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Originally we thought of titling this session "CERAMIC
TILE FOR DUMMIES" to pick up on the latest book
title craze. However I felt that no one would admit
to being a ceramic tile dummy and there would be no
attendees. We hear it all the time: "My father
(uncle or cousin) has been in the business for 50 years
and he always did it this way, and taught it to me.
It must be right." Or: "I know what I'm doing
and don't need any more information."
Is this true? Are you a dummy or a tile genius? Probably,
if you are human and in this business you are somewhere
in between. You have some knowledge but could use some
more. I have been in the tile business for over 15 years
and every day at work, something new comes to my attention.
You can never learn enough. Even if you rank an eight
or nine out of ten on the knowledge scale, you can bet
that something new is coming along that requires further
study.
Have you ever gone into a floor covering store, a tile
outlet, or a big box store and met the super salesperson?
The one who says: "Sure you can tile over Oriented
Strand Board (OSB). I do it all the time. And sure,
throw down a sheet of Luan underlayment that'll level
your floor real well. Caulk, what is that? I never caulk
any joints, they don't look good and aren't needed anyway."
Then is the "Interior Designer" who says:
"I don't care about the specifications, I just
want the look. I don't want any control joints, they
spoil the look." Do these things sound like they're
coming from a genius? Maybe if the consumer hears them
they have to accept these statements as facts because
"these are the experts!"
How about the self-styled tile gurus on the Internet,
or who write handyman columns, or magazine writers who
intermingle fact and fiction, or even (yes) even some
speakers at seminars? I hope not this one. Yes these
examples are all real world examples.
It would be impossible in one 45-minute session to
educate an audience in all facets of ceramic tile from
the factory to the installed product. My intention is
to briefly discuss the areas that most frequently come
to our attention. Many of the installation issues have
been, or will be covered in detail in other sessions
at Coverings. I hope that you have been using your time
wisely to educate yourselves by attending those sessions.
TILE
Ceramic tile itself can be a complex subject. Let's
slice down the layers of complexity and make it simple.
There are two major types of tile, quarry tile: that
is tile that is made by extrusion from natural clay
or shale and tile that is made by the pressed dust method.
This category includes wall tile, mosaic tiles, and
floor tile. Either type of tile can be glazed or fired
as unglazed. Glaze is a ceramic surfacing material that
is used to provide a certain appearance. Let me restate
this point: any ceramic tile type may be glazed or unglazed.
This includes porcelain tiles.
What are porcelain tiles? They are tiles with a water
absorption less than 0.5%. How can a tile absorb water,
you ask? It is a dense body of minerals that is heated
to a high temperature and is not like a sponge. The
answer is that it can. One dries a tile then weighs
it, soaks it in water and then measures it again. The
weight change represents the % of water absorbed. (Weight
after soaking minus weight when dry divided by weight
when dry is % water absorption.)
Water absorption of tile is controlled by the selection
of raw material used for the body and the manufacturing
process. It is the body that absorbs the water not the
glazed surface. (In fact the glaze may be sawed away
from the surface while running the test.) The water
absorption determines the classification of tile. Wall
tile has from 7-20% water absorption (that's right,
it's a lot). That's why you shouldn't use wall tile
outside where there can be freezing temperatures. The
water goes into the body when it rains, snows, from
pools and fountains, and even condensation, and then
it expands when it freezes and the tile cracks. So don't
put this tile outside in most places in the U.S. Even
Florida and California have some freezing days in most
parts of the state. The same holds for "Saltillo"
tile that rough looking hand pressed Mexican tiles.
These can have water absorption up to 30%.
Wall tile is made for a purpose, sticking on a wall
(although it can be used on countertops and sometimes
on floors. It requires beauty as it is frequently at
eye level, or near one's field of vision. The size must
be close to uniform as it usually has a small space
between each tile (called a grout joint). The relatively
soft body of wall tile makes it easy to cut to fit (including
round holes for plumbing fixtures) and helps the tile
to stick to the wall without sliding.
Is it a good idea to use tiles that can absorb 7-20%
water (usually they absorb about 12-14%) in wet areas?
Well actually the surface glaze is impenetrable to water
and acts as a barrier when this tile is used in bathtubs,
showers, pools, and elsewhere where there is water.
