The largest selling resilient flooring product in terms of square footage is Vinyl Composition Tile or VCT. It's inexpensive to buy and easy to install but like any other flooring product there are ways to do it well and ways to cut corners so the installation will not be as good as it could be. I see a lot of VCT installations in my travels, from schools to supermarkets to big department stores. I am amazed how sometimes I see a job that looks great - with nice tight seams and a smooth surface, and other times I see floors with gaps, cracks and bumps and I know that the installer was probably under the gun and had to get the job done quickly without proper preparation or testing. Here are some hints for a successful VCT installation, and some feedback from two of the most knowledgeable "tile guys" in North America.
Solid Vinyl, or SVT has higher vinyl content than VCT and is another category altogether. The term "Luxury Vinyl" has created unnecessary confusion in the industry. The fact is, there is not an industry standard for LVT. Some solid vinyl tile products that imitate wood, stone and other materials are often called LVT. However, there are also products marketed as LVT that are residential grade and are actually VCT because they don't have enough vinyl content to be called SVT. So, "Luxury Vinyl" can be SVT or VCT. The manufacturers would do the industry a favor by clarifying this difference in their marketing and sampling. I've covered solid vinyl in past columns, so for now we'll talk about the entire VCT category
To make sure the floor is smooth ASTM F 710 says, "Surface cracks, grooves, depressions, control joints or other non-moving joints, and other irregularities shall be filled or smoothed with latex patching or underlayment compound recommended by the resilient flooring manufacturer for filling or smoothing, or both. Patching or underlayment compound shall be moisture-, mildew-, and alkali-resistant, and, for commercial installations, shall provide a minimum of 3000 psi compressive strength." Check with the VCT manufacturer to see if they have specific product recommendations for floor preparation. Above all, make sure the substrate is very smooth before you start laying the floor. Any dips or low spots in the floor can be a cause of bubbling or cracking after installation, as can installing over expansion joints or trench cuts in the floor where the concrete is not yet dry.
Another area of concern in regard to floor preparation is removing old tile and dealing with the adhesive residue. In his July, 2000 article for FCI, Ray Thompson talked about one of the challenges in renovation projects, which is what to do about old black cutback adhesive. "It depends on the circumstance. A cutback adhesive that is active (not scaly or poorly bonded) can be scraped down to a thin residue, and a clear thin-spread can be applied directly over the residue. Do not apply a cutback adhesive over a cutback adhesive, as they tend to create excess and will bleed." Ray makes a good point about bleed through, which can happen when there is a concrete moisture problem, when excess adhesive is applied because of too large a trowel notch, or when new adhesive is applied over old adhesive. Although many adhesives available today say "can be used over old cutback", if you do this it needs to be done right. I tend to be pretty conservative with my recommendations in this regard and I have a simple rule. If it's black adhesive, scrape it down to a thin transparent residue and then "skim coat" with a good quality cement based patching compound that is made for going over cutback residue. If it's not black, it must be completely removed from the floor. Whatever you do, don't just remove the old tile and skim coat over what's there, or apply adhesive over what's there.
Once the issues of testing and preparation are addressed, spreading the adhesive is next. One thing a lot of installers tell me they like about VCT installation is that large areas of adhesive can be spread at one time and there is a very long working time so you don't have the "stop and start" that you do with wet lay adhesives. However, some of the vinyl enhanced, premium or other high-end VCT products are installed more like SVT and use a variation on the wet lay method of installation. Check the installation specs, because these products usually don't get installed with standard VCT adhesive so there may be a higher cost for adhesive and more time needed for installation.
Depending on the job, you have several choices in adhesive for VCT with regard to open time and working time. Open time is how long the adhesive stays open to the air after you spread it and working time is how long you have to cover it once the open time has expired. Some VCT adhesives, such as acrylics and epoxies, have short open times and working times, and are a "wet lay" installation. Other "thin spread" adhesives have open times of 30-60 minutes and working times of 6 to 24 hours. Make sure you match the adhesive you are using to the type of installation you are on. Even with adhesives designed to have a long working time, I prefer not to leave adhesive over night because it will attract dust, dirt, and worse when nobody is there to keep an eye on it. Pay attention to trowel notch size as well when you are looking at adhesive selection for VCT. Some adhesives are designed to go down with a fine notch (1/32-inch) and others a larger notch (1/16-inch). More is not better! Too much adhesive can cause bleed through, tile shifting, cracking, or indentations. Another point that gets missed is rolling the floor. Some adhesives require it and some do not. Don't forget to roll the floor if the instructions call for it because failure to do so can mean a very weak bond to the substrate.
Once you get into laying the tile, "run off" is a big problem for a lot of installers. Ray Thompson listed three causes of this. First is the flatness of the substrate. "The more undulation there is in the surface of the floor, the more the tendency for the tile to run." Another cause, Ray said, is the way the installer sets the tile into the adhesive "The installer needs to be aware of the tile joints during the installation by keeping the opposing corners aligned. Installers may pull the tile during the installation because they hold it by the corner, twisting and moving it out of alignment. The tendency is for a right-handed installer, holding the tile by the right corner, to pull the right side of the tile in tighter than the left side. A tile needs to be held in the center." Finally, tile run off often gets blamed, incorrectly, on the tile being "out of square", but, Ray says "It has been my experience that tile is rarely out of square, but often gets the blame for the above two reasons."
John Kozak also had some feedback on this subject, saying "As in all things, correcting the situation before it gets out of hand is important. Make sure while installing to follow your accurately placed layout lines. It is more important to be sure the lines are followed rather than letting the tile guide you while installing." What about "correcting" the tile if it starts to run off? "Small corrections while working can keep run off under control," Kozak said, "Making an occasional cut-back or leaving out a tile and doing a sweat-in when needed also helps." By "cut back," John means stopping and cutting the tile a small amount to create a straight line again. A "sweat-in" means to skip a tile or tiles, start a new straight row, and then heat up tiles to fit into the slightly smaller space that is left.
Some of these practices add time to the job, but like all of the other details we have mentioned here, a little extra time spent can make the difference and give the owner a good looking finished product that is flat and tight.