By Jeffrey B Johnson, FCIS Business & Marketing Manager, MAPEI Corp.
Luxury vinyl tile (LVT) has become one of the most widely installed resilient flooring categories in North America and Europe. Its combination of design versatility, durability and cost‑effectiveness has made it a preferred choice for both residential and commercial environments. Yet beneath its popularity lies a persistent technical challenge: dimensional stability. LVT is a thermoplastic composite, and like all thermoplastics it responds to environmental forces—temperature, humidity and mechanical stress—with measurable dimensional change.
Dimensional stability refers to a material’s ability to maintain its original size and shape when exposed to environmental or mechanical forces. For LVT this includes linear expansion and contraction, curling/cupping, gapping/peaking at seams and shear creep under load.
LVT is primarily composed of polyvinyl chloride (PVC) blended with plasticizers, stabilizers, fillers and pigments. PVC is inherently rigid, but plasticizers make it flexible and resilient. This flexibility is desirable for comfort and durability, but it also makes the material highly responsive to temperature changes.
PVC’s coefficient of thermal expansion (CTE) is significantly higher than that of ceramics, wood or rigid core flooring. As temperatures rise, the polymer chains gain mobility and expand; as temperatures fall, they contract. This expansion/contraction cycle is the root of many dimensional stability issues.
Additionally, since PVC’s CTE is 5-10 times higher than concrete, even small temperature changes can create significant shear forces at the adhesive interface. Large-format planks amplify this effect: a 48” plank experiences twice the linear expansion of a 24” tile under the same temperature change.
Modern LVT is made of a laminated structure usually including a wear layer, printed film, PVC core, fiberglass scrim (in some constructions) and a backing layer. As these layers expand or contract at different rates, internal stresses can develop and manifest as curling (edges lifting), doming (center lifting) and shear slip between layers. Fiberglass scrims are often added to reduce movement, but they do not eliminate it.
The primary environmental factors influencing LVT movement are temperature swings (HVAC setbacks, sunlight exposure and radiant heat), moisture changes (subfloor moisture and humidity), and mechanical loading (rolling and point loads). Temperature is the most significant; a swing of 20-30°F can produce measurable dimensional change, especially in large-format planks.
Dimensional instability within the LVT itself arises from a combination of material science, manufacturing variables and installation conditions. While plasticizers are essential for flexibility, they are not permanently bound to the PVC matrix. Over time they can migrate into adjacent layers and the adhesives or out of the product entirely. Plasticizer loss increases stiffness and reduces flexibility, altering the product’s response to temperature and stress. Migration into adhesives can also soften the adhesive film, reducing its ability to restrain movement.
LVT can also be influenced by variations in manufacturing. Even small deviations in factors including core density, plasticizer type/loading and scrim placement can create tiles that behave differently once installed. That is why maintaining the subfloor temperature is critical. Installing LVT on a cold slab that later warms can create post‑installation expansion, leading to peaking or tenting. Conversely, installing on a warm slab that later cools can create gapping.
It is extremely important for the installer to exercise as many installation controls as possible, including acclimating the product and controlling the temperature before, during and after installation. Limit the amount of direct sunlight reaching the floor; UV radiation will increase the internal temperature of the material and cause it to expand. Lastly, select an adhesive with the appropriate shear strength that matches the environmental conditions to which the floor will be exposed.
Understanding PSAs
Pressure‑sensitive adhesives (PSAs) are widely used for LVT because they offer releasability, moisture or humidity tolerance, ease of installation and better resistance to plasticizer migration. But PSAs are often misunderstood. They are not mechanical anchors; they are viscoelastic films whose performance is governed by glass transition temperature (Tg), modulus and creep behavior.
The Tg is the temperature at which the adhesive transitions from a glassy, rigid state to a rubbery, flexible one. For PSAs, the Tg is typically well below room temperature (‑20°C to +10°C), ensuring tack and flexibility. If the ambient temperature is below the Tg, the adhesive will be stiff, brittle and glass-like with extremely high modulus (inherent stiffness). Conversely, if the ambient temperature is above the Tg, the adhesive will become soft and tacky, with very low modulus or shear strength—meaning a higher potential for creep.
The good news is most of the PSAs used for LVT operate far above the Tg, meaning they are in a rubbery state during service. Those with long working times and super aggressive, sticky films typically have very low Tgs, meaning the polymer films are going to be much softer and more prone to creep. On the other hand, LVT adhesives with shorter working times and not as aggressive tack may have higher Tgs and greater shear strength.
A well‑formulated PSA can resist moderate shear forces, minor gapping and peaking and tile drift under rolling loads. This is especially true when the adhesive includes high‑Tg polymers, reinforcing resins or crosslinking agents. PSAs excel at stress relaxation. They can absorb small dimensional changes without debonding or telegraphing stress into the tile.
However, it is important to note PSAs cannot stop thermal expansion of the flooring materials. If a 48” plank wants to grow 1/8” due to heat, the adhesive cannot prevent it—the PSA can only modulate the rate and direction of movement. That said, it cannot prevent movement when the ambient or surface temperature exceeds design limits. It also cannot compensate for poor installation conditions. Cold slabs, unacclimated material or large temperature swings will overpower any PSA.
The relationship between LVT dimensional change and a PSA’s Tg is dynamic. As temperature rises, LVT expands and the PSA softens. As temperature falls, LVT contracts and the PSA stiffens. This creates a double‑amplification effect. At elevated temperatures, the tile wants to move more, and the adhesive resists less. At low temperatures, the tile wants to shrink more and the adhesive resists more—sometimes causing stress concentrations that lead to curling. This interplay is why temperature control is the single most crucial factor in LVT dimensional stability.
Use adhesives with appropriate shear modulus. This might mean forgoing the ease of PSAs. Water-based, acrylic adhesives with high Tgs can only be installed into while wet; they dry into a hard, glass-like mass which is not nearly as affected by changes in temperature as their PSA cousins. Reactive adhesives—such as epoxies, polyurethanes or modified silane products—create thermoset bonds which are unaffected by changes in temperature. They should be used in areas where the ultimate in bond and movement control are required.
