Copper – the uses in roofing

This is an extract from an article taken from Hoffman Architects Journal and was written by Juan Kuriyama, AIA and William Hayes, Assoc. AIA.

‘Traditionally, there are three types of copper roofing, each with its own distinct aesthetic qualities and applicability for a given roof condition.

Flat Seam Unique to copper roofs, flat seam construction is generally reserved for low-slope roofs or curved surfaces, such as domes or vaults. Cold-rolled copper sheets are folded over at adjacent sides, with copper cleats installed in the seams. Typically, the longitudinal seams are continuous, whereas transverse seams are staggered. For slopes of 3”-in-12” or less, the flatlocked seams are soldered to improve water-tightness.

Standing Seam Pre-formed or field-formed pans are used to create standing seam copper roofing. One side of each pan is formed longer and folded twice over the adjacent pan, joining the panels together. These double-locked standing seams run parallel to the roof slope, with fixed copper cleats securing the roofing to the structural deck.

Batten Seam With its characteristic box-shaped seams, batten seam construction is commonly used on domes, barrel vaults, and cupolas to create a dramatic roof line. Like standing seam roofs, batten seam construction positions copper pans parallel to the roof slope. Panels are separated by wood battens, which are covered with copper batten caps that are loose-locked to adjacent pans to accommodate expansion and contraction. In addition to its use as a roof cladding, copper is also widely used for roof flashings, gutters, downspouts, and cornices, in conjunction with other roofing types and materials. Its resistance to corrosion and its malleability allow copper to be readily shaped to accommodate intersections, bends, and curves without failure.

Aesthetics Regardless of type, copper roofs both new and old are standouts in any building skyline. Beyond practical considerations, such as low life-cycle costs, salvage value, longevity, and low maintenance demands, copper is often selected for roofing because of its distinctive color and texture. With natural weathering, copper changes from the color of a new penny through a series of dull brown shades to a striking blue-green. Depending upon the climate and application, copper roofing weathers and changes hue gradually over time, lending each copper-clad roof a unique appearance’.