SBJ/June 2-8, 2014/Facilities

Stadiums’ grand openings: Retractable roofs at 25

Twenty-five years ago this week, Toronto’s SkyDome opened its doors as the world’s first retractable-roof stadium and a funny thing happened. The roof itself became an attraction.

Baseball fans hung around after Blue Jays games to watch the massive structure begin its journey after the final pitch and slowly roll across the top of the building. Outside, motorists would stop their vehicles on a downtown freeway to watch, said Bob Hunter, SkyDome’s former president and CEO.

Rogers Centre, formerly SkyDome, was the first of its kind.
Photo: COURTESY OF TORONTO BLUE JAYS

“It was the most unique and expensive roof design,” Hunter said. “Given the fact that the stadium has been open 25 years and the roof is opening and closing [about] 100 times a year, it still runs pretty well. And I still think it’s a beautiful stadium.”

Just as the moving roof attracted the attention of Toronto, it also drew the eyes of those who develop sports facilities, who found that their game had been irreversibly changed. With the innovation, outdoor venues could allow fans to stay dry on the bad-weather days and soak up the sun on the good ones. Teams could be confident that the players would play, and the fans would spend money, regardless of the forecast. And, unlike in domes, teams could still play on grass if they chose to.

Since that day in Toronto — June 3, 1989 — 10 more retractable-roof stadiums have opened across MLB and the NFL, and an NFL project in development in Atlanta, with a roof that opens and closes by mimicking a camera shutter, could set the tone for future buildings. But change has been slow, in part because retractable roofs remain an anomaly in sports: Of the 44 MLB and NFL facilities built over the past quarter-century, only 10 of them have such roofs. (BC Place, home to MLS and the CFL, also has one.) 

Each stadium with a retractable roof had its own set of environmental factors as drivers, whether it was heat, humidity, hurricanes, rain, snow or freezing cold, said Lee Slade, a structural engineer and senior principal with Walter P Moore, a consultant for more than a half-dozen retractable roof projects. Special events such as the Houston Livestock Show & Rodeo, a three-week-long event with nightly concerts that is the Texans’ co-tenant at NRG Stadium, also persuaded officials at some buildings to incorporate a roof. The desire to host the NCAA Final Four and Super Bowl played a part at multiple NFL buildings.

All told, retractable roofs have largely paid off for teams, especially over the course of baseball’s 81 home games every season, the architects designing these super-structures and the stadium managers operating them said, though there is little hard data available to determine revenue generation connected to retractable roofs.

The Brewers, for example, increased game attendance by nearly 50 percent over the first six years of operation at Miller Park, compared with the previous six years at County Stadium, their old ballpark, according to research mentioned in a 2009 essay written by Bart Riberich, president of Uni-Systems Engineering, the manufacturer for most retractable roof mechanization systems in sports.

Shiny new stadiums often record big attendance gains over their aging predecessors, but over those six years at Miller Park, stadium officials said, they played host to more than 600 events without a weather-related delay or cancellation, a result that only a roof could produce. 

Miller Park’s roof has been instrumental in generating group sales and attracting fans statewide, said Rick Schlesinger, the team’s chief operating officer, allowing Brewers fans in distant locales to make the drive knowing they’re guaranteed to see a game. 

Said Scott Jenkins, who has managed three retractable roof stadiums: “Particularly in baseball, it’s a godsend to have a roof and know that you’re going to play the game and not get stuck in a rain delay or have to do a doubleheader.”

The Toronto Blue Jays played their first 12 seasons at old Exhibition Stadium, an open-air football stadium on a site where two venues had burned down before a final rebuild in the late 1940s.

It made for a poor layout for baseball, and Toronto sports fans made fun of the place. “They called it the mistake by the lake,” said Hunter, now chief facilities and live entertainment officer for Maple Leaf Sports and Entertainment. 

Toronto winters’ reach into the spring and fall didn’t help matters. On the Blue Jays’ first Opening Day in 1977, 6 inches of snow covered the ground at Exhibition Stadium. The game was played, after the snow was swept off the field.

“It was a bad baseball stadium designed for football,” Hunter said. “Plus the climate here in April and October is not conducive to having great attendance.”

Football didn’t necessarily fare much better. The CFL’s Toronto Argonauts also played at the stadium, and the 1982 Grey Cup game was played there in a driving rainstorm that caused the restrooms to overflow, leading public officials to pursue a new indoor sports facility.

