood floor. Most have a Good initial grab and firm-setting. Excellent water resistance. Low VOC, nonflammableFREE Wood Flooring Quotes and easy water clean-up. Interior uses only

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