By Robert Blochinger
The newest types of luxury vinyl flooring are WPC (wood plastic composite) and SPC (stone plastic composite) floors. These are often marketed as waterproof floors with rigid cores. Despite their waterproof attributes, both types of rigid-core flooring will require moisture testing of the substrate and underlayment.
This is worth repeating: Before installing waterproof flooring, the substrates and underlayment will need to be moisture tested. It should go without saying to read the product labels and manufacturer guidelines before starting; however, due to all the installation failures I am called on to inspect, I must stress the importance of this vital step.
Of the many stages of any flooring installation, substrate preparation is the most important. The prep work you complete (or don’t complete) can make or break your finished installation—as well as your reputation.
Whether the substrate is wood or concrete, it will need an evaluation prior to laying down the first plank. This includes a visual review, condition of the workspace, and condition of the substrate surface. Substrate preparation will be based on the results of these evaluations and the moisture testing that has been performed.
In the case of a wood substrate, sand and fill the surface as needed. If a self-leveling underlayment is needed, ensure you coat the wood surface with a primer and, if required, a mesh to hold the self-leveler in place. Keep in mind, the manufacturer’s guidelines for installation and maintenance should supersede all other publications, no matter what industry expert or trade organization may have published them. Do not install over an existing finished wood floor; this is a manufacturer guideline as well.
For acceptable surface flatness, each manufacturer will have a variable they approve, such as 1/8“ in 10’ or 3/16” in 10’. Ensure you follow manufacturer specifications; planks are not designed to span a depression. They will move vertically, and the click system will become damaged. This vertical movement will also cause glue-down applications to fail.
Grinding the concrete surface to a CP2 or 3 profile is normal. This will allow the concrete to absorb the moisture barrier and any cement patch used. During this floor preparation stage, I would suggest product acclimation under a HVAC operating system for a minimum of two to three days. While it may not be required by the manufacturer, this step can help eliminate future issues.
When installing the floor, you must start in a straight line, and square off a start wall. Keeping in mind the proper distance between end plank seams (usually a minimum of 6”) will provide a stable interlocking and integral system. Layouts resulting in “H” plank seams, or a step pattern should not be used, as these could negatively affect the floor’s integrity. Look to manufacturer guidelines for suggested patterns.
Keep the expansion space continuous around the perimeter and keep the planks equal in line along the vertical. One plank touching the vertical can create a negative issue in that row. The same rule applies for columns. Don’t use erratically cut or wildly different lengths along the vertical, which can contribute to peaking of the planks and other issues.
Use the same caution for transitions. An end molding is required for expansion space, and at some junctures an expansion T molding may be needed. Do not glue or nail moldings on top of or through planks. This will restrict movement and cause other problems.
Cupping—or any physical change from a flat appearance—can be attributed to HVAC conditions and ambient interior conditions such as the temperature, relative humidity and dew point. Vertical restriction of movement can also cause cupping issues. This condition may also be related to manufacturing process.
A convex physical change is called doming and is akin to crowning in wood. While this too can be site-related, it can also be a result of the manufacturing process.
Once again, reading and understanding the manufacturer guidelines is imperative. If there is a site issue, call the manufacturer. Get their direction and keep good records of site issues, any testing you perform and multiple photos of the “before, during and after” of the installation process.