Tiles. The use of tiles for roofing, although by no means a modern practice, has or :ate years become more general in this country. 'files are made in t, variety of shapes, the general principle, in all cases, being that of a. slab of baked clay, moulded with an interlocking roll or rim. Tiles are laid on battens or on boarding, as described for slates; the difference being, that instead of a double lap for tightness, the tightness of tiling depends upon the fitting of the tiles into each other. Some of the modern forms of tiles are shown in Fig. 157. With tiles should he used copper or zinc for valleys and flashings, but ridges and hips are gener ally formed by tiles of special patterns. Plain tiles have long been used in England and are in most cases found to be in as good condition as when new. Tiles may be used on roofs which have a pitch of more than 22!, degrees, hut will need a free use of elastic cement, especially in valleys, hips, and ridges. In appearance, tiles should be of even color, free from fire checks, but well burned and non-absorbent, of uniform size and without blisters, cracks or warped surfaces.
Composition Roofing. For roofs of a pitch of + inch to the foot, or less, a composition roofing, made of several thicknesses of paper coated with tar, and covered with gavel on top, may be used to advantage. The mode of constructing a composition roof will be to first cover the boarding, or, in case a fireproof roof, the smooth top.of the concrete with dry resin-sized felt with a lap of two inches, tacked only often enough to hold it in place. Over this are laid three full thicknesses of tarred felt, each sheet lapping two-thirds of its width over the preceding one, and the whole covered with a uniform coat of pitch mopped on. Upon this coating, two layers of tarred felt are tacked, each lapped about twenty-two inches, and the whole mopped over and a thick coat of pitch flowed on. As the durability of the roof depends upon the paper, only the best should he used, and the pitch should not be so hot that it will destroy the life of the paper. Upon the final coat of pitch is spread immediately a coat of clean white gravel, completely covering the whole, as a protection. This composition of tar and gravel makes a very good roof, but is suitable only for roofs tip to a grade of three-quarters inch to a foot.
If much steelier, the heavy coat of tar will run in hot weather, and settling down, will gradually fill the gutters.
A composition of pulverized slate and asphalt, applied in layers with felting, has been placed upon the market, and is more adaptable to various pitches than tar and grave].
The same precautions regarding the flashing of vulnerable parts will be needed in the laying of composition roofs that we have noted for slates or tiles, except in the case of the Plastic Slate roofing; here the composition itself is of such a nature that it may be applied with a trowel directly to the walls or copings against which the finish is made, and being of an elastic and adhesive nature, no great amount of metal flashing is needed.
Inspection. The supervision of roofing work of all kinds deserves the closest attention. Nothing is more unsatisfactory than to find leaks in the roof of a new building, and the time spent in securing a first-class ,job will be well spent. Slates and tiles are easily broken, and unless discovered and brought to notice at once, will probably be overlooked by the contractor. Composition roofs are easily slighted, and when finished give little indication of defects.
The only safeguard is constant watchfulness, which is well repaid if the roofs prove satisfactory.
Gutters and Conductors. The best material for metal con ductors is copper, but galvanized iron and tin are used to some extent.
The usual form of a copper gutter is shown in Fig. 15S, but it is often necessary that the face should be formed of mouldings to match or form part of a stone or wooden cornice. In this case, the gutter is formed behind the finished moulding. (Fig. 151.) The gutter shown in Fig. 158 is made of sheet copper, turned over an iron bar A, and moulded to form the trough, and made wide enough to run well up on the roof boarding, under the slates or other roof covering. Bars of copper or galvanized iron are bolted to the outer bar, and nailed mul soldered to the roof. These bars should be given a short twist, as shown, so that the wash of the roof will drip oft into the glitter, and not follow the strap down and soil the fare of the gutter. In the case of the lined gutter, Fig. 1341, the outer edge of the metal is tacked to the wood or tucked under nil iron bar previously secured.
Standing gutters (Fig. 160) are sometimes used where they will not he objectionable by reason of binding back the snow, but arc often a source of trouble.
In a great many cases of city building, especially with flat roofs, it is necessary or convenient that the outer walls shall be carried up as a parapet, and the roof water taken care of inside of the }milling.
In this case a ''cant-lmard" is used, shown in Fig. 161. This consists of a board surface set •m the angle of roof and wall, aid graded to the desired outlets where conductors are placed in side of the wall.