Do you really konw floor adhesives?

The task of wood floor adhesives is to firmly bond organic wood floor elements to a usually inorganic mortar layer. The adhesive must hold the wood in place, connect it to the underlying mortar layer, and transfer the stress generated by the natural expansion and contraction of the wood to the usually hard mortar layer. The undesired but natural motion of the wood becomes apparent during cupping, seam formation, or in extreme cases when the adhesive or mortar fails.

1.Classification of adhesives used for bonding wood floors

Wood floor adhesives are characterized by their performance under shear stress, which is closest to the situation when they are installed and attached to the wood to the mortar layer. The lap shear value described in the European standard EN 14293 is often referred to as the classification of the corresponding adhesive in the product data sheet. The adhesive used for wood floor bonding is divided into three categories:

(1)Hard adhesives

Often these are only partially adapted to the movement of the wood, so its stress is directly transferred to the ironing plate. If the ironing plate is not strong enough, it will fail and break inside the ironing plate. If the adhesion force is not strong enough, adhesion failure will occur at the interface.

(2)Hard elastic adhesives

These are a compromise of some of the advantages of hard and elastic adhesives. Strong enough to limit the movement of the wood and elastic enough to absorb and adapt to the pressure of the ironing plate. This type of hard elastic adhesive is recommended for gluing large plank floors.

(3)Elastic binding agent

These elastic binders are now very commonly used to bond engineered wood floors, as well as smaller solid natural wood with limited movement. Elastic adhesives are the best solution for absorbing and regulating the stress from the wood to the mortar layer, while only partially limiting the natural motion of the wood.

2.Inactive wood floor adhesives

Water-based (also known as dispersions) or solvo-based adhesives cure into rigid films by losing their liquid support medium. Water is released into the ironed plate and wood, while the solvent mostly evaporates into the air. Water-based and solvent-based binders are older technologies that are rarely used commercially today to any extent due to their limitations on wood and mortar layers, as well as their EHS/VOC issues.

However, these types of binders were widely used before modern reactive adhesives were widely known and fully validated, but they are still available, although there is no real benefit to using them today other than their low cost.

3.Active wood floor adhesives

Today, wood floors are commonly installed using reactive adhesives, as these technologies offer several important advantages:

(1)Easy to use, with the best opening time, pouring and smearing ability, stability of the spatter, odor, cleaning ability and other characteristics.

(2)Thick film application, can compensate for the inhomogeneity like using leveling mortar, thus saving time.

(3)For the initial grasp, the wood needs to be held in place until the adhesive is cured. This initial grasp is essential especially when laying larger planks that are never completely leveled.

(4)A wide range of applications, suitable for laying different mortar layers and laying different types of wood and different sizes of wood.

(5)Curing time, after which the wood floor can be walked on and further treated as needed (e.g., sanding, polishing, painting, etc.).

(6)Safety, i.e. bonding and system construction (ironing plate - binder - wood) is stable. This means that the movement of the wood is restricted, preventing the formation of cups and gaps; In addition, the adhesive layer absorbs and absorbs the stress, thus protecting the ironed plate from stress cracking and preventing adhesive and cohesion failure in the system.

4.Wooden floor installation method

There are several ways to install wood flooring. The most common methods are traditional mechanical fixation, full surface bonding, cordon (strip) bonding, and so-called floating mounting.In general, the best way to install wood flooring today is always to use full surface bonding of wood boards/elements with mortar or other substrate.