Fig. 85 -Ridding formed with Wood Roll and Lead.

Table V. Weight Of Roofs

Iustead of lead gutters, like those shown in figs. 76, 79, and 81, cast-iron gutters of the requisite section and ¼, ¾, or ½ inch thick, are sometimes used. The joints may be either lap-joints, or butt-joints with flanges bolted together; the- joints must be carefully made with a mixture of red and white lead, or with a mixture of iron-borings, sulphur, and sal-ammoniac. Iron gutters of this kind condense moisture, and are somewhat apt to leak (for a time at least), besides being damaged by rusting. In certain circumstances, however, they can be used with advantage.

In this connection a few words may be said about rain-water pipes. They are now seldom made of wood, although here and there a prejudice lingers in favour of this material. .Most frequently cast-iron pipes are used; they are made circular and rectangular, the former being the stronger and more durable. Rainwater pipes should be fixed so as to stand about 2 inches from the wall in order that they can be painted all round, and that in case of a leak the wall will not be saturated with the water. This object may be effected by wood blocks, or (better) by using a special pipe such as Law's, or the Perfection, as shown at P in Plate III. Solid-drawn lead pipes have recently come into use. They are expensive and easily bulged, but on the other hand they do not need painting, and do not crack as easily as iron pipes; nor do they rust. The thickness of the metal should be from 3/32 to 1/8 of an inch, i.e. from 6 to 8 lbs. per sq. foot, and the pipes must be secured to the walls by lead tacks not more than 3 feet 6 inches apart. It is a mistake to use small rain-water pipes; the smallest size allowable is 2 inches in diameter, and this should only be fixed to the roofs of bay-windows and other minor roofs. Pipes 3, 3½, and 4 inches in diameter are better

Rain-water pipes should not on any account be connected directly with the sewage-drains, but should discharge over or into trapped gullies. The position of rain-water pipes should be so arranged that they help to flush the drains; e.g. a rain-water pipe near a sink-waste or a soil-pipe greatly assists in keeping the drains clean. They may also with advantage be connected with an automatic flushing-tank at the head of the principal drain.