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Ceramic tile is
simply a mixture of clays which have been shaped and fired at high
temperatures resulting in a hard body. This hard body may then be
left untreated or it may receive a glazed wear layer. To put it a
different way, ceramic tile is nothing more than beautiful, baked
clay.
DURABILITY
A discussion about
durability should precede other basic information about ceramic
tiles. That’s because it’s important that customers first access
their needs and make sure they’re selecting a tile with the
necessary durability. Luckily, tile is rated, which eliminates the
guesswork when it comes to making a selection.
PEI Wear-Rating
System:
To avoid
inappropriate installation, most manufacturers use the following PEI
(Porcelain Enamel Institute) guide to rate the durability of their
tile. In the PEI system, Group 1 represents the least durable tile
and Group 5 signifies the most durable.
-
Tiles suitable
only for residential bathrooms where softer footwear is
worn.
-
Tiles suited to
general residential traffic, except kitchens, entrance halls, and
other areas subjected to continuous heavy use.
-
Tiles suited for
all residential and light commercial areas such as offices,
reception areas and boutiques.
-
Tiles suited for
medium commercial and light institutional applications such as
restaurants, hotels, hospital lobbies and corridors.
-
Tiles suitable
for heavy traffic and wet areas where safety and maximum
performance are a major concern. Used in exterior walkways, food
service areas, building entrances, shopping centers and around
swimming pools.
IMPORTANT:
The wear rating of tile has nothing to do with its quality or price,
only its durability. Some of the most expensive and luxurious tiles
in the world rate only a 1 or 2.
Glazes:
The glaze applied
to some floor tiles is simply a liquid glass that has been sprayed
or poured onto the surface of the tile. It is then fused and
hardened by means of tremendous heat.
Glaze colors are
created by mixing a variety of minerals, including gold, silver,
zinc, copper, mercury, cobalt and many others. The strength and wear
resistance of the glaze depends on its hardness. The harder the
glaze, the better it will stand up to pressure and abrasion. Glaze
hardness is determined by:
-
Temperature—the
higher the kiln (oven) temperature, the harder the glaze.
-
Color—light-colored glazes are usually harder than darker-colored
ones.
-
Gloss
Level—matte or satin-finished glazes are generally harder. Shiny
glazes are usually softer and less durable.
The Clay:
The baked clay
body, which is also called a bisque, is made up of various types of
clay and other minerals. Combined, these raw materials give the
bisque its strength and stability.
The strength of
the bisque is also determined by its density. The strongest bisques
have the greatest density, which is characterized by the smallest
and fewest number of air pockets in the clay. High-density tiles are
suited for heavy commercial installations as well as residential
projects.
The density of the
clay also determines if the tile is suitable for outdoor use.
Low-density tiles that are too porous and absorb more than 3%
moisture will freeze and crack if installed outdoors in cold
climates.
TILE
DENSITY
The density of the
tile is measured by the amount of water it absorbs. Based on that
amount, a tile falls into one of four categories. Those categories
determine whether a particular tile is appropriate for indoor or
outdoor use. Remember, a higher density bisque, one with only a few
air pockets, results in a stronger flooring tile. High-density tile
is also more suitable for outdoor use because it will absorb less
moisture and be less prone to cracking in freezing temperatures than
porous, lower density tiles (those absorbing more than 3% moisture).
Tile
Density Classifications:
Non-vitreous tiles
absorb 7% or more of their weight in water. They are suited for
indoor use only.
Semi-vitreous
tiles absorb 3% to 7% water and are suitable only for indoor use.
Vitreous tiles
absorb 0.5% to 3% water and are considered frost-resistant. They are
suitable for both indoor and outdoor use.
Impervious tiles
are the strongest available. They absorb between 0 and 0.5% of their
weight in water. These frost-resistant tiles are appropriate for
indoor and outdoor uses.
Types Of Ceramic
Tile:
Ceramic tile is
available for flooring in both glazed and unglazed forms.
Glazed tiles are
made exactly the same way as unglazed tiles, but they undergo an
additional process. A glass wear layer is applied then subjected to
tremendous heat in a kiln. This process liquefies the glass and
fuses it to the bisque.
Glazes offer an
unlimited array of beautiful colors and designs and create a surface
that is practically stainproof. While appropriate for uses that
range from light residential use to medium commercial traffic, most
glazed tiles are not considered suitable for heavy duty commercial
use.
There are a few
glazes, thanks to recent technological advances, that are now hard
and durable enough to stand up to the most demanding commercial
applications.
