Specifying Copper

by Jonathan McGaha | October 31, 2016 12:00 am

What you need to know when specifying copper

Copper has been used in architecture for hundreds of years. From roofs to walls, copulas to spires to gutters, copper is easily recognizable in many architectural buildings throughout history. It has many features such as its malleability and durability that make it very attractive to architects and designers. And, it’s ability to be recycled without any loss of performance, makes copper a very sustainable product.

Since there are many aspects to know when it comes to specifying copper in architecture, we turned to the experts to find out some highlights of what you need to know.

 

The Basics

The most commonly used copper for sheet and strip applications complies with ASTM B370. Consisting of 99.9 percent copper, it is available in six tempers, designated as: 060 (soft), H00
(cold-rolled), H01 (cold-rolled, high yield), H02 (half-hard), H03
(three-quarter hard) and H04 (hard).

“[Tempers] depend on the method of fabrication,” explains Jim Walas, architectural manager at Revere Copper Products Inc.[1], Revere, N.Y. “Panforming operations usually tend to approach the half-hard, while people using individual sheets tend to have a product that is between 1/4-hard and 1/8- hard.”

Stephen Knapp, director of the sheet, strip and plate program at the Copper Development Association Inc.[2] (CDA), says in general, cold-rolled, 1/8-hard temper (H00) copper is recommended for most roofing and flashing installations. “Soft copper may be used where extreme forming is required such as in complicated thru-wall flashing conditions,” he says. “However, it should be noted that cold-rolled copper offers far more resistance than does soft to the stresses induced by expansion and contraction. Copper roof sheet of higher temper should be specified only if indicated for specific and engineering applications requiring such higher tempers.”

Copper is available in 12 ounces to 48 ounces, but Knapp says 16 ounce to 20 ounce is the most typical. It comes in 8-foot and 10-foot flats or coils, and pans are typically 14 inches to 18 inches wide when finished. “The 16-ounce is the most popular, and probably consumes about 75 to 80 percent of the total demand of architectural products,” Walas adds.

Sixteen-ounce copper is 0.0216-inch thick, while 20-ounce is 0.027-inch thick. Walas says widths vary depending on the end use, with the typical 18-inch, 20-inch and 24-inch coils supplied for pan-forming equipment. Sheets are generally 2 feet or 3 feet wide and 8 feet or 10 feet long. Applications for gutter coil are generally 9 inches to 24 inches wide, and through-wall flashing material is generally supplied in much lighter ounce weights.

 

Color Options

Copper is available in a variety of colors and alloys, ranging from the typical salmon-colored 110 alloy pure copper to yellows, silvers and others, all of which will patinate. However, different copper manufacturers offer different options. For example, Revere Copper offers Continental Bronze, copper with a pre-aged natural oxide finish, or the Liberty Collection of textured copper in different patterns. “Color is a choice that architects have,” Walas says. “The most common is bare classic copper that will oxidize and patinate over time. Other choices include coatings like tin and zinc FreedomGray, tin alone, and lead.”

Additionally, Walas says there are treatments to artificially patinate copper to a brown or a green, which can be supplied by some manufacturers, and field applications can also be accomplished with chemical treatments.

“The CDA recommends that copper and copper alloys be allowed in most cases to weather naturally to adapt to the local conditions and circumstances,” Knapp explains. “This will allow the copper or copper alloy to form a naturally occurring and tenacious patina that will protect the material and ensure a long service life.”

“Architects need to remember that copper is going to change with time, and to expect contrasting colors on a roof surface, and contrasting colors and shades between the north and south sides,” Walas adds. “It’s a very changeable product, especially when it is newly installed.”

 

Sheet versus Coil

When deciding whether to specify copper as a sheet or coil, Knapp says it usually depends on the configuration of the roof or wall. “The choice to specify coil will allow for long pans to be formed, thus minimizing transverse seams,” he says. “It can also minimize waste, as you can design pans as long as you need or want them.”

“The method of fabricating a coil or sheet can produce the same roofing pan,” Walas says. “However, the length of the pan is constrained when using a sheet. Sheets are normally supplied in 8-foot or 10-foot lengths. Coils can produce longer panels if the design wants to avoid transverse seams.”

 

Copper and Other Metals

When specifying copper, it is also important to keep in mind what other metals it will be around. Copper and its alloys, such as brass and bronze, are the most noble building materials currently in use today. “That means in the presence of water, they will corrode other less noble metals-like zinc, aluminum and steel-if they come in contact with them,” Knapp says. “It is important to physically separate them and also ensure that water or other forms of run off do not bridge any gaps between them. For example, this could be a situation with a copper roof and an aluminum skylight.”

“Architects and specifiers should feel confident that they are selecting a material that is one of the man’s oldest building materials, and that has great natural beauty and unrivaled service longevity when properly designed and installed,” Knapp adds.

More information on copper can be found in the “Copper in Architecture Handbook,” available for free from the Copper Development Association atwww.copper.org[3].

 

Photos, from top to bottom: David Braley Health Science Centre in Hamilton, Ontario, Canada. Photo: Norr Architects, Courtesy of CDA; This photo shows fully aged green copper, recently installed copper and copper being installed at Harvard University, Cambridge, Mass., Photo courtesy of Revere Copper Products Inc.; Currie & Mackenzie buildings roof replacement at the Royal Military College, Kingston, Ontario, Canada. Photo: Colbourne & Kembel, Courtesy of CDA.

Source URL: https://www.metalarchitecture.com/articles/specifying-copper/

---