Bridging Centuries

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For nearly a century, Congregation Emanu-El in San Francisco, California, has stood as a spiritual and cultural anchor in the city’s Richmond District. Its pink-hued dome rises 150 feet above Lake Street, visible from many corners of the city, and its architecture reflects the artistry of Bakewell and Brown, Bernard Maybeck, and G. Albert Lansburgh—three of the Bay Area’s most influential designers. More than a landmark, the synagogue is a place where generations of San Francisco’s Jewish community have celebrated milestones, honored traditions, and found belonging. Preserving this historic complex required not only sensitivity to its architectural legacy, but also innovative engineering to ensure it will thrive safely into its second century. This work was made possible through the collaboration of Forell Elsesser Engineers (Structural Engineer of Record), Mark Cavagnero Associates (Architect of Record), Page & Turnbull (Historic Architect), Plant Construction (General Contractor), and Equity Community Builders (Owner’s Representative).

The Emanu-El complex comprises several interconnected structures built in 1925. The Sanctuary Building and Temple House were framed with structural steel encased in reinforced concrete, while the Courtyard Building—a smaller structure forming the interior connector building of the L-shaped site—was built of conventional reinforced concrete without steel framing.

A seismic evaluation by Forell Elsesser Engineers using ASCE 31/41 Tier 1 identified multiple deficiencies in the Courtyard Building: under-reinforced shear walls, discontinuities, lack of seismic joints to adjacent buildings, and evidence of water intrusion and slab decay. Some shear walls terminated abruptly at mid-height landing on transfer beams and slabs not designed for the seismic forces, creating discontinuities that would concentrate stresses during an earthquake. Reinforcement levels in several walls were well below modern code expectations, and core samples from those walls revealed deterioration from decades of moisture infiltration. Compounding these issues was the absence of seismic separation joints; the Courtyard and Sanctuary buildings were seismically connected together, greatly increasing the likelihood of a damaging interaction in a strong seismic event.

Because the Courtyard Building and Sanctuary had been constructed integrally with continuous diaphragms at aligned floors and shared concrete shear walls, they were originally expected to act together during an earthquake. In reality, the taller, stiffer Sanctuary would likely overpower the shorter, weaker Courtyard in a seismic event. The evaluation underscored the need for the buildings to behave independently, ensuring safety for the many congregants, students, and visitors who rely on the facility daily.

One option was to maintain the existing structure and perform a major retrofit with new shear walls, foundations, and collectors. While feasible, this approach would have required significant intrusion into the existing building, reducing usable space and altering circulation patterns. The costs were projected to be disproportionately high compared to the long-term benefit. At the same time, the congregation recognized that the Courtyard Building had reached the end of its useful life. Together, the project team explored replacing the structure while preserving the presence of its historic facade on Lake and Arguello Streets. This approach balanced practicality with stewardship: upholding community safety while maintaining the familiar character of the neighborhood streetscape.

Architecturally, the replacement reimagines the courtyard as a central gathering place, framed by a new transparent structure that brings light, openness, and modern functionality while maintaining dialogue with the historic fabric.

The new Courtyard Building adds four levels—one fully below grade and three above—designed to integrate with the existing campus. Structural steel was selected for the gravity system to simplify erection and reduce the weight of the building, which in turn reduced seismic demands on the foundation. Concrete shear walls provide lateral resistance, chosen both for compatibility with the surrounding basement retaining walls and for their flexibility in accommodating doors, circulation paths, and mechanical ducts above grade. Alternative systems, such as steel braced frames, were considered, but they were found to conflict with key architectural openings and limited duct routing. Concrete shear walls also offered mass and stiffness that helped reduce drift, an important factor given the adjacency of the new Courtyard Building to the more rigid Sanctuary. The 2019 San Francisco and California Building Codes were used for the design, which reference ASCE 7-16, the standard for new buildings.

