On April 18, 1906, San Francisco was struck by a magnitude 7.9 earthquake. The initial shaking destroyed some homes and commercial structures, but it was the fires — ignited by broken gas lines — that created the catastrophe that ultimately destroyed roughly 28,000 buildings. Now, 120 years later, the city is still grappling with gas line safety and the safety of buildings constructed before modern seismic safety codes. These older buildings are integral to the city’s identity and economy, but without proactive retrofitting, they pose significant risks to public safety and economic stability in the event of a major earthquake. SPUR’s latest policy brief, 120 Years After 1906: San Francisco’s progress toward earthquake-safe buildings — and what needs to happen next, outlines the city’s current seismic safety efforts and vulnerabilities. We asked author Sarah Atkinson to discuss both in the context of San Francisco’s many other priorities and its current fiscal deficit.
How old is San Francisco’s building stock, and how does that relate to the city's seismic safety?
Approximately 60% of San Francisco’s buildings were constructed before 1940, long before modern building codes were adopted. Consequently, many have structural vulnerabilities that require retrofitting to improve safety.
The first voluntary seismic provisions were added to the national model code (known then as the Uniform Building Code) around 1930. The 1933 Long Beach earthquake sparked the adoption of the California Field Act, which mandated earthquake-safe construction for all public schools, and the Riley Act, which mandated the establishment of building departments to inspect new construction. Modern codes were adopted in the 1960s and improved upon in the 1970s through the 1990s. These modern codes prioritize structural safety to prevent collapse and save lives, and they also address structural deficiencies of certain building systems, such as non-ductile concrete buildings, also known as brittle concrete because of their collapse-risk vulnerability in major earthquakes. Seismic building codes continue to improve as structural engineers learn from earthquake damage around the world.
What actions has the city taken to improve the safety of older buildings?
Various reports, including SPUR’s The Dilemma of Existing Buildings, have advocated for strengthening San Francisco’s older building stock. That report and our Resilient City initiative influenced the city’s development of the Community Action Plan for Seismic Safety, a plan to reduce earthquake risk in existing privately owned buildings and to set guidelines for repair and rebuilding after an earthquake. These efforts led to initiatives such as mandatory retrofit programs, technical studies to assess vulnerabilities of the city’s tall buildings, and outreach and education programs that assist the city and private property owners in advancing necessary updates. For example, in 2013, the city adopted a mandatory retrofit program for soft-story wood-frame buildings. As of now, that program is 95% complete, meaning 95% of the identified at-risk apartment buildings — about 4,700 buildings — have been retrofitted.
Additionally, the city has improved emergency response infrastructure to safeguard residents in the event of an earthquake or other disasters. For example, implementation of the Earthquake Safety and Emergency Response bond program has been critical in funding retrofits for essential public buildings, such as fire and police stations.
What challenges still exist regarding building retrofitting?
Thousands of buildings remain at risk, and many have yet to undergo retrofitting. The cost of retrofitting can be a barrier for many property owners, particularly those who may not have the financial resources or knowledge to navigate the retrofitting process. To encourage retrofits, San Francisco will need a robust set of financing options including state grants to local or state-run low-interest loan programs and tools like infrastructure financing districts. In downtown San Francisco, where many vulnerable concrete buildings are concentrated, the city should seek to integrate seismic safety into downtown revitalization planning, such as the city’s recently created Downtown Revitalization Financing District.
Additionally, post-earthquake fire risks have not been adequately addressed in San Francisco. When the next major earthquake happens, the combination of damaged gas lines and compromised water supply could lead to devastating fires like those seen after the 1906 earthquake, exacerbating the disaster’s impact. In densely populated areas with older infrastructure and many wood-frame buildings, fires following seismic events could be difficult to control. Cities like Los Angeles and Berkeley have mandated the installation of automated gas shut-off valves at gas meters, a low-cost mitigation initiative to reduce post-earthquake fires fueled by natural gas. SPUR recommends San Francisco pursue a similar policy.
Another challenge is the regulatory environment. For example, California recently adopted a bill (AB 130) that is meant to reduce the costs of developing housing in California by freezing building code updates. The bill’s language limits building code updates for both new and existing buildings, meaning that cities like San Francisco that want to adopt mandatory seismic retrofit ordinances (for existing buildings) may be forced to wait until the state’s building code freeze is lifted. SPUR has been working with our partners to make smart amendments to this bill.
San Francisco is facing a huge budget deficit. How can it fund retrofitting efforts?
For city-owned buildings, the Board of Supervisors has placed the Earthquake Safety and Emergency Response (ESER) Bond on the June 2026 ballot. The ESER bond, or Proposition A, would authorize the city to issue a $535 million general obligation bond to finance the construction, acquisition, renovation, expansion, and seismic retrofitting of critical emergency response and transit infrastructure. Voters approved ESER bond measures in 2010, 2014, and 2020. General obligation bonds are a way for cities to borrow money to finance capital improvements that cannot be funded through the General Fund. Although the city is experiencing a significant budget deficit, Proposition A, if approved by voters, will support the city’s continued investment in improving its emergency response infrastructure to better prepare for earthquakes.
For privately owned buildings, the question of “who pays?” is more complicated. SPUR believes that the city must support private building owners in accessing low-interest financing or other incentives. The cost to retrofit a non-ductile concrete building is estimated at about $50 to $200 per square foot, compared with about $10 per square foot for tilt-up concrete buildings. In the past, the city has passed bond measures to provide low-interest loans for retrofits of privately owned buildings, but the success of these loan programs is uncertain. The city should revisit these past financing strategies to determine if they could be viable. Additionally, it could explore partnerships with private investors and non-profit organizations to create funding mechanisms that support retrofitting initiatives, especially for vulnerable populations who may need financial assistance. Advocating for statewide grant programs could also provide much-needed resources for retrofitting efforts.
The bottom line is that by investing in seismic safety today, the city can recover more swiftly and effectively when disasters occur. This commitment to resilience not only protects lives and property but also strengthens the community’s social fabric and enhances its economic stability.