Standing Seam Roofing - Alum vs Steel?

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Author Message Nathan Woods, CCCA, LEED AP Senior Member Username: nwoods Post Number: 379 Registered: 08-2005 Posted on Monday, January 31, 2011 - 12:34 pm:    I have a project on southern coast of California where a standing seam metal roof is proposed. There is a discussion among the various parties involved in this project regarding the use of aluminum verses steel for the roofing material. We are less familiar with aluminum standing seam roofing and would appreciate your feedback regarding the strengths and weaknesses in comparison between the two materials. (Unregistered Guest) Unregistered guest Posted on Monday, January 31, 2011 - 06:08 pm:    The only difference is cost, and coating warranty. Both perform exactly the same, but the finish warranty for "coastal" areas is not provided for the steel panels. This is because of the potential for the coating to separate from the substrate at the edges in environments that are near bodies of water. Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 369 Registered: 10-2002 Posted on Monday, January 31, 2011 - 07:28 pm:    Contrary to the previous post, both DO NOT perform exactly the same. As is typical with most construction materials, every product has its’ own set of pro’s and con’s. Generally, the most important issues to a metal roof are wind and snow loads. Aluminum is much softer and weaker than steel but more chemical- and salt-resistant. I have successfully used standing seem aluminum in projects on the Atlantic coast from FL, NC, VA, and MD. Depending on the specific location (ie, hurricane “alleys”), additional/stronger fasteners may be needed. Aluminum tends to be more expensive. Aluminum also tends to have more aesthetic issues (ie, waviness, distortions, and “oil-canning”). Aluminum does not have a Class A fire-rating but can the system can achieve a Class A rating with the proper underlayment and sheathing. Aluminum must have a finish. Steel can be, but is generally, not used in coastal and other environmentally-hostile areas. In some cases, it is specifically not recommended by the steel mfr. Steel is a Class A product. Steel is almost always used in high snow load regions. You never (I know the rule is to never say never) see aluminum roofs in the really high snow load (typically 100-psf) regions. Both the steel mfrs. and metal roofing accessory mfrs. (ie, snow retention devices) fully agree that steel should be used. I have successfully use specified standing seam steel roofs in western Maryland and in the Rocky Mtns of Colorado and Montana. Steel also offers a wider variety of material choices - steel, stainless steel, and lead-coated/glavalum type hybrids. Finishes affect the final cost of a metal roof more than anything else. Both aluminum and steel have an interesting variety of finish choices. High-performance (siliconized polyester and others) and high-reflective coating are now available (hey, they even have “green” finishes available). I believe (I could be wrong here but it seems to be the case) that there are a wider variety of color choices available from the steel industry. Steel (depending on the alloy and thickness) can also be left unfinished and left to rust (very popular in the mountain chalet resorts). Last, but not least, is the rapidly changing technology of underlayments. The old asphalt felts (15# and 30#) are largely no longer recommended by the metal roofing industry. In your Southern CA project, I would suggest that you consider a high-reflective coating on aluminum with a high-temperature underlayment over the roof sheathing. "Fast is good, but accurate is better." .............Wyatt Earp Nathan Woods, CCCA, LEED AP Senior Member Username: nwoods Post Number: 380 Registered: 08-2005 Posted on Monday, January 31, 2011 - 09:23 pm:    Thanks Ron! Richard Howard, AIA CSI CCS LEED-AP Senior Member Username: rick_howard Post Number: 247 Registered: 07-2003 Posted on Monday, January 31, 2011 - 10:38 pm:    We had a school in our area (Ohio) with an aluminum standing seam roof. The expansion and contraction caused popping sounds as clouds passed overhead during the day. The owner made sure he didn't get another aluminum roof. Not that steel won't exhibit some of the same, but it is somewhat slower to react and has a lower coefficient of expansion. Jeffrey Wilson CSI CCS Senior Member Username: wilsonconsulting Post Number: 43 Registered: 03-2006 Posted on Monday, January 31, 2011 - 10:55 pm:    There can be a big difference between aluminum & steel roof panel performance with respect to thermal expansion -- particularly w/ roofs that have curves, unusual shapes, or long runs. With some configurations, it might be necessary to accommodate several inches of movement in aluminum panel systems. I have been involved in projects where this consideration alone was a deal-killer for aluminum. J. Peter Jordan (Unregistered Guest) Unregistered guest Posted on Tuesday, February 01, 2011 - 10:02 am:    I had difficulty with aluminum on a project located right on the beach near Galveston. They had a very hard time finding a manufacturer who had a system that would withstand the wind load required (resulting from 130 mph wind speed). Did finally find one who would accept the responsibility. In the same thickness, aluminum is not as strong as steel although it is stronger by weight, Have you thought about stainless steel? John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1298 Registered: 03-2002 Posted on Friday, February 11, 2011 - 12:27 pm:    I wonder if the popping could be reduced by the new ceramic-containing coatings that reflect heat? Maybe that would slow heat gain and loss to reduce that problem.