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In the wake of the 1989 Loma Prieta earthquake, San Francisco founded a study to mitigate the earthquake risks in the city.  According to this study, after a 7.0 magnitude earthquake on or near the San Andreas Fault, up to 90 percent of the current soft story building stock in San Francisco will not be habitable.  After retrofit, that number is expected to be below 10 percent. 

A year after the mandatory soft story program was launched in 2013, the city rolled out accessory dwelling units (ADU) to allow building owners an option to recuperate the retrofit costs by adding new income units.  Other than single-family residential zones, the ADU ordinance overrides existing zoning restrictions to add new units within the existing envelope.  It additionally allows complete or partial waivers of the planning code requirements for parking, rear yard set back, dwelling unit exposure, and usable open space. 


While the cost of retrofitting can be passed through to the tenants, the cost of new units is relatively lower compared to new construction because their usually smaller square footage and use of existing structures.  As noted in the city's detailed ADU handbook, "ADUs can provide flexibility for families over generations, offsets the costs of homeownership, and/or provide a more affordable housing option for some households."


This combination of soft story and ADU program is the lowest-hanging fruit to tackle two criteria to become a more resilient city:

(1) preparedness in an earthquake event and

(2) a stronger housing stock by reclaiming underutilized spaces within existing buildings


A great equation for success is: Resiliency = Earthquake preparedness + Strong Housing Stock.


Since most building owners associate ADU with soft story retrofit, their first and only contact with a building design professional is often an engineer.  They may assume the engineer can also draw up plans for the new units, thus saving on design fee.  However, short-term savings does not equate to long-term value.  Understand that one of the many great assets of an architect is his or her master planning skills.  Since the ordinances require phasing of permits, a thoughtful strategy to ensure the retrofit work will eventually support future improvements is incredibly valuable.

As architects, we are trained to address multiple aspects of a site all at once - light, views, access, zoning, and economics.  As we prepare conceptual plans that illustrate the potentials of your site, we continue to fine-tune a strategy that you or a future owner may wish to pursue.

Whether you are thinking about taking advantage of the city incentives to add a unit or not, architects provide a comprehensive roadmap for future improvements, such as decks, additions, and remodels, and ensure that the retrofit work will not limit those opportunities.  Architects, in turn, can collaborate with professionals across the design community to provide a comprehensive approach to your design with a full team of experts, including landscape architects, interior designers, and lighting designers.  Having a master plan backed by an understanding of cost and return makes sure that work done today will not preclude possibilities for the property in the future.

Planning an attractive new unit within the existing building envelope presents challenges that require creative thinking and knowledge of the building systems, codes, and how we inhabit spaces.  A well-executed design is one where the new enhances the existing in the process.  We communicate through drawings, models, and renderings so that the owners can visualize their new space and understand how it impacts the existing building as a whole.  Building on the initial studies, architects - working side by side with an engineer - progressively add details and specifications to create a set of drawings ready for a builder to provide accurate estimates. This is a well-tested process for an architect, engineer, and builder to do their parts efficiently in order to provide maximum return for the development of your great investment - your building. 


The way ADU permitting is set up, either a mandatory soft story or a voluntary seismic upgrade permit needs to be obtained first. Then, a separate permit for the new units can be submitted.  You can consult with your design professional to guide you through the permitting process. 


Your architect, working with the engineer, builder, and other design experts, can provide you with a team that is trained to work together with all the skills needed for a successful project.  A collaborative starting point can creatively address both architectural and engineering needs.  There is nothing more irksome than an out-of-place braced frame or walls blocking out light.  In the end, it is the experience you feel in these living spaces and overall improvement to the longevity of the building that yields maximum return on your investment.


A close collaboration between an architect, an engineer, and other design professionals is critical to ensure success in a retrofit project. A comprehensive understanding of existing site condition, proposed space use, structural performance and efficiency, and cost-return analysis are strategies for adding value to your property.

When you work with Q-Architecture, you have a uniform team of architects and engineers to "see the whole picture".  

Our solution is therefore more comprehensive and effective without sacrificing aesthetic and historic character of your building.


1. 100 Resilient Cities

2. "Since 2014, the City has adopted new programs that would allow an ADU beyond a parcel's density limits in certain conditions." 

3. "In 2014, Mayor Lee pledged to construct 30,000 new and rehabilitated homes throughout the City by 2020, with half available to low, working and middle income San Franciscans."  San Francisco is well on track towards those goals. "since announcing his Housing Plan in January 2014, over 9,500 units have been built or completely rehabilitated, with over 3,200 of those units permanently affordable to low and moderate income San Franciscans."

4. 2015 SF-ADU Handbook

Michael Robbins, AIA, LEED AP, and Dawn Ma, PE, Assoc. AIA, are members of the Small Firms Committee of the American Institute of Architects, San Francisco Chapter.  The committee provides a source for sharing knowledge among architects of small firms for mostly residential projects.  Many of our members are actively working on retrofit/ADU projects. For more information, feel free to contact Michael at or Dawn at

Note: This article appears in the San Francisco Architecture Small Firms, Great Projects, Publication. Please check out, "Designing Strong Structures To Replace Soft Story Stock" by Dawn Ma, PE, Assoc. AIA, and Michael Robbins, AIA, Leed AP, with contributions by Randy Collins, PE

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