Water will penetrate the grout joints no matter how
careful the installer is. This means that some method
of protecting the underlying backing material needs
to be used, in wet areas, such as a liquid or solid
water-proof membranes or waterproof materials (i.e.
cementitious backerboard).
It should be mentioned that, although any tile can be
glazed or unglazed, unglazed wall tile is not a commonly
used product as it absorbs too much water and was made
for decorative effect in the first place. Floor tiles
(pavers) are tiles made by the pressed dust method and
can have water absorption from zero to five percent.
They have lower water absorption than wall tiles because
they have a denser body. They must be strong enough
to walk on and therefore require this stronger body.
You may ask at this point, how can a pressed dust body
produce a strong tile? Dust isn't very strong is it?
Well, this process is one in which the mineral components
of the tile body are milled to very small particles
(like dust) and then pressed under very high pressure
to form the tile body. If all the particles are the
same size and very small, they will compact into a strong
body that when heated in a kiln will fuse into a strong,
dense, and low water absorbing body. A small amount
of water is left in the body during pressing to help
hold the body together (about 5%, if you are into details).
Then the tile is dried to about 2% water before putting
it into the oven (lovingly called a kiln). Most tile
today is single-fired. That is, it goes through the
kiln once. So if it is to be a glazed tile, it is glazed
after drying and then fired to h a high temperature
(over 2000 degrees Fahrenheit).
Glazing today is a very sophisticated matter. Modern
high volume plants have a plethora of devices on a conveyorized
glaze line, such as silk-screeners, waterfalls, sprays,
dry glaze dispersers, printing rollers, texturizing
machines, and other devices. Some factories have 15
or more applications of glaze material on one line before
firing the tile. Why? To make the tile look natural
and random. It is harder to replicate nature than to
make a regular flat-colored glazed tile. It's not nice
to fool Mother Nature is it?
Quarry tile has water absorption less than 5% too.
When it is extruded, a dense surface forms that reduces
the staining and surface porosity of the unglazed tile
(remember all tile can be glazed). It can be made very
thick and therefore strong. This makes quarry tile a
good candidate for warehouses, fast food places with
high traffic, commercial kitchens, dairies, meatpacking
plants and other areas where strength and ability to
clean are paramount. If it is used unglazed (which it
generally is) it doesn't have a thin surface to wear
out and will last a very long time.
And now for the tile of the moment: "Porcelain
Pavers". This is probably one of the most misunderstood
products based on our current telephone traffic and
written information being published. Simply put, this
is within the previously mention paver category but
is tile that has water absorption less than 0.5%. This
is very low and that makes these tiles very strong and
dense. Because they are so dense that they can be left
unglazed and used on the floor. If so they have no glaze
to wear out and therefore will stay the same color and
look for a very long time, maybe thousands of years
and long enough that we don't have to worry about this
anymore. Because they are the same color through out
the body (through-body tile) they can be polished and
ground to size just like stone. Grinding can make the
size and geometry of the tile very precise and permit
narrow grout joints.
Let me interject a word about grout joints. Grout is
used to fill the space between the tiles. The current
tolerance for tile size permits a fairly wide variation
in the actual body size (ANSI A137). Pavers can vary
up to 3% and still be classed as standard grade. The
new ISO standards have reduced this to plus or minus
1% but on a twelve-by-twelve tile this is plus or minus
3mm (a little over 1/10 of an inch). If one tile is
bigger and one is smaller that is a range of 1/5th of
an inch. The purpose of the grout joint is to allow
for this potential size variation. Manufacturers can
sort the tile into size ranges (called caliber) and
mark the box accordingly. You then need to remember
to use one caliber on a job. Still the sizes will vary
from tile to tile and a proper width grout joint must
be selected.
But wait a minute; if these porcelain tiles are so perfect
why not use them everywhere? Well, there are some consequences
of making a tile with near zero water absorption. First
of all, it is harder to get adhesive to stick to the
tile. Wall tile with its high water absorption will
"grab" into the adhesive fast and stick well
to a vertical surface. You can use porcelain tile on
a vertical surface but it needs to be physically supported
while the adhesive sets, for example with plastic spacers
or boat rope. We recommend using the best adhesive available
for these tiles, latex modified thinset or epoxy.
