By Robert Blochinger
This is such an important topic that certain manufacturers of adhesive provide a clip-on attachment for your trowel with every container – FREE! This attachment has the proper notch size and shape for that adhesive’s design and purpose for performing, and to apply the correct volume.
Whether resilient, wood or carpet each product has various backing systems which can determine the volume of adhesive required to bond the product to the substrate. Substrate porosity will also dictate adhesive volume, as well.
And, how fast will the vehicle used within the adhesive be absorbed leaving only the solid component?
Consider these questions in determining the proper adhesive volume:
- Is the tufted carpet backed with woven polypropylene mesh? What is the pitch of mesh?
- Is it an applied cushion back? soft or hard?
- Is it a woven carpet, no backing?
- Is it carpet tile with vinyl back?
- Is it engineered wood?
- Is it solid plank wood?
- Is it LVT/LVP?
Each flooring product requires a different volume of adhesive. Each container of adhesive has an amount of spread per square foot/yard based on the trowel notch size and shape. A trowel with a U-notch applies more adhesive to the substrate than a V-notch shape trowel. The width of the notch as well as the depth will also determine the amount of adhesive applied. That’s why you can’t use a resilient trowel for installing carpet. Look at ceramic trowel with very large notches, this is to deliver the volume of setting materials to the substrate necessary to ensure correct bond.
Hard back (smooth, dense) carpet requires less volume than the Woven (coarse) style carpet as well as a typical mesh back carpet. There is also the question of the substrate porosity, how fast will it absorb the vehicle used within the adhesive and leave only the solid component? Have you tested for porosity? Is a primer or sealer required to disallow accelerated absorption of the adhesive vehicle? These questions must be answered prior to application, if not a bond failure will be in the future. Then we have the question of the type of adhesive, pressure sensitive has a different bond design than a “normal” adhesive.
Then we have the spray on adhesives, there is a volume per square foot, and a photo of what the substrate looks like. Although an individual judgement call, you are instructed to mark out the basic square foot coverage. This way, if you don’t meet the parameter of the area, you sprayed too much, if you have contents within the can left over, you sprayed too little.
There are important reasons for the guidelines and instructions on the container and within the flooring product installation directions.
Within the manufacturing process, there are chemical Engineers who do formulate and test the adhesive for specific functions. The properties of the adhesive, or the formula, is on each container, to an extent, such as the liquid content versus the solids. The solids are what gives the adhesive the bonding strength required for the different materials to be installed.
I have been asked on inspection sites, either just before commencement or during the begging where there are questionable conditions, by Installers, what’s wrong? Well, after review of the site conditions, reading the guidelines on the materials, I ask, you have not followed the conditions of application by the Manufacturer. Who are you to go against the Engineers who formulated this product? Are you smarter than they are? Do you have a good insurance policy? Why?
Keeping in mind the backing of the product to be installed does determine the adhesive volume. A solid type such as vinyl, which is smooth and non-porous will have a lesser volume of adhesive than a tufted or woven carpet back.