By next summer, some of downtown Worcester’s newest residents will begin their days in former courtrooms, serve dinner on countertops made from former judges’ benches and arrange their books on a shelves that once belonged to a law library.

The former Worcester County Courthouse is undergoing a sprawling transformation to become 118 mixed-income apartments that are expected to open by the middle of next year. Named the Courthouse Lofts, the development will include a mixture of units that range in size from studios to three-bedrooms.

“It’s a very unique building,” said Michael Lozano, vice president of developer Trinity Financial. “We’ve worked hard to make sense of the circulation.”

The historic building dates back to 1843 and has been vacant for more than a decade.

Trinity has begun framing out apartments and conducting plumbing, electrical and HVAC work. Windows will be replaced with energy-efficient replicas in the coming weeks, and the building’s historic components — from marble walls to detailed woodwork — will be preserved and restored.

“Whatever is still there and survived the years of use, we’re bringing back, for the most part,” Lozano said.

That includes judges’ benches, intricate plasterwork, ornate radiators and even a brick fireplace. High ceilings in some units call for a lofted bedroom design, while existing hardwood will be kept in others.

“They range drastically,” Lozano said. “Pretty much every unit in the building is different in some way.”

The company expects to begin taking applications for the apartments next spring with an opening date sometime in the summer.

“As soon as we can, we’ll have people moving in,” Lozano said.

He added that Trinity has already reached out to the Worcester Art Museum and other institutions in the city to come up with initiatives to get residents acquainted with the area.

“We very much want to be part of the neighborhood, we think we will be part of the neighborhood,” Lozano said. “We feel we’re sort of bridging the northern part of the city down into the northern part of Main Street and into downtown.”

The renovated building will also include a public museum dedicated to cyclist Marshall Walter “Major” Taylor, who trained and competed on the streets of Worcester more than 120 years ago.

It will be located in the former Registry of Probate space.

Trinity is using state and federal historic tax credits to help fund the $55 million project.