ASTM F 1700, Standard Specification for Solid Vinyl Floor Tile* classifies SVT in three categories – Class I Monolithic, which means through color tile with no backing; Class II Surface Decorated, which usually means an “inlaid” type tile with a backing, and Class III, Printed Film Vinyl Tile, which is a photographic print film with a clear vinyl wearlayer and a backing system. A minimum wearlayer thickness of 0.020” (20 mils) will classify the Class III product as “Commercial”.
ASTM F 1066, Standard Specification for Vinyl Composition Floor Tile* also has three different classifications; Class 1 for solid tile, class 2 for through pattern tile and class 3 for surface pattern tile where the top layer is at least 0.01” thick. It is important to note that many products sold as “Luxury Vinyl” may or may not fit into one or the other of these categories. There is no definition for “LVT” despite the fact that dozens of manufacturers and journalists continue to use the term. Generally, what is called “LVT” is a patterned, decorative product such as wood look vinyl plank, stone, marble and granite looks that may meet F 1700 Class III, OR VCT – type products with a decorative top layer that don’t have a high enough vinyl content to be SVT and might be meet F 1066 Class 3, or may not if the top layer is thinner than 0.10. ”
Confused? Imagine how people who are not in the floor covering industry feel. A designer or architect has a sample of “LVT” and would like to use it on a project but has no details on the product to see if it is rated for the intended use. That is why I originally titled this column “LVT? No such thing!” As long as the major resilient manufacturers and even some of my fellow journalists continue their obsession with the term “Luxury Vinyl,” this situation wont get any better.
Enough about all that! Let’s talk installation. SVT installation is often different from VCT, and failure to understand that is the cause of many failures. Here are some examples:
Adhesive selection: For trowel applied adhesives, “Clear Thin Spread” is the most commonly used product for Commercial VCT and installers usually like working with this product because of its long working time - you can put adhesive down over large areas, and after waiting for it to turn clear and dry to the touch, there are several hours of working time to get the tile in place. This is also known as a “pressure sensitive” process. Although some SVT products are now also able to be installed with a pressure sensitive adhesive, it is not the same adhesive product, so don’t be tempted to use VCT adhesive on SVT. I’ve inspected several failures where that happened and the SVT curled and/or shrunk in such cases. When the adhesive was tested and found to be the wrong one; the installer was responsible for the complete replacement of the job and it was a very expensive mistake.
Trowel Notch:You should purchase new trowels with the appropriate notch size for the adhesive, the substrate and the tile you are installing. SVT adhesive will often be applied with a finer notch trowel than the standard VCT or carpet adhesive. So what’s the big deal? A little extra can’t hurt, right? Wrong! Too much adhesive can lead to failures such as adhesive oozing, tiles shifting or indentations in the finished floor, so do not fail to pay attention to this detail. A good trowel costs no more than 2 cents per square foot and that is an important investment. Bottom line on adhesives is to match the adhesive and the trowel to the product; the substrate and the expected traffic load for the finished floor and quote the job accordingly.
Site Conditions and Moisture Testing: A common assumption is that VCT is somehow more moisture tolerant than SVT or that it “breathes.” Neither of these assumptions is true, although we are seeing adhesives with moisture limits that are getting higher and higher. Regardless of what floor covering you are installing – resilient, carpet, wood, tile or stone - you need to be sure the slab is tested for moisture. ASTM F 710 Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring* says, “All concrete floors shall be tested for moisture regardless of age or grade level,” so don’t skip this part of preparation. The substrate needs to be dry, smooth, solid and dimensionally stable. Make sure you are installing in a building that is climate controlled. The product, the adhesive, the moisture testing and the surface preparation will not be at their best if they are used in very cold or very hot conditions. If you are installing over concrete, make sure that moisture testing has been done and that the slab meets the requirements of the adhesive and/or the flooring manufacturer.
