Which option lists the two types of iron commonly found in North American buildings?

• A. Cast iron and wrought iron
• B. Cast iron and steel
• C. Wrought iron and steel
• D. Cast iron and aluminum

Answer: (A)

Two common forms of iron in buildings are distinguished by how they’re made and how much carbon they contain, which directly affects their properties and uses. Cast iron has a relatively high carbon content and is melted and poured into molds. This gives it hardness and excellent compressive strength, but it is brittle and performs poorly in tension or bending. Because of that, cast iron is found where shape, wear resistance, or surface hardness matter, such as decorative columns, facades, pipes, or radiators in older construction. Wrought iron, on the other hand, is produced by working the iron after smelting to lower its carbon content, making it ductile and tough. It can be shaped, twisted, and bent without cracking, so it’s ideal for elements that must handle tension and dynamic loads, like ornamental railings, brackets, and other ironwork. In North American buildings, especially older ones, you commonly encounter both forms, whereas modern framing is typically steel (an iron alloy) rather than these two forms of pure iron.