The definition of porcelain tile is simply that it has less than .5 percent absorption. That makes these tiles very strong and dense. Because they are so dense they can be left unglazed and used on the floor. As they have no glaze to wear out they will stay the same color and appear the same for generations to come. One of the misconceptions that persists is the durability of glazed porcelain. When a porcelain tile is glazed it is the glazed surface that takes the wear, not the body. There are glazed porcelains (porcelain tiles) on the market that are only suitable for light duty or residential. Granted, this is not the norm, but they certainly are not unusual to find. On the other side of the spectrum we see double-charged porcelain tile where the effects we typically have only seen in glaze tile are being created by the addition of pigments to the second layer and then fused into rather than on the body; double charging is more for the infusion of stain resistance than it is to infuse a different color.
You cannot write an installation article without talking about thinset coverage and that is where we are going to start. As long as I have been doing this it never ceases to amaze me that some do not see the importance of this issue. You cannot believe what a difference this makes to the performance of the installation, even in instances where it probably should not have been installed in the first place. Time and time again we see failures where you can see all the ridges on the back of the tile. We do a demonstration to show the difference between full and partial coverage as part of our training classes. We can take any substrate you desire, give tile 100 percent coverage and carve a hole in the tile without cracking. Something we hear often is, "Well the instructions on the bag said use xx notch with xx tile." Instructions on the back of the bag are a guideline to give a general idea of what is recommended. The thinset manufacturer has no way of knowing what type of back the tile has which can drastically affect the size notch needed. Coverage of 80 percent minimum is the rule, not notch size; more is better.
Cutting porcelain can be a challenge, especially if you want to score and snap the tile. Porcelain comes in a seemingly wide variety of hardness. But, there are many scoring cutters that will do the job even on textured porcelain. The ones that work best are on the pricey side typically and even then, some are better than others. We receive a lot of discontinued tile for our training programs so we always have a wide variety available. Before I had access to all these wonderful tools, while I was contracting, we would always run for the wet saw whenever we had a porcelain tile job. If I knew then what I know now, I could have made a lot more money in much less time. Do they work all the time? No, but I am hard pressed to think of more than a half dozen instances in the last six years where I could not score and snap a porcelain tile acceptably enough for a wall cut. In demonstrating these tools on a regular basis I can also tell you it takes a certain touch to be successful. People tend to score way too hard and take too much time before they snap the tile. I demonstrate scoring with a two-finger hold on the scoring tool and give the breaker a little slap to snap the tile. If you have a good wheel it works, try it. Speaking of cutting wheels, they are not all created equal either; that can be a problem all by itself.
When it comes to setting porcelain tile a few things come to mind. Narrow joints seem to be the rage these days. All tiles vary in size, some more than others. Porcelain tile like all ceramic products shrinks to size when it is fired in the kiln. Production equipment comes into play to a certain degree as newer equipment and technology has given manufacturers a much better ability to hold tighter tolerances. Quality control determines what goes in the carton you receive, regardless of equipment used in the manufacturing process. Size variation is inherent in all fired clay products. If your customer wants tight joints they should consider purchasing rectified tile, eliminating the risk of size variation.
Level is a good thing but it always cost more than flat. Using self levers is a commitment and once you start, you're committed. They do provide an outstanding substrate and I would use them at every opportunity. It would be wise to use a product from the same manufacturer you chose to provide the rest of the setting materials to avoid any compatibility issues. If self levelers are not in budget and some undulations are present in the existing floor, it makes the job simpler if the floor is flattened prior to installation. I have tried to flatten a floor by adding a little thinset to the tile while installing more times than I care to admit. It never did work very well; flat at one doorway and 3/4-inch higher at the other. If you have tried it you know what I am talking about. That is about all the space I have this month. Hope you find this helpful in your endeavors. Because we want to be your source and provide the most up-to-date installation related information available, we would like to encourage you to submit topics or questions that you would like to see in future issues. Please feel free to email the editor or myself with your interests and we will do our best to address your areas of interest.