One of the key challenges was detailing the interface between the new structure and the preserved historic facades. Rigid connections would have engaged the fragile, lightly reinforced concrete walls during seismic events. Instead, the design incorporates anchor assemblies specifically detailed to resist wall out-of-plane tension and compression forces only, allowing the new building to move and deflect independently while the facades remain non-structural, self-supporting elements. Anchors of small diameter, which were flexible enough to allow the main building to drift without imparting significant forces on the facade, were designed to resist tension. Larger diameter anchors assembled with Belleville washers were designed to resist compression with rotation, and avoiding the resistance of horizontal forces. This detailing ensures the historic walls are purely decorative and no longer relied upon to resist seismic or gravity loads.

12-inch wide seismic gaps were introduced between the Courtyard and adjacent buildings at every level to prevent pounding, with discrete cuts and steel plate covers blending into the existing concrete.

Preserving the facades required intricate sequencing. Temporary bracing supported the walls until they could be supported by the new structure. The most challenging element was the Lake Street Arch, the iconic entryway to the synagogue complex through the Courtyard Building. Forell Elsesser designed a nested series of HSS steel frames that fit within the arch cavity and anchored to the interior of the existing arch concrete, supporting it for both gravity and seismic forces. The walls of the arch structure were confirmed to have adequate capacity to serve as shear walls and now bear directly on new framing at the fourth level.

Construction logistics added further complexity. Underpinning was required not only for the new basement but also for adjacent buildings and sidewalks along Lake and Arguello Streets. Forell Elsesser coordinated with the geotechnical and shoring engineers to design systems that maintained support during excavation and transferred loads seamlessly to the new permanent foundations. Permanent underpinning was installed under the existing shallow Sanctuary footings that were exposed by the new excavation, to reduce large surcharge pressures on the new building’s retaining walls. Temporary shoring and underpinning was installed at all adjacent sidewalks for use during the temporary excavation, with these smaller surcharge pressures being carried by the new building’s retaining walls. These measures ensured surrounding structures, some of which were also historic, remained stable throughout the multi-year construction effort.

These solutions allowed the congregation and neighbors alike to retain the historic character of the complex—ensuring that familiar views of the arch and dome remain unchanged while the structure behind them is entirely renewed.

The project also created new opportunities for programming through the architectural interventions by Mark Cavagnero Associates, whose design introduced a rooftop play terrace, transparent community spaces around the courtyard interior, and a reinvigorated entry sequence aligned with the dome and Sanctuary—all supported by structural solutions that enabled these features.

Half of the previously unoccupied roof is now an open-air, elevator-accessible playground for the synagogue’s nursery school. Surrounded by glass guardrails, the space offers striking views of the dome and arch that were once invisible from street level. Inside, engineering solutions support features such as a dramatic stairway rising from the Lake Street arch entry to the main courtyard, a curved steel bridge spanning overhead, and recessed framing to accommodate sunken garden beds planted with olive trees.

Design and documentation utilized a range of structural modeling software, including ETABS for system analysis and Revit for coordination with the architect and contractors. Close BIM integration with a laser scan of the existing structure allowed complex facade interfaces and carefully detailed connections to be resolved in 3D before construction, reducing field conflicts.

After 13 years of planning and construction, the new Courtyard Building opened in September 2025. Within days, it was bustling with students, educators, clergy, and congregants—a sign of how deeply this building is woven into community life.

The project demonstrates how sensitive design and technical innovation can extend the life of historic structures in seismically active regions. For Forell Elsesser, Mark Cavagnero Associates, and the full project team, it was both a technical and design challenge, as well as a profound opportunity to protect a cultural landmark while strengthening its role as a place of gathering, learning, and faith. ■

About the Authors

Allen Nudel, SE, DBIA, is a Principal with Forell|Elsesser Structural Engineers in San Francisco, CA.

Susan LaFore, SE, is a Senior Associate with Forell|Elsesser.

Keri Scholte, PE, is a Project Engineer with Forell|Elsesser.