Undertaking a huge overhaul at the heart of Utah, the LDS Church will close its landmark Salt Lake Temple for four years starting Dec. 29 to strengthen the 126-year-old structure against earthquakes, replace several adjoining buildings and give a face-lift to the adjoining plaza and Temple Square, the state’s most visited attraction.

On Friday, top leaders of The Church of Jesus Christ of Latter-day Saints unveiled details of their previously announced plans to upgrade the faith’s pioneer-era temples in Salt Lake City, Logan, Manti and St. George.

At the center of the makeover in Utah’s capital is an effort to dig deep beneath the iconic granite temple and alter its foundation for a seismic retrofit.

The global faith’s president, Russell M. Nelson, spoke about the closure and renovation plans at a news conference complete with historic photos, computer renderings and video simulations of the revamped result.

“This temple and others built in Utah by these pioneer forebears represent some of the finest examples of architectural design, engineering and use of materials then available,” said Nelson, accompanied by his two counselors in the governing First Presidency. “We have a sincere desire — yes, a sacred responsibility — to care for them, that they may continue to serve as sacred houses of the Lord for many generations to come.

“You will love the results,” the 94-year-old Latter-day Saint prophet pledged. “They will emphasize and highlight the life, ministry and mission of Jesus Christ in his desire to bless every nation, kindred, tongue and people.”

The plans were welcomed by state and city officials, with Gov. Gary Herbert, Salt Lake City Mayor Jackie Biskupski, City Council Chairman Charlie Luke and several Utah legislators in attendance on Temple Square for the media event.

Herbert called Friday’s announcement “exciting” for the state and predicted that natural curiosity about the construction might draw additional visitors to what is already Utah’s top tourist destination.

“This shows the vitality of Salt Lake City,” the governor said. “We’re expanding and growing, remodeling and modernizing. This goes to the heart of Utah and where the growth is taking place.”

Church leaders declined to put a price tag on the overhaul. But, by any measure, it amounts to a major investment to attractions that draw up to 5 million visitors a year.

“To some extent, buildings are like people. Not only is the aging process inevitable, but it can also be unkind,” Nelson said. “The good news is that buildings can be renovated. The bad news is that needed renovation takes time, and it also takes the buildings out of commission for a season.”

126 years old and counting

The Salt Lake Temple, begun by Mormon pioneers in 1853 and dedicated 40 years later, will reopen in 2024, church officials said, with a public open house — allowing outsiders to view for the first time since 1893 what previously only faithful Latter-day Saints have ever seen — followed by a rededication.

Bishop Dean M. Davies, first counselor in the church’s Presiding Bishopric, which oversees the faith’s vast real estate, financial, investment and charitable operations, issued an early invitation for church members and nonmembers to take advantage of “a wonderful and unique opportunity” to attend the open house in 2024.

“Yes, we have these wonderful models,” Davies said, “but they do not really give a true sense of the feeling and the love of the Savior that exists within the temple.”

Until then, area residents will notice scaffolding around the temple and multiple cranes towering over the square as work unfolds.

The temple’s granite exterior and gilded Angel Moroni at its crown will be restored. An addition made in the 1960s on its north flank for “sealing rooms” will be demolished and rebuilt. Latter-day Saints believe they can be “sealed” to live with their families in the eternities.

Significant renovations are planned to the temple’s baptistry. Live performances that attend the “endowment” ceremony inside the temple will be preserved but with additional capacity to show the ordinance in more than 80 languages.

The highly symbolic endowment includes ritual reenactments of the creation, Adam and Eve’s expulsion from the Garden of Eden and humankind’s mortal journey and ultimate return to God’s presence. In the Salt Lake and Manti temples, live actors have portrayed these scenes for decades. In all other Latter-day Saints temples, the story is told through film. In January, the church altered the endowment to contain more inclusive language and more gender equity.

Members consider temples houses of God, places where the faithful can perform their religion’s highest sacraments, including eternal marriages, for themselves and, vicariously, for their ancestors.

Beyond restoration of some of the Salt Lake Temple’s original historic aspects, the feel and character of its rooms, murals and interior architectural flourishes will be unchanged.

