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Ceramic
Tile Floors
John P.
Bridge (
5-23-05
)
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 on 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 Wonder Board http://www.custombuildingproducts.com
, Durock http://www.usg.com , Hardi-backer
http://www.jameshardie.com 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 http://www.noblecompany.com
and Ditra. http://www.schluter.com
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.
Adhesives
"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. http://tileusa.com
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. http://www.ttmac.com
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. http://johnbridge.com/ceramic_tile.htm
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. 
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