Who Invented the Original, Corrugated Iron / Steel Roofing Style?
Henry Robinson Palmer learned his civil engineering under Scotsman Thomas Telford, the greatest builder of roads, canals and bridges in the British Empire in the early 19th century. In 1821 Palmer applied for a patent for a single elevated rail supported by pillars spaced ten feet apart that sported wheeled carriages hanging down from either side that would roll along the rail when pulled by a horse. Henry Robinson Palmer had invented the world’s first monorail.
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If you research Palmer’s life today, every source details the creation of the monorail. For most thumbnail sketches of Palmer’s life that is the end of the story, but Palmer himself did not concern himself much with the monorail after building the first one in 1825, about one mile long, in Cheshunt, a town twelve miles from London. Two years later the 32-year old Palmer landed a job as resident engineer for the London Dock Company. It was his responsibility to construct the walls along the Thames River to keep the world’s busiest port humming.
The aging wooden docks were in constant need of upgrade. To keep up Palmer patented a lightweight metal building panel that was self-supporting due to a series of waves or folds molded into the sheets. Palmer’s manufacturing process consisted of pushing his sheet metal across fluted rollers to create the ridges that gave the metal strength. He called this “corrugation”, from the Latin word for “wrinkled.” It remains a common method for manufacturing corrugated metal today.
Palmer erected the world’s first corrugated building on the Thames River docks in 1829 and he continued to patent improvements in the construction of arches and roofs. It is ironic that today Henry Robinson Palmer is remembered for the invention of the monorail, which is rarely encountered outside of amusement parks, airports and a classic Simpsons episode. He is scarcely recognized for the development of corrugation, which became so ubiquitous in the 19th century for cheap shelter that most people – and historians – assumed it had been with us since antiquity.
Historical Significance of Corrugation
Without corrugated metal there would have been no rapid development of the United States frontier, a less frantic California gold rush, much slower settling of farm land on the Great Plains and much harsher living conditions on the battlefield. The strength to materials imparted by corrugation extended beyond the metal sop to other industries; it was critical to the development of the cardboard, for instance.
By stiffening the metal sheets, corrugation permits a greater span across a lighter framework, ideal for the balloon construction techniques that became widespread in the 19th century. But metal for roofing has been used for centuries, although it was rare in early America. Thomas Jefferson was a metal roof fanboy and installed tin-plate iron on the roof of his beloved Monticello in rural Virginia. A metal roof could be fabricated with shingles or a “standing seam,” a technique which involved folding the edges upwards and laying the sheets over one another. Fasteners would hide under the upraised ridge where the sheets interlocked, producing clean, aesthetically pleasing lines.
Metal Shingles Vs. Standing Seam Vs. Corrugated Metal Sheets
While metal shingles are also available today and can be produced to mimic any material, standing seam and corrugation remain the two most common types of metal roofs. Let’s have a look at them side by side as you consider your upcoming remodeling project.
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The earliest metals used in roofing were lead and copper. Both could last for centuries, which is fortunate since those metals are prohibitively expensive. Today, lead is most often found in roofing as a coating for steel and copper is mostly reserved for flashing or architectural details.
Tin and its close cousin terne, a lead-tin mixture that appears lackluster (hence its French name which translates as dull), were the most common metal roofing materials of the 19th century and are important in authentic historical renovations. Zinc had a brief run of popularity in the early 1800s as a roofing material, but it became most critical to metal roofing in 1837 when French metallurgists coated iron and steel with zinc to invent galvanization and (mostly) rust-proof metal.
In the 21st century, galvanized steel is the go-to metal roofing material. It is the least expensive roofing material and can be coated in many ways for appearance. Corrugated metal can be fabricated from a G-60 steel that is thinner grade and less expensive. Standard standing seam roofs can be made from G-90 grade steel, a higher-end Galvalume steel, or aluminum. Galvanized steel is fabricated in a range from 9 gauge (0.1532 inches) to 32 gauge (0.0134 inches). Standing seam metal panels typically begin as rolls of 24-gauge steel (G-24) or the thicker 22-gauge (G-22) before ferrous metal coatings are hot-dipped. Corrugated steel paneling can be formed from G-26 or G-29 steel, which makes its cost less expensive; standing seam roofs will never use steel thinner than 26-gauge.
Even galvanized steel can corrode. Galvalume is a trademarked product from U.S. Steel that takes carbon steel and coats it with an aluminum-zinc alloy that performs like galvanized steel on steroids. But even Galvalume will eventually lose the corrosion battle against the salt spray of ocean near the coastal regions. In such cases, aluminum is the metal of choice. Although more expensive than steel, initially, aluminum’s longer life expectancy helps level the eventual bottom lines.