Standing Seam Roofing

Galvanized

Iron or steel are galvanized by coating them with zinc. Rather than producing the simple coating created by tinplating, a rust resistant alloy of the two metals forms on the surface. In 1839, two years after galvanizing was patented in Europe, the material was used on the roof of the Merchants Exchange in Manhattan. Though the sheet iron was hand dipped in the zinc, much as it was in tin, larger sheets were used (24 by 72 inches in the 1850s). This meant fewer joints, and when used as corrugated sheets, less supporting framing. Even as the production of galvanized iron and steel roofing products increased, the price remained higher than that of other metals. The price differential did not shrink sufficiently for galvanized roofing to exceed tin and terneplate in popularity until the 20th century.

Tin and Terne

Tin-plated iron appeared as a roof covering in the United States at the beginning of the 19th century. Thomas Jefferson chose it for Monticello in 1800. Tin was often referred to as "bright tin" to distinguish it from the lead-tin mixture, terne (meaning "dull"in French). Because the plating process required that the base iron be dipped into molten tin, it could only be produced in small sheets. The sheets measured 10 by 14 inches in the 1830s, but by the 1870s, advances in manufacturing increased the size to 20 by 28 inches. Tin's availability and reasonable cost made it a very common roofing through much of the 19th century. It could be quite durable, but only if kept well painted.