The seismic upgrade of the Salt Lake Temple was a major component of the extensive renovations that took place from late 2019 through 2025, designed to greatly enhance the building’s earthquake resilience while preserving its historic structure. Here are the key details:

What Did the Seismic Upgrades Entail?
The core of the seismic enhancement was the installation of a state-of-the-art base isolation system. This involved:

• Nearly 100 base isolators strategically placed beneath the entire foundation of the temple. These devices are designed to allow the building to sway safely—up to five feet—in any direction during an earthquake, dramatically reducing the potential for structural damage.
• Foundation reinforcement through the insertion of steel reinforcement tubes using a “jack and bore” technique—these steel components, filled with concrete, strengthen the base and distribute seismic forces evenly.
• Vertical granite wall coring: 46 deep holes (~150 feet deep) were drilled through the granite walls (vertical coring). These holes housed post-tensioning cables that anchored the spires to the reinforced foundation, providing additional structural stability.
• Structural support enhancements: Heavy-duty steel roof trusses were added to connect and support the roof and spires, ensuring they could withstand seismic forces without damage.

The Process and Timeline

• Start Date: The seismic upgrade efforts commenced around late 2019, concurrent with the overall renovation project.
• Major Work Duration: The seismic strengthening and foundation reinforcement primarily occurred between 2020 and 2023, with the installation of base isolators and structural reinforcements completed by 2023.
• Completion Date: The entire renovation, including seismic upgrades, was finalized in mid-2025.

Cost of the Seismic Upgrades
While a detailed breakdown of costs is not publicly reported, the total renovation project cost for the Salt Lake Temple—including seismic retrofitting, structural reinforcement, interior restoration, and expansion—was approximately $125 million. Seismic upgrades constituted a significant portion of this budget, reflecting the complexity and importance of safeguarding the historic structure.

Challenges During the Seismic Upgrade
During the seismic retrofit, there were technical challenges common to such large-scale historic renovations:

• Preserving the historical appearance: Working within the tight constraints of maintaining the temple’s exterior and interior aesthetics, while upgrading its structural safety, required precise engineering and craftsmanship.
• Limited access and delicate structural work: Installing base isolators and drilling into granite walls demanded meticulous planning to prevent damage and coordinate around ongoing construction activities.
• Unforeseen conditions: As with many renovation projects, unexpected issues like hidden weaknesses or structural irregularities in the old stonework occasionally arose, requiring adaptive solutions. However, no major delays or major issues have been publicly reported.

Summary
The seismic upgrades to the Salt Lake Temple incorporated advanced base isolation technology, deep foundation reinforcement, and structural supports, all aimed at ensuring the temple’s resilience against earthquakes. The work spanned from late 2019 to mid-2025, within a total project cost approaching $125 million, with careful engineering to maintain its historic beauty and significance. The successful completion of these upgrades now secures the temple’s safety for future generations, honoring its legacy and protecting its sacred purpose.