Safeguarding against the big one

A major motivator of the project — and much of the reason it will take four years — is the earthquake retrofit and protecting the temple and church members in the event of a major temblor along the time-is-ticking Wasatch fault.

In complex work involving reinforcements threaded from underground through the temple and its 223-foot-tall spires, crews with Jacobsen Construction plan to restructure the foundation and install a series of base isolators to lessen the effects of seismic shifts, similar to work completed on the nearby Tabernacle in 2008.

Digging around the base will have to be done in careful stages to ensure the temple’s stability, church engineers said.

A base isolation system will be installed, digging deep under the temple to protect it from seismic forces, said Brent Roberts, managing director of special projects for the church. The system “is a collection of structural elements which should substantially decouple the temple from the earth.”

“Once complete,” he added, “it will help protect people, the historic building and the beautiful interior finishes in the event of an earthquake.”

Underscoring safety, church officials outlined a series of rigorous fire precautions to be in place during the construction work to prevent a repeat of Monday’s devastating blaze at Notre Dame Cathedral in Paris.

“We understand,” Roberts said, “that construction puts any project at greater risk for a fire incident.”

Like Notre Dame, the Salt Lake Temple sits at the heart of a major city, with all Salt Lake City’s street coordinates in its grid system emanating from that spot.

“The Salt Lake Temple is the center of Temple Square and the church headquarters campus,” Davies said.

Other renovations to the church’s 10-acre downtown campus will center on the eastern part of Temple Square, with the brunt of the work running through the middle of the block from North Temple to South Temple. The east gate will be closed for the duration of the work, while other gates will remain open.

The South Visitors Center will be torn down and replaced with two new, smaller centers.

“It is expected that the North Visitors Center, Tabernacle and Assembly Hall will remain open to the public during construction,” the church said in a news release. “Tours by missionaries from the Temple Square Mission will continue to be available for guests during construction.”

The North Annex, where devout Latter-day Saints can enter the temple, will be demolished and replaced with two new member-entry buildings, along with renovations to connecting underground areas and a parking garage beneath that portion of Temple Square.

Those parking at the Conference Center to the north will be able to walk underground to the temple entrance. And a new skylight over the below-ground temple reception area will offer patrons glimpses of the temple’s majestic spires above.

Mechanical, plumbing, electrical and heating and cooling facilities will also be upgraded throughout.

Goodbye, walls

The Temple Square renovation is designed to bring a more welcoming, open and transparent feel, with extensive landscaping to refresh its grounds.

Crews will add new fountains and flower beds, upgrade walkways and replace portions of the perimeter walls with metal fencing along North Temple and South Temple to create new street views of the site’s crown jewels.

Occasional sidewalk and road closures are expected as the huge construction project moves through a series of flexible phases.

During the extensive work on the temple, said Larry Y. Wilson, executive director of the temple department, members with “recommends” attesting to their adherence to certain beliefs and behaviors will be encouraged to take part in ordinances at nearby temples — from Bountiful to the north to three edifices in the south Salt Lake Valley (Jordan River and Oquirrh Mountain in South Jordan, and the Draper Temple). But that will mean no marriages at the Salt Lake Temple, a popular place for area Latter-day Saint couples to wed, for four years.

These other temples are making preparations to welcome more patrons, he said, and visitors should expect some added wait times.

Wilson said he anticipated a surge in reservation requests for marriage sealings in the temple before the Dec. 29 closure, adding that “there are still many opportunities to sign up for open times to do that.”

Otherwise, church officials said, much of the busy yearly schedule of events on Temple Square and nearby buildings will continue, from choir performances and Christmas light displays to regular tours for millions of visitors, though some may be reduced in scale as work proceeds.

The Family History Library, Church History Museum, Church History Library, Conference Center, Joseph Smith Memorial Building, Lion House and Beehive House will be accessible to visitors during the renovation.

No major impact is expected to twice-yearly General Conferences — at the Conference Center across North Temple — beyond lack of access to some parts of the plaza during breaks.

Tribune editor David Noyce and reporter Sean P. Means contributed to this story.