These comprise tiles which are flat, square, or rounded at one end, and round or variously shaped tiles.
These are greater in length than breadth, and of variable dimensions (Figs. 416,417); the best known ones are .27 x .15 and about .015 thick (about 10 in. x 6 in. x 1/2 in.); they weigh about 1 kilog. (2 lbs.). They are fixed to the laths with a hook, and most of them have one or two holes (Fig. 417) by which they can be nailed down. They are arranged in horizontal rows which overlap one another from the base to the ridge; only one-third of the tile is left visible, and this part is called the "pureau" Each tile is over three laths (Fig. 418), and thus the roofing is three tiles thick, and is of considerable weight, averaging 60 kilog. per square metre. The slope should be from .75 m. to I m. per metre (30° to 45°).
Figs. 416 to 430. Ancient Tiles of Various Shapes.
These only differ from the foregoing in the lower part, which is semicircular (Figs. 419, 420), or pointed, which gives the roofing a tasteful appearance resembling the scales of fish (Fig. 421), whence the name.
In order that a roofing may be successfully laid, the tiles must be perfectly smooth, which is not often the case.
The roofing of towers and domes requires the tiles to be cone-shaped so as to follow the curvature of the roof (Fig. 422).. They are laid in the same way, being nailed to the laths when necessary.
This differs very little from the tile of the ancient Romans; its shape is trapezoidal (Fig. 423), and the joins are covered by round tiles (Fig. 424). Roofings of this kind (Fig. 425) are still found in Champagne, in the south of France, and in Italy.
These are used alone or in conjunction with the preceding kind. In the former case they are laid in different ways according to the locality; they are generally placed upon connecting battens, for which are sometimes substituted terra-cotta squares (Fig. 428), and the whole is sometimes bound together with mortar, making a solid but very heavy mass (Fig. 429). In the south of France, the tiles are merely placed upon triangular joists (Fig. 430); the slope must not be very great, about .4 to .5 metres per metre (210 to 26°), for the tiles are only kept in position by their weight.
These tiles are provided with a hook which holds them to the laths (Fig. 405), and they can therefore be more sloped than the previous kind. To make the roof more water-tight, the joins are usually filled in with mortar.
The invention of fitting tiles by Gilardoni was a great advance on earlier tiles, which had many other disadvantages besides their weight; they offered a great hold to the wind, they allowed snow and often rain to pass through, and they were costly to maintain.
The first tiles have been improved upon, and we possess types to-day which make excellent roofs; but modifications are always being sought after, and every year new shapes of tiles appear, which, however, are all based on the same principle, and frequently offer no sensible advantage over existing types.
It may well be asked, with reference to this, whether inventors are well advised in trying, under pretext of improvement, to complicate the shape of tiles by an infinitude of details. What should be the natural shape of a tile that it may be suited to its destined position? This shape should be one which will. render the roofs absolutely proof against snow and rain in any quantity; it should make the tiles as light as possible consistently with their stability under any pressure of wind. A detailed examination of the principal types of tile will show how this question has been answered.
Fitting tiles are divided into two classes according as they are laid overlapping, that is to say, with vertical interrupted join, or in a straight line, that is to say, with vertical continuous join.
This tile has average dimensions of .4 x .24, and thirteen are required to the square metre, which represents a utilisation of five-sixths of the total surface. The joint is at the left, and is formed of a groove with a strong inner edge; at the right is the counter-joint; at the top is a simple flange.
The lower part is of larmier shape and has a hollow (Fig. 451) in the middle, in which the counter-joint of the lower row rests. In the middle of the tile is a lozenge - shaped strengthening rib, hollow inside; it is below this lozenge that the triangular projection caused by the hollow at the bottom of the tile is placed, and it has also the effect of directing water to the two sides of the lower counter-joint (Fig. 433). The tile is fastened to the laths with two hooks, and some types are furnished with holes through which they can be nailed to the rafters, others (Fig. 448) are furnished below with a projection pierced with a hole through which a wire is passed and attached to the laths (Fig. 449).
Figs. 431 lo 449. Modern Tiles of Various Shapes (Gilardoni Brothers and Muller),
This type of tile, which was the first to be manufactured, is now made by many firms (see table), as the patent has expired.
It requires half-tiles (Fig. 432). The perfected model No. 4 (Fig. 440) is double-fitting at the top and at the side. The surface of the tile forms two channels (Fig. 441) separated by a rib.