The cracked window of the Millennium Tower could be part of bigger problems

San Francisco officials were still working on Thursday to determine whether a cracked window on the 36th floor of the millennium tower, which was sinking, was an isolated incident or a symptom of the building's most serious problems.

The City's Building Inspection Department sent a field inspector and two structural engineers to Thursday morning's luxury tower to take a closer look at the crack. They responded to a preliminary assessment conducted by the ministry on Wednesday, said spokesman Bill Strawn.

As a security measure, the City's public works department has erected barricades on Mission Street to prevent pedestrians from straying under the area where the glass could explode or explode. Supervisor Aaron Peskin described the problem as a "serious concern for public safety".

The assessment of the city will be accompanied by a report on the crack and its causes of the Millennium Management, due to officials of the inspection services by Friday afternoon. The city asked Millennium to specifically assess the condition of the so-called curtain wall or exterior facade. The windows are part of the curtain wall.

The gaps in the curtain wall may be emblematic of the building's deeper problems. Since it opened in 2009, the tower has sank about 18 inches and has tipped to the side, raising serious concerns about the structural integrity of the building – and a series of lawsuits and blame for those responsible.

Last year, millennium officials filed an action against Curtainwall Design Consulting, the company that designed and installed the curtain wall of the tower, due to alleged defects.

Curtain walls, sometimes referred to as the "skin" of a structure, generally bear only their own weight and are common features of multi-storey buildings. They could be the source of alarming security issues beyond the cracked window on the 36th floor.

In 2016, while she was investigating a millionaire's complaint about strange odors in her unit, an architectural engineering firm found that parts of the curtain walls were "displaced by excessive settlement." of the building". the "fire and smoke barrier" between residential units, said the company in a report.

The authorities hope the new crack is an isolated incident caused by defects in the glass, temperature changes or other factors rather than structural constraints caused by the sinking and tipping of the entire building.

"I hope that when we get the engineering report, it will become clearer and it will be relatively simple to fix it," Strawn said. The inspection service was alerted on Tuesday after receiving an email from a reporter from the NBC Bay Area, who had reported crack information for the first time.

Jerry Dodson, the owner of the Millennium, who knows the residents of the unit with the cracked window, said they were shaken early Saturday morning by "a strong accident" and saw their windows break.

Dodson and 19 other Millennium residents sued the developer of the tower, Millennium Partners – as well as the city's inspection department, the city's attorney and Transbay's authority – claiming that the builder and officials of the city did not tell it to buyers. The city and the developer have denied these allegations.

"If you live in a unit where (the crack) has occurred, you have to be continually concerned if it's the only window, or just the first one," said Dodson.

Several architects refused to talk about the crack window in the folder. But two architects who closely followed the saga of the building drew parallels with the John Hancock Tower in Boston, which made headlines in the 1970s for a series of disastrous technical flaws that delayed its opening for years.

The tower was known for swinging and twisting to the point where the windows creaked in their frames and sometimes clashed with the street below. In 1988, the New York Times called the Hancock Tower "one of the most extraordinary stories of contemporary American architecture."

In an e-mail sent Monday to the inhabitants of Millennium and obtained by The Chronicle, the head of the tower, Michael Scofield, said that the crack could be "related to other problems in the building", but did not given details. Scofield has not responded to requests for additional comments.