Substrate Preparation: Resilient flooring will conform to any irregularities in the substrate, and Vinyl tile is no exception, so floor prep is key to success. Take extra care to be sure the substrate is smooth by installing the proper underlayment or patching compound to smooth the existing surface. This is especially true on smooth and/or dark color tile. This is a good example of knowing the product before you install it. Textured resilient flooring is more forgiving of slight irregularities in the substrate then smooth products are, so it may take a little extra time for surface prep with these smooth products.
Adhesive Open Time: Before you start to spread adhesive, make sure you are comfortable with the required amount of open time so that you can lay out the job and spread the right amount of adhesive at a time. This is especially true on the wet lay or semi wet lay adhesives often used with SVT. Leaving too short an open time may cause poor bond and more chance of tile shifting or adhesive oozing up between the tiles. Allowing too long an open time may mean the tile might adhere initially but the long term bond strength will not be good. Open time can be affected by temperature and humidity so it should be checked on a job-by-job basis. In dry warm weather the open time may be shorter and in humid weather it may be longer. Adhesives with a shorter open time requite that the installer spread small areas of adhesive at a time.
Spreading the adhesive and rolling: When installing VCT, you lay into “dry” adhesive, where large quantities are spread using a 1/16” square notch trowel, and allowed to “tack up” so they are dry to the touch and do not transfer to the back of the tile. Generally SVT needs a harder setting adhesive such as a “wet lay” acrylic or a reactive adhesive, which often are applied using a smaller trowel notch such as a 1/32” notch. “Wet lay” adhesives must be spread in small areas at a time, covered within the recommended open time (usually 15-20 minutes), and rolled with a 100-lb roller. There should be transfer of adhesive to the back of the tile and the trowel ridges should be flattened out. If the open time is too long these adhesives “skin over” and won’t transfer to the back of the tile. If this happens, the adhesive must be scraped off the floor. If they are not rolled, the tile sits on top of the adhesive but is not fully adhered. In both cases, there may be enough tack to hold the tile down but the bond will not be nearly as strong so the floor may develop gaps over time. If the floor fails on a wet lay installation, the cause can be diagnosed by lifting a tile. If trowel ridges are visible and/or there is no adhesive transfer to the back if the tile, it’s a good bet there was too much “open time” so the adhesive “skinned over,” or the floor wasn’t rolled. Another type of SVT adhesive is a “semi wet lay” or “tacky lay” type, where the adhesive is left open long enough that it develops some tack, is still wet, but is not open long enough to turn clear. The best way to tell if this type of adhesive is ready is to touch it lightly with a finger. If you get a “smudge” on your finger it is not ready. If you see lines from the trowel notching then it is ready. Set the tile and roll it with a 100-lb roller.
After installation: Once all of the tile is laid, check for any loose or popping tiles and if there are any, weigh them down so the tile and adhesive will be in full contact with each other when the adhesive sets. This weight can usually be removed after 12 hours or so. Check the flooring and adhesive manufacturer’s recommendations for how long to protect the floor from traffic. When in doubt, prevent all foot traffic for the first 12 hours and allow light foot traffic from 12 to 24 hours. As far as rolling traffic and furniture, that may depend on the adhesive. Generally I would recommend preventing rolling traffic for 48-72 hours after the tile is set.
Protection: If there will be construction on the floor after installation it should be protected from damage. Tools, ladders, carts and the like can make permanent indentations if they are allowed on the floor while the adhesive is still wet. Wait 24-48 hours for the adhesive to set up, then sweep the floor and cover with brown Kraft paper and ¼” or thicker panels of plywood or hard board. Don’t use colored paper because it can stain the floor if it gets wet and don’t use plastic because it may hinder adhesive drying. Also, don’t put the panels directly on the floor because they may scuff or scratch it. Put paper down first.
As the categories get blurry it pays to take a little extra time before you work with VCT or SVT; check the adhesive and trowel notch recommendations and don’t assume if it looks like VCT and smells like VCT that you install it the same way. The term “LVT” has created some confusion in that regard so be sure you have the right procedure in place before you get started.