• Ceramic Tile Floors
- John P. Bridge ( May, 2005 )
“Ceramic tile floors. Sounds simple, doesn’t it? Pull up the rug and “put down” tiles. Smear grout in the joints, clean it up and move back in. If you have vinyl on the floor you can go right over it with the new tiles, as vinyl makes a wonderful uncoupling membrane. Tile mastic works better for tile floors than thin set mortar does, especially when using large tiles. If the floor structure seems a little spongy, you can correct it by nailing down cement backer board before installing the tiles themselves.”
You have just been presented with a paragraph-size synopsis of the type of tile misinformation you might receive on the Internet, in tile and flooring outlets, at big box stores and in certain printed publications, not to mention home improvement shows on radio and TV. Yes, there are thousands of “experts” out there poised and eager to set you straight and get you on your way to tile flooring bliss. Don’t buy into it for a minute.
In the next few paragraphs I intend to give you a very brief overview of the correct ways that ceramic tile flooring should be installed. I’ll list sources of further reading at the end.
First of all, ceramic tiles (to include porcelain tiles, quarry tiles, various paver tiles and others) are hard, brittle and breakable. For them to be installed successfully on floors they must be well bonded and well supported underneath. If your floor is the least bit springy or “mushy” when you walk on it, it will be necessary to do some serious shoring up before tile setting begins. I cannot over-emphasize this. For our purposes, the tiles themselves have no structural value of their own. The use of cement backer boards or various membranes will not ameliorate an unsound floor structure.
• Cement Backer Boards
Cement backer boards, such as PermaBase, Wonder Board, Durock, Hardi-backer, and others are used to “uncouple” a tile installation from the subfloor below. Before they are fastened, CBUs, as they are called, are bedded in thin set mortar, which is the usual adhesive used in setting floor tiles. The panels are then nailed or screwed to the subfloor following manufacturers’ specific directions. CBUs do NOT improve the stiffness or structural value of the floor.
• Anti-fracture Membranes
There are various membranes on the market that accomplish the same uncoupling effect that CBUs provide. Two of the biggest names are Nobleseal and Ditra. I happen to be in cahoots with Schluter Systems, makers of Ditra, and I consider it among the best products on the market. But membranes will NOT rectify an insufficient floor structure. Vinyl linoleum and tar paper certainly won’t do it either.
“Thin set mortar” is a portland cement product that is used to adhere ceramic and stone tiles to a “substrate.” The substrate is the layer directly under the tiles, i.e., cement backer board, Ditra membrane, etc. Thin set comes in a powder form that must be mixed with water just prior to use. Thin set cannot be pre-mixed before it is needed. It will “set-up” and become hard just like any other cement product. It does not need air to do this, and you can’t keep thin set in a can or plastic tub on a store shelf.
Therefore, any product you see on the shelf purported to be “pre-mixed thin set” is not thin set and cannot be used to install floor tiles. It is instead some sort of mastic, which is an organic glue that might be used to install certain very small tiles on a kitchen back splash, for instance. The same goes for “pre-mixed grout.” Real tile grout is made from portland cement also, and in my opinion, pre-mixed grout should not be used for anything at all.
Remember that thin sets and grouts will ALWAYS come dry in a sack or box, and remember that it is impossible to pre-mix them and keep them from setting up hard as a rock.
Tile mastic, the organic glue, can be used only on small tiles and in areas that don’t get wet. It should not be used on stone tiles at all as it can be absorbed into the stone where it can cause stains. And tile mastic should not be used for ceramic tile floors.
• Movement Joints (Expansion Joints)
Nothing is static. Everything moves constantly, and this is especially true in a house. Concrete expands and contracts with heat and moisture changes. So does wood, and so do other building materials. Ceramic tile floors must be installed so that they don’t bump up against building materials and other objects when they expand.
All tile and stone floors must incorporate provisions for independent movement. This means that perimeter joints must either be left open, or they must be “grouted” with something elastic like caulking or special expansion joint material. In the new homes we work on, perimeter movement accommodation is achieved by installing the tiled floors before the baseboards (skirting boards) are put on. The tiles then slide under the boards when expansion occurs.
In very large floor areas, expansion joints must be left in the tiled “field.” The maximum distance a tiled floor can stretch without an expansion joint is 30 feet, and most tile setters would consider that extreme. I insert movement joints when the field of tile exceeds 25 feet. In some cases this will mean having a caulked joint in the middle of a ceramic tile floor.
• Concrete Slabs
Installing ceramic or stone tiles directly to a concrete slab is not the best thing in the world a person can do. Concrete expands and contracts at a very different rate than does ceramic tile. This difference in “coefficient of expansion” can cause tile and grout to crack, and in severe cases the tiles can actually delaminate from the concrete. The judicious use of soft movement joints can help prevent this, but there is no guaranty. Likewise, anti-fracture membranes can be used under the tile installation, but again, nothing is guaranteed.
• What to Do
I’ve covered only a bit of the material you’ll need to make an informed decision as to your ceramic or stone tile floors, but greater, more bountiful sources of information are available to you. In the United States the standards guiding the ceramic tile industry are developed by The American National Standards Institute (ANSI), and they are published by the Tile Council of North America. General installation procedures are contained in the “Handbook for Ceramic Tile Installation” which may be purchased from the Tile Council. The complete standards are contained in ANSI A-108 and A-118. The ANSI standards are also available at the Tile Council.
The Terrazzo Tile and Marble Association of Canada (TTMAC) provides guidance to our friends to the north.
• Other Resources
My current book, Tile Your World: John Bridge’s New Tile Setting Book, is available at the Tile Your World On-line Store or at Amazon.com. It can also be special ordered from any brick and mortar book store in the U.S. and Canada.
For an explanation of porcelain floor tiles, see my article on that subject.
For more information on the Schluter Ditra uncoupling membrane, see Ditra Floors.
And for everything and anything you might want to know about any aspect of the ceramic tile industry, you can log onto the John Bridge Forums and ask questions of any of a number of tile professionals who routinely gather there. You will also find a reference “liberry” containing links to numerous pictures, diagrams and articles.
See you at the forums.
Additonal information on tiled floors