Most of the 31 high-rise window failures reported during March’s windstorms in San Francisco were found to have occurred long before the storms hit. This is according to an investigator’s report presented to the San Francisco Building Inspection Commission.
Broken glass from compromised windows at several high-rise buildings crashed into the streets of downtown San Francisco during fierce windstorms this past winter. The winds, topping 75 mph, wreaked havoc on windows that were apparently already damaged due to existing issues. The report, conducted by Wiss, Janney, Elstner Associates Inc. investigators, discovered that dozens of the broken glass lites had previously been affected by heat or debris. There were also problems with window hardware and glass contamination.
“The report indicates that the glass failures were largely preventable and were primarily caused by existing broken windows that had not been repaired,” a San Francisco Department of Building Inspection spokesperson said in a written statement. “It is critical that building managers identify, secure and fix broken windows immediately so they don’t endanger the public or cause additional property damage, especially before a large storm.”
In the report, investigators recommended facade designers and contractors avoid using spandrel glass. They also recommended building owners adopt more specific systems for detecting, reviewing and documenting damage to building facades. Additionally, they suggest visual inspections of any building opening that contains glass be required at a five-year mark, following periodic facade inspections for buildings 15 stories or taller.
As a result of the findings, the San Francisco Building Inspection Commission plans to inspect all buildings 15 stories and taller constructed after 1998. Neville Pereira, deputy director of Permit Services, says the Commission is also considering local law changes to update its façade inspection program.
The report’s investigators found that the first reported window to fail, which broke free from the former Bank of America Building and fell more than 130 feet, suffered prior cracking damage due to heat stress. The investigators indicated the stress was likely the result of temperature changes between the center and the corner of the window, possibly due to contact with insulation.
Another instance, this time at the Millennium Tower, involved a 49th-floor window. The window broke free from its support arms and eventually shattered when it slammed against the building. Investigators learned the damaged system had faulty window hardware. Shards from the broken window shattered several windows below the site and broke 17 glass lites at the Salesforce East building.