In November 2016, Randy Collins, S.E. and Nik Favretto, P.E. presented on Soft Story Retrofits at the Structural Engineers Association of Northern California (SEAONC) Fall Seminar. This seminar was attended by structural engineers from all over Northern California, and Nik and Randy gave the only presentation on Soft Story Retrofits.
Randy and Nik shared their knowledge and experience gained from designing over 80 retrofits in San Francisco, and their extensive involvement with SEAONC’s Existing Buildings Committee SF-DBI Code Advisory Committee meetings over the past three years.
What is the Soft Story Retrofit Ordinance?
The Soft Story Retrofit Ordinance was passed into law and requires the seismic retrofit of some of San Francisco’s most seismically vulnerable buildings. The Soft Story Retrofit Ordinance applies to buildings that are:
• 3 stories or taller
• 5 units or more
• of wood framed construction
• constructed before 1978
• Have a ground floor or under-floor space that is different from the rest of the stories above
What do I have to do?
The City sent notices to the building owners on the soft story retrofit list. Owners need to file a screening form with the Building Department to confirm whether or not the building is subject to the Ordinance. Then, if the building is subject to the ordinance, the owner will have to perform a seismic retrofit.
Buildings subject to the Ordinance will be assigned to one of 4 tiers, which determine deadlines if the retrofit work is necessary.
What are all the steps?
How much will it cost?
After the September 15 deadline, FTF Engineering will perform a site visit (if deemed necessary), fill out the screening form, and file it with the Building Department for a fee of $750.
Construction costs are expected to be on the order of $50,000 – $150,000 for a typical building. Larger buildings (greater than 10 units) and buildings with extensive open ground floor space or on steep slopes will cost more. Engineering fees will vary depending on the complexity of the specific project, ranging from $15,000 – $30,000. Buildings with commercial, retail, or restaurants will need architectural services also to comply with ADA requirements.
Existing brick foundations may be incorporated in the retrofit design if they are in good condition. Brick tests are required to determine the strength of the existing brick, and cost on the order of $4500 to $5500. If the existing brick is not in good condition, a partial or complete foundation replacement may be required.
In addition, as-built drawings are required for the engineering, costing on the order of $3,000 for smaller buildings to $8,000 for larger buildings. Permit fees are approximately $3,000. If steel framing is used, special inspections by a third party are required, and cost on the order of $3,000 – $5,000.
Will I have to remove tenants from my building?
Typically the retrofit work will only need to be done on the ground floor and basement if one exists. Only ground floor tenants may need to be temporarily relocated.
How will I pay for the retrofit?
100% of the cost of doing work mandated by law can be passed through to tenants over 20 years, and local banks are lined up to provide capital improvement loans on a corresponding 20 year term. All costs of the work can be passed through – design fees, permit fees, inspections, construction costs, and interest. Click here for a list of Financial Institutions that attended a financing workshop cohosted by ESIP (Earthquake Safety Implementation Program) and SFAA (San Francisco Apartment Association).
My building made it through the 1989 Loma Prieta earthquake just fine, so why does it need to be retrofitted?
The 1989 Loma Prieta earthquake was centered near Santa Cruz, 70 miles south of San Francisco, and resulted in what engineers would consider moderate ground shaking in most of San Francisco except soft soil sites like the Marina District and South of Market, where most of the damage was concentrated.
The level of ground shaking engineers expect in an earthquake on the Hayward Fault, 10 miles from San Francisco, will be 3 times stronger than the 1989 event and will result in much more widespread damage to buildings.
Why is this particular type of building being targeted?
Studies of damage patterns in past earthquakes indicate that, not only are soft story buildings very vulnerable to collapse, but the resulting loss in housing units and rental income from these structures will place a significant burden on the recovery process. If we can prevent these buildings from collapse, the residents can remain in them after the earthquake, owners can protect their asset and income stream, and San Francisco can recover quicker. On top of that, San Francisco will not lose the significant historical resource these buildings represent.
In the near future, the City will be studying further retrofit ordinances for other types of known hazardous buildings. More details can found in the CAPSS reports and ESIP Plan, available here.
How did San Francisco come about this ordinance?
The City commissioned a 10-year study into the impacts of expected earthquakes on San Francisco, and found many vulnerabilities that will greatly impact the city: damaged buildings, lost housing, lost jobs, lost lives. Most of these issues, while they may appear expensive to fix now, are far more expensive to fix after a damaging earthquake. So the city has turned the study into a 30-year implementation plan to address the critical issues and building types. Please see the following reports for more information on this plan:
San Francisco’s Community Action Plan for Seismic Safety (CAPSS) and Earthquake Safety Implementation Program (ESIP)
SPUR’s Resilient City Initiative
What if I already retrofitted my building?
If the retrofit was performed to an approved standard, and done after 1998, the retrofit may satisfy the requirements of the Ordinance. Please call FTF Engineering for more information on if your retrofit is compliant.
Has the City released the list of buildings that were sent notices?
Yes, it is available on the SF DBI Website under the “Subject Buildings” section and is updated frequently.
Will this make my building “Earthquake-Proof”?
Buildings can only be made “earthquake-proof” at extraordinary expense compared to achieving “life safety”, which is the expected performance for typical new buildings. Life safety means that the building will be damaged in a large but expected earthquake, but will remain safe for the occupants. Only hospitals and other critical facilities are designed to “Immediate Occupancy” performance.
Furthermore, in order to make the ordinance palatable to owners and renters, the Ordinance was written to limit the work to mitigating the soft story condition, since this is the most severe seismic hazard in these buildings, and the most cost-effective to remedy. But without doing work in the entire building, the rest of the building may still suffer damage in a large but expected earthquake.
Why Soft Story?
San Francisco’s Community Action Plan for Seismic Safety (CAPSS) is an earthquake hazard study that took 10 years to complete. It resulted in the Earthquake Safety Implementation Program (ESIP), a 30-year action plan to make San Francisco less vulnerable to the inevitable earthquakes that are expected to strike the region. The program is intended to make San Francisco more “resilient”, to minimize the damage to infrastructure and the economy, and to expedite recovery from the effects of these damaging earthquakes.
In the CAPSS report, researchers studied what would happen to San Francisco in the event of a (very likely) magnitude 7 earthquake on the nearby San Andreas Fault. The impact on buildings, utilities, communication systems, schools, commercial and business centers, emergency response systems and the resultant effects on the entire city were studied.
Soft-story, wood framed buildings were found to have a 90 percent probability of being uninhabitable following that earthquake. As a solution was sought, it was discovered that, by retrofitting the ground floor only, this probability goes down to 10%. Additionally, the retrofit costs are a very small fraction of the total cost of rebuilding the building, to say nothing of what would happen to the overall local economy if that many residents were suddenly displaced. And of course tenants don’t pay rent on apartments that they are unable to occupy.