The latest resilient product category that everyone in the industry seems to be talking about is rigid core. Known by many names including WPC, SPC, waterproof core, multilayer flooring and more, this type of product is a close cousin to luxury vinyl in its looks and durability. But there the similarities end. We spoke with several manufacturers to learn the ins and outs of this category, how it performs compared to luxury vinyl and—most importantly—how to install it.

According to David Altman, Metroflor’s director of research and development, the number of names associated with rigid core products has caused “mass confusion” within the industry. The Multilayer Flooring Association (MFA) was formed in 2016 to help bring clarity, he noted.

“After many discussions within the MFA Technical Affairs Committee (TAC) and considerable industry consultation, the MFA board of directors unanimously agreed upon two category names to describe rigid products in the multilayer vinyl flooring category. The categories are defined basically by the type of core makeup within the product.

“WPC represents the class of rigid vinyl flooring products with an expanded or foamed polymer core. Originally called ‘wood plastic core’ or ‘wood polymer core,’ it is often referred to as waterproof composite or core. SPC products refer to the class of rigid vinyl flooring products with a solid polymer core.”

While both WPC and SPC are both part of the rigid core product family, each flooring type has significant differences, Altman stated. “Generically speaking, the typical construction of WPC products includes an expanded or foamed core, topped with a vinyl layer, design layer, wear layer and finish top coating such as UV cure urethane. Think of it as an extruded core with an LVT layer bonded on top. Many WPC products include a pre-attached underlayment to aid in underfoot comfort and to provide better sound properties.

“The SPC core has a much higher concentration of limestone, less polyvinyl chloride (PVC), and is not expanded by the use of foaming agents. SPC construction thermally fuses the design layer directly to the core, eliminating the vinyl layer that’s used between the design layer and core in WPC construction. Typically SPC products are thinner, denser and heavier than WPC.”

Other general considerations that Altman shared: WPC’s foamed core reduces weight, providing more quiet, warmth and comfort underfoot than SPC; SPC is harder to cut than WPC but also more dent- and impact-resistant; both products are waterproof and hide minor subfloor imperfections, and both can be installed in larger areas than laminate or floating vinyl floors before T-moldings are required.

John Jarvis, Karndean’s technical supervisor – field services, stated that while the MFA recognizes WPC and SPC categories, ASTM recognizes one overall rigid polymeric core category. “In general, these products are defined by the amount of limestone within the core, but because this category is so new it’s important to check the technical specifications of a particular product before specifying or installing to ensure that the product will perform exactly as you want it to, as there are variances in product thickness, flexibility, etc.”

Natalie Cady, Shaw’s resilient category manager, said the lighter and softer feel of WPC makes it ideal for residential settings, while SPC’s density makes it great for commercial and Main Street applications. “However, both WPC and SPC are excellent flooring materials, as they both are rigid and waterproof.”

According to Jeremy Kleinberg, Armstrong senior product manager, rigid core products are engineered to help solve problems that traditional LVT cannot. “For example, rigid core products are easier to install over imperfect subfloors and are less likely to show subfloor irregularities. Rigid core products are also waterproof and water-resistant.”

Ben Korman, Tarkett North American senior product manager, noted that WPC offers “a similar thickness and durability to laminate products but is significantly lighter, while SPC offers a similar durability and profile but is made heavier with additional fillers.”

Installation Tips

Altman said while WPC and SPC are both installed with click locking systems, be sure to consult manufacturer directions first. “There are several types of click locking systems on the market (i.e. angle/angle vs. angle drop), and these require specific application methods and techniques to ensure a connection without compromising or breaking the joints.”

While rigid core products will work with minor subfloor imperfections compared to LVT and glue-down sheet vinyl, any abrupt changes in height along the subfloor will cause the flooring to fail. Altman noted, “A substrate that is too uneven may create a trampoline effect when walking on the floor. Over time, this bouncing or vertical movement could cause the floor to unclick and/or break the joints.”

He added that expansion space for rigid core products is typically 1/4 in. around all walls and fixed objects, but “may vary by product or areas of usage such as commercial, residential or three-season rooms. Additionally, some manufacturers may allow material to be installed underneath residential kitchen cabinets so long as they are not anchored through the flooring and into the substrate.”

Jarvis explained how to install Karndean’s Korlok Select and Korlok Reserve products. “Korlok Reserve has the patented and proven 2G locking mechanism, which is an angle-to-angle lock. Korlok Select is equipped with the HoldFast 5G drop and lock mechanism, which uses a single action installation method to facilitate an even faster install. Neither a hammer nor a mallet is required to secure Korlok planks in place.

“Korlok products require a 3/16 in. expansion gap around the perimeter and every 50 linear ft. in each direction in spaces up to 1,000 sq. ft. For areas larger than this, increase the expansion gap to 5/16 in. Waterproof, 100% PVC K-Core technology within Korlok allows for installation over most hard surface floors, including ceramic tile (so long as the grout lines are 3/16 in. wide or less).

“SPC and WPC ... can be installed without acclimation, making them an excellent choice for projects on a quick timeline.”

– Natalie Cady

“In addition, Korlok can be cleanly scored and snapped and the pre-attached acoustic foam backing will not flake apart on the job site, allowing for a clean installation.”

Cady said one of the benefits of rigid core products is the minimal subfloor prep. “Planks lock together and can be installed above existing flooring. An even greater benefit of SPC and WPC is that the products can be installed without acclimation, making them an excellent choice for projects on a quick timeline.”

Kleinberg noted of Armstrong’ Pryzm rigid core flooring that “flooring contractors can get started installing right away—no acclimation time is needed in most installations. Its innovative reinforced thermoplastic core enables a smooth installation over subfloors with irregularities and the installer can span large areas without the need for transition strips. The planks are backed with an acoustical cork underlayment for greater sound absorption.”

Korman added, “All these products have similar installation methods, since most of them are designed to be floating floors with click systems. Rigid core is a more forgiving material to work with than glue-down options.”