Unglazed tiles are
simply baked pieces of clay whose colors are determined by the
mineral content of the clay. These tiles are the workhorses of the
industry. Generally thicker and denser than glazed tiles, they
include products such as quarry tiles and porcelains. The rugged
surface texture and matte finish of the these tiles give them good
slip-resistant qualities for use in wet areas.
The toughness of
unglazed tiles make them ideally suited (but not limited to) extra
heavy commercial installation.
Colors, which are
limited to the natural colors of the clay, range from light sand to
darker red brick tones. To increase the color range, manufacturers
achieve a wide range of beautiful colors by mixing color pigment in
with the clay.
Popular unglazed
tiles include:
Quarry Tiles:
Made from natural
clays and shale, these unglazed tiles are generally in earth tone
colors ranging from light tan to reds. Some manufacturers have
increased the color range by adding color pigments to the clay.
The body of a
quarry tile is thick and dense with good slip resistance, making
them a popular choice for both heavy commercial and residential
installations.
Porcelain Tiles:
Porcelain tiles
are made up of special clays and minerals similar to those found in
chinaware. The special clays allow the tiles to be fired at extreme
temperatures (2500 degrees F), resulting in a denser and harder body
than most other tiles. Highly stain-resistant and strong, they are
available with plain, rough or polished finishes.
The combination of
beauty and durability makes them ideal for heavy commercial and
residential installations.
Terra-Cotta
Tiles:
Terra-Cotta Tiles
are either handmade or machine-made.
Handmade
terra-cottas are usually crudely made and not appropriate for
outdoor use in all geographic areas except those that are hot and
dry year-round. The most popular handmade tile is the Saltillo tile
from Mexico. These tiles vary widely in size, shade and texture from
one another, which many customers believe adds to their charm.
Occasionally, they will even be marked with animal tracks.
When used indoors,
they must be sealed and waxed in order to prevent staining and wear.
Colors range from terra-cotta to yellow and brown. Additional colors
can be achieved with stains.
Machine-made
terra-cottas are much denser. Because their increased density makes
them frost-resistant, they can usually be installed outdoors.
Mosaic Tiles:
Mosaic tiles are
usually less than 6 square inches in size, and generally come
mounted on perforated paper sheets or latex mesh for easy
installation.
Very dense, tough
and stain-resistant, mosaics are ideal for countertops and wall
tiles. They’re also great for shower floors, because their small
size gives them the flexibility to follow the contour of the floor
as it slopes to the drain. The numerous grout joints also aid in
slip resistance.
While most quarry,
porcelain, terra-cotta and mosaic tiles are unglazed, all of them
can be produced with a glaze.
Wall And Floor
Tiles:
Wall Tile:
Any ceramic tile is suitable for walls, but those that are very
thin, high-glossed and decorative are most commonly used. The most
popular size for wall tile is still 4 1/4" x 4 1/4" but there
appears to be a trend toward larger, more luxurious tiles.
Wall tiles have a
very soft glaze and porous body and therefore should never be used
on floors or for outdoor applications.
Floor Tiles:
Glazed or unglazed floor tiles have sufficient strength, impact and
abrasion resistance to withstand weight and foot traffic. They are
usually thicker, denser and heavier than wall tiles.
If the substrate
is strong enough to support the weight, floor tiles may also be used
on walls and countertops.
Gloss Levels of
Floor Tiles:
Glazed ceramic
tiles vary in gloss levels depending on the look the manufacturer
wants to achieve. Options include matte, satin and high-gloss
finishes. Generally, the higher the gloss, the softer the glaze.
Areas of the home that don't receive heavy wear, such as bathrooms,
can use a higher gloss level than high-traffic areas such as
kitchens.
The information on
specific product labels or literature will always list the proper
areas to install the tile.
TILE VARIATIONS
Throughout the
ages, ceramic tile has been praised for its versatility. While
carpet and vinyl are produced mainly for floors, ceramic tile can be
used in countless applications. These possibilities include:
Sizes, Shapes and
Finishes
-
Floor tile sizes
range from small mosaics of less than a square inch to 24”x24”
tiles. In the United States, most floor tile measures 8”x8” or
12”x12”, but there is a growing trend toward larger tiles.
-
The most popular
wall tile sizes are 4 1/4" x 4 1/4" and 6"x6", but there is a
trend toward larger tiles such as 6" x 8" and 8" x 10".
-
Square tiles
still dominate the market, but there are many other available,
including rectangles, hexagons, elongated hexagons, octagons and
many more.
-
Tiles also come
with a variety of shaped edges, including straight, scalloped and
cushioned edges that are heavily beveled to simulate handmade
Mexican tiles.
