Taking flight

Experts craft a singular roof system for a giant hangar that showcases American air and space history’s artifacts

By Fiona Maguire-O’Shea

ransferred from the U.S. Air Force to a volunteer group in 1994, Wings Over the Rockies Air & Space Museum is located in Hangar No. 1 of the former Lowry Air Force Base in Denver. The 182,000-square-foot museum houses iconic aircraft, space vehicles, artifacts, military uniforms and more.

Visitors can experience flight simulators and participate in educational programs and other museum-sponsored events. Each year, the museum welcomes about 160,000 people.

Installed in 1938, the 20-gauge corrugated metal roof on the airplane hangar performed well but had reached its useful life and required replacement. The structure was retrofitted with 92,400 square feet of curved standing-seam roofing. The roof also features ColorGard by S-5!, a snow guard solution made for standing seam metal roofs. This feature is especially critical to have in the Rocky Mountain region.

The challenge was to remove and replace the structure during winter while keeping the museum open. Adding to the difficulty was the shape and height of the roof—curved and more than 100 feet off the ground with a circumference measurement from eave-to-eave over the top of the barrel at 308 linear feet.

Another challenge was to meet the standards of the City & County of Denver’s Historical Landmark Preservation Commission. The new roof was not to change the look of the historic hangar.

For a roofing system that echoed the original material, new metal had to be historic in finish, profile and installation technique.

Lightweight retrofit

Project consultant Alec Garbini and AH Architecture brought in Colorado Custom Metal Inc. as the roofing contractor and proposed to leave the existing corrugated metal roof in place and retrofit a new lightweight roof system. This approach would allow the museum to remain open while the new roof system was built.

Mill-finished Galvalume from Fabral was selected for the standing seam panels to preserve the look of the old hangar and meet the criteria of the landmark commission. Fabral shipped in roofing coils to make the standing seam panels, as well as more than 300 flat sheets to custom fabricate the flashings, trims and components for the project.   

From the Fabral substrate, Colorado Custom Metal fabricated 25,000 linear feet of 6-inch-high Zee (Z) purlins from 16-gauge steel in its shop. Installers attached the Z purlins through the existing corrugated deck and into the main frame of the building. By securing the Z purlins to the main frame, workers transferred the load of the new roof system and raised the new fastening point 6 inches higher. 

Next, the installers laid down 6 inches of ridged insulation nested tightly between the Z purlins and used two layers of 3-inch-thick, foil-faced isocyanate insulation board, providing the building with an added R-value of 38. Workers enclosed the insulation and Z purlins with a high-temperature ice and water shield membrane.

An architect, a metal roofing designer/fabricator and a producer of snow guards all worked together to protect the infrastructural integrity of the museum, which preserves historic military and civilian aerospace artifacts.

Colorado Custom Metal then manufactured the 308-foot-long, 24-gauge, 18-inch-wide standing seam roofing panels, using four panels that were each 77 feet long. The company designed a custom expansion joint end-lap detail to attach the panels together, making them span the full length of the barrel.

High elevations

Mark Orsborn, president and owner of Colorado Custom Metal Inc., says his company’s expertise is completing projects at high elevation, “and keeping material on the building in niche climates.” These include work in Crested Butte, Aspen, Telluride and other alpine locations.

The 20-year-old shop was contacted by Alex Garbini, the project consultant. “I did some engineering and found we could put a new roof on top, add R value and not disrupt the occupancy. They accepted our proposal,” Orsborn says. The $1.2 million project lasted four months.

To start, “I started shopping for coil from anyone that would give us a 20-year manufacturer’s warranty. I ended up going with Fabral [for the coil and sheets] because they would write a watertight warranty,” Orsborn says, adding he is eager to work with Fabral again.

He then designed the new roof on paper and sent each component design back to Fabral to warranty all the applications that the coil and sheet would handle, including flashings and trim. Orsborn custom designed all the components but used a local fastener company to test and supply all the roofing fasteners.

Next, the shop had Winslow Crane Service lift a 15,000-pound New Tech Series SSQ II MultiPro roof panel roll-forming machine and suspend it inches above the center of the barrel of the roof. “We manufactured all our panels from the top of the roof.”

Because the project was completed over winter, “we moved snow a few times,” says Orsborn. Once the new roof was installed, the project consultant observed heavy snow sliding off the panels in greater volume than the pre-existing corrugated roof panels. He advised that something would need to be done to control rooftop avalanche conditions.

Preventing avalanches

Colorado Custom Metal contacted S-5! of Colorado Springs, which designed and engineered the ColorGard snow retention system to mitigate the avalanche problem. Manufactured from high-tensile aluminum and tested for load-to-failure results, ColorGard reduces the risks associated with rooftop avalanches and complements the appearance of the roof with matching finishes. The system is designed to last the life of the roof.

“I was particularly impressed with S-5!,” says Orsborn. “They were the only snow retention company in the marketplace that could give us the mathematical equation required to calculate the snow loads for their products. There was no guesswork. The ColorGard system also provided added strength to the overall diaphragm of the new roof system.”

After the project was finished, Orsborn says he met with the building engineer, who said there hasn’t been a single problem with the roof.

“We only used a crew of eight to do all the custom roll forming, plus the architect. I became great friends with Art Hoy. He was there to oversee and provide some guidance.”

Hoy, owner of AH Architecture in Denver, says he was called in by the museum’s operators because the old roof was leaking and “required a wholesale transformation.”

Hoy sought to specify a roofing system that echoed the original material, new metal “that was historic in finish, profile and installation technique. I picked the profile and finish color that was historically appropriate,” he says. “The original roof had a series of skylights so we changed the color and position to replicate the skylights.”

Hoy is confident about the future of the museum’s structure. “The durability is going to be outstanding. The roof looks as good today as it did when it was first installed. The weathering is perfect. Its longevity is going to outlive us.”

Hoy credits Colorado Custom Metal with doing “a fantastic job helping us match this to the right look of the building and giving us something that was highly functional.”