Summers can be sunny and beautiful in Toronto, though, and the Blue Jays preferred to play as much outdoor baseball as possible. So when a design competition was held, a small architecture firm headed by the late Rod Robbie and his partner, Michael Allen, won it with a blueprint providing the largest roof opening among the finalists. 

SkyDome opened two months late after going through hundreds of millions of dollars in cost overruns, mostly due to the magnitude of the project, said Hunter, who originally was hired as senior vice president of operations in 1987 to oversee the development. The total cost was in the neighborhood of $600 million in U.S. dollars, he said, a hefty sum for a stadium in those days.

After seeing the complexity of the Toronto roof, designers kept it simple in Houston.
Photo by: COURTESY OF HOUSTON ASTROS

The roof itself ate up more than 25 percent in construction costs, said Earl Santee, a senior principal with Populous and a designer of three retractable-roof stadiums. Years ago, Santee researched SkyDome to design Minute Maid Park in Houston, his first retractable-roof project. Today, efficient design and improved technology has dropped those costs considerably, Santee said.

“SkyDome was revolutionary because it was the first retractable-roof stadium, and being in Canada with snow loads and the multi-use nature,” Santee said. “Therefore, the roof was big and heavy. It was just different than the rest of them, and it cost a lot of money because of that.”

At the time it opened, though, SkyDome and its motorized roof, the first of its kind in sports, was an engineering marvel and Canadians framed it as the Eighth Wonder of the World, Hunter said. 

The 11,000-ton roof was composed of two panels moving along parallel tracks and a third panel rotating in a circular motion around the ballpark’s perimeter. 

Newer retractable roofs are controlled by laptop computers linked to cameras and sensors that track the roof’s motion on its path, but the early retractables such as SkyDome worked on basically a four-button system with a joystick, Slade said. The roof took a leisurely 20 to 25 minutes to cover the field, much slower than newer versions. 

“It was designed beautifully … and it has worked quite well over years,” said Slade, whose firm is consulting for the Blue Jays to overhaul the roof operations system (see related story).

Fast forward to 2014 and more than 60 million people have passed the gates of the stadium, now known as Rogers Centre, for more than 2,000 events, including two Blue Jays World Series championships. In 1997, the stadium booked a record 302 event days. It has won multiple industry awards.

The stadium stands alone as a “trailblazer and it’s hit a milestone no other roofs have ever seen,” said Dave McCormick, the Blue Jays’ manager of engineering and the roof’s caretaker.

For all those factors driving SkyDome’s roof design, the opposite held true in the heat of the Arizona desert. Nine years after SkyDome debuted, Bank One Ballpark (now Chase Field) opened in 1998 as the majors’ second retractable-roof project and its first with a grass field. 

The roof’s design and operation is much different than SkyDome, in large part because the Arizona climate provided its own set of issues far apart from those in Toronto, said Bill Johnson, a senior principal with 360 Architecture and designer of the Arizona Diamondbacks’ stadium when he worked for the former Ellerbe Becket. 

The challenge that then-Diamondbacks owner Jerry Colangelo presented them was that of playing baseball on grass in 100-degree summer heat. Unlike Toronto, designers did not have to deal with keeping the space warm or keeping out the cold and snow, Johnson said. 

Arizona’s heat, and the Diamondbacks’ grass field, created new demands for roof designers.
Photo by: KATIE WARREN / ARIZONA DIAMONDBACKS

“The way all those roof pieces came together [at SkyDome], there had to be big [rubber] bladders that were inflatable to seal it and make it weather tight,” Johnson said. “It was ugly and hugely expensive. It was wrong on so many levels … so it was not anything we really explored.”

Instead, Ellerbe Becket started from scratch to develop a new version of a retractable roof, one less expensive than SkyDome’s structure. Johnson and his crew won the job after building a model for their interview containing a small motorized roof to prove their concept would work.

“It was a fun time, a research and development situation,” he said. “Now, it seems commonplace that we have all these stadiums with all these roofs, but back then, there wasn’t anything out there [for grass fields]. No one had really attempted this.”

It was on the Diamondbacks job that Johnson first learned of the operating principles behind the mechanisms that operate most retractable roofs, an education that paid off for him in the long run.

