When I answer questions on my site I am always telling people to backbutter their tile. It has recently been brought to my attention that normal people (the ones who don’t stand in showers all day) have no idea what that means.
Backbuttering tile simply means spreading a flat layer of thinset onto the back of the tile before installing it on your wall or floor or whatever.
First you have to ‘comb’ the thinset onto the substrate – that means it is spread with the notched side of the trowel leaving little ridges. It should look like that first photo there on the right with the ridges all combed in one direction. This allows any air to escape from beneath your tile more easily.
In Tile and Stone Sealers Part 1 I explained how sealers work. If you haven’t yet read that please do so. It will give you a base understanding of how they get into your tile and what they protect against. It will help you understand what you’re looking for and also help decode some of the terms you may find here.
When choosing a sealer the first decision you should make is what you are trying to protect against. Silicone-based sealers protect against water-based stains – coffee, tea, beer Pepsi, stuff like that. Fluoropolymer-based sealers protect against oil-based stains – cooking oil, body oil, shampoo, stuff like that.
What is the difference between modified and unmodified thinsets?
Which unmodified thinset is better?
What makes a modified thinset modified?
Why do you drink so much beer?
These are questions I get asked a lot, along with ‘why is my dog on fire’ (because you used the incorrect product for a specific installation).
Unmodified thinset is simply a thinset which does not have any latex polymers or other products added to it. It is essentially portland cement, silica (sand) and lime. Recipes vary, but those are the basics.
History (pay attention – there may be a quiz…)
To understand modified and unmodified you should understand why modified exists. Way back in the 1940’s Henry M. Rothberg was a chemical engineer. Back then the standard installation procedure for floor tile was the full bed method. This was a 2″-3″ deck of portland cement and sand upon which tile was installed. The need for the thickness is at the heart of the development of modified thinsets.
It needed to be that thick in order to retain enough moisture for the cement to fully cure.
I get a LOT of questions from my readers about basic shower construction. I understand that my readers don’t consider this stuff basic and there’s no problem with that. The problem is that I end up answering the same questions over and over and over… So, to save what very little is left of my sanity (which is a number roughly equivalent to absolute zero) I will cover some basic things here so I can simply reply ‘read this’.
If you’ve been channeled to this page by one of my smart-ass comments please take no offense to it, I’m here to help. Please understand that I currently have over 12,000 comments (questions) on this site (seriously) which I’ve answered – every one of them. I’m just trying to make your life (mine) easier. I will continue to answer every question I’m asked, I’m just super cool like that. If, after reading through this, you still have questions feel free to ask them in the comments below.
You can also download my shower waterproofing manual which should answer a lot of questions and cover basic techniques and methods you may be confused about. Go ahead, it’s free. So without further ado (doesn’t even look like a word, does it?) let’s get on with it. (For all my readers who feel the need to correct me: I KNOW it’s actually ‘adieu’ – I was being facetious. Thanks. )
I am not writing this to tell you why your tile is cracking or why your grout is cracking – I have other posts that may tell you that. (Click on the pretty little links ) If you happen to have Schluter Ditra as your substrate, this post will tell you why either one of the above may be happening.
While Ditra is my preferred membrane for floor tile installation (as well as countertops and tub decks) it absolutely needs to be installed correctly. The two main techniques for this are fairly simple:
Make sure the cavities (waffles) are filled correctly
Install it over an approved substrate (and with the correct type of thinset mortar)
In my previous post I beat you to death with the reasons why you absolutely need a soft joint (control joint) in certain tile installations. Sorry about that, I have a hard time expressing how important they are without being a dick. They”re important – really. So now that I’ve properly reprimanded you it’s time to show you how to do it.
I know there are some people out there (not my regular readers like you!) that read what I write and think to themselves ‘okay, but I’m sure that won’t happen with my installation’. So periodically I’m gonna post things like this that show exactly what happens when things aren’t built correctly. And yes, it will happen to yours, too, if the proper steps aren’t taken. If you care to see more train wrecks you can check out my ‘flawed‘ page wherein I post photos of absolutely horrible tile installations which I’ve torn out and replaced.
See that crack in the tile right there? (The line down the center is not a grout line – it’s a crack. You can click on it for a larger version) That bathroom floor is less than eight months old. It was installed with hardibacker over the subfloor and thinset. At least that part is correct, but that was about it. There was no thinset beneath the hardi and the seams between the sheets were not taped and thinsetted. To a lesser extent the correct screws were not used in the hardi – they committed the cardinal sin of using drywall screws in the backerboard. Yeah. Wrong.
To understand this you should understand what designates a particular tile as a ‘floor’ tile. A couple of different things determine this including the PEI Rating and Static Coefficient of Friction (that’s just fancy ass talk for how slippery a tile’s surface is).
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. 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.