The Salt Lake Temple has gone through several renovations throughout the years, but in 2019, President Russell M. Nelson announced the largest renovation yet, saying, “Obsolete systems within the building will be replaced. Safety and seismic concerns will be addressed.” Later, in the October 2021 general conference he added, “We are sparing no effort to give this venerable temple, which had become increasingly vulnerable, a foundation that will withstand the forces of nature into the Millennium.”
The temple, as the house of the Lord, will be the ultimate focus of Temple Square. In addition to improving the foundation and support system, the renovation will also accommodate additional languages and enhance accessibility to the temple for members with limited mobility. The areas around Temple Square will also better highlight Jesus Christ’s life, ministry, and mission while making it easier to view and access different parts of the temple.
Using the latest seismic engineering technology, the temple will undergo seismic upgrades from below the foundation to the tip of the spires. These upgrades will involve complex seismic design and construction methods using base isolation and structural reinforcement.
Base isolation is the process of installing mechanical systems below the building that isolate the earth’s movement from the structure above. In an earthquake, the earth below moves underneath while the building above remains more stable.
Because the base isolation improvements aren’t perfect, structural reinforcement can reduce the remaining risk of damage to the building. With structural reinforcement, if the building moves during an earthquake, it will move as one consolidated building.
The Salt Lake Temple will be strengthened by a base isolation system and structural reinforcement. New foundations will be built in a precise sequence to keep the temple stable and secure during the process.
The process of temple strengthening is a complicated effort. Here is how the process works:
1. Expose existing stone foundations. The soil surrounding the existing stone foundations is removed down to the bottom of the existing stones. As President Nelson said, “If we examine the foundation closely, we can see the effects of erosion, gaps in the original stonework, and varying stages of stability in the masonry.”
2. Consolidate the stone foundations. The existing foundation is made up of rough-cut stones with many gaps between the stones. Holes are drilled at different angles to inject high strength grout that consolidates (or unifies) the existing foundation by filling holes and gaps and voids. Tensioned steel rods are then grouted into the foundations to add strength.
3. Add a shoring wall. The 187-million-pound temple imposes an extreme pressure on the soil below the stone foundations. A shoring wall, made of interlocking concrete piers and steel column reinforcements, is installed around the outside of the temple to keep the soil contained and stable while workers dig below the level of the original foundation.
4. Install cylindrical beams. Cylindrical beams made from large steel pipes are pushed into the soil below the consolidated foundation from step 2. These beams are filled with high-strength concrete and large steel reinforcing bars and ducts (to accommodate future steel cables). The beams will become part of the new upper foundation platform. The soil around the temple is excavated or removed deep enough to install the beams. Grout is pumped into the space between the cylindrical beams and the soil so that the weight from the temple can be supported below the cylindrical beams.
5. Shore and excavate the soil. Once the cylindrical beams are installed, a shoring wall is added on the inside of the temple. The shoring wall allows the soil inside and outside of the temple to be excavated about 17 feet (5.2 m) below the original foundation on both the inside and outside of the temple, down to where the new lower foundations will rest.
6. Construct lower foundations. Large concrete foundations, which are 6 feet (1.8 m) thick, are constructed on both sides of the shoring walls. These foundations are reinforced with many steel bars. The 98 base isolators are placed on top of the new lower foundations (see “Base Isolation” above). Each isolator is 7 feet (2 m) across, weighs 18,000 pounds (8,165 kg), and allows up to 5 feet (1.5 m) of horizontal movement in any direction.
7. Construct transfer beams. These very large concrete beams are 15 feet (4.6 m) high and are supported on top of the base isolators. The transfer beams are strengthened by an enormous amount of reinforcing steel and tensioned steel cables. The reinforcing bars and ducts from the cylindrical beams are extended into the transfer beams.
8. Transfer the temple’s load. Steel cables are inserted into the ducts through the transfer girders and cylindrical beams. The cables are tensioned, or pulled, to provide more strength to the concrete. This will unify the new and existing foundations as one. Once tensioned, these cables help transfer the weight of the temple from the soil, which has been supporting the temple, into the transfer beams and then into the base isolators and concrete foundations.
9. Remove soil and shoring walls. Once the load transfer is complete, the shoring walls and the soil below the cylindrical beams are removed, and the temple is completely supported by the upper foundation platform and the new lower foundations. The base isolators are now free to move up to 5 feet (1.5 m) in any horizontal direction in a large earthquake.
10. Strengthen the roof. New steel roof trusses, or frameworks, are installed on both sides of the original trusses (which continue to support the plaster ceiling over the assembly room below). The new trusses support the weight of new mechanical systems. The trusses also strengthen the temple by connecting the walls and towers together at the roof level. The trusses are encased in large concrete bonding beams on the north and south walls.
11. Install vertical cables. Holes are very accurately drilled through the stone columns from the top of the columns and towers to below the cylindrical beams. Tensioned steel cables are installed, anchoring into the concrete bonding beams and the tower columns and extending down to the underside of the cylindrical beams to strengthen the columns.
12. Add steel reinforcement to the towers. Structural steel reinforcement is installed up to the top of each tower.
The base isolation system and the tower, roof, and wall strengthening allow the Salt Lake Temple to resist the forces of nature for centuries to come.
The Salt Lake Temple closed in December 2019 for renovation. The surrounding area on Temple Square and the plaza near the Church Office Building are also undergoing renovation and restoration. The following are regular updates about the progress of the Salt Lake Temple renovation and other updates on Temple Square.