Excess lippage is when there is a difference in height between your tiles. They become uneven, rigged and, depending on the degree of lippage, painful to walk on. Just imagine your unsuspecting bare foot catching the sharp edge of a porcelain tile. Ouch!
There are a few different things that can cause excess lippage, but a large part of it comes with improper installation. There's a lot of preliminary work that has to be done carefully before the floor installation process starts. The subfloor needs to be examined and leveled, the mastic (adhesive that holds your tile down) needs to be spread evenly, and spacing between the grout must be considered. Don't try to guess when it comes to something so important as the floor you will be standing on!
If you've hired an expert we suggest you sit down with them and hear their thoughts and plans for installing your tile. They should be able to tell you if there are any problems with your subfloor or the materials being used before they start to their work. As the homeowner, you have the right to stay updated on potential concerns, even if you don't fully understand all of them. If you're attempting a DIY project, be sure you do some more in-depth research on these processes before laying your tiles down.
Now, let's say the tiles are already installed and you're worried about whether or not you have a lippage problem. Well, one way to find out is with your credit card. Don't worry, this isn't a plug to make you spend money. We're simply suggesting you try the "credit card test". Run your credit card or a quarter over your floor from one tile to another. Ideally, it should slide smoothly without ever getting caught. The floor was installed very well if this is the case. If you find the tiles are slightly uneven but the card still slides from one to the other fairly well, you shouldn't worry. It's when the card is stopped in its tracks that you should question the integrity of the installation job.
If you find that your floor fails the credit card test, you'll have to start looking into repair options. Unfortunately, there's usually not an easy fix for excess lippage. Minor problems can often be fixed by filling the grout joints if they are all low. You may have to remove the trouble tiles altogether and replace them once you've evened out the area below. In extreme cases you'll have to save up for a new floor entirely.
The moral of this story is that you should be diligent in the preparatory details when tiling a floor. No action should be taken before you've mapped everything out and are confident that the job will get done correctly. If these precautions aren't taken, you could end up spending a lot more time and money than you had originally intended on the project. And remember, you always have the option to ask for help or to hire a professional! While the work may cost a little extra initially, the benefits far outrun the risks if their past work proves to be high quality. All you'll have to lose is the terror stories that come with a job poorly done.