Seattle’s Space Needle – behind the scenes of the $100m restoration project

Built in anticipation of the World’s Fair, it became a defining shape on the Seattle skyline and had the dubious honour of housing the world’s first revolving restaurant.

Its eye-catching design made it one of the most visited tourist attractions in the city but, with an average footfall now amounting to 1.3 million people annually, its owners decided it was time for a revamp.

The $100m project saw architects Olson Kundig replacing the original opaque floor of the restaurant with one-sided glass and expanding the observation platform windows with unbroken floor-to-ceiling glass panels unobstructed by mullions to more closely match the 1962 original concept sketches.

Other works saw renovations to parts of the building that had seen considerable wear and tear since its opening, along with replacement of the building service systems and the addition of a cantilevered ‘floating’ staircase.

The works took a year to complete, finishing this August, in a truncated schedule designed to minimise the impact of the project on its frequent visitors.

Arup provided much of the behind-the-scenes engineering on the upgraded Space Needle and E&T spoke with the firm’s Cress Wakefield, project manager and lead electrical engineer for the renovation project.

“Architecturally the vision was to take it back to its original concept, revealing the structure and expanding the views,” she said.

“The Space Needle has always been seen as a symbol of progress and commerce and technology, which was the vision that it first had when it was made for the World Fair. The owner really felt like it needed a refresh, needed something to bring it back to hold those values for the community.”

She explained that prior to the renovation, there had never been a front-of-house staircase connecting all the levels of the structure.

The Oculus Stairs, as they are called, cantilever off the inner wall and are built from steel tube columns with a plated, curved, rectangular tube stringer beam; all of which is hidden behind an architectural wood slat wall.

Each stair tread is fabricated out of a folded 20mm-thick plate that cantilevers out from the stringer beam creating the appearance that the stair floats within the oculus opening.

The rotating floor of the restaurant was also replaced, probably the most extensive rework carried out during the project.

“The project has landmark status, which means that it can’t look different from the exterior. The renovation needed to look the same on the skyline as it had in the past because that’s what people were expecting to see,” Wakefield said.

“The soffit glass needed to look opaque from below as it did before, but you want to be able to see through it from above.”

But adding the additional glass to the building (176 tonnes including the top façade), brought with it another set of challenges as the developers had to ensure that the original structure could bear the extra weight.

Where strengthening needed to be added, in the form of welds or stiffeners, it couldn’t affect the look of the building so every detail was considered and discussed within the design team.

This proved to be a “challenge for both the design team and the construction team”, Wakefield said. “The sequencing of the work and how you do that when you’re 500ft up in the air and you’re keeping the building open to the public throughout construction.”

These improvements were made more difficult after it emerged during the renovations that some of the original structures were inaccurate when compared to the original design briefs.

“In 1962 they didn’t have the type of surveying technology that we have now and so you see those inaccuracies when you open it up,” she said.

To remedy this, the team would have to take each design detail and modify it to create multiple versions to account for every difference on site. This involved lots of back and forth between the construction and design teams while construction was taking place.

This proved particularly tricky considering the compressed schedule, which was imposed to take advantage of the off season. It involved the contractors “working around the clock” in order resolve issues as fast as possible.

The renovations were ultimately successful despite some of these difficulties and the works were completed within the original schedule reopening on 3 August this year.

Wakefield recognised that much has changed since the Space Needle was first built in 1962. “The unique shapes of the structure were really pushing the boundaries at the time,” she said. “With today’s 3D modelling and manufacturing advancements it would be much easier to build.”