The popularity of metal roofing is both a benefit and a curse, according to Richard C. Schroter, P.E., CDT.

The popularity of metal roofing is both a benefit and a curse. "You don't have to sell people on the appearance and durability of metal," according to Richard C. Schroter, P.E., CDT. "People just know that it's better and that it's beautiful."

Designed and installed properly, metal roofing can last centuries. Done poorly, it becomes a daily misery for owners, architects, and contractors alike.

Schroter is a leading expert in metal roofing applications, a Fellow at the Construction Specifications Institute currently working as a staff consultant for Simpson, Gumpertz and Heger Inc., San Francisco, Calif. He spoke to contractors during the Architectural Contractors Forum at SMACNA's recent annual meeting in Hawaii.

Although he proclaimed himself "a technical guy," Schroter said both architects and contractors must acquire an almost Zen-like appreciation for the properties of architectural sheet metal.

"Learn to live with the nature of metal," he said. "For example, snow slides off it. Also, metal will do what it wants to do and you can't stop it with fasteners. Make sure your guys in the shop understand that the joint is going to move."

Schroter used examples of installations, including many in Europe, where form and function merged perfectly. A job at Court Number One at Wimbledon in England featured tapered curved panels to form a 3608 dome. The panels were measured and cut so expertly that when the installers came to the last opening, "the panel just dropped into place with a tight, perfect fit."

But Europeans have no monopoly on craftsmanship, Schroter said.

"It's a myth that European sheet metal workers are more skilled than those in the U.S. There's just a difference in the culture of what people expect. We need to build a culture that will accept only the quality of work that we like to do."

Too often, though, bad designs and inexperienced low bidders combine to create twisted, ugly roofs that "will kill the market for us," he said.

"Idiots try to stretch curved metal with vice grips. They use snap-on fasteners that snap off just as easily. They tell people that metal roofing can solve ice dams, when it can't. You cannot straighten out a crooked building with some sheet metal on the outside.

"We've got to get back to fundamentals. We need to train our people from zero."

Common sense

Schroter presented a list of "common sense" suggestions for ensuring a quality installation.

1. Architects should use proven details. "Find out what you should have before you bid out the job. Don't let the low bidder choose. Verify system performance. Specify a roof rib profile of proven performance, compatible with the desired perimeter details. Verify contractor and manufacturer claims. "

If the designer doesn't do these things, the contractor isn't off the hook for a bad job. "I tell contractors, if you run into design problems that you can't get changed, write a letter explaining the conditions," Schroter said.

2. Require continuous seals. "That should be obvious. When you have a hole in a boat, it leaks. Roofing is like aviation. Rain and wind look for the weakest link." Keep the use of sealants to a minimum.

3. Allow for thermal movement. Extreme daytime climates followed by night sky radiation and can cause temperature differentials of up to 2008. Design all details to accommodate expansion and contraction, including perimeter and penetration details.

4. Use compatible materials. Verify that dissimilar materials are kept separate to avoid galvanic corrosion. Eliminate contact of sheet metal roofing with sharp corners that may cause wear.

5. Assure underlayment drainage. Verify that the material is appropriate for the conditions and that leakage does not freeze or build up internally.

6. Require complete shop drawings that show isometrics of complex intersections with position and description of fasteners and sealant. Use factory-fabricated assemblies to minimize intricate field work. Make a mock-up of conditions that are not easily resolved with drawings.

Schroter said the metal roofing industry needs to take specific steps to upgrade its professionalism:

  • Adopt standards of quality that apply to all installations.

  • Develop specifications for those quality standards.

  • Add sealant guidelines. ("We're basically a soldering and welding industry, but sealant is here to stay, especially as long as prefinished metal is used.")

Design for humidity control and venting.

  • Fund research on the effect of wind on metal roofs.

    Finally, the success of metal roofing is dependent on the workers who install it, Schroter said. "Hire for attitude, train for skills. Get down to basics. Your people can do good work and they need to like their work. Reward them financially and with recognition."