Tiles are often used to form wall and floor coverings, and can range from
simple square tiles to complex mosaics. Tiles are most often made from
ceramic, with a hard glaze finish, but other materials are also commonly
used, such as glass, slate, and reformed ceramic slurry, which is cast in a
mould and fired.
In the past twenty years, the technology surrounding porcelain tile and
glass tiles have increased, moving both from a niche marketplace to a
place of prominence in the tile community.
Roof tiles are designed mainly to keep out rain, and are traditionally made
from locally available materials such as clay or slate. Modern materials
such as concrete and plastic are also used and some clay tiles have a
waterproof glaze.
A large number of shapes (or "profiles") of roof tiles have evolved. These
include:
• Flat tiles - the simplest type, which are laid in regular overlapping
rows. This profile is suitable for stone and wooden tiles, and most
recently, solar cells.
• Roman tiles - flat in the middle, with a concave curve at one end at
a convex curve at the other, to allow interlocking.
• Pantiles - with an S-shaped profile, allowing adjacent tiles to
interlock. These result in a ridged pattern resembling a ploughed field.
• Mission or barrel tiles are semi-cylindrical tiles made by forming clay
around a log and laid in alternating columns of convex and concave tiles.
Roof tiles are 'hung' from the framework of a roof by fixing them with
nails. The tiles are usually hung in parallel rows, with each row
overlapping the row below it to exclude rainwater and to cover the nails
that hold the row below.
There are also roof tiles for special positions, particularly where the
planes of the several pitches meet. They include ridge, hip and valley tiles.
Invention
The earliest finds of roof tiles are documented from a very restricted area
around Corinth (Greece), where fired tiles began to replace thatchet roofs
at two temples of Apollo and Poseidon between 700-650 BC. Spreading
rapidly, roof tiles were within fifty years in evidence for a large number of
sites around the Eastern Mediterranean, including Mainland Greece,
Western Asia Minor, Southern and Central Italy. Early roof tiles showed
an S-shape, with the pan and cover tile forming one piece. They were
rather bulky affairs, weighting around 30 kg apiece. Being more
expensive and labour-intensive to produce than thatchet, their
introduction has been explained with their greatly enhanced fire
resistance which gave desired protection to the costly temples.
The spread of the roof tile technique has to be viewed in connection with
the simultaneous rise of monumental architecture in archaic Greece. Only
the appearing stone walls, which were replacing the earlier mudbrick and
wood walls, were strong enough to support the weight of a tiled roof. As
a side-effect, it has been assumed that the new stone and tile
construction also ushered in the end of 'Chinese roof' (Knickdach)
construction in Greek architecture, as they made the need for an
extended roof as rain protection for the mudbrick walls obsolete.
These are commonly made of ceramic or stone, although recent
technological advances have resulted in glass tiles for floors as well.
Ceramic tiles may be painted and glazed. Small mosaic tiles may be laid in
various patterns. Floor tiles are typically set into mortar consisting of
sand, cement and oftentimes a latex additive for extra strength. The
spaces between the tiles are nowadays filled with sanded or unsanded
floor grout, but traditionally mortar was used.
Natural stone tiles can be especially beautiful. However, as a natural
product they are often less uniform and require more planning for use
and installation. Stone tiles described as "gauged" have very uniform
width and length dimensions; "ungauged" stone tiles may vary from their
nominal dimensions. Stone tiles such as granite can be sawn on both
sides (and then polished on the facing up side) so that they have a
uniform thickness. Other natural stone tiles such as slate are typically
"riven" (split) on the facing up side so that the thickness of the tile varies
from one spot on the tile to another and from one tile to another.
Variations in tile thickness can be handled by adjusting the amount of
mortar under each part of the tile, by using wide grout lines that "ramp"
between different thicknesses, or by using a cold chisel to knock off high
spots.
Some stone tiles such as polished granite and marble are inherently very
slippery when wet. Stone tiles with a riven (split) surface such as slate or
with a sawn and then sand-blasted surface--granite is occasionally
prepared this way--will be more slip resistant. Ceramic tile for use in wet
areas can be made more slip resistant either by using very small tiles so
that the grout lines acts as grooves or by imprinting a contour pattern
onto the face of the tile.
The hardness of natural stone tiles varies such that some of the softer
stone tiles are not suitable for very heavy traffic floor areas. On the other
hand, ceramic tiles typically have a glazed upper surface and when that
become scratched or pitted the floor looks worn, whereas the same
amount of wear on natural stone tiles won't show or will be less
noticeable.
Natural stone tiles can be stained by spilled liquids; they must be sealed
and periodically resealed with a sealant in contrast to ceramic tiles which
only need their grout lines sealed. However, because of the complex, non
repeating patterns in natural stone, small amounts of dirt on many
natural stone floor tiles do not show.
Most vendors of stone tiles emphasize that there will be variation in color
and pattern from one batch of tiles to another of the same description
and variation within the same batch.
Stone floor tiles tend to be heavier than ceramic tiles and somewhat more
prone to breakage during shipment.
Ceiling tiles
Ceiling tiles are lightweight tiles used in the interior of buildings. They are
placed on a steel grid and, depending on the tile selected, may provide
thermal insulation, sound absorption, enhanced fire protection, and
improved indoor air quality. Also frequently called Ceiling Panels, or Drop-
Ceiling Tiles, they offer the advantage of easy access to wiring and
plumbing above the ceiling grid, and can be easily changed, removed, or
replaced as needed. They are fabricated from perlite, mineral wool, plastic,
tin, aluminum, and fibers from recycled paper. They frequently have
patterns comprised of holes, to improve their sound absorption
properties, though many have a molded surface providing a textured,
sculpted, or pressed-tin look to the ceiling. Some tiles are available with
decorative photo/transfer surfaces, some are approved for installation
under fire suppression sprinkler heads so the sprinklers do not show,
some are approved for use in food preparation areas, and some are
certified for indoor air quality by the GreenGuard Institute. Tiles are
available that resist mold and moisture damage, that have enhanced
acoustical properties, and that can be easily trimmed with household
scissors. Recycling old tiles depends upon the material used to make
them, and some landfills no longer accept traditional mineral fiber tiles, so
they must be recycled to the manufacturer. Some plastic tiles can be
100% curbside recycled.
Decorative tilework
Decorative tilework typically takes the form of mosaic upon the walls,
floor, or ceiling of a building. Although decorative tilework was known and
extensively practiced in the ancient world (as evidenced in the magnificent
mosaics of Pompeii and Herculaneum), it perhaps reached its greatest
expression during the Islamic period.
Some places, notably Portugal and São Luís, have a tradition of tilework
(called azulejos) on buildings that continues today.
In the United States, decorative tiles were in vogue, especially in southern
California, in the 1920s and 1930s. Prominent among art tile makers
during this period was Ernest A. Batchelder.
Islamic tilework
Perhaps because of the tenets of Moslem law (sharia) which disavow
religious icons and images in favor of more abstract and universal
representations of the divine, many consider decorative tilework to have
reached a pinnacle of expression and detail during the Islamic period.
Palaces, public buildings, and mosques were heavily decorated with
dense, often massive mosaics and friezes of astonishing complexity. As
both the influence and the extent of Islam spread during the Middle Ages
this artistic tradition was carried along, finding expression from the
gardens and courtyards of Málaga in Moorish Spain to the mosaics of the
Hagia Sophia in Constantinople.
Azulejo- Small Arabic tiles that are glazed and are used as dadoes in
palaces and courtyards
The Mathematics of Tiling
Certain shapes of tiles, most obviously rectangles, can be replicated to
cover a surface with no gaps. These shapes are said to tessellate (from
the Latin tessera, 'tile'). For detailed information on tilings see the
tessellation page.
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