-
Ceramic tile is
also available in various surface finishes. These include smooth
surfaces, textured surfaces that simulate slate or stone,
undulated surfaces that imitate handmade tiles, and gritty
surfaces for slip resistance.
Production
Methods
Monocottura:
This term is an
important one to know because many people relate it to quality.
Monocottura is an Italian word meaning "single-fired." This new
method shapes, glazes and fires the tile in one step.
The development of
the Monocottura technology completely changed the industry for the
better. The process dramatically speeds up production resulting in
cost savings passed to the customer. Prior to the development of the
Monocottura method, some tiles were baked in the kiln for days.
Today, these tiles can be produced in less than an hour.
Monocottura tiles
also have a denser body and harder glaze compared to previous
methods of production, which results in a more durable tile.
Single-fired
products are produced with a flat back which makes installation much
easier than the old-fashioned button- or lug-backed tiles.
Bicottura:
Bicottura means
"double-fired" in Italian. The clay body is baked on the first pass,
and the glaze is applied on the second. Actually, Bicottura tiles
may go through the kiln as many as four times. This method of
production has been replaced by the Monocottura method for making
floor tiles for many reasons.
Bicottura floor
tiles have a softer body and weaker glaze than Monocottura tiles and
are generally not recommended for outdoor use. Bicottura floor tiles
are also produced with lugs on the back making installation more
difficult.
However, the
Bicottura method is still considered by many to be the best way to
produce decorative wall tiles in multiple colors.
There are other
methods of production, but these two provide the basis of what you
need to know when making a floor tile purchase.
White Body vs.
Red Body:
The clay used in
glazed tile production is characterized as either white body or red
body.
While some people
claim that one color or the other is superior, the quality of a tile
has much more to do with the quality of the manufacturing process
and the care taken during production.
Shading and
Sizing:
Many tiles, both
unglazed and glazed, are deliberately produced with a wide shade
variation to capture the natural beauty of the product.
A certain degree
of shade variation is inherent in all ceramic tile. To limit the
amount of variation within a carton, manufacturers simply sort tiles
and package similar colors together.
To minimize any
noticeable shade variations, installers generally work out of
several cartons at the same time and blend tiles together.
Tile sizes will
almost always vary slightly. This is inherent with most tiles, and
is concealed by grout joints. Most manufacturers will keep sizing to
an acceptable level by sorting the tile by size prior to packing it.
Although most
tiles are advertised and sold in nominal sizes such as 8" x 8" or
12" x 12", the actual sizes will be more like 7 7/8" x 7 7/8" or 11
7/8" x 11 7/8".
A good installer
will usually not install tiles with size or shading variations that
are too pronounced.
TILE
CHARACTERISTICS
All ceramic tiles
share unique and exceptional qualities found in no other type of
decorative building products. It’s important to consider these
characteristics and their variations as you make your selection.
Abrasion
Resistance:
How a tile's glaze
or surface will hold up under continuous wear is a very important
consideration when choosing a glazed floor tile. Commercial areas,
as well as areas of the home subject to heavy use (kitchens,
foyers), require good abrasion resistance. If the right tile is
chosen and properly maintained, it can easily last for the life of
the house.
Unglazed tiles
naturally provide the abrasion resistance necessary for safety.
Water Absorption:
The glaze on
ceramic tiles is nonporous. When referring to the water absorption
of glazed tile, the reference pertains only to the tile’s body. The
water absorption of glazed tiles is also important to know when
selecting outdoor tiles. Any tile that absorbs more than 3%
moisture, glazed or not, is not suited for outdoor use in cold
climates where it may freeze and crack.
Frost Resistance:
Frost resistance
goes hand in hand with water absorption. The less water the tile
absorbs, the greater its frost resistance.
Stain Resistance:
In general,
ceramic materials are among the most stain-resistant building
products. Glazed tile and even some unglazed tiles resist
practically all solutions that could cause staining in other types
of products.
Slip Resistance:
The slip
resistance of ceramic tile in ordinary applications is comparable to
most hard flooring materials. And it is significantly better than
some. Unglazed tiles have greater slip resistance than glazed tiles
and are recommended for areas subjected to frequent water spills.
Many glazed and unglazed tiles also feature an abrasive grit on
their surface, increasing their slip resistance substantially. These
tiles are particularly suited to public areas with direct access to
the outdoors.
Color Permanence:
While most colored
materials will be altered by long exposure to light, the colors in
ceramic tiles will not fade from light exposure.
Dirt Resistance:
Ceramic tiles do
not retain dust or residues. Plain water or a damp cloth is
generally all that's required to keep the tile clean. With the
exception of tiles such as terra-cotta, which may be optionally
oiled or waxed, no polishing or buffing is necessary to maintain the
finish.
Fire Resistance:
Ceramic tiles are
completely fireproof at any temperature. They will not burn or feed
a fire. Their surface will not alter, nor will they give off any
toxic gases, smoke or fumes during a fire.
In addition to
being fireproof, tiles have been found to provide protection for
structural surfaces during fires.
CERAMIC TILE
SUMMARY
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Ceramic tile is
a mixture of clays that have been shaped and fired at high
temperatures resulting in a hard body.
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There are two
basic types of tile: glazed and unglazed.
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There are two
distinct advantages of glazed tiles: unlimited color range and
stain resistance.
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The two
advantages of unglazed tiles are wear resistance and slip
resistance.
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The glaze is a
nonporous, protective glass coating.
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The strength of
tile is determined by the hardness of the glaze and the density of
the clay body.
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The PEI
wear-rating chart was developed to help customers select a tile
that’s appropriate for its intended use.
TILE SUBSTRATES
Substrate is the
term used to describe the subfloors, subwalls and subcountertop.
Preparing a good substrate is the most important step in ensuring a
beautiful tile installation.
General
Requirements
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New concrete
subfloors must be left to cure 28 days before tiling.
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All floor and
wall substrates must be rigid. Any spring in the substrates may
crack the tile.
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All substrates,
particularly floors, must be structurally sound.
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All substrates
should be flat and level or plumb.
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All substrates
must be completely free of oil, grease, dust, loose or peeling
paint, concrete sealers or curing compounds. If these contaminants
are not removed, the tile will not adhere properly to the
substrate.
Suitable And
Unsuitable Substrates
Suitable tile
subfloors include those that structurally sound and free of
excessive movement. They include:
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Concrete (in
good condition) (cured 28 days)
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Terrazzo or
natural stone
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Ceramic tile
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Non-cushioned
vinyl and linoleum
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Cement backer
boards
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Double layered
plywood (exterior grade) combined 1 1/4"
Unsuitable
subfloors for tile are those that tend to flex, expand and contract
or warp. Any excessive movement will loosen the tile and pop the
grout. These subfloors must be replaced or covered with a suitable
underlayment. Unsuitable subfloors include:
Frequently Asked
Questions About Tile (FAQ's)
The following is a
list of the most common questions asked by customers:
Q: Will ceramic
tile chip and crack?
Prior to installation, ceramic tile is very brittle. Once it is
installed, it becomes a permanent part of your construction, and
will not chip or crack unless struck with a heavy object.
Q: How durable
is ceramic tile?
If the right tile is selected and maintained properly, that is, kept
free of grit and sand, it should last the lifetime of your home.
Q: What is the
difference between glazed and unglazed tiles?
Glazed tiles are coated with a liquid glass which is then baked into
the surface of the clay. The glaze provides an unlimited array of
colors and designs, and will not stain or fade. Unglazed tiles are
essentially the same as glazed tile, except that their surface is
not coated. Unglazed tiles do not show wear because their color
extends throughout the tile, making them ideal for heavy traffic.
Q: What types of
tiles are used for outdoors?
Any tile that is frost-resistant may be used outdoors. For safety
reasons, only unglazed tiles with a slip-resistant surface should be
used on patios, walkways, pool decks, etc. Glazed tiles should only
be used on vertical surfaces when installed outdoors.
Q: Isn't ceramic
tile slippery?
Tile is about as slippery as vinyl or wood. Naturally, if the floor
gets wet, any of these hard surfaced materials will become slippery.
There are many tiles that have slip-resistant surfaces, but the more
abrasive the surface is, the more difficult it will be to maintain.
You might consider using a mat in wet areas.
Q: Should
ceramic tile be waxed?
Glazed tile should never be waxed. The purpose of the glaze is to
give you a maintenance-free floor. To keep your tile looking new,
use a small amount of neutral detergent in warm water, plus a clean
rinse.
Q: Should sealer
be used on ceramic tile?
Glazed tile is already stainproof, so sealers are not necessary. You
may put a penetrating sealer on your unglazed tile. The penetrating
sealer is an invisible, stain-resistant shield that is absorbed into
the surface of the tile. We do not recommend using a surface sealer
because it wears unevenly and requires constant touching up in
traffic areas.
Q: Isn't ceramic
tile cold on the feet?
Many people assume this, but it is not true. Ceramic tile is a
thermal product that absorbs both heat and cold, depending on the
room temperature. The tile stays cool in the summer and warm in the
winter.
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