Second, this tile is harder to cut. Your grandfather's
snap cutter or carbide blade will be challenged when
cutting this product. You need a diamond wet-saw. While
on this subject and in case you feel like going home
to set tile tonight, do not under any circumstance use
a dry blade in a power saw to cut tile or any other
product that contains silica. The watchdogs at OSHA
are developing standards for exposure to silica dust
as I speak to you. It's not as good idea to breathe
this stuff even if the medical science is still being
evaluated.
Third, even with low water absorption, because the
surface may be unglazed, there is a surface micro-porosity
(real little holes on the surface) that can allow staining.
Not good if you drop ink on your floor. The manufacturers
are solving this by adding a clear glaze to the surface
of the "unglazed" tile.
Fourth, up to now the color ranges and finishes of
unglazed porcelain pavers has been limited and considered
more of an institutional look. This too is being addressed
and many new styles and colors are coming into the market.
Back now to glazed pavers. These can have low water
absorption, as low as zero, but generally the manufacturer
makes them with 2-3% absorption in order to improve
the bonding, and ease the cutting operation while still
providing adequate break-strength and frost resistance.
Yes, these lower water absorption tiles from zero to
5% can be used outside even where it freezes.
We have not yet discussed mosaic tiles. What are they?
They are small porcelain tiles that can be either glazed
or unglazed, and I won't say that again, I promise.
They are less than six square inches and generally are
sheet-mounted at the factory to save time in installation.
Who wants to put little one by ones in a 40,000 square
foot shopping mall piece by piece? They are strong and
have low water absorption and have some real advantages.
Because they are small (about 2-1/4" by 2-1/4"
maximum) they will follow a contour such as in shower
floor. They allow for many drainage channels in wet
areas to improve the slip-resistance (more on this later)
and they provide for many geometric designs. They recently
have become quite popular as accents to larger tiles.
If they are left unglazed, they will last for a very
long time.
And now to the finishing touch: glaze. Glazes are a
thin finish that can and will eventually wear off of
the tile. Selection of the area of use for different
glaze ratings is important. Currently the industry is
using the following glaze wear rating system (as is
ISO, the International Standards Organization and most
of the world):
0 - Decorative tile only (look but don't scrub)
1 - Non-traffic area tile (put it on the wall)
2 - Light traffic (like in the bathroom with slippers
and bare feet)
3 - Residential inner rooms (kitchens, sunrooms, etc)
4 - Light commercial (office buildings, showrooms, entry-ways)
5 - High traffic (shopping malls, fast food, etc.)
Finally, a lesson on coefficient of friction (COF)
and then I'll slip out of here. There are no national
standards or requirements for coefficient of friction.
There are some local municipalities that have building
codes, however. The American's with Disabilities Act
(ADA) recommends a COF of 0.6 or greater on flat surfaces
and for people with disabilities and 0.8 on ramps and
inclines, but there are no laws, standards or whatever
specifying the COF.
Furthermore, the method of measurement must be specified
in order for this to have technical meaning. In the
US, we use the ASTM 1028 sled method where a 50-pound
weight is placed on a sled with a special material (to
represent a shoe sole) contacting the tile and it is
pulled by an operator using a fish-scale. It is a dry
measurement although it can be performed wet with water
for investigation. The pull force needed to just start
the sled moving, divided by the 50-pound weight determines
the COF. Example: if it takes 30 pounds of pull to start
the sled, divide this by 50 and you get 0.6, just enough
for the ADA recommendation.
But after the tile is installed, it must be kept clean.
Ceramic tile is water resistant and stuff stays on the
surface such as water, grease, banana peels, and other
things too gross to mention. So the spills need to come
up fast and the water needs to be removed or the COF
goes down. Tile can be made very slip resistant but
then it is harder to clean. A judicious choice must
be made when selecting tile.
Time does not permit further discussion about tile
and we have not even touched upon installation. The
majority of phone calls that we get concern installation.
That's where the rubber meets the road and detailed
training is required.
The standards used in the US are the ANSI A108/118
for installation and the A137.1 for tile itself. The
TCNA publishes both of these along with the Handbook
for Ceramic Tile Installation and they are available
from our office and here at the show. Give us a call
at 864-646-TILE (8453) for more information and we'll
do our best to make geniuses out of dummies.
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