No commercial roof products are made of pure tin. Beginning in seventeenth century Bohemia, rolled steel was coated with tin to prevent rust. In the nineteenth century United States, “tin” plates or shingles were widely used as roofing material. The lightweight tin products were less expensive to ship. They were durable, with some manufacturers predicting 50 to 100 years for the life of a tin roof. Lightweight tin roofs saved money in construction, because they required fewer struts and beams. Tin roofs were painted as additional rust protection, usually with an iron oxide red paint or sometimes a pale green to imitate weathered copper.
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In western culture, copper and lead roofing originated in ancient Rome and was used in Europe through the Middle Ages. The longest lived copper roof was installed on a cathedral in Hildesheim, Germany in 1230 and remained intact until bombed in 1945. Metal roofing material was produced by heating and hand hammering the metal to a thin sheet. The first tin-plated steel was produced in the same costly way. In the late 1600s in Germany, heated steel was first thinned by rolling, a less expensive process. Tin plated steel food containers and utensils originated in Bohemia (Czech Republic) and first appeared in England in 1725, as noted in port books in Gloucestershire. Steel rolling mills were patented in England in 1728. During the 1700s, rolling mills were installed at mints, first in Cassell (central Germany) and Sweden.
Just before 1800, tin shingles began to be imported to America from Wales, where tin was mined. In Philadelphia, Christ Church was completed by 1744 with a copper roof, but the Arch Street Meetinghouse was designed in 1804 to have tin shingles. By that time, the Pennsylvania Statehouse (Independence Hall) also had a tin roof. In 1818, Thomas Jefferson was among the architects planning metal roofs for the campus that was later the University of Virginia. Jefferson commissioned a study of tin shingle roofs already in use in the town of Staunton, Virginia. A builder who had worked for Jefferson at Monticello reported that the Staunton roofs were of good quality, and quoted the Staunton builder’s claim that similar roofs had been in use without failure in Canada for 50 years. Jefferson installed a tin shingle roof at Monticello.
Tin roofs were not used in ordinary residential construction until after the Civil War. The materials were expensive and imported. The installation of large tin plates involved a labor intensive “standing seam” made by bending the edges of each plate upward and then folding the pieces of metal over each other. Later, when tin was more available as shingles that could be installed with nails, tin roofs became common for residences. Prices declined further when pure tin coatings were replaced by 65:35 lead to tin alloys that created a dull finish termed “terne” plate. Tin roofs were most common in areas of that could expect heavy snowfall, because a smooth roof surface encouraged snow to slide. The shingles were embossed with designs and sold as individual shingles, interlocking individual shingles, and strips of roofing embossed to appear to be a row of shingles.
Tin roofs were most popular in the United States between 1860 and 1920. The first tin roof in the Arizona territory was installed onto a retail store in Yuma in 1861 by a “mechanic” brought by rail from San Diego to do the job. In 1885, advertisements of the National Sheet Metal Roofing Company of New York City offered charcoal backed tin shingles that attached without solder, metal cleats or double-seaming and therefore allowed for expansion and contraction while resisting condensation. In 1910, as the N&G Taylor Company of Philadelphia celebrated its 100-year anniversary as a supplier of tin roofing materials, its advertisements featured interior photographs of a fire gutted department store where only the tin roof had survived the flames.
The tin roof plate and shingle production technique used through the nineteenth century began with rolling heated iron bars as many as six times, each time flattening the mass to double the length and width. The next step was removing rust, at first with sand and water, and after 1747 by “black pickling” in a fermented rye or barley solution, and after 1760 in hydrochloric acid. Then, with the first annealing, the thin sheets were slowly cooled to “soften” them to a strength that could flex and readily “polish” (seal) when cold rolled. A rough, unpolished surface had more area to plate and therefore required more tin. Cold rolling hardened the steel, so a second annealing allowing 10 hours to cool was necessary. Then, a second pickling again removed rust.
In the eighteenth century, palm oils from west Africa began to replace the literally stinking baths of rendered animal tallow that were first used in tin plating. An oil bath boiled off any moisture on the surface of the steel. Then, bundles of steel sheets were immersed in a bath of molten tin, tended by a “tin man” who separated the sheets with tongs to make sure that all surfaces were exposed to the molten tin. From the tin man, the plated sheets went to a “wash man,” who used a thick hemp brush to remove any excess tin before the next rolling added shine. In the final step, women removed the oils with sawdust and hand-polished the sheets.