Glue Gives the Primary Assist

By John Brown and David Jackson

In recent years, there has been a growing focus on using flooring adhesives to assist with nail-down or stapled installations of wood flooring. Known as a glue-assist installation, this approach utilizes glue as an aid in fastening wide planks in particular. The need hasn’t seemed to have been highlighted until recently due to wood planks being manufactured at increasingly wider dimensions, necessitating a supplementary tactic for stability and security in many flooring installations.

As the trend toward manufacturing wider wood planks progresses, using a nail-down-only approach becomes increasingly challenging. Wider solid wood and engineered planks, especially those 5” and wider, placed in unfavorable environments can result in unwanted movement in the wood, instability, cupping, crowning, and noise. Even when following the proper nail schedule or recommended spacing, stability in unfavorable environments cannot be guaranteed with wider planks.

It must be noted that without an industry guideline related to the glue-assist method, many in the industry have generated varying and conflicting instruction. Many wood flooring manufacturers opt not to provide glue-assist guidelines at all. Further contributing to potentially confusing or absent instructions from manufacturers is the fact that glue-assist is not a requirement, but simply an optional aid for flooring installation.

Fortunately, for our industry, the NWFA has been assembling definitive glue-assist methods in the Installation Guidelines updates. Brett Miller, VP of Education and Certification for the NWFA, has stated “the wood flooring industry could anticipate the release of the updated Installation Guidelines by the end of summer 2019.” With the NWFA adding clarity to this previously murky installation approach, these new Guidelines will likely help installers gain clarity and confidence.

Amidst disparate opinions on the ideal implementation of glue-assist, the prevailing viewpoint is that a bead of adhesive should be applied in a serpentine or similar pattern that covers the entire length and width of each plank. Some manufacturers indicate that this pattern should run perpendicular to the direction in which the flooring is being installed, while others assert the pattern should be applied in a parallel fashion.

A fully troweled layer of adhesive is above and beyond what most consider a glue-assist to be. Instead of traditional pails, therefore, sausage and cartridge dispensed adhesives have become increasingly popular options for glue-assist. Affording greater accuracy and precision when applied with dispensing guns, sausages and cartridges feature minimal waste, easy cleanup, easy transport, and an extended shelf life. While managing the flooring nailers, injecting adhesives into the equation can become a difficult and messy balancing act. When glue is being utilized as an assist-method rather than the primary fastening-method of the installation, the use of these lightweight adhesive-dispensing options for installers is tremendously important.

As MS polymer and urethane wood flooring adhesives have become widely available in cartridge and sausage packaging alternatives, installers must determine which wood flooring adhesive technology suits their needs best. Regardless of which technology is preferred, it is critical to apply an even serpentine bead or pattern across the wood planks to prevent the board from tilting one way or another.

Installers must also be aware that a glue-assist does not fully eliminate the potential for cupping, crowning, or other physical issues with wood planks on its own. Proper subfloor preparation and moisture control must be executed in addition to nail-down and glue-assist. Further, as with any installation, the installer must properly weigh environmental factors. Climate and geography play a role in dictating the proper flooring installation style, as could the arrangement of the building. If installing over a crawl space, for instance, glue-assist might not be the right installation method when moisture is emanating from below. As long as the aforementioned elements are properly contemplated, glue-assist is a valuable asset that could minimize plank movement, strengthen overall stability, and combat a noisy floor.

The pending release of the glue-assist guidelines from the NWFA signifies a turning point for glue-assist flooring installations, indicating its inevitable widespread usage among wide-plank wood flooring jobs. Installers should garner all possible information going into any installation to determine if a nail-down and glue-assist approach is best. Adhesive manufacturers have made a range of glue-assist choices available and will undoubtedly continue to evolve their repertories to suit this growing industry need.

John Brown is Southeast Technical Sales Manager for DriTac. He can be reached at jbrown@dritac.com. David Jackson is Field Technical Services Manager for DriTac. He can be reached at djackson@dritac.com.

3 thoughts

  1. We’ve been using and recommending adhesive in conjunction with cleats or staples for thirty years on all widths of solid planking starting at 2-1/4″. From the start, this eliminated the normal seasonal callbacks we received from many clients during the winter heating season here in Northwestern Ontario.

    We have always suggested using a “s” style bead (or serpentine as the article refers to it), using an adhesive that retains its flexibility (standard hardwood flooring adhesives gunned out of a quart tube, urethane for years, and now adhesives like Bostik GreenForce).

    We have argued for decades with contractors and suppliers who have either scoffed at the extra cost and labour or threatened us with loss of warranty, but we persisted due to the success we’ve had with thousands of floors. The original idea came from a client of ours, a contractor from Finland who glued all his unfinished strip floors and insisted he never had a squeak, minimal shrinkage, and very little cupping, all in an area where homeowners notoriously neglect to add humidity during the winter. We have not sold a roll of underlay paper for decades.

    One word of caution though: avoid selling adhesives that can’t be easily removed from the surface of prefinished hardwood. Many installers are a bit careless and often walk in the uncured adhesive and then on installed planking sections. The resulting glue haze on boards becomes impossible to remove after. Test all adhesives first to be certain they won’t ruin your client’s new floor.

    Richard F. Anderson
    President
    Design Building Centre
    Thunder Bay, Ontario

  2. I’m all in favor for glue-assist floor installations in most all situations wider than 3 1/4″ (up to 3 1/4 width I favor a bit narrower nailing pattern to assure holding power)!
    Additionally it is important that when using this method that the sub-floor is well prepared (read “always sanded well” to remove all and any contamination that affects proper glue adhesion especially on water repellent OSB sub-flooring where glues are challenged for adhesion due to the water repellent nature).
    Maintaining a good bead size is important also!
    I often run into comments “what about a moisture barrier”? Frankly speaking on a good quality subfloor that is not so critical IMO since the glue lines inbetween the plies functions already as a moisture barrier. On an old plank subfloor that is a different story though but you can always run a good bead of caulking along each plank seam, yes extra work, but so-what?
    If it makes for a better installation it would be a good reason to do.
    The type of adhesive is something that should be looked at carefully though and testing should be performed before releasing a recommendation or endorsement.
    IMO a Hybrid adhesive may be a bit weak (fine for full throwel jobs), a straight Urethane adhesive may be a better/stronger option here as it has a much higher “Shear Strength” than Hybrid adhesives. Remember with glue assist we partially rely on perhaps 3-5% contact areas over the whole back of the board.
    And it eliminates pretty much all potential for squeaking.
    General Construction Adhesive is absolutely a bad choice!

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