Time is running out for more than 1,100 San Francisco property owners who thus far have ignored a deadline to bring their apartment buildings up to current seismic safety standards.

With the Sept. 15 deadline less than two weeks away, owners of roughly one-third of “tier three” buildings — wood-frame structures of from five to 15 units — have not submitted permit applications. That’s the first step in the process needed to comply with the city’s 2013 mandatory soft-story law, which targets buildings vulnerable to collapse in an earthquake. Of 3,489 buildings in the category, owners of 2,329 have filed for permits, and owners of 1,160 have not.

Property owners who don’t comply will be served with an unwelcome poster-size “Earthquake Warning” placard that lets tenants and neighbors know — in bright red ink — that the building “is in violation of the requirements of the San Francisco building code regarding earthquake safety.”

Landlords who continue to ignore the warnings will be summoned to a hearing at the Department of Building Inspection to explain why. After that, the city will start fining any noncomplying property owner for code violations, a lien could be slapped on the property, and the case could be referred to City Attorney Dennis Herrera for legal action.

“With only (two) weeks left we’d like to see a lot more come in,” said Bill Strawn, public affairs manager at the Department of Building Inspection. “We would like to avoid code enforcement action.”

The soft-story ordinance applies to wood-frame structures in which the first story is substantially weaker and more flexible than the stories above because of a lack of walls or frames at the street level — many of the buildings have garages or other open areas on the first floor. The program was launched with just six institutional and educational buildings, which all came into compliance. The next phase focused on 509 buildings with more than 15 units, of which 95 percent are in the process of doing upgrades. Tier three includes the buildings between five and 15 units, and the final tier, due next year, includes 913 structures with a ground-floor commercial use.

The area with the highest number of noncompliant buildings is supervisorial District Five, which includes the Haight, Western Addition and Hayes Valley. Of 729 tier three buildings in District Five, 252 have yet to submit a retrofit plan. Second on the list is District Eight, which includes Noe Valley, the Castro and Glen Park. Of 430 tier three properties in District Eight, 220 are noncompliant.

Contractor Henry Mak said landlords are starting to feel the heat from the city. Mak has four crews doing soft-story retrofits around the city and can barely keep up with demand. A basic retrofit costs from $70,000 to $150,000, although a complicated project can cost three times that amount.

“We have six to eight jobs going at any one time,” Mak said. “The past month has been crazy. The property owners who a couple of months ago didn’t want to talk to us? Now that it’s almost too late, they want to talk to us. Maybe people think they will get more extensions. I doubt it.”

The tier three buildings house more than 110,000 residents. A 2009 report from Community Action Plan for Seismic Safety, a city panel charged with improving earthquake safety, found that buildings with no retrofitting are projected to have a 1-in-4 collapse rate during a serious quake, while those with minimum retrofitting have a 1-in-30 chance of falling down.

Janan New, executive director of the San Francisco Apartment Association, which represents landlords, said she expects a flurry of applications once landlords return from late summer holidays.

“A lot of people don’t really start paying attention until next week — unfortunately, it’s a little late,” New said.

In addition, some property owners don’t understand that it’s just the application — not the retrofit project itself — that needs to be completed by Sept. 15. Finally, there are not enough architects, engineers and contractors to do all the work.

“It’s not rocket science, it’s a supply-and-demand issue,” she said.

New said that most active landlords in the city are up to date on the paperwork, but some apartment complex owners are less hands-on.

“For some reason, these folks are unable to get from point A to point B,” she said. “If they have not filed by next week, there is probably some reason why. They are old and checked out. Or they are young and checked out. Or they haven’t been able to get a contractor to show up. Or they are absentee and don’t know what is going on.”

Despite the short time frame, the Department of Building Inspection will be able to process applications that beat the deadline. “Just walk in,” Strawn said. “We can handle a pretty substantial volume.”

J.K. Dineen is a San Francisco Chronicle staff writer. Email: jdineen@sfchronicle.com Twitter: @sfjkdineen

Permit filings

Compliant and noncompliant buildings per district: