TILE, a thin, flat slab, usually of burned clay, glazed or un glazed, used either structurally or decoratively in building. The usage of the word varies widely; in connection with roofing, flat slabs of any material are sometimes termed tiles, as for instance, the marble tiles occasionally used in Greek temples or the bronze tiles used extensively in ancient Rome, and occasionally in China. Similarly, stone slabs, used for roofing, as in certain parts of England, are termed stone tiles; slate, however, is never so called, and wood shingles are so called only rarely. Many forms of rough terra-cotta used structurally in building are called tiles; thus an arch of hollow terra-cotta blocks between steel beams is known as a "tile arch"; partitions built of hollow terra-cotta blocks are known as hollow tile partitions, and the steel forms used for casting certain types of reinforced concrete floors are frequently referred to as steel tiles. The differentiation between tile, terra-cotta and brick is thus exceedingly vague.
Tiles divide themselves naturally into several classes : structural tile, such as the hollow terra-cotta blocks referred to above, for which see TERRA-COTTA ; roofing tiles ; floor tiles ; and wall tiles.
These were laid in overlapping courses, and were all of equal size so that the joints of each course occurred directly in a line with those of the courses above and below. Convex covering tiles, also overlapping, were then laid over the joints of the flat tiles below, and were so profiled as to cover, not only the joint, but the raised edges of the lower tiles; in this manner an absolutely watertight roof could be produced. In order to make the archi
tectural effect more delicate the ends of both lower tile and cover ing tile were rebated, so that the thickness of the overlapping por tion was only half the thickness of the tile. At the bottom of each row of covering tiles was either a marble or tile upright, curved, decorative member known as an antefix (q.v.).
In some cases the covering tiles were of pointed, straight line section—the most common Greek type—in others a tile of semi circular section was used, easy to manufacture, but lacking in the extreme refinement of the other type; in the simpler domestic work, the lower courses were also of curved section, a segmental concave shape replacing the flat tile with raised edges. The nimble tile used in some Greek temples, as in that of Bassae (c. 43o B.C., by Iktinos) is universally of the type with flat under tile and pointed covering tile, although at times, in order to reduce the number of joints, the covering tile and the under tile are cut from the same piece of marble.
Two other types of roof tile were common in Roman times and probably represent common Mediterranean types of much earlier origin. These are the so-called "Spanish tiles," with a contour resembling a letter S, in which the convex part of each tile fits over the edge of the concave portion of the next, and the shingle or flat tile found frequently in the Roman ruins of the northern provinces. These flat tiles are often of stone.
The usual material of all of these types of tile is burned clay, varying in colour from orange-yellow to purple-red. It is known, however, that bronze tiles were relatively common on the most monumental buildings of the Roman empire. Due to the rarity and value of bronze during the middle ages and the Renaissance, no examples of ancient bronze roof tiles are now known.