Understanding Flooring Adhesive Terminology – Part I

Mar 25, 2021

By: Seth Gladden, Director of Marketing, Taylor Adhesives  https://tayloradhesives.com

As appeared in The Flooring Specialist magazine:  https://cfitheflooringspecialist.com/

The North American flooring adhesives market is estimated to reach $1.1 billion dollars by 2023 (fcimag.com), comprising nearly 16% of the global flooring adhesives market ($6.95 billion by 2023 – adhesivesmag.com). Any market of this size invites competition, leading to lots of options when it comes to flooring adhesive manufacturers, product chemistries and application methods. This is why knowing what products to use, and when, is so important.

Truly understanding the differences between flooring adhesives and when to use them can save you countless amounts of time and money. And while it is true that all flooring adhesives are sticky, getting stuck with the wrong one can really trip you up. Remember, not all adhesives are created equal, so be sure to understand what you are buying, and that it is the right product for your job.

How do you know which product is right for you? There are many factors that go into choosing the right adhesive, but one of the easiest ways is to look at a product’s data and warranty. Really understanding the terminology that flooring adhesive manufacturers rely on is key to knowing the capabilities, and just as importantly, the limitations of a product. Let’s take a closer look at some of these well-known, but often little-understood terms that can make or break your installation.

MOISTURE… I hope that word caught your attention! Dubbed as “The Billion Dollar Question” (TAYLOR TIME LIVE – S1 E1), moisture leads to more flooring-related claims every year than any other source. And while the terms below may look familiar, you might be surprised at what they actually mean.

  • RH = Relative Humidity – This is not to be confused with atmospheric relative humidity, although that does play an important part as well (temperature, humidity, air pollutants, dew point, barometric pressure, sunlight, airflow). In the flooring industry, RH testing refers to the process of drilling and placing a test probe in a concrete slab. It measures how much moisture is present in relationship with how much moisture could be present, or in other words, a percentage of saturation. The higher the number, the closer to standing water you get. It is important to remember that this is dependent upon atmospheric conditions and that RH is only a snapshot in time and can change with time and seasons. Remember high-school chemistry? Whether you were a fan of it or not, one of the easiest ways to think of RH is like potential energy (stored), whereas MVER is like kinetic energy (moving).
  • MVER = Moisture Vapor Emissions Rate – also known as the Calcium Chloride test (CaCl), this is a measurement of how much moisture vapor is emitting from a concrete slab (ASTM F1869). The higher the MVER number, the more moisture is emitting from the slab, which can lead to flooring failures, mold, mildew and a host of other problems. An MVER of 8 lbs means that eight pounds of water vapor is emitting from every 1000 square feet every 24 hours. Water weighs in at just over eight pounds per gallon, meaning that almost a gallon of water is coming out of that 1000 square foot every day.
  • pH = A measurement of the acidity, or alkalinity of a substance. As it relates to flooring, this applies primarily to concrete slabs. Newly placed concrete holds a pH of 12-13 on the inside and often 10-11 on the surface. If concrete drops below this healthy internal pH level, the rebar will begin to corrode and the concrete will lose strength, durability, exhibit spalling/cracking and can lead to complete structural failure. However, higher levels of pH can attack adhesives and even floor covering materials. Be sure the products chosen can withstand or even block unwanted alkalinity. NOTE: pH is measured on a logarithmic scale, meaning that every number the pH increases, it is ten times more alkaline (ex. pH of 12 is ten-times more alkaline than a pH of 11).
  • Waterproof Bond = This means that an adhesive, once fully cured, will achieve a bond that cannot be broken down, or re-emulsified by water alone. However, this does not mean the adhesive provides any protection against moisture. Always check for moisture barrier products vs. moisture tolerant products. Water is a great carrier and can bring high alkalinity (pH) to the surface along with it, so if an adhesive that forms a waterproof bond does re-emulsify, it is typically indicative of a high pH environment.
  • Water-Resistant Bond = This is referring to an adhesive that once fully cured, will be resistant to its listed levels of water vapor. However, if exposed to higher levels of water vapor or standing water, these products can lose their tack and lead to a loss of proper bond, likely resulting in a flooring failure.
  • ASTM E1745 = This is the “Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill under Concrete Slabs”, or as most in the flooring world know it, the requirement of having an intact, sub-slab moisture vapor retarder. Even though it’s considered standard practice in new construction to install sub-slab vapor retarders, older concrete slabs, especially 20+ years, may not have one. Even if an older slab does have one, it is likely not intact due to disintegration and time, making it vital to verify if there is one present and in good condition. Typically, this requires drilling a core sample and can still give inconclusive results. It is important to know that most products designed to go over concrete, including patch/level products, adhesives, coatings and primers require an intact, sub-slab vapor retarder be present in order for their warranty to be valid.
  • Hydrostatic Pressure = According to Dictionary.com, this is defined as “the pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above”. Despite how scary hydrostatic pressure sounds (and can be), it is actually a very rare problem, although many moisture issues are mistakenly given this label. Essentially, it is pressure in the capillaries and pores of the concrete, being driven through the concrete slab by some external force. The most common culprits leading to hydrostatic pressure are improper drainage or a high water table. Often, leaky or broken water pipes are lumped into hydrostatic pressure, however they are technically considered hydraulic pressure but result in similar issues.
  • Moisture Barrier vs Moisture Tolerant Adhesives = This is one of the most widely misunderstood concepts regarding flooring adhesives today. When adhesive manufacturers assign RH, pH and MVER data points (numbers) to their products it means that the adhesive can withstand, or “tolerate” those levels. However, just because an adhesive can tolerate high moisture (ex. 99% RH, 12 lbs MVER, 12 pH) does not mean that the adhesive will offer any sort of moisture protection for the floor covering material being installed. If you are looking for a product that can both withstand and block moisture, then you need to look for moisture barrier adhesives.

Picture of an MVER (CaCl) test (ASTM F1869)

Picture of an MVER (CaCl) test (ASTM F1869)

Picture of a Sub-Slab Vapor Retarder (ASTM E1745)

Picture of a Sub-Slab Vapor Retarder (ASTM E1745)

Clearly there is a lot of meaning behind these terms, and this article has only scratched the surface. Speaking of surface, in the next edition of this publication, we will continue with “Part II” where we will dive into the meaning behind the terms surrounding substrates, time, traffic and sound as they relate to flooring adhesives.

Now you know, and as they say, knowing is half the battle. Next time you are selecting a flooring adhesive product, remember the meanings behind the data and terminology. Installing with confidence is easy when you Stick with the Facts.

For more information and great advice on this topic from flooring experts, you can watch “Stick with the Facts” TAYLOR TIME LIVE – S1 E3 at www. TaylorAdhesives.com/TaylorTime or on our YouTube channel.


Seth Gladden

Seth Gladden

Director of marketing and commercial business development for Taylor Adhesives

Seth Gladden is focused on the brand’s communication strategy and market positioning. Before getting stuck in the adhesives industry (pun intended), Gladden gained sales and management experience in industries ranging from security to oil. Shortly after joining Taylor, Gladden rebranded the company, with its focus on being an industry leader in mind. He chairs the Taylor Advisory Council to stay informed of market trends and installer needs from distributor partners.