A.Rob Haddock of the Metal Roof Advisory Council responds: If this roof is 120 years old, that would mean it was built around 1880. In those days, the options were copper, lead, tin-coated iron, and terne-coated steel. Tin-coated malleable iron was disappearing at the time. Copper and terne rolled roofs were very popular during that vintage -- terne more so because it was less expensive.
Terne is an alloy of lead and tin that provides excellent corrosion protection for steel. It was recently taken off the market due to the politics of lead, although no specific health threat was ever established. The replacement material, manufactured by Follansbee Steel, is a zinc-tin alloy called Terne II (800/624-6906, http://...
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