Metal Cladding For Domes: The Why And The How

by Freda Parker

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Why would someone want to cover a Monolithic Dome with metal cladding? David South, Monolithic's president, says "Metal cladding is an arrow in the quiver -- a problem solver -- that's especially useful when things get really nasty."

The really nasty, according to David, happens over time to domes that have had their Airforms pulled off or not properly coated and maintained.

"That may take ten years or more, depending on circumstances," David says, "but eventually it happens. When the urethane foam blanketing the dome is left unprotected, it suffers from exposure to both sunlight and moisture. At night, dew forms on the dome. You won't even see that layer of dew, but it's there every night. In the morning, the sun drives that water vapor into the foam and you get blisters."

Once that happens, the solution may not be to simply cut off the blisters and recoat the foam. "You can still trap moisture inside the foam," David warns.

So, how does metal cladding prevent the moisture-trapping from happening? "There's air movement under the metal shingles that provides an escape route for the water vapor. The moisture rises to the surface and evaporates," David says. "Nightly dew still forms on the metal clad dome, but instead of working its way into the foam, it simply slides off the shingles."

Monolithic knows of a number of domes that have been successfully metal clad. Most of these are among the first domes built when Airforms were removed for reuse.

Various thicknesses, widths and colors of steel metal cladding can be ordered from manufacturers and distributors listed on the Web or in local phone directories, usually under roofing or building materials. And since it's flexible, metal cladding can be more easily fitted over window and door framing.

While the application process is not particularly difficult, it does require some special equipment. In 2001, Monolithic covered Bruco, its factory, with metal cladding.

David recalls that the steel cladding arrived on coils weighing 4000 pounds. It measured .020 inches thick, 2 feet wide and 2000 feet long. He says, "We put the coil on a kind of sleigh, so the metal could slide under rollers that look like old-fashion washing machine rollers. We used a knife to cut rhomboid shaped lengths. Then, we put them together over the foam, lapping the shingles like fish scales, and securing them to the foam with stitch screws."

Properly applied, a quality metal cladding, with a finish that should last 40 years, is easy to maintain, usually requiring only an occasional water hose shower to remove surface dust.

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• Exterior Design 101
• Lessons Learned by Monolithic in Exterior Coatings
• Exterior Coating Options: MDI experiments can save you time and money

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