This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
—The use of galvanized iron for general roofing work has increased greatly during the past few years. It has many features which commend it as a roofing material, but difficulties have been experienced by beginners as to the proper method of applying it to the roof. The weight of material used is rather heavy to permit of double seaming, but a method has been evolved that is satisfactory. Galvanized iron roofing can be put on at low cost, so as to be water-tight and free from buckling at the joints. The method does away with double seaming, and is considered more suitable than the latter for roofing purposes wherever it can be laid on a roof steeper than 1 to 12.
Galvanized iron of No. 28 and heavier gauges is used, the sheets being lap-seamed and soldered together in strips in the shop the proper length to apply to the roof. After the sheets are fastened together a l.25-inch edge is turned up the entire length of one side of the sheet, as indicated in Fig. 1. This operation is done with tongs having gauge pins set at the proper point. The second operation consists in turning a strip J inch wide toward the sheet, as shown in Fig. 2. This sheet is then laid on the roof, and a cleat about 8 inches long and 1 inch wide, made of galvanized iron, is nailed to the roof close to the sheet and bent over it, as shown in Fig. 3.
A second sheet having 1.5 inches turned up is now brought against the first sheet and bent over both sheet and cleat, as shown in Fig. 4. The cleat is then bent backward over the second sheet and cut off close to the roof, as in Fig. 5, after which the seams are drawn together by double seaming tools, as the occasion demands, and slightly hammered with a wooden mallet. The finished seam is shown in Fig. 6. It will be seen that the second sheet of galvanized iron, cut 1/4 inch longer than the first, laps over the former, making a sort of bead which prevents water from driving in. Cleats hold both sheets firmly to the roof and are nailed about 12 inches apart. Roofs of this character, when laid with No. 28 gauge iron, cost very little more than the cheaper grades of tin, and do not have to be painted.