In 1998, the Minneapolis Warehouse District was still gritty and industrial — a long way from the swanky North Loop of today, dotted with upscale restaurants and boutiques.

That was the year architect Garth Rockcastle was tapped to design the conversion of an old downtown warehouse into loft-style condos, one of the first such transformations in the area.

This particular warehouse was a 1913 brick building that had already lived many lives — as a farm implement factory, a car showroom, a storage facility for the Guthrie Theater and for Architectural Antiques.

Rockcastle, a founding partner of MSR Design, was drawn to the building’s original, time-tested materials, including brick and concrete block walls, heavy timbers and wood and concrete flooring.

“It was clear it had a history, and it was fascinating to me,” he said. “I wanted to live in this detail and design a building I wanted to live in.”

He and his wife ultimately bought two units, one for themselves and one for their two teenage daughters, and moved from their home in Kenwood to the converted warehouse on Washington Avenue, which was completed in 2003. Rockcastle foresaw the transformation that was coming to the neighborhood.

“He said, ‘This is all going to be lofts,’” recalled his wife, Mary, a novelist who also serves on the creative writing faculty at Hamline University.

Rockcastle’s design for the building included retaining and, where possible, exposing the original elements, but adding an interior galley and skylights to bring light into the heart of the building.

His own two units were especially challenging to design because a brick-enclosed freight elevator shaft ran through both.

He used the empty shaft to create a multilevel “house within a home,” with mezzanine levels that allowed him to add square footage of living space to the original envelope.

In the “house within a home,” he positioned interior windows to offer views of artwork, framed by repurposed windows from his Kenwood house, which function like shutters.

He also designed an eye-catching steel-and-clear acrylic staircase to connect the levels, and to the girls’ unit below, which the Rockcastles have since sold. His innovative, space-saving storage systems include slide-out and rollout closets in the master bedroom.

“It was a laboratory for my own curiosity,” he said of the loft.

Other distinctive features include a double-sided built-in “peek-a-boo” glass bookcase, a master bedroom with an interior balcony and a private deck, and even a private fourth-floor greenhouse where vegetables, herbs and spring bulbs thrive in frosty February. The sunny glass-enclosed space could also serve as a beautiful studio for a painter, writer or musician, noted real estate agent Cynthia Froid, Keller Williams.

The Rockcastles recently put their 2,200-square-foot loft on the market for $945,000. Garth, who has launched a new consultancy on adaptive reuse of buildings, art and furniture, travels frequently. And Mary is ready for a smaller, one-level home.

The loft is ideal for an art lover, with its gallery wall, slate display ledges, art lighting (also designed by Rockcastle), and openings in walls that allow artwork to be experienced from multiple vantage points.

“It’s truly one of a kind,” Froid said of the loft. “So unique, inspiring and creative.”

Cynthia Froid, 612-578-1303, Keller Williams, has the listing. There will be an open house noon to 2 p.m. March 1, 801 Washington Av. N., Minneapolis.