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.
Metal Roof Construction
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.
In the popular imagination, “corrugated” metal roofs are often associated with rusting frontier store fronts, old barns and dilapidated rural shacks. While it remains primarily a commercial roofing application, modern corrugated metal with its bevy of attractive colors, is finding its way onto more and more residential roofs.
Standing seam roofs with their distinctive vertical panels still hold sway in residential construction and upscale commercial applications. They too, are available in dozens of standard colors, and roof colors can be customized as well.
Metal is no different than any other roofing material – if it is not done right the first time leaks and costly repairs can follow. Corrugated metal panels can be installed in many cases directly on top of an existing asphalt shingled roof due to its light weight.
Anchoring a standing seam roof to a shingle roof is more problematic, because the metal will contract and expand with the temperature and the scraping against the rough shingle surface could cause unseen corrosion under the panels. Metal roofs, unlike tar-based products, are easily installed in the winter.
When looking at installation costs, begin with the complexity of the roof. Corrugated metal is the cheapest to apply and expect to pay anywhere from 100% to 200% more to install a standing seam roof. The disparity will be even greater, obviously, if a tear-off of the existing roof is not necessary to put up the corrugated metal roof.
Galvanized steel roofs typically carry warranties of up to 50 years. Aluminum and copper-zinc roofs will have a life expectancy twice that. While metal roofs cost more than asphalt shingles up front, they will last three to five times longer. While you may not be staying in your house 50 years the presence of a metal roof will enhance your asking price at sale time as the next owner will not have to worry about installing a new roof anytime soon.
While metal can last on a roof for centuries, the coating on metal can not. This could lead to the need for painting or re-coating in areas subject to harsh weather and acid rain. In the meantime a metal roof can be kept looking fresh with just a regular hose down. Also the fasteners on corrugated metal roofs should be re-tightened and re-caulked about every ten years.
When properly installed, both corrugated metal and standing seam roofs are capable of handling 110 mile per hour winds and higher (that is Category 3 hurricane level). Some systems offer uplift protection up to 160 mph. Corrugated metal roofs, with their exposed fasteners, are a bit more susceptible, so an extra twist of the washer-protected screws is a good idea in wind-prone areas.
More problematic are the things wind blows down. Both types of metal roofs will withstand damage from all but the largest fallen branches. Metal roofs will also stand up to the pounding of hail. In winter, snow will slide off a metal roof, preventing accumulation of heavy snow and ice dams from forming.
Metal roofs will also not ignite like cedar and asphalt shingles in wildfires. In fact, FEMA recommends the installation of metal roofs in high-risk areas, and homeowners can realize insurance savings with a metal roof on their house.
Metal roofs can also save on your monthly energy bills. The reflective surface sends the sun’s rays back into the atmosphere in the summer helping homeowners reduce their AC expenditures.
Metal roofs are fabricated from recycled metals – as much as 40% for some materials. And when your metal roof is ready to come down – long after you are gone – it will go 100% into a futuristic recycling system. That is not a claim petroleum-based asphalt shingles can make.
Both standing seam and corrugated metal panels can be outfitted for solar power generation, either with traditional PV solar panels or, in case of standing seam, with photovoltaic solar laminates designed to adhere directly to the metal surface.
Myths, Misconceptions and Downright Wrong Information
Noisy! Not going to lie to you. If you live in an uninsulated shack with a metal roof laid across open lath framing you are going to hear the rain hit your roof. If, however, like most people you live in a normal house with an insulated attic space or work in a standard building, a metal roof is no noisier than an asphalt roof.
It’s a thunderstorm! We’re all going to fry! Well, no. While metal indeed conducts electricity, a metal roof dissipates the energy harmlessly away – even without being grounded. And no, a metal roof is not a giant lightning rod that will attract repeated lightning strikes. That’s why many home insurance companies are comfortable offering reduced rates to homeowners with metal roofs.
All that snow sliding off the roof is going to trap us in the house until spring! You can easily install snow guards on the roof that will keep the white stuff from piling up at your front door. 😉
No doubt about it, a metal panel roof will cost more up front than traditional asphalt roofing. But that metal roof will still be up there when that asphalt is being replaced for the second, third or fourth time.
The two most common choices for a metal roof are corrugated metal and standing seam. Corrugated metal is most often associated with utilitarian installations but can also be applied to residential roofs. The clean lines and unexposed fasteners of a standing seam roof are considered more attractive and earn the bulk of the residential trade.
The price for that sharp look is in the installation that is more expensive, especially if a tear-off of the existing roof is involved. Both styles are available in a rainbow of popular colors, many more than asphalt shingles. Metal roofs are almost maintenance free, but corrugated metal roofs do require a bit more attention to tend to exposed fasteners every several years or so.
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