A Glassy Makeover Gives the Space Needle New Life

by Jordan Scott

The Space Needle has stood 605 feet above the city of Seattle since 1962, giving locals and tourists alike a way to view the city below. In an effort to improve those views and to create a fresh experience for visitors, Seattle-based architecture firm Olson Kundig turned to glass.

“Since 1962, the Space Needle has been a treasured landmark where the public can observe the changing city of Seattle. With the Century Project (the Space Needle renovation), the design intent was to ‘widen the lens’ of that human perspective. Providing a new sense of transparency, the redesign hearkens back to the Space Needle’s original guiding principle: providing unparalleled views,” says Alan Maskin, design principal at Olson Kundig. “On the observation level, new seamless floor-to-ceiling glass walls, structural glass barriers and integral glass benches allow visitors to lean into the city below them. Inside, the new Oculus Stair connects all three top levels with a glass-floored oculus at its base. At the 500-foot level, The Loupe is now the world’s first and only revolving glass floor.

Taking the Floor

The Loupe has two circular segments, an inner solid portion, which constitutes a third of the floor, and the outer segment which consists of ten layers of structural glass. The glazing system includes a sacrificial lite of glass that, if broken, will not compromise the integrity of the structural glass. If the sacrificial lite is broken, it is easier and less expensive to replace than the structural laminated glass it is protecting.

“The unique properties of the interlayer enabled the guards, rotating floor and glass benches to be designed so that if the glass should break, the safety of the occupants would not be compromised and the glass would stay in place,” says Ron Hull, Americas marketing manager for Houston-based Kuraray North America. “This also allowed for thinner glass constructions that could not be achieved with traditional flexible interlayers.”

Hull says the biggest undertaking for Kuraray was demonstrating that the glass design would be safe in the unlikely event that all the glass broke and the structure had to be retained by the interlayer. All glass structures include a minimum of three structural layers of glass each.

The glass used in the rotating floor was fabricated by Pulp Studio, based in Gardena, Calif. The glazing system is comprised of two 6-mm, low-iron glass lites with a 1.52-mm SentryGlas Ionoplast interlayer on the bottom. A 20-mm Argon gap separates this laminated section from another, comprised of three 10-mm glass lites with two 2.28-mm SentryGlas interlayers. A 0.2-mm clear safety film and a 6-mm glass lite complete the glazing system.

A soffit with a grey frit on the no. 1 surface was installed on the underside of the floor to mimic the color of the Space Needle’s original materials. The soffit is made up of two laminated sections, consisting of two 6-mm lites of non-tinted, low-iron glass and an interlayer, separated by a 16-mm Argon gap.

DowSil 795, a structural sealant, was used to adhere the floor glass to the custom aluminum extrusion designed by contract glazier Herzog Glass of Tukwila, Wash.

“What’s so unique is that the insulating units were made where the interior lite and exterior lite are both laminated and heat treated. We used an anti-reflective glass in conjunction with a soft coat low-E, and the glass is on a 15-degree incline,” says Bernard Lax, CEO of Pulp Studios.

Code-required loads and testing are typically 60 pounds/square foot and 300-pound point loads on floors. The glass floor at the Space Needle was designed for more than 100 pounds/square foot and 600-pound point loads all throughout the floor’s surface.

While much has changed about the Space Needle’s interior, the exterior has not. Seattle’s Landmarks Preservations standards prohibit changes to the exterior profile.

In Full View

The redesigned observation deck of the Space Needle also includes new 11-by 7-foot glass barriers, which tilt outward to match the angle of the building, creating seamless sightlines. These barriers replaced the wire “caging” on the outer observation deck. Twenty-four glass benches, dubbed Skyrises, were also put in place against the barrier,
leaning out 14.5 degrees to give visitors a more expansive experience of Seattle.

Not only does the addition of glass give visitors more views of the city, it gives them access to parts of the Space Needle’s structure that were previously hidden.

“The new design allows visitors to observe the city of Seattle below—as it was always intended to do—and to see the engineering ingenuity of the original structure in new ways. Original steel columns have been revealed, along with a 10-foot-tall steel girder circling the mezzanine level,” says Maskin. The original steel trusses holding the gold ‘halo’ have been repurposed to support the observation deck’s glass benches. The Loupe gives visitors never-before-seen views of the elevators, the mechanical apparatus powering the floor’s rotation and the Space Needle structure itself.”

Glass Gets a Lift

A challenge faced by the architect and design team was making the necessary mechanical, building envelope and structural updates, including seismic retrofitting and accessibility improvements, while dramatically increasing the amount of glazing.

“The building is now significantly more efficient than before, meeting current energy codes with an EUI of 306 kBtu/sf/yr, with most energy use occurring in the elevators. This is a significant achievement in a city with one of the most stringent energy codes in the country, especially considering the redesign added 196% more glazing,” says Maskin.

The glass installation required custom equipment to handle the glass and elevate it to the top of the Space Needle because many of the glass lites would not fit in the elevators.

“For The Loupe, we worked our way from one side of the structure to the other,” says Josh LaSharr, who was an estimator at the time with Herzog Glass (Editor’s note: LaSharr has since left the company). “[The glass] was installed starting in one location and then rotating the floor. We had a couple guys push the floor around to move the bay we were working at so we could bring the glass up by elevator. We grabbed it, pulled it from the cart and flipped it over so it was lying flat and then we lowered it down in place.”

LaSharr says installing the glass for The Loupe was less of a challenge than
installing glass in the Oculus Stair and the upper observation deck.

“For The Loupe, every piece of glass fit in the elevator. We did have to modify some glass carts and cut them down so they would effectively fit into the elevator. That required a little bit of ingenuity on our crew’s part,” he says. “When we got over to the Oculus, it became considerably more challenging, since the pieces wouldn’t fit in the elevator. The glass had to come up via a custom davit crane that had been set up to bring some
of the larger glass pieces on the project up, as well as some of the structural stringers for the stairs. Then we built a gantry crane on the interior of the space and used that as a way to hook the glass up and lower it into position.”

A temporary work platform was put in place so the glass installation and other updates could occur with the Space Needle still open to the public.

“There was plenty of room under the floor where we had a 3-foot walking space, but as we got out toward the edge, that narrows down to about 18 inches. So our guys had to come up with unique ways to climb in underneath and fasten these pieces of glass down to make sure they weren’t going to slide around,” says LaSharr, who added that the field leads Robert Wallace and Barry McCann were instrumental to the project’s success.

The $100 million Century Project was completed in the summer of 2018.

Jordan Scott is the assistant editor of USGlass magazine. She can be
reached at jscott@glass.com.

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