ROOF COVERINGS.
Roofing treating- of the ang,le of inclination of roofs (p. 48), it was mentioned that this depended chiefly upon the roofing matcrial. The angle varies very much according to the material and the shapes of the individual parts, or is applied differently even \viten material and shape are the same. The following divisions of material may be made: (t) Tile; (2) Slate; (3) Metal; (4) Glass; (5) Wood, in the form of boards or shingles; (6) Veg-etable matter of rough character, such as straw, rushes, etc.; (7) Vegetable matter refilled and specially prepared, such as heavy carton paper or linen; (8) Composition—paste, asphaltum, clay, etc. Con sideration be restricted to the first four of the above divisions of roofing material; for the description of the other species, not so generally interesting, the reader is referred to special text-books.
Tile Roofing. —Tiles are slabs of baked clay' perforated and shaped in various way's. They are not so intich used for roof covering- as formerly, as a result of the popular recognition of the superior qualities and the moderate cost of slate. Formerly the business of tile roofing maintained a separate class of mechanics, but the work is now performed by the brick layer. Tiles for roofing are sometimes colored and glazed, and those of the same style are applied in different ways. The most common are the plain fiat tile, the concave gutter tile and roof plate, the ridge tile, and the pan tile. To those forms which appear separately' belong the different kinds of rebate tile—a tile with turned-up edges.
The Plain Flat Tile is a plate 14 inches in length by 5Y2 inches in breadth and is -t2,- of an inch thick. It is provided with shallow grooves and fillets on the upper side, running lengthwise, to facilitate the discharge of the water, and with a lug in the middle of a narrow rim on the reverse side, so that it can be hung up on the roof laths. The other narrow and lower end is generally' rounded off into a slight curve. I3y suspending these tiles to the laths in rows, courses are formed which overlie one another more or less., depending upon the width of the lathing. The greatest over lap or smallest gauge makes the securest work, though it does not present so good an appearance externally as the longer gaug-e, and it requires, moreover, a greater number of the tiles and laths, thereby adding materi ally to the weight and cost of the roof.
Single ana' Double Tiling. —111 the single-tile roofing—seen on Plate 7 (fig. width is about to inches. To support the mortar at the joint between each two tiles, small shingles are used. The shingles are about 12 inches long, 2 inches broad, and inches thick. The second form, or double roofing (jig. lb), is decidedly better, the distance between the laths being only 6 inches; so that the first course projects beyond the point on the second below which the third begins. Shingles are not required in this case. Lime, mortar, or occasionally' hydraulic mortar, is the con necting medium in the joints and between each two courses where they overlap. In a third form of roofing two courses of tiles are hung, one directly over the other upon each lath, the distance between the laths being inches.
Ceilier Tiles were used for roofing, by the ancient Greeks and Romans, either alone (Jig. 2a) or in combination with the flat tile with raised edges (jig. 2b). They' are conical in shape, the diameter being 914/ inches at the head and SY2 at the tail, and the length inches; while the flat tiles of the same length are to inches wide at the head and 12 inches wide at the tail, the edges being raised t of an inch. The manner in which the roof ing is laid—mortar being employed, as in the use of the plain flat tile—can be clearly seen in the illustration. Glitter tiles are seldom employed ex tensively in roofing, on account of their great weight, but the ridge and hip lines of tile roofs are always covered in with them. 13y usage in England, large concave tiles are invariably chosen to cover the hips and ridges, both in plain tiling and in pantiling; they are not generally inade to overlap, but are set in mortar and fastened to the timbers of the roof by a special kind of hooks and nails. An ornamental cresting or ridging is also frequently added in a variety of patterns. Tiles of the third order (pi. 7, fig. 3a) have a raised edge on one side and a semicylindrical addition on the other, by which each tile grasps the edge of the one next to it. They are about in! inches long by 8.1. inches broad, slightly overlapping in each row, the sus pension being effected by means of the lug.