When picking out your tile how do you make sure that the surface is durable enough to last in that particular area? Well, being a hands-on kinda guy I use to walk into the tile shop with a belt sander and test it. If the sandpaper wore out before the surface of the tile we found a winner! This tended to piss people off, though. Then I found out there is, as most things I do, an easier way.

For everyone else in the world this is determined by using what is called the PEI, or Porcelain Enamel Institute, rating of your tile. The PEI rating is between I and V with a V being the most durable. Those are Roman numerals, not the 19 letters between I and V. :D  I’ll just call them 1 to 5 – you know, since I’m not from, nor am I in, Rome.

This scale is used by most tile manufacturers to determine the surface wear durability and should be printed on the box of tile somewhere. If it is not you can always contact your tile manufacturer for the information.

General guidelines for proper installation areas are as follows:

  • Group I: Tile suitable only for residential or commercial walls – stuff you don’t walk on unless you’re Spiderman. Not suitable or recommended for foot traffic (unless you are, indeed, Spiderman).
  • Group II: Tile suitable for general light residential traffic. Not recommended for kitchens, entryways, heavily used bathroom floors or any other area subject to continuous use foot traffic.
  • Group III: Tile suitable for all residential and light use commercial foot traffic areas. You can pretty much put this everywhere in your house except your garage floor.
  • Group IV: Tile suited to all residential, medium commercial, and light industrial applications such as restaurants, hotels, and hospital lobbies.
  • Group V: Tile suitable for all residential, heavy commercial, and industrial applications such as airports, malls, subways, and the Space Shuttle.

The particular group number or PEI rating is a measure of the durability of the tile surface only. It does not determine the slip resistance, overall strength, moisture absorption, or quality of the tile itself, only the quality and durability of the surface or glaze. For most residential flooring applications it is always best to go with a PEI rating of three or higher, although a two is suitable for some applications.

By taking the PEI rating into consideration when choosing your tile you can ensure you have a properly durable tile for your particular installation.

The PEI rating is only one aspect to consider when choosing your tile. There are a few others which must be taken into account for an overall proper tile choice. These include the Mohs hardness, density of the tile, absorption rate, the Static Coefficient of Friction (S.C.O.F.), and the most important aspect – does your wife like the way it looks?

You can always simply walk in someplace and pick out a tile without utilizing the available information, however, taking advantage of the different rating systems ensures a proper choice for lasting durability of your tile installation.

Or at least take a belt sander with you.

{ 18 comments… add one }

Leave a Comment

  • Fran

    Hi Roger,

    I’m going to attempt to tile my small bathroom and have a couple of questions concerning the work, which I hope you can help with, before I begin.

    1. As the bathroom floor is quite uneven, I will need to level it first. What is the easiest way to go about this? The floor area is 3 square meters and lined with linoleum tiles.

    2. I’m planning on tiling over the existing tiled walls (I believe this is okay to do, although probably frowned upon?!) which surrounds the bath tub. What would be the best adhesive to use in this case?

    Also, I’m a little concerned about whether the walls will withstand the additional weight. I’ll be covering three walls in total, only one of which is a solid wall. I’m going to be using 60x30x1.1cm large, ceramic tiles to cover the existing 15x15cm ceramic tiles. I don’t know what their PEI rating is as the website I purchased from only listed them as ‘Grade 0; wall tiles’, but they feel quite heavy, hence my concern. What do you think given the limited information i’ve been able to provide?

    Many thanks,

    • Roger

      Hi Fran,

      1. Self-leveling cement is the easiest and quickest way to do it.
      2. Any thinset designed specifically for a tile over tile application. Mapei ultraflex 3 and laticrete 255 or 4xlt will work.

      I think your walls will be just fine, the weight is all distributed to sheer force, it won’t be pulling the wall ‘away’ from the framing, it’ll be pulling it ‘down’. That’s not a problem.

  • raj

    Hi Roger,

    your website is really good and very informative,really appreciate it.

    I am thinking to install porcelain tile on my garage floor. could i do tile installation directly on concrete or do i need to have backer board first.

    i live in north virginia. people keep on saying do epoxy floor in garage. but i like tile and i believe its more durable and more appealing than epoxy. I want to use garage for more than car parking. infact i want to park car only in winter.

    also, i have unfinished basement. i wanted to install tile in there as well. I guess for basement backerboard is mandatory.


    • Roger

      Hi Raj,

      You can not use backerboard over concrete. If you are installing tile over it you can bond directly to the concrete or use a membrane like ditra or strata-mat.

  • Bobbie

    We have 6×6 Vitromex Ceramic tile on the floor of our shower. The edges are so sharp I wear flip flops because the tile cuts the bottom of my feet. Are there tile that should not be used on the floor? We’ve never had a problem like this before. The house is one year old, we had it built. We’ve had this problem since we moved in. The edges are not rounded.
    Thanks for your input.

    • Roger

      Hi Bobbie,

      Yes, I would say that if they have a sharp edge they shouldn’t be used on a shower floor.

  • Gary

    I’m redoing my bathroom shower and was looking at all the choices of tile and had a concern. Some tile have the look of one solid color, others look like they have a printed pattern on them. The edges have a different look with a lighter color like a border. Am I just being picky or are there different ways tiles are colored. Do these tiles with the “printed patern” wear as well as the regular non-printed ones?

