Tall & Urban News

Months before two cracks were discovered on interior windows of Salesforce Tower – San Francisco’s tallest building, owner Boston Properties enlisted a drone to inspect the building’s exterior for potential damage. At 1,070 feet (326 meters), the tower is a major example of the growing use of drones for building and construction inspections.

The small aircraft, which now have high definition cameras, are cheaper, faster and safer than traditional human inspections, said Zeev Braude, CEO of SiteAware, which created the drone software used in the Salesforce Tower inspection.

Historically, building owners have used aerial platforms, known as swing stages, to hoist up inspectors who take photos — the same platforms used by window washers. Inspecting a building as large as Salesforce Tower traditionally would have taken 400 to 500 hours over four to five months, according to Braude. “It’s risky. It takes a long time,” he said.

In contrast, the drone inspection was completed over two weekends. A typical drone inspection costs tens-of-thousands of dollars, about a third of the cost of human inspections, he said. SiteAware, which is headquartered in Tel Aviv, builds the software that automates the drone flights and digitally scans building photos to identify where potential problem areas are.

“We interviewed the firm and were impressed by them,” said Helen Han, spokeswoman for Boston Properties. “We thought the technology was cutting edge. It’s much more efficient than having a window washing rig lowered down the building since the photography is just as good.”

The commercial drone industry has grown primarily in the construction, mining, agriculture, surveying and real estate sectors, according to a 2018 report from DroneDeploy, a San Francisco drone software company. There were 1.3 million registered drones as of February, with 322,376 drones registered primarily for commercial and public agency use, according to the Federal Aviation Administration, which regulates drones. DroneDeploy expects commercial drone registrations to grow to 410,000 in 2019 and 605,000 in 2021.

For the Salesforce Tower inspection, SiteAware partnered with DroneHive, a Corte Madera operations company that works with 700 independent drone pilots around the country.

Safety concerns were heightened because in September, 2018, a drone crashed while inspecting a cracked window at Millennium Tower, which is across the street from Salesforce Tower. KPIX-TV, which captured video of the crash, reported that the drone lost it signal. A person later rappelled down the tower to inspect the crack.

“GPS in cities is definitely a challenge,” Braude said. “You need to be smart about where you’re flying, where you’re taking off.” At Salesforce Tower, sidewalks were closed off and drones were flown in the morning to avoid winds.

Building inspections have been a growing business, increasing from a few hundred flights to 10,000 in 2018 for DroneHive, said CEO Paul Huish. In addition to skyscrapers, drone inspections are well suited for sprawling industrial sites like food processing plants or energy centers, he said.

Five San Francisco city agencies are authorized to use drones for operations: the Office of the Controller, Fire Department, Public Utilities Commission, Port, and the Recreation and Park Department. In 2017, the San Francisco Public Utilities Commission paused its own use of drones because of concerns that the leading drone manufacturer, Chinese company DJI, could be transmitting infrastructure data to China. DJI denied the allegations.

Will Reisman, a spokesman for the utilities commission, said the agency has since resumed using drones and flown about 10 times in the past year for environmental monitoring and inspecting infrastructure. Drones save money and are safer for workers, he said.

Drone flights are generally allowed near tall buildings in San Francisco with proper permits. They aren’t allowed near airports. They’re also banned in national parks, including the 80,000-acre Golden Gate National Recreation Area. The Golden Gate Bridge is also a no-fly zone, because a drone crash could severely disrupt traffic.

“We’ve seen consistent steady growth,” Huish said. “It hasn’t been rapid, because of the regulatory constraints.”

For more on this story, go to The San Francisco Chronicle.