Wood Floor Adhesives: What Product for What Application?
Who has not dreamed about a beautiful long-lasting wood floor in their home? But do you know the best way to install your wood floor? And do you know what to consider to make your dream come true?
Type of installation
There are three main ways to install your wood floor: nail it down, glue it down or use a combination of these two methods. It is then called “glue assist.”
The nail down method, while cheaper, is labor intensive and has higher risks of joint and gap between the planks. Thinking long term, it doesn’t prevent the floor from becoming noisy and squeaky.
On the other side, the glue-down installation respects the natural movement of the wood, by allowing it to contract and expand, preventing the noise and the failures. It also creates a strong bond between the wood and the subfloor, ensuring the durability of the floor.
The glue assist installation is a mix of nail and adhesive, usually used for wider plank (over 6”). The adhesive can be installed according to the cordon system or as a serpentine at the back of the board. This type of installation is better than nail-only but doesn’t offer all the benefits of a glue down installation.
Now that you see the benefits of gluedown installations, here are the parameter to consider.
The National Wood Floor Association (NWFA) recommends the substrate be at least 3,000 psi. If that is not the case, especially for gypcrete/lightweight concrete substrate, you need to consolidate the subfloor prior to putting down the floor.
You also need to make sure the substrate is flat. Typically, manufacturers will specify a flatness tolerance of 1/8” to 3/16” in a 10-foot radius.
Finally, if you’re going over concrete, you need to consider the level of moisture inside the slab. If it is over 75% Relative Humidity, you need to mitigate the substrate or use an All-In-One Adhesive.
Type of Adhesive
The Adhesive you want to use mainly depends on the type of wood you choose. If your choice is a solid wood, it will be more sensitive to the environment, and will be more prone to expansion and contraction. The risk of breaking then becomes higher and you need to choose a very flexible wood floor adhesive to prevent any breakage. The flexibility of an adhesive is called “elasticity.” This parameter can be found on the Product Data Sheet of the product. As of today, you can find adhesive with an elasticity up to 400%.
If your wood floor is an Engineered wood, you can consider using a less elastic wood floor adhesive. From 100 to 300%, your floor will be in good hands.
You can also consider choosing a multi-function adhesive. Over the last few years, the market has evolved to offer powerful solutions. At the forefront of recent breakthroughs is All-In-One technology. While obviously gluing down wood, this technology also allows you to mitigate the concrete subfloor, to protect it against sound propagation and to bridge cracks of the substrate. These adhesives can glue down engineered and solid wood, though I always recommend mitigating the subfloor with a different solution for solid wood. This is due to the fact that you need 100% coverage when also using the adhesive as a moisture barrier. But the back of a plank of solid wood is not flat and thus, the 100% coverage is hard to get.
In any case, always check the moisture limitation of the adhesive you are going to use. While some are unlimited, some All-In- One products have a level of RH limitation.
You can also find on the market a system that offers a high level of sound control. These systems usually combine a wood floor adhesive with a pre-holed mat. You will put down the mat first, without gluing it, then, fill the holes with the adhesive. In these systems, the adhesive is provided in sausage packing instead of pails.
This type of system is mainly used when high sound control protection is required by the builder, who usually specifies an IIC or an STC (technical parameters for sound protection).
Chemistry of Wood Floor Adhesives
A last choice you can make regarding the adhesive you are going to apply is the chemistry of the formulation. As of today, you have the choice between urethane formulas and hybrid formulas. Urethane products will be mainly used for flexibility and trowelability while hybrids will be used for the easiness of cleanability and low-VOC content.
One last thing to consider when gluing down a wood floor is the warranty you can get from the wood floor manufacturer and from the wood floor adhesive manufacturer. Currently, some wood floor adhesive warranties match the wood floor warranty, ensuring your floor against any problems related to the adhesive.
As with everything else in the construction, attention must be paid to the way you are going to install a wood floor: nail or glue-down installation, or even glue assist installation. While the glue-down installation provides the best results in term of quality and durability, there are different adhesive solutions on the market, as well. Be conscious about what you want to achieve (sound control? moisture mitigation?), about what type of wood you’re going to put down (engineered? solid?), about the quality of the substrate and finally, about the warranty you can get from the manufacturer.
And don’t forget, manufacturers are here to help you choose your best fit!