The time frame for the State Capitol’s $307 million extreme makeover is half over, but the work is only 30 percent done.

The situation belies the hive of construction activity at the domed fixture of St. Paul’s skyline. Hundreds of workers are simultaneously refurbishing its stone exterior, laying a new roof and restoring every nook and cranny of its interior with fidelity to its architectural origins in mind.

“You basically have three distinct and equally major construction projects happening on top of each other,” said Curt Yoakum, spokesman for the state’s Department of Administration.

Yoakum has helped document a project that’s the single biggest upgrade to the Cass Gilbert-designed building since it opened in 1906. In the process, he’s uncovered fascinating and sometimes grim bits of building trivia, like the stories of five workers who died during its original construction.

Construction safety standards have risen considerably in the century since — Yoakum said pictures of the original project show scaffolding that was little more than bound-together tree branches. The current project, which got underway in 2014, has been free of serious mishaps.

Jason McMillen, senior project manager for lead contractor JE Dunn Construction Group, said the company would be adding workers, from about 265 currently to 315 in the coming months.

“Our time is half gone,” McMillen said. “But we’re not half done.”

Around the building’s perimeter, crews are moving massive slabs of exterior staircase, some weighing more than 6 tons and requiring a special, extra-large crane. McMillen said “awful, horrible” water damage was discovered throughout the building’s lower reaches, so the workers are installing water protection measures under the steps.

On the main levels, crews are reinstalling heating, ventilation and air conditioning; remaking major portions of multiple floor plans; peeling off decades of plaster and particle board that obscured original trim and furnishings, and adding new bathrooms. Perched atop a scaffolding floor that lies just feet below the vaulted ceiling of the House chamber, a craftsman from Conrad Schmitt Studios of New Berlin, Wis., repainted a Latin dictum transcribed on the wall: “Vox populorum est vox Dei” (The voice of the people is the voice of God).

McMillen said it has been difficult at times to find subcontractors capable of the painstaking restoration work the building needs. When it first went up, he said, immigrant craftsmen supplied the kind of labor that’s no longer in such ready supply.

In a few areas on the top floor, the renovation revealed skylights long obscured by drop ceilings and other offenses to good design. Those windows have been uncovered, and the rooms underneath will largely comprise public spaces — something that was in surprisingly short supply in the pre-makeover Capitol. Members of a state panel overseeing the project have suggested those areas might even be available for wedding rentals and other private functions.

For now, the building is entirely empty of its regular occupants. The House chamber will temporarily reopen next March for a planned legislative session of about two months; the Senate will meet across the street.

JE Dunn is supposed to hand the building’s keys back over to the state at the beginning of 2017, in advance of a legislative session that will start in early January.

DFL and GOP leaders at the Capitol have so far maintained an uneasy truce about the taxpayer expense involved in such an ambitious undertaking, even as its total cost has spiked by more than $30 million.