To find the best experts possible to help design the 4 1/2-acre structure, Johnson reached outside his typical network of consultants and hired Hatch Engineering, the same Toronto firm that conducted a peer review of SkyDome’s motorized roof, he said.

Hatch’s real expertise was designing and building gantry cranes that unload shipping containers from ocean freighters at sea ports. The same low-tech approach to the cranes’ motorized system could be applied to a retractable roof, the consultant said.

It made sense, Johnson thought. Gantry cranes operate 24/7 and most of their parts are off-the-shelf components. If a motor burns out or a gear is stripped, a replacement can be found quickly and delivered on site in a matter of days.

“When we went in to see Colangelo, we told him there were are all these unknowns and the last thing we need to do is make some highly automated, technical solutions,” Johnson said. “We need to use tried-and-true technology … and that’s the way it went.”

To this day, the roof runs smoothly, and its motion has become part of the fan experience, accompanied by an original team composition that the Diamondbacks call their “rain dance,” he said. It opens down the middle with sliding plates moving in opposite directions. The size of the opening can be adjusted to trace the sun’s daytime path. The roof opens and closes in about five minutes and remains one of the fastest in sports, Johnson said.

“It was simple, cost-effective and because it is kind of bulletproof, it is one of the most operated and utilized roofs to this day,” he said.

For the most part, stadium developers plan retractable roofs as simple as possible, considering the scope of these gigantic mechanized structures and the key role they play in stadium operations.

Minute Maid Park opened in 2000 and project officials’ intent was to “spend the money where the fans are and not necessarily up in the roof,” Santee said. “Keeping the roof cost efficient and functionally efficient was really important.”

The keep-it-simple mantra hit home for teams, architects, engineers and manufacturers after they saw the cost escalation at SkyDome. 

“There was a feeling of significant risk because of difficulties with [SkyDome],” Riberich said. “I know Earl and the whole Houston team went into the Astros’ project cautiously.”

To avoid making the same mistake in Houston, project officials developed a roof that unlike SkyDome had multiple redundancies built into the mechanization system. If one piece failed, the roof would still operate and the game could go on unaffected by the weather, Riberich said.

“You don’t want to build a watch, but you are building an outdoor mechanism and it needs to be designed with a failsafe approach,” Slade said.

Riberich said designing the roof system to ensure redundancy with a multitude of smaller, off-the-shelf parts readily available instead of using larger custom-built components did not increase the cost of the Minute Maid Park project.

Miller Park was a different story. Brewers fans preferred a roof as part of an early 1990s survey to determine whether they would drive long distances to attend a game if the team could guarantee it would be played, said Santee, originally involved in the team’s research. 


The ballpark, designed by HKS and NBBJ, opened in 2001, one year after Minute Maid Park, with a dramatic

The distinctive fan-shaped roof at Miller Park, shown open and closed, has worked smoothly since problems early in the building’s history. It was designed to work as part of the design rather than overpower it.
Photo by: SCOTT PAULUS / MILWAUKEE BREWERS (2)

new roof design shaped like a seashell or a peacock spreading its feathers. Most described it as a fan-shaped roof.

“What we were so focused on at Miller Park was a departure from the way retractable roofs had been done to that point,” said Bryan Trubey, a principal at HKS who worked on the project. “We wanted to do something that was part of the architecture rather than overpowering it.”

Whatever it looked like, it failed to live up to the Brewers’ initial expectations. Over the ballpark’s first few years of operation, millions of dollars were spent to replace defective parts in the mechanization system originally produced by Mitsubishi Heavy Industries of America.

Lawsuits were filed on both sides. In 2005, after a three-year court battle, a financial settlement was reached between Mitsubishi and the Southeast Wisconsin Professional Baseball District, the stadium’s owner.

Over the past eight seasons, Miller Park’s retractable roof has performed largely error-free with the exception of the occasional leaks caused by heavy storms hitting at just the right angle to seep through the structure.

“There was nothing wrong with the design, as it’s shown now with the proper equipment installed,” said Riberich, whose firm completed a peer review of the replacement project. “Unfortunately, because of some of the problems at Miller Park, people feel like the fan design is too complicated.”

Johnson applauds the creativity behind Miller’s Park roof because it was something different.

