Corrugated Metal Roofing
Corrugated means folded to produce ridges and grooves. The purpose of corrugating is to increase the tensile strength of a material. The first corrugated metal roofing materials used was galvanized iron and was referred to by the initials CGI (corrugated galvanized iron). The corrugating process increased the bending strength of the galvanized iron in one direction, perpendicular to the grooves. When used on a roof CGI sheets overlap by at least a couple corrugations to insure waterproofing. Later other materials were galvanized for roofing, and strengthened in the same way.
Origins of Corrugated Metal Roofing
The idea for making CGI came to an engineer for the London Dock Company named Henry Palmer during the 1820s. Originally wrought iron was used for CGI, and due to its lightweight, corrosive-resistant nature, it quickly became a popular material for construction in the rural, poorer areas of the U.S., India, New Zealand, Chili and Australia. Additionally, for some of these countries the material went on to become popular in cities as well. Near the end of the 19th century, mild steel replaced wrought iron yet the initials CGI were still used.
Advantages of Corrugated Metal Roofing
Corrugated metal roofs were, and still are, popular for many reasons. Mainly their lightweight combined with their portability made them a convenient roofing material. Today these roofs are continuing in popularity due to their durability; corrugated metal roofs will last 2 to 3 times the length of less expensive asphalt shingled roofs. Large building or buildings that may experience large snow accumulation particularly benefit from a lightweight yet strong metal roof. Additionally metal roofs shed snow more easily than other types of roofs.
Corrugated metal roofs will resist the harmful effects of nature better than roofs made from other materials. Practically imperious to fire and hail these roofs will harmlessly dissipate the electric charge of a lightning strike and stand up to high winds better than asphalt shingles. Their ability to withstand the ravages of nature make any building beneath them less expensive to insure.
When combined with a high reflectivity coating, these roofs can cut air conditions cost by reflecting instead of absorbing heat from the sun.
Favorably affecting the thermal efficiency of buildings is not the only way corrugated metal roofing can save money. They are labor efficient because they require less man-hours to install; once installed there is little to no maintenance. Furthermore, there is less wasted material; the roofing material comes in sheets which can be ordered individually. Likewise the trim and ridge material can be ordered in this manner so leftover material is minimal. These sheets can even be ordered to specific lengths making less on the job modifications necessary. Additionally, the metal can be recycled saving material and energy as well as reducing waste sent to landfills. These roofs also afford a flexibility that other roofing materials cannot. A corrugated metal roof can be installed over an existing roof, a solid substrata or even an open frame.
Disadvantages of Corrugated Metal Roofing
Installation can be tricky due to the problems presented by thermal expansion and movement. Movement can loosen panel fasteners and, on occasion, produce annoying noises. The noises are rare occurrences and routine maintenance can help solve both problems.
A more worrisome problem is rapid corrosion brought on by the use of incompatible materials, specifically dissimilar metals. A knowledgeable installer should be able to foresee and avoid any problems in this area.
Metal corrugated roofing is seldom a local product and therefore must be mined, refined, produced and transported often over long distances. However with the increasing incidence of metal roofing be recycled this is less of a disadvantage. Corrugated metal sheets when purchased may be made of recycled material and after having served its purpose may be again recycled. Thus using this roofing material cuts waste, reduces pollution and conserves natural resources.
Cost can be considered a disadvantage, but only if the short term is considered. In the long term, a metal corrugated roof is not anymore expensive. It lasts longer, and due to its fire, hail and wind resistance, reduces insurance premiums. Finally, thanks to the rising cost of oil needed to make asphalt shingles, the difference in price between corrugated metal and asphalt shingles is shrinking.
Maintenance of Corrugated Metal Roofing
The amount of maintenance required of a corrugated metal roof is dependent on its quality/utilization. An inexpensive outbuilding, containing only “AG” or a “Utility” grade material, may need repainting with a roof coating. The original factory painting with an acrylic or polyester coating can allow corrosion and fading. New polymer coatings, like Kynar, are becoming common. A polymer coating is superior to older coatings in longevity, lasts a lifetime without experiencing fading or corrosion. It is important to note that panel fasteners exposed to the elements may require occasional re-caulking or re-tightening to avoid leaking.
When seen as an investment rather than an expense the cost of a corrugated metal roof is easy to justify. The same attributes that made it popular over a century ago are still present, and new features make it an even more attractive choice for today’s consumer.