The most used metal in the small house is the so-called tin-plate or roofing tin. It is not a true tin-plate, for it contains 75 per cent lead and 25 per cent tin, applied to a base of soft steel or wrought iron. It comes in two grades, IX and IC, the former being No. 28 gauge and the latter No. 30 gauge. The lighter is used for roofing and the heavier for valleys and gutters. The tin does not entirely protect the base metal, so that it is necessary to paint both sides before it is applied.
Galvanized iron is another form of sheet metal which is extensively used for work on the small house. It consists of sheet iron or steel, covered with zinc. This coating should be free from pinholes or bare spots, and of a thickness to prevent cracking or peeling. If the coating is sufficient and well done, it is superior in lasting quality to the ordinary tin-plate.
Copper, since the war, has come back into use again as a sheet metal for the small house, for its cost has dropped within reason. In order to meet a certain popular demand a light grade of copper sheet roofing has been placed on the market, although it has generally been considered that sheets weighing less than 16 ounces per square foot were not suitable for roofs.