Unfortunately, “we lost the innovation momentum because I think people got nervous,” he said. “You were setting yourself up for some big risk if you pushed the envelope on this stuff.”

That is exactly what 360 is doing with its groundbreaking roof design for the Atlanta Falcons’ planned $1.2 billion stadium. The motion of the eight-sided structure mimics a camera shutter, and a large video screen rings the inside of the roof, flashing images tied to the event on the field.

“It’s distinctive architecturally, and functionally it’s a brilliant design,” said Scott Jenkins, the Falcons’ general manager for the new stadium.

The architect’s focus is on doing a better job integrating the structure’s design with the seating bowl and concourses below. Johnson feels there has been a disconnect between those elements because of roof complexity and cost dictating stadium design. By creating a better flow between the two, he believes stadiums can become even more attractive to potential naming-rights sponsors and founding partners.

“What we’re hoping to do in Atlanta is turn that around and say that we want the roof to not be independent of a great stadium design,” Johnson said. “I think that’s a big milestone and a big change.

“We’re going to bring it all together and make it more of an icon and less of a stadium in a box.”

The “stadium in a box” image was one criticism of the Diamondbacks’ stadium, Johnson’s previous retractable-roof project. Critics said it didn’t feel like the shape of a ballpark. The result reflected all the unknowns at the time for those structures, he said.

The Falcons’ roof looks complex but it’s really not, Johnson said. It simply moves smaller, lightweight pieces shorter distances in a straight line. The roof can stop and start at any point in its motion to control the amount of sunlight shining through and still look beautiful doing it, he said.

“We’re really not pushing the envelope so much on the operable technology in Atlanta but we are pushing the envelope in terms of the integrity and holistic design of the facility,” Johnson said.

What do the next 25 years hold for retractable roofs? Retrofits are the newest trend. In 2011, BC Place replaced its dated inflatable dome-style roof with a new cable-supported fabric structure atop the Vancouver stadium, which opened in 1983. The new retractable-roof structure has steel posts providing greater reinforcement than the old roof, which collapsed during a 2007 snowstorm. A second fabric layer underneath the main roof effectively cuts seating for MLS games. The $520 million project included other building upgrades driven in part by its use for the 2010 Winter Olympics. 

In New York, meanwhile, early construction has started on the installation of a moving fabric roof at Arthur Ashe Stadium, the centerpiece of the U.S. Open tennis tournament.

Two more soft roofs could be coming in the NFL. The Miami Dolphins, pending the resolution of funding issues to pay for a retrofit, have a plan to put a roof canopy at Sun Life Stadium, in an effort to get the Super Bowl back to South Florida.

The Jacksonville Jaguars are considering a movable fabric roof for EverBank Field, but it’s just a concept at this point, team President Mark Lamping said. 

The Marlins considered a soft-fabric roof cover for their new ballpark until they saw Hurricane Ike hit the Texans’ NRG Stadium and rip a portion of its fabric roof to shreds in 2008.

“A lighting protector blew off the building and it worked like a razor blade, sliced the roof and left it famously in tatters,” Slade said. “It wasn’t a structural problem, but it made the Miami client nervous, and so we went away from the fabric to a hard roof.”

A new leading-edge material, PTFE, a lightweight, flexible, synthetic surface common for sports projects in Europe, is being used for the Arthur Ashe Stadium retrofit. Its cousin, ETFE, is a more translucent material being used for the fixed roof for the Vikings’ new stadium.

Those materials are more expensive because of their transparent qualities, allowing views from inside and outside the facility, Slade said. 

“It’s a very exciting time because we feel like we can do more than we used to be able to,” he said.

There will always be budget pressures in developing retractable roofs, Slade said. “They create a building that cannot be created otherwise,” he said. “But they will continue to be far and few between. There’s just not that many of them.” 

Riberich says there will always be a need for “convertible stadiums.” Fans like to be outside but teams can’t afford to have events wiped out by weather conditions, and he believes the trend will trickle down to new construction in the college ranks.

It’s not just the roofs that keep moving. Several stadiums have retractable glass walls in the outfield and end zones in addition to operable roofs. The Vikings’ stadium roof won’t move, but it will have giant glass doors on one end and a large chunk of retractable seats in the bowl. 

“The big change is these buildings are transforming themselves in a three-dimensional way rather than just one thing moving,” Trubey said.

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