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. Please read on for descriptions of the the types of adhesives for wood flooring.
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.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.
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.
Important Points to Consider …
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 adhesiveto 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.
