Metal Roofing Materials
There are a variety of metal roofing materials available.
Galvanized Copper Pre-Painted Terne
A product that became popular in the 1920's, Galvanizing is a process which involves a piece of steel or metal being submerged in melted zinc. It is during this process that the zinc chemically reacts to the molecules in the metal, permanently bonding it to the metal. The zinc provides protection against rust and corrosion that the natural elements have a tendancy to cause; elements that weaken unprocessed steel or metal.
Copper has played a role in architecture for thousands of years. In the 3rd Century B.C., copper roof shingles were installed atop of the Loha Maha Paya Temple in Sri Lanka. And the Romas used copper as a roof covering for the Pantheon in 27 B.C. Centuries later, copper and its alloys were integral in European medievil architecture. The copper roof of Hildersheim Cathedral, installed in 1280 A.D., survives to this day. And the roof at Kronborg, one of northern Europe's most important Renaissance castles that was immortalized as Elsinore Castle in Shakespear's Hamlet, was installed in the 1585 A.D. The copper on the tower was renovated in 2009.
Terne Coated Copper (Freedom Gray), Lead Coated Copper
There is a wide variety of colors available on either pre-painted galvanized or prepainted galvalume materials.
Terne - ( not currently available )
Terne is an alloy coating that was historically made of lead and tin used to cover steel, in the ratio of 20% tin and 80% lead. Currently, lead has been replaced with the metal zinc and is used in the ratio of 50% tin and 50% zinc. This alloy has a low melting point approximately 360 degrees Fahrenheit.
Terne metal must be painted. If the paint is maintained, terne metal can last 90 years or more. Terne coated stainless steel (TCS) or copper is commonly used to replace terne metal roofs as either material will outlast terne metal. TCS or copper roofing can last 50 years or more unpainted.
The "Galvalume" process is virtually the same as the galvanizing process except the steel or metal is submerged in a melted mixture of 55% aluminum / 45% zinc.
Zinc roofing was first used in the United States in the early 1800's. Though its popularity was cyclic over the following decades, zinc roofing has become the most popular form of roofing in Europe, covering approximately 70% of residential buildings. Zinc roofing strips are today an architect’s favorite roofing material, as they are versatile in use, appearance, and application. Many people are slowly discovering the great advantages of zinc roofing as its popularity increases.
To begin with, Zinc roofing is an optimum investment, as it is able to resist corrosion by naturally developing its own protective patina. This distinctive patina also provides durability, and together these features allow a zinc roof to live for about 100 years in a rural environment – 4 times that of steel roofing. What’s more, is that this patina will also allow zinc roofing to self-repair imperfections and scratches, and eliminate the need for a coating or varnish, and regular maintenance. Zinc roofing strips are highly malleable and can adopt any shape, including low radius curves and complex shapes unachievable with other materials, allowing for great freedom of design. Zinc roofing is also a natural material and can be recycled indefinitely, making your building environmentally friendly. The only possible downside of applying zinc roofing strips is that they are initially quite expensive.
For centuries lead sheet has been the standard for roof coverings on some of the world's most prestigious and important buildings. When correctly installed they outlast all other commonly used roofing materials for many years. Whether used as the main roof material or as flashing, lead is unsurpassed in its durability and longevity.
Lead is the softest of the common metals. The most important of leads many properties is its resistance to hardening. As lead is quickly self annealing at ambient temperatures it can regularly be shaped by bossing without the frequent application of heat. When bossed correctly lead will not become brittle, crack or be reduced in thickness significantly.