This section is from the book "A Treatise On Architecture And Building Construction Vol3: Stair Building, Ornamental Ironwork, Roofing, Sheet-Metal Work, Electric-Light Wiring And Bellwork", by The Colliery Engineer Co.. Also available from Amazon: A Treatise On Architecture And Building Construction.
A corbel-table gutter is shown in Fig. 41. It is supposed to form a belt all around the building, being located about 4 or 5 feet below the eaves. Such gutters, being so far below the eaves, do not carry much water at any time; they simply serve to carry off the drip. The greater part of the water shed by the roof during heavy showers, shoots over the gutter, this action being most pronounced when the roof covering is of a corrugated character.
A corbel table a, which rests on corbels b, b, forms a support for the gutter. The lookouts c are made of cast iron and are set at about 2 feet centers all along the table, their prongs being let into the mortar joint at the back about 2 inches. The crown molding and its wash are made of copper, the lower edge being lapped about 4 inches over the top of a. The top edge is secured by cleats to an iron bar. Another iron strap, or bar, at e runs the full length of the gutter, and the copper is secured to it with brass bolts. When the molding is in position and properly lined up, the mason fills in the gutter with cement to form a curved bottom with the proper grade. Strong cold-rolled copper cleats f are secured to the wall to hold down the back of the gutter d; the front edge is double seamed and soldered as shown. The back is counterflashed in the ordinary manner. If the counterflashing is of lead, the top joints g should be locked into one another at the lower edge, as shown, to prevent the wind from raising the corners.
52. When such gutters are long, some provision must be made for expansion and contraction, otherwise they will soon tear apart and leak. In Fig. 41 this is accomplished by introducing a saddleback joint at h, a cross-section of which is shown in Fig. 42. A plank i, 2 inches thick, which has been previously soaked in oil or asphalt, is set on edge and bedded in the concrete. If the gutters are laid during hot weather the upstands j,j should be fitted to almost touch the plank, so that during winter, when the gutter becomes intensely cold and contracts, the upstands will be drawn away from the board and take the position shown by the dotted lines. This forms an expansion joint of the best type.
The cap, being short, is nailed to the wood and the nail heads are covered with a copper disk, which is soldered water-tight around the edge.