Metal roofing is one of the most important achievements of the 19th century in America. Before this time, only lead and copper were used, copper for more extravagant and expensive buildings, and lead for protective flashing. These metals were used to cover the surfaces when standard materials like wood, slate, and tile were not feasible.
The Evolution of the Metal Roofing
Copper roofing with standing seams was used on more notable pieces of architecture such as the Christ Church in Philadelphia. When applied as with flat seams, copper was ideal for covering domes and cupolas. Initially, all copper sheeting was imported from England but at the end of the 18th century, facilities developed in America to roll sheet metal and importing was no longer needed.
Sheet iron was the first metal to be produced in this fashion and was manufactured first by Robert Morris, a Revolutionary War financier. His mill in New Jersey was responsible for producing the roof used for his mansion as well as to replace the roof of Princeton’s Nassau Hall which was destroyed by fire in 1802. After this, sheet metal became the must-have material for roofing. To create sheet metal, the iron needed to be corrugated. This process was patented in England originally in 1829 and allowed the metal to become stiff, so it had a greater span over lighter frameworks. These sheets also reduced the amount of time needed for installation and labor costs.
The next metal to be incorporated into roofing was zinc, in France in 1837. Galvanizing zinc was done to protect the base metal from rust and by the 1850s this zinc was used for post offices and customhouses, trains sheds, and factories. One of the first metal roofs in the South was installed in 1857 on the U.S. Mint in New Orleans, consisting of fireproof galvanized, corrugated iron. In Canada, the metal roofing was tinplate iron and eventually, this became used in the United States as well. Thomas Jefferson was an early advocate for tin roofing installing it on “Monticello” and later the Arch Street Meetinghouse was covered with tin shingles laid in a herringbone pattern.
Tin soon became the most common roofing material as rolling mills become more established, because of its lightweight and low-cost properties. Zinc was also used throughout this time as a less expensive alternative for the lead. However, the advantages of zinc were controversial and it never ended up being widely used across the country, leaving tin to be the more popular metal roofing material.