Building inspection sweeps in Berkeley, prompted by a deadly balcony collapse last year, found that almost 20 percent of residences investigated need fixes to meet safety requirements.

After the June balcony collapse killed six young people and injured another seven, the city created the inspection program to check whether certain exterior features like balconies, landings and decks were safe for residents. Out of 2,176 multifamily buildings reviewed, 402 need repairs to make them safe, according to a city staff report.

“It’s really a wake-up call to the entire region and possibly the state,” said Berkeley Mayor Tom Bates. “We have a ticking time bomb on our hands.”

City officials attributed last year’s balcony failure at the Library Gardens apartment building in downtown Berkeley to severe dry rot. In the wake of the horrifying collapse — which happened during a 21st birthday celebration and killed five Irish nationals and one Rohnert Park woman — the city changed its regulations surrounding balcony design. New balconies built in the city cannot be enclosed, like the one at Library Gardens, because those without ventilation systems can lead to moisture buildup, said Matthai Chakko, the city spokesman.

The inspection program’s findings, first reported by local news site Berkeleyside, examined residences with three or more units and looked at building components that were raised several feet from the ground and exposed to weather elements. About one-quarter of property owners did not respond to the city’s letter notifying them of the inspections, the report said.

Councilman Jesse Arreguin, who represents the area where balcony collapse occurred, said he was surprised by the number of buildings that need work. He attributed the issue, in part, to owners deferring maintenance on their buildings.

“People are willing to rent practically anything,” Arreguin said. “We need to make sure corners aren’t being cut.”

Sid Lakireddy, president of the Berkeley Property Owners Association, said the report was not shocking considering the relatively large number of old buildings in the city.

The owners of residences that need repairs have 60 days to apply for a permit and another 90 days to complete the work. The report, which will be discussed at the Feb. 23 city council meeting, did not elaborate on what kinds of problems inspectors found or their severity.

Kimberly Veklerov is a San Francisco Chronicle staff writer. E-mail: kveklerov@sfchronicle.com Twitter: @kveklerov