We invited Darryl Wilson of MAPEI Inc. to share his experience on the subject in an interview.
Darryl has 35 + years of flooring experience, as an installer, retail sales rep, floor inspector and senior technical representative in the adhesive manufacturing sector. He currently sits on the Board of Directors at the BCFCA.
Q: Darryl, thanks for taking the time to talk to us. In your opinion, what are the top three reasons adhesives fail?
1. Wrong adhesive used for the chosen flooring
2. Excessive moisture in concrete substrate beyond the adhesive or surface preparation products capabilities
3. Using the wrong trowel specified for the floor covering (not enough adhesive)
Q: What can be done to address these three causes?
· Sales and order desk personnel need to be educated on appropriate adhesive choices
· The moisture content of the concrete should be evaluated in advance of starting the project using a recommended test. Details of which can be found in the Floor Covering Reference Manual under the section ‘substrate testing’.
· Installers, specifiers and sales staff need to be educated on correct trowel choices and how important it is that the correct amount of adhesive is applied (too little or too much adhesive is equally problematic).
· Trowels wear down quickly and need to be replaced or re-grooved to original notch size.
Q. In your experience, have you found that there is an issue with the specified adhesive not showing up on site? If so, why does that happen?
DW: Human error and product availability are the most probable causes. If it’s simply the wrong adhesive delivered, return it and get the correct adhesive.
But if the correct (specified) adhesive is unavailable, there are usually other appropriate choices that can substituted. That question should be directed to the adhesive manufacturer’s representatives to confirm if the adhesive is in fact appropriate for the floor covering being used.
Q: Why do the wrong adhesives show up on site?
DW: The most common reason is the recommended adhesive is unavailable and an incorrect adhesive is accidently substituted. In addition, there are a lot of new backing types on the different flooring materials available. The sales people and specifiers are sometimes unaware of the changes.
Q: What are the pros and cons of 'pressure-sensitive' adhesives?
Pro: These are generally designed to have flooring installed into them when they are no longer wet to the touch. This makes them installer-friendly.
Con: Most, if not all, pressure sensitive adhesives have a window for the allowable open time. If they are left exposed to air for too long, the adhesive may start to lose bond strength. The installer needs to be aware of, and read, the different adhesive manufacturers’ technical documents for correct usage.
Q: Pressure-sensitive adhesives…quick and easy to install but not strong over the long haul. True or false?
DW: That is not true. There are many pressure-sensitive adhesives used today, and their long-term performance, due to advances in technology, is excellent.
Q: What are the pros and cons of 'wet set' adhesives?
Pro: Wet set adhesives have the reputation of better bond strengths and some are designed to have harder setting characteristics.
Con: Depending on substrate porosity with a homogeneous vinyl, it can be extremely challenging to do an installation and not have air bubbles, adhesive displacement and adhesive bubbles throughout the installation.
Q: What adhesive type do you recommend for spaces subject to extreme changes in temperature such as south-facing rooms with lots of windows or a BC interior location (hot during the day and cold at night)?
DW: Generally, a softer setting adhesive with flexibility and memory so the floor covering has the ability to shrink and expand without shearing the bond.
Q: Fly Ash concrete…what adhesive type should be specified and why?
DW: The answer to this question is more about the percentage of fly ash in the mix design, as a high enough percentage of fly ash may affect most of the adhesives on the market today. Currently, to the best of my knowledge, there are no adhesives specifically designed to address possible bonding problems with fly ash concrete.
Q: Slab on grade - resilient flooring…what are the most important things a specifier should consider when choosing an adhesive?
· Has the slab been tested for moisture content and correct pH level?
· Is there a high percentage of fly ash in the concrete?
· What is the type of backing on the flooring (vinyl, mineral felt or some recycled content)?
· Residential or commercial?
· Is it institutional (like a hospital) with heavy rolling loads?
· Is it an antistatic flooring?
· Is it being used in a wet area?
Q: What’s new in adhesive technology? Has there been anything you’ve seen that’s proven/tested that you’ve been impressed with?
DW: One significant change to some adhesives is that many are now allowed to be used over concrete that has vapor emissions of up to 8 lbs moisture vapor emissions rate (mver) and 95 % relative humidity.
The old standard is 3 lbs mver and 75 % relative humidity, which is still true for many adhesives. So it’s important to confirm the condition of the concrete slab and be aware of the adhesive’s capabilities prior to starting a project.
Q: What are the pro's and con's of low VOC adhesives?
DW: The health and safety factors. When the industry first started using low VOC adhesive, there were some occasional hiccups with the decreased bond capabilities due to the lowering of the solvent content. However with the advances in technology, manufacturers have been able to design environmentally friendly adhesives with excellent performance characteristics that often use recycled content.
Q: Finally, if you could change one adhesive-related thing in the flooring industry, what would it be and why?
DW: The confusion that surrounds pressure-sensitive adhesives and release adhesives.
Some adhesives are transitional, meaning they can be used for a wet set and/or pressure sensitive (dry) application. However these products are still permanent bond adhesives. There are also very specific pressure-sensitive adhesives on the market that are designed to facilitate easy removal and replacement of flooring such as carpet tile.
There have been instances where some fibre glass reinforced vinyl floorings that were designed to be installed with pressure sensitive release adhesives, were installed using transitional pressure sensitive adhesive. The result as you can imagine was a nightmare to remove. Again, this just shows the importance of confirming not only that the correct adhesive is being used but also making sure the adhesive is used in the correct manner.
We’d like to thank Daryll for sharing his expertise.