The Duluth School Board was told Tuesday it would cost $48.5 million to restore and repair Historic Old Central High School.

The cost breaks down into three categories: building enclosure, interior and systems. The building enclosure, or exterior, repairs is estimated to cost about $24 million. This number, provided by Pam Jergenson, a senior building enclosure consultant with InSpec, was arrived at by taking the estimates from the building inspection done in 2015 and 2016 and accounting for inflation. Jergenson said inflation costs were estimated at about 7.9 percent.

Interior upgrades and repairs are estimated to cost about $11 million. This estimate, provided by DSGW partner John Erickson, includes updating the clock system, replacing the fluorescent lighting with LED lights, renovating the bathrooms and fixing other cosmetic issues.

Systems repairs and replacements are estimated to cost about $13.5 million. This cost, provided by Obermiller Nelson Engineering principal mechanical engineer Chip Jacobs, includes replacing the current steam heating system, which only has seven years left on its life span and needs to be replaced before then.

Jergenson said before work is done on the heating and ventilation systems, it's recommended that the exterior be addressed to ensure the building no longer has water leakage.

Any and all restoration or repairs made on Historic Old Central must adhere to the strict preservation guidelines set by the National Register, which the building was put on in 1972.

The school district currently has no money available to complete the full restoration and rehabilitation project, so the source for the estimated $48.5 million is unknown. Now that the district has a firm estimate, the next steps lie in the hands of the School Board.

Superintendent Bill Gronseth said the first decision that should be made is whether the building should continue to be under the ownership of the district or another public entity, or whether it should be sold to a private developer.

"At the heart of that decision right now is this building is iconic to our city and is arguably one of the most identifiable buildings in the city," Gronseth said. "And if it is in the public domain, we as a community need to figure out how to finance this. If that isn't the answer, then we need to have a discussion about where does the central office of this school district go if (Historic Old Central) is not it."

Gronseth said those discussions will happen over the course of the next few months to a year with the steam system deadline in mind.

In 1892 when Historic Old Central was built, the lumber and shipping industries had made Duluth a thriving, wealthy city. The Richardsonian Romanesque-style school was considered one of the greatest examples of that style of architecture in the United States. Designed by Emmet S. Palmer and Lucien P. Hall, it was modeled after the Allegheny County Courthouse in Pittsburgh.