Last year, designer John Larsen took on a challenging new client: himself.

"I had never been an architect for me before," said Larsen, who has a master's degree in architecture and is co-founder of the residential design firm Design 45. "I had a lot of fun playing architect in my own home."

That home, a big white clapboard overlooking Minneapolis' Lake of the Isles, underwent a massive makeover to become this year's designer showcase home. A team of interior designers collaborated on the finishes, fixtures and furnishings that will be on public display for the next three weeks. But first, Larsen reconfigured and expanded the 1899-built house to make room for modern living, guests, gatherings and state-of-the-art green technology.

While he had "a blast" designing his own home, he wasn't his only client. His life partner, Mike Stewart, was an active participant in the project. "We've been together 14 years. We're very different, but there are more things we do like in common, so there wasn't a conflict," Larsen said. Both like to cook, garden and entertain, so spaces to accommodate those activities were a high priority.

And there was a third "client" to consider: business partner Ted Barnhill, who shares Larsen's home-based office. Larsen and Stewart will move into their remodeled house after it ends its showcase run next month. Larsen and Barnhill have already moved Design 45 into the new carriage house, which is not part of the tour.

Integrating the vision of more than 30 different designers was yet another balancing act. "It's our home, and we wanted to respect it. They want to stand out," Larsen said. But he appreciated the expertise they brought to the project, suggesting tiles, colors, paint techniques and window treatments that he wouldn't have dreamed of. "That's not my bailiwick at all," he said.

The kitchen, which Larsen bumped out to make room for a big center island and breakfast nook, was a great example of collaboration, he said. Larsen had chosen white cabinets, then designers Bonnie Birnbaum and Karen Soojian suggested bold navy-blue walls to set them off. For the backsplash, "I wanted tile. They said, 'Let's do stripes,' and I said, 'Let's make 'em random.' It was a wonderful give and take."

Passing the civic torch

When Larsen and Stewart first looked at the house in early 2010, it was beyond their budget, but they fell in love with its setting, a half-acre lot on the northern tip of Lake of the Isles, with plenty of room to grow organic vegetables.

"We both are gardeners, and we wanted a great big lot, which is a real challenge in the city," Larsen said.

But staying in the city was non-negotiable. "We like to be connected to the community, culture and vibrancy that the city offers," said Stewart, who works with crime victims.

The house needed updating, but Larsen knew all the ingredients were there. "The lot was sited perfectly, and the home's bones were just gorgeous," he said. "The things I couldn't change, I didn't have to change."

And there was an added bonus: The home had a history that Larsen and Stewart appreciated and wanted to continue. Its longtime owners, Stanley and Martha Platt, had been very involved in civic life. Martha, in particular, who died in 2008 at the age of 100, committed her time and opened her home to a host of progressive causes, including women's rights, racial justice and world peace. The Platts had hosted many fundraisers, with guest lists including visitors as diverse as Jane Fonda and Jesse Ventura.

Larsen and Stewart also have a passion for social justice and are involved with several nonprofits, including Project 515, which advocates rights for same-sex couples, and the GLBT Host Home program, which provides shelter for homeless teens.

So Larsen and Stewart wrote a letter to the Platts' children, telling them they admired their home and their parents, and wanted to continue their legacy.

"It ended up being an important letter," Larsen said. After considering multiple offers, some of them higher than Larsen and Stewart's, the family decided to sell the house to the men, and Larsen began his redesign.

Structural challenges

Even with "gorgeous bones," the home needed some significant changes to live the way Larsen and Stewart wanted it to.

"The big architectural feats were the tunnel [which connects the carriage house to the main house], the addition and gutting the core," Larsen said. He carved space out of the former living room to add a library that looks like it could have been there all along, as well as a mudroom, powder room and coat room. He also reconfigured the back staircase, which he described as a cramped "head-hitter."

"The stair[case] was really tricky because it connects to four stories," he said. Larsen changed the direction of the staircase and opened it up to the third floor, adding a skylight and a stained-glass window that originally graced the master bedroom.

"Before, every landing was behind a door," Stewart said. "Now it's a wonderful open space."

At the onset of the project, Larsen challenged himself "to be as green as we could be," aiming for Gold-level certification (pending) from Minnesota GreenStar.

"We took all the skin off and reinsulated from the outside," Larsen said. Other sustainable features include geothermal heating and cooling, photo-voltaic solar panels, reused and recycled materials and two green roofs, planted with five varieties of sedum, to capture and filter runoff that would otherwise flow into the lake. "Plus it looks cool," Stewart noted.

Now the home is ready for its next chapter. "This house will have no problem making it for the next 100 to 200 years," Larsen said.

Members of the Platt family have already visited and given their blessing, along with original light fixtures they'd taken out for safekeeping. "They've been very dear, sharing things," Stewart said.

He and Larsen are eager to continue the Platts' tradition of using the home as a gathering place for friends and neighbors and causes. And they've designed a Host Home guest room on the third floor so that they can welcome youths who need a place to stay.

"This is a generous home," Stewart said. "Part of taking it on is to share it."

Kim Palmer • 612-673-4784