Soft Story Retrofit Program


On April 18, 2013 San Francisco signed into law the AB-107 Mandatory Soft Story Retrofit Ordinance to ensure the safety and resilience of San Francisco’s housing stock through the retrofit of older, wood-framed, multi-family buildings in San Francisco with a soft-story condition.  The Ordinance requires all mandatory seismic work be completed by 2020.

ZFA knows the code.  Throughout San Francisco and the Bay Area, we have worked with many soft story building owners and managers to reduce the risk of collapse during the next major earthquake and to bring structures into compliance with the AB-107 Mandatory Soft Story Retrofit Ordinance. 

More than 40 years of retrofit expertise. ZFA's extensive seismic practice includes hundreds of residential retrofit projects in areas of high earthquake activity. Our executive principals are recognized for their seismic expertise and serve on the committees responsible for developing systems and solutions to improve building seismic performance, including SEAONC, ASCE 41 and USRC.

Our designs are efficient and thoughtful. We design unique solutions tailored to the goals of each client and the structural requirements of each building.  Through thoughtful designs we help clients maintain the aesthetic of their building, and minimize the impact and disturbance to tenants throughout the retrofit process.

Assess, design, implement.  We work closely with clients to assess their needs, perform screenings, develop a seismic solution, and complete the retrofit plan, in accordance with the new seismic code requirements.  

Projects and praise. Scroll down to browse select soft story retrofit projects and see what our satisfied clients have to say.

Talk with an engineer today.  Our team is ready to assist with your soft story project and we provide clients with a list of trusted contractors who can implement your custom retrofit plan.  Call or email us to learn more or set up an assessment:  [email protected]

San Francisco | 415-243-4091   San Carlos | 650-394-8869   Santa Rosa | 707-526-0992


Waller Street :  Retrofit

San Francisco | California

The three-story building was constructed in 1900 and is located between Pierce Street and Scott Street in the Lower Haight neighborhood. ZFA was retained by the building’s owner, to complete a retrofit. The retrofit seismic force-resisting system consists of sheathed wood cripple walls in crawl space and new wood framed shear wall at ground floor.

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Praise for Waller Street Retrofit  "Many thanks again for referring me to ZFA Engineering. They were able to create plans for what is a somewhat problematic building, and came up with a solution that won’t destroy the lobby and the bottom unit. They were the only ones who came up with that solution; everyone else just scratched their heads or proposed something pretty ugly." - Karin Burger, Owner of Waller Street property

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Dolores Street:  Retrofit

San Francisco | California

ZFA was retained by the building owner to perform a screening, evaluation and retrofit of the this three story, 4,600 sf structure.

Praise for Dolores Street Retrofit "ZFA worked with us to develop a retrofit design that was economical, caused litle disruption to the tenants, and integrated with the buildings's existing aesthetics. ZFA completed the required work in a timely manner and assisted us with obtaining the permit form the San Francisco Building Department. Throughout the process, their engineers were responsive and esy to work with.  

Most importantly, the completed cost of construction was less than we originally anticipated. We attributed this to ZFA's throughtful approach, which met the requirements of the SF Mandatory Soft Story Retrofit program with out "over-designing" and addding unnecessary cost.

ZFA delivered what they promised and I highly recommend their consultation services to al building owners required to meet the SF Soft Story Retrofit ordinance." - Dave Arthurs, HOA Representative and Unit Owner

18th Street:  Retrofit

San Francisco | California

ZFA delivered a cost effective design that minimized demolition and impact to the tenants in the upper floors for this three story building. We developed creative solutions to challenging architectural requirements.

Soft story 18th street SF

Praise for 18th Street Retrofit  "ZFA Structural Engineers, Santa Rosa, provided creative structural solutions to our soft story retrofit architectural projects that were cost effective and met bot the code requirements and demanding architectural elements.  ZFA provided excellent support throughout the many phases and was instrumental in making the project a success.  The effects of this contribution added an aesthetic dimension to the quality of our work and empowered our client's lives through the power of structural and architectural design ." - Fani Danadjieva Hansen, AIA Architect, 18th Street property

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Oak Street:  Retrofit

San Francisco | California

Located in the Hayes Valley neighborhood and constructed in 1961, this three story building required a complete seismic retrofit.  The seismic force-resisting system consists of sheathed wood stud walls and a steel special moment frame in the garage. 

Praise for Oak Street Retrofit "EVERYONE compliments the plans.  Every contractor I've met, talks about how well drawn and well done your plans are.  Congrats ZFA's San Francisco team!! You did a great job." - Building Owner, Oak Street property

Hyde Street:  Retrofit

San Francisco | California

This project is composed of two buildings side-by-side, adjoining each other at the center of the property. A new retaining wall was added at the back of the site and new shear walls and diaphragm strengthening were added to mitigate the soft story condition.

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Lyon Street:  Retrofit

San Francisco | California

Built on a brick foundation in 1900, this four story single family was converted into a five-unit multi-family home in the 1960’s.  ZFA was retained to perform an evaluation and retrofit. The design solution was unique due to its brick foundation and consisted of strengthened shear walls in the first floor with holdown anchors drilled through to the base of the brick footings. This solution was deemed most cost efficient and effective. 

Church Street:  Screening + Drawings

San Francisco | California

This four story, 3,000 sf wood-frame structure was built in 1907 and ZFA provided Structural Engineering Services based on the requirements of San Francisco Ordinance #66-13 “Mandatory Earthquake Retrofit of Wood Frame Buildings.”  ZFA completed the required Screening Form for submission to the City, prepared retrofit drawings, and discussed retrofit solutions with the owner.

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lyon jackson street

Lyon Street/Jackson Street:  Retrofit

San Francisco | California

Located in the Pacific Heights neighborhood, this building was constructed in approximately 1907 and has three stories on the downhill end and two stories over a partial basement on the uphill end. The de-facto seismic force resisting system appeared to be wood-framed walls with sheathing. ZFA was retained by the building’s owner, to complete a seismic retrofit in accordance with AB-107. The retrofit solution consists of strengthened shear walls and a steel special moment frame in the garage.

Page Street:  Retrofit

San Francisco | California

ZFA was retained by the building owner to perform an evaluation of the structure with respect to the Soft Story Ordinance. The project included evaluating and retrofitting a 6,221 sf three-story building. The retrofit seismic force-resisting system consisted of plywood overlays of existing basement walls and improved anchorage to foundation.

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Jefferson Street:  Retrofit

San Francisco | California

This wood framed condominium building is four stories, had been screened and was subject to the SFBC Chapter 34B Wood framed Seismic Retrofit Program.Following the Loma Prieta Earthquake the building was seismically improved, including the addition of a steel frame in the garage and shear wall strengthening on the ground floor. ZFA performed an analysis of the existing steel frame and added welded plates to reuse the existing steel frame and comply with the new ordinance loads.


Montgomery Street:  Screening

San Francisco | California

ZFA completed the required screening for thisFour Story, 9,300 sf building to determine if the structure required a retrofit. We prepared retrofit drawings and discussed retrofit solutions with the owner.