*This article by INSTALL executive director David Gross was originally featured in The Construction Specifier.

Not What It Seams: Educating Specifiers About Heat Welding and Why It Matters in Healthcare Flooring 

Heat welding resilient or vinyl flooring seams may appear to be a straightforward task that any installer can perform, but in a healthcare environment, this skill is anything but incidental.  

Joining two sheets of flooring material with a perfect heat weld that is visually imperceptible  and impervious to moisture and dirt  collection requires a specialized set of practiced skills. From fresh-edge cutting, net-fit tolerances, and controlled grooving, to post-weld skiving and flash coving, every step impacts the integrity of the final seam and flooring performance, and healthcare environments leave no room for errors. 

For specifiers, understanding what it takes to properly execute heat-welded seams is essential to selecting a qualified installer. To educate specifiers on important aspects of the process, and alert them to areas where installers may misstep or shortcut best practice, the following overview explains what specifiers need to know about heat welding to ensure their floors, and their installers, meet the high standards of healthcare. 

It Starts With a Fresh Edge 

The first step for an installer in achieving a successful heat-welded seam is cutting a fresh edge on the material before it is adhered  to the floor. When a sheet good is delivered to a jobsite, it is typically on a six-foot wide roll that can be up to two feet in diameter, and the roll is commonly stored upright on its end, not flat on the floor. A vinyl roll can weigh well over 250 pounds, depending on the product type.  The pressure of that weight can compress the edge of the roll that is in contact with the floor, creating damage and changing its shape. The material may be thinner along that edge or bowed in a concave or convex direction.  

To remove these irregularities, best practice is to use a straight edge or edger tool to remove roughly half an inch of material along this edge to give it a clean, uniform shape and thickness. This is a logical first step in setting up the conditions for a strong, clean weld. Surprisingly, it is also a step that is often missed by installers who either don’t know they should do it or who skip it to save time on the job. In both instances, failing to cut a fresh edge puts the heat-welded seam at risk right from the start, as the installer will then be trying to join two unmatched edges.  

If one edge of the material is thicker than the other or if it is bowing in places, these conditions can lead to misalignment of the flooring material and create a cascading series of issues affecting the subsequent grooving, welding, and skiving steps. Installers who take the time to cut a fresh true edge (and know that this is a best practice in the first place) set up the material for success at the start of the process.  

Minding the Gap 

After cutting a fresh edge and before grooving, the resilient or vinyl sheet flooring must be installed with a true net fit for the weld rod to make optimal contact with the flooring material.  

True net fit describes the actual fitting of the sheets so that its seam edges are freshly cut, aligned, and placed to the precise spacing specified by the manufacturer, typically around 1/32 of an inch. It is a controlled fit that avoids both excessive gaps and overly tight joints. True net fit ensures sufficient material remains after grooving, which is the next step taken to create the U-shaped channel to accept the weld rod. Most manufacturers specify a ½ to 2/3 deep groove centered to the adjoining sheets.  Strict adherence to this tolerance is essential for the heat weld to create the structural integrity of the seam.  

When seams are heat-welded along gaps that are too wide, the subsequent grooving operation is difficult to center and provides insufficient sidewall and bottom contact for the weld rod to properly fuse. In these cases, the weld lacks an adequate bonding area, significantly compromising seam strength and longevity. 

Conversely, when the seam edges are too tight and the material edges are butted together, a different set of problems is introduced. Some untrained installers believe tight installation preserves material mass, but more often it produces peaked seams that make it difficult for mechanical groovers to maintain a consistent groove depth. This increases the chances of tool runoff, uneven groove geometry, and damage to the surrounding seam edges—all of which negatively affect weld quality.  

Beginning an installation with a true net fit that follows manufacturer specifications sets up the seam for more precise grooving, welding, and finishing. 

Skiving: It Takes Two 

Once the flooring is properly cut and fitted, the installer grooves the seam to receive the weld rod and then melts and fuses the weld rod into the channel using a heat-welding gun. When seams are correctly fitted, uniformly grooved, and welded with proper heat and travel speed, the weld rod achieves a strong bond along the bottom and the sidewalls of the groove.  

Because the weld rod is cylindrical, a portion of the rod remains above the sheet flooring surface after welding. [See illustration.] This excess material is then skived, or trimmed down, so the weld rod becomes level with the two sheets that it is joining to create a flat and uniform finished surface.  

Certified installers are taught that best practices for skiving the weld rod is to perform it in two distinct passes that result in a weld that is on plane with the flooring surface. During the first pass, installers attach a spacer to the skiving tool. This first pass removes approximately one-half to two-thirds of the excess weld material. Precision in this step is critical, as slicing the weld rod requires measurable downward force, regardless of blade sharpness, due to the volume and geometry of the material. This force inherently causes a slight upward deflection or lift in the seam that the installer must accurately account for when performing the pass.  

After removing the bulk of the material in the first pass, the force required for the second pass will be  significantly reduced. This lighter touch will create less lift during the final pass and leave the weld rod flush with the flooring surface. When the weld rod is properly coordinated with the installed material, the resulting seam should be visually imperceptible, meaning no visible distinction and no raised or recessed area at the seam.  

Some installers without specialized heat-weld training shortcut the skiving step by performing only one pass with the skiving tool. To compensate for skipping a pass, installers will often place excess pressure on the skiving tool and take off too much material at once, believing the single pass is more efficient.  This causes the seam to lift more drastically during cutting, and when it settles back into place, the trimmed weld sits below the finished surface. This results in a concave seam profile that readily traps dirt, contaminants, and moisture. Such seams typically fail visual acceptance criteria and result in difficult, if not impractical, repair scenarios that can disrupt the daily operations of the healthcare facility. In worst cases, poor skiving will escape early detection and become a problem as the floor is being utilized and the seam starts to collect dirt and is difficult to clean.  

Ironically, single-pass skiving does not result in meaningful time savings for the installer or the project at large. Any perceived efficiency is quickly negated by increased rejection risk, corrective labor, and damage to reputation and client confidence.  

Comparatively, following best practice and performing two-pass skiving requires a minimal time commitment, especially when compared to rework time.  

And Then, Flash Coving 

For a healthcare facility, flooring that fails due to inadequate knowledge and deficient skills for heat-welded seam construction can mean disruption of patient services and costly downtime. And heat welding is a very common and critical component of a typical healthcare flooring installation.  

Even more demanding in precision and technique is flash coving, also known as integral base installation, which requires its own set of highly specialized skills. Flash coving is a type of installation that utilizes the heat-welded seaming principles of flat seams and applies them in continuation along with the flooring material up the wall four inches or more.  The resilient flooring is therefore serving not only as the flooring material but also as on-cove base material.  

Flash coving installations require a host of additional considerations, including: maintaining a visually consistent and straight wall line termination, assuring the material is firmly adhered to the radius at the floor-wall junction, tending to the special demands of inside and outside corners, and navigating floor or wall penetrations. It is highly visible, unforgiving of shortcuts, and notoriously difficult to repair. This type of installation is very common in the most sensitive and high-stakes healthcare spaces, such as operating rooms, ICUs, and laboratories where cleanability, durability, and long-term performance are critical.  

The second article in this two-part series on heat welding will explore flash coving in greater detail.  

Avoiding the Emergency Room: Tips for Specifying Healthcare Flooring Contractors  

Successful flooring outcomes for healthcare projects go well beyond selecting the right materials. Specifiers also need to vet their installers for verified manufacturer certifications, documented training, and proven competency in healthcare-specific installation practices.   

One of the most recognized and respected certifications for healthcare installers in addition to flooring acumen is Infection Control Risk Assessment (ICRA). ICRA training teaches installers how construction activities, even those as localized as flooring preparation and seam welding, can introduce contaminants and pathogens into healthcare environments. ICRA-certified installers understand how to classify risk areas, establish contaminant barriers, control airflow and dust, manage debris removal, and coordinate their work with infection prevention teams. They are also trained to perform installations in occupied facilities without compromising adjacent patient care spaces, a skill that is essential amidst the boom of expansion and renovation occurring within our aging healthcare infrastructure.  

Flooring installers who also possess specialized healthcare training bring a fundamentally different mindset to the jobsite. They recognize that a failed seam is not just an aesthetic or warranty issue but a potential infection reservoir. This awareness influences every step of their installation process, from substrate prep and seam geometry to heat welding and flash coving. Certified installers have taken the extra steps to demonstrate a commitment to industry’s established standards, and their certification acts as an insurance policy for the installation.  

Ultimately, heat-welded seams that perform in healthcare environments are the result of deliberate skill, training, and discipline. By looking beyond product selection and asking informed questions about installer training, certification, and healthcare-specific experience, specifiers can better align design intent with field execution. The reward is flooring that supports infection control goals, withstands rigorous cleaning, and delivers long-term performance without surprises after turnover.

Author’s note: This article is one of a two-part series on heat-welding techniques used in healthcare resilient and vinyl flooring installations. Part two will explore flash coving, providing specifiers with an introduction to best practices, cautions on where flash coving can go wrong, and tips for how to select an installer with the right skills for success. For additional information, refer to manufacturer recommendations and/or ASTM F1516.