Techniques > Briefs > Roofing for Historic Buildings > Historic Roofing Materials in America > Metal

Slate Tech Note

• galvanizing
• Prince Albert's corrugated iron bldg.
• US mint in N.O. - HABS image?

• Examples
• Architectural Conservation Audit • Wood species
• Shingles vs Shakes

Sheet Iron

Sheet iron was first known to have been manufactured here by the Revolutionary War financier, Robert Morris, who had a rolling mill near Trenton, New Jersey. At his mill Morris produced the roof of his own Philadelphia mansion, which he started in 1794. The architect Benjamin H. Latrobe used sheet iron to replace the roof on Princeton's "Nassau Hall," which had been gutted by fire in 1802.

The method for corrugating iron was originally patented in England in 1829. Corrugating stiffened the sheets, and allowed greater span over a lighter framework, as well as reduced installation time and labor. In 1834 the American architect William Strickland proposed corrugated iron to cover his design for the market place in Philadelphia.

Galvanizing with zinc to protect the base metal from rust was developed in France in 1837. By the 1850s the material was used on post offices and customhouses, as well as on train sheds and factories. In 1857 one of the first metal roofs in the South was installed on the U.S. Mint in New Orleans. The Mint was thereby " fireproofed" with a 20-gauge galvanized, corrugated iron roof on iron trusses.