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Q.How common is aluminum standing-seam roofing? It seems that this profile would be better suited for heat-related expansion and contraction than corrugated aluminum panels fastened through their face, but my local suppliers carry only steel standing seam.

A.Todd Miller, president of Classic Metal Roofing Systems in Piqua, Ohio, responds: Aluminum is a perfectly viable material for standing seam, though probably 85 percent of metal standing-seam roofing is produced from either galvanized steel (which has a protective metallic coating that is primarily zinc) or galvalume (which has a protective coating that is primarily aluminum). Aluminum and copper each make up about 5 percent of the market, with other types of metals — zinc, stainless, terne — accounting for the remaining 5 percent.

One advantage of aluminum is its permanent rust resistance. Even though aluminum roofing always has a prepainted finish, less care is required during installation to protect cut edges or prevent minor scratches than with steel roofing, most of which is also prepainted (though galvalume is sometimes supplied with a clear-coat finish). Also, because aluminum roofing loses heat more rapidly than steel roofing, it can be a more energy-efficient choice in warm climates.

For a given thickness, aluminum standing-seam roofing doesn't have as much structural rigidity as steel roofing — which is often installed over purlins — but there are aluminum standing-seam panels that are strong enough to be installed without decking. Typical thickness for aluminum standing seam ranges from .032 inch to .050 inch, with the heavier products being the ones that can be installed over purlins rather than decking. By comparison, steel standing-seam roofing typically ranges from .015 inch to .030 inch thick.

You should expect to pay about 10 percent to 20 percent more for aluminum standing-seam roofing than for galvanized steel and galvalume standing-seam roofing panels (which are generally similar in price). Companies that offer aluminum standing seam include ATAS International (800/468-1441, www.atas.com); Classic Metal Roofing Systems (800/543-8938, www.classicroof.com), and Petersen Aluminum (800/722-2523, www.pacclad.com).