    • Roger

      Hi Gary,

      There are, literally, millions of combinations of tile and colors. If you don’t like the one or two you’re looking at – look around. The wear pattern of a particular tile will depend on a lot of factors – ceramic or porcelain, mohs hardness, etc. It has nothing at all to do with the color or print on the surface.

  • Mary Lee

    HELP please! We are planning a total renovation of our 1933 bathroom and are in a quandary re what kind of tile would be best to support the weight of a cast iron tub with claw foot legs. The contractors know they have to make sure the joists will hold the tub weight as well as at least a 3/4″ plywood subfloor. (1) Should they use that “concrete board” on the subfloor? (2) MARBLE vs. porcelain on the floor below such a tub?? The porcelain we like has a rating of PEI 4. We cannot find such a rating for real marble tiles! Looking forward to receiving some info re this matter–have exhausted online searches. PS: This site is the most entertaining!

    • Roger

      Hi Mary,

      Porcelain or marble will support your tub just fine if it is installed correctly. All your support comes from the substrate and framing. There are several ways to prepare the substrate which would support that, cement backerboard is one that will.

  • william peterman

    we had tile instilled in our house it has only ben three weeks and we have chips in kitckens dinning room and liveing room we dont on if tile is bad or not. the contractor has look at it and said he would check has distributor.how can check the tlie we have no boxes left i have five tlies left it was made in Brazil.the tlie looks great in house it just keeps chipping.granted we no that you are not to drop anything on or it will chip but this is like walken on eggs.

    • Roger

      Hi William,

      What kind of tile is it? You didn’t say, but the fact that it is from Brazil leads me to believe it’s slate – is that correct? If so then it’s not the tile itself that is the problem, it’s the fact that you used slate in an area where slate should not be used and/or that particular slate is low-end stone. Slate ‘cleaves’, which simply means that it is a layered stone which will tend to peel or chip layer by later. Higher end slates are compressed enough to prevent this (for the most part) but the lower end stuff is not. Any tile contractor worth his salt would have told you that.

      Is it slate?

  • Diana

    Hi! I really enjoyed reading your shower floor instructions. And sense of humor ;). I have an out door deck totally exposed to the elements. The floor of the deck is at the same level as the indoor floor (for awful reasons I don’t want to go into now). But the contractor wants to waterproof this deck by using the same techniques for a shower color. We have had numerous water problems. The deck area measures ten by twenty feet with a curb on 3 sides and stucco wall on the 4th side. There is about 1.5 inches of height at the furthest point from the drain. This drain is 20 ft away.

    Would building a ‘shower’ floor work?


    • Roger

      Hi Diana,

      It depends on what you mean by building a shower floor. There are a number of ways that can be done. If he is talking about a pvc or cpe liner with deck mud on top of it – no, it won’t work. Is your deck currently sloped? If he can install deck mud and slope it toward the drain then use Laticrete Hydroban over the top of it – it would work, but is not necessarily the correct manner.

      To have a proper deck build there needs to be a 1/4″ / foot slope to an open end or out-vent (an open channel going through one of your curbs) to drain water. But a liquid topical membrane would work, I just don’t know about the long-term durability concerning any other aspects of the deck, like where it meets the house and any flashing necessities there.

  • Kimberly

    Would like suggestions on flavor of tiles. I am putting it in a heavy traffic room…I will be rolling heavy parrot cages across it, the dogs will be running across it as will the children. So heavy dirt and the occasional heavy crockery thrown down. I need slip resistance and if you could suggest one that is less echoey as the cockatoo yell is loud enough without it being magnified by flooring, also one that helps solve world peace or the energy crisis.

    • Roger

      Hi Kimberly,

      You’ll need to look at a couple of different aspects of any tile you’re choosing and use the applicable numbers to determine whether or not it’s suited to your little mini-zoo. :D I would suggest looking at different porcelains, a class III porcelain tile would be the way to go. The aspects of any porcelain you find that you need to pay attention to are the Mohs hardness and the COF number. You can read through my post about choosing the correct tile for an explanation of COF.

      The Mohs scale is a bit trickier, the exact number doesn’t always translate to what you are looking for so it will be more relative to the overall aspects of the tile. In other words it would be the least exacting factor on which to base your decision. Mohs scales go from one to ten – the higher the number the harder the surface. Look for a porcelain around 6.8 – 7.0. A high mohs number coupled with a good COF should give you a very durable porcelain which may outlast the noisy bird. :D

  • Debbie

    What PEI rating, Mohs hardness, density, absorption rate and Static Coefficient of Friction would YOU recommend for a home shower?

    • Roger

      Hi Debbie,

      There are actually two different sets of numbers to consider – the vertical surfaces (shower walls) and the horizontal surfaces (anything you walk on).

      The vertical surfaces would be fine with a PEI above II, a Mohs of 4, SCOF of 3 dry or wet, and an absorption rate of less than 0.5% (porcelain).

      The horizontal surfaces are a bit more tricky since you’ll be walking on wet tile. I like a PEI above III, a Mohs of 4 or 5, SCOF of 4 dry, 5 or 6 wet, and an absorption rate of less than 0.5% (porcelain).

      All these number are subjective, though! Marble breaks just about every one of those to a less than ideal condition, but marble bathrooms have lasted thousands of years. It is entirely dependent on your particular bathroom. How much maintenance do you want to put in? How often do you want to deep clean? How many kids do you have that will slip on it? How many pets do you have that will scratch it? Do you live near a beach where sand is a common material being grinded underfoot?

      See what I mean – subjective.