52. Lead, in building construction, is used in the form of sheets of varying thickness, and in specifications is stated as weighing so many pounds to the square foot, as " five lbs. to the foot lead." Its use is chiefly confined to the lining of cisterns and of gutters, and the formation of what are called "flushings" to gable ends and to chimney shafts. The object of a lead flushing, illustrated in fig. 417, is to keep the wet out at the junction formed by the roof covering and the vertical face of the chimney, or coping of gable, as the case may be. The flushings are strips of sheet lead varying from 8 to 9 inches in breadth. Fig. 417 illustrates a lead flushing to a chimney stack. Part of the mortar is scraped out of a joint / in the vertical face of chimney, and a piece of lead e inserted and bent down at d, the bent part covering the other piece of lead b c, which is retained or bent, so as to lie against the face of chimney at c, and on the surface of slates at b. Fig. 418 represents a form of lead flushing adapted for a parapet or cornice behind which there is a gutter, as at e in fig. 419. In fig. 419 the lead a c e is turned up at f, so as to go under the roof covering at g. Fig. 420 illustrates the lead lining of a valley gutter, for a "ridge and valley" roof. The lead flushing for the ridge of a roof closely resembles in section the ridge tile illustrated in Chapter I. of the next division of this work.
53. Zinc is much used for the covering of roofs; the various methods of using which, for this purpose introduced by the Veille Montaigne Zinc Company, whose gigantic works are near Liege, in Belgium, having done much to extend its use amongst the trade. We illustrate various methods introduced by them for adapting zinc to roof covering. In fig 421 we illustrate the method of "expansion" fitting in diagram A and B; diagram A illustrates the covering of flat roofs with a roll of wood, part of which is shown at a b, being rounded at b and flat at a, at which part it is nailed to the boarding or joists; a strip of zinc c is placed under the roll, returned up its side, and finished off with a bent part, as at d. The flat spaces between the rolls are covered with zinc plates d e, which are returned or bent, as at f.. These ends d f, and the upper part of the roll a b, are protected from the rain by the cover g g, which is bent. By this arrangement perfect expansion is permitted. In B, fig. 421, the expansion system of covering ordinary roofs is illustrated; the plate a a is bent, as at b, and clasped by a covering piece c c, which is secured to the boarding or joists by the rail d, which is placed in a slot e e, allowing of free expansion; f f is the next plate in succession. Fig. 422 illustrates the method of joining zinc plates, as a a, to wrought-iron rafters, part of one of which is shown at b b'; the zinc plate covering the roof surface is retained at c, and a covering plate d d passes round the rafter, being finished on the other side in the same way, as at c d, and is secured to it by the screwed nail or pin e b'. In fig. 423, at A and B, we illustrate two methods of forming gutters of zinc. Zinc is generally used rolled flat, but in some cases it is used in the corrugated form, as at C in fig. 421, which illustrates the method of joining two corrugated plates with rivets. Corrugated zinc is so much strengthened by the corrugations or alternate flutings and hollows, that boarding maybe dispensed with, and the sheets, bent or curved over the space to be covered, being secured only to the side walls or gutters of cast-iron, if these be used, as at C in fig. 423. In fig. 416 we illustrate part of a roof of corrugated zinc of this kind, a a the curved corrugated zinc plates - this curving of the plates gives additional strength to the roof - secured to the cast-iron gutter b, fixed to wall c; wrought-iron ties d e give additional strength to the arrangement, and strengthens it against the action of winds acting from below, as well as from the weight of the roof itself. At C, in fig. 423, we illustrate an arrangement of zinc roof of corrugated plates a a, which are secured, as at 6, to the cast-iron gutter c c, rain from which is carried off to the drain by the hollow part of the column d, as shown by the dotted lines, to which the gutter is bolted at intervals. In place of sheets of zinc, so called "tiles" of the metal are used to cover roofs. Fig. 424 illustrates the adaptation of these to a timber roof, each tile, as a, is secured, at b, by two nails to the battens c c; d d is the gutter.