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In their new outdoor living room, Coco and Rosie have lounging areas, exercise equipment, fragrant plants, tasteful lighting accents and a water fountain. The three-season sanctuary is connected to the main house with a stylish elevated breezeway.

Coco and Rosie think they're worth it.

After all, they're cats.

The outside hangout for the two middle-aged Animal Humane Society adoptees was created by Suzy Kronfeld and her husband, David Baum.

They used to let their cats roam outside, but the Edina couple became increasingly worried about them being injured by cars or coyotes — or that they would harm other wildlife. When Coco insisted on being let out, the couple would follow her to make sure she didn't get into trouble.

"I wanted the cats to be safe. I wanted the birds to be safe. I wanted Coco to enjoy nature," Kronfeld said. "She really loves to be outdoors."

Then Kronfeld read about cat patios, better known as catios.

In recent years, do-it-yourself cat owners, pet companies and cat-friendly contractors have begun creating screened enclosures — which range in price from less than $50 to $30,000 — that keep cats safe while letting them enjoy fresh air, sunshine and the sights, sounds and smells of nature.

Kate Benjamin, founder of the Hauspanther.com website and co-author of "Catification," a book about cat-centric interior design, said catios started to become a thing about 10 years ago. They've become so much a part of the cat culture that some cities (including Portland, Ore., Seattle and Austin, Texas) have catio tours. They've even become a niche in the home improvement industry, with contractors specializing in costly catios and designers turning out catio kits.

A catio can be as simple as a wire-mesh box attached outside a window. But it also can be a screened-in apartment balcony, or a custom-designed, room-sized deck fenced in and outfitted for felines.

That's what Kronfeld and Baum opted to build for their cats this summer. The wood-framed screened enclosure in their backyard measures about 10 by 13 feet and about 9 feet high.

Inside are elevated lounging and observation platforms, hiding places, cat-friendly plants, a large red pine branch for climbing and a sisal-wrapped pole for scratching. There's some human furniture there, too, as well as a potting bench.

The cats get to their catio by going through a pet door installed in a window of the house and then walking along an enclosed, elevated catwalk — a sort of kitty-sized skyway — that extends about 30 feet, rising over a trellis, wrapping around the garage and connecting to the catio. Access hatches are built into the walkway in case a human needs to reach in to help out a cat.

Wind in the whiskers

The couple hired general contractor John Denn, owner of the Home Team, for the job this summer — even though he admitted he'd never heard of a catio before. He said the project was similar to building a screened-in porch, except with some feline-oriented features.

"My wife helped with some of the design," he said. He estimated the project took more than 100 hours of labor. "It's very custom."

(Kronfeld did not want to reveal how much the project ultimately cost.)

But Denn said the project went so well that he is looking forward to building more catios.

"It's definitely something I will offer to my customers," he said.

Across the country, specialty companies have already sprung up to cater to customers seeking outdoor cat spaces.

Robert Johnston used to build animal enclosures for businesses like veterinary clinics and pet boarding companies. But now he calls himself Catio BoB, working full time building catios at homes with options like external litter boxes and elevated "skyboxes."

Johnston is based in the Atlanta area, but he's getting calls from New York City and Miami asking him to do jobs costing thousands of dollars. "There's a whole big demographic I can fill," he said.

"The catio is more involved than knocking out a bird house in your garage," said David Murphy, an Austin, Texas, woodworker who has built more than 150 catios as The Cat Carpenter, a business he started about five years ago after he got laid off from his previous job as an accountant. "People who build things usually aren't cat people. And people who like cats typically don't know which end of the hammer to hold."

"My goal is to make sure the catio complements the home and garden, so that the home supports and serves all members, including the fur family," said Cynthia Chomos, a catio designer, feng shui consultant and founder of Catio Spaces, a Seattle-area company that builds custom catios and sells do-it-yourself plans.

"An outdoor catio allows a cat to enjoy the wind in his whiskers and be safe," Chomos said, in settings ranging from skyscrapers to houseboats.

"They can go anywhere from a couple hundred dollars to something very, very elaborate," she said. Chomos said she designed one catio project that cost more than $30,000.

"I've seen some that are insane, huge, bigger than my entire condo," said Benjamin, who installed a $5,000 catio at her home in Phoenix. "I do not think this is a fad. I think it is a growing trend."

Mental stimulation

According to Johnston, customers consider money spent on a catio well spent, because it can prevent expensive vet bills for a cat injured while roaming outside.

Dr. Lindsay Merkel, chief of small animal internal medicine and associate professor at the University of Minnesota College of Veterinary Medicine, said cats that run free are in danger of everything from cars to catching a fatal disease spread by preying on diseased rabbits to picking up something from other cats.

But cats that are kept in the house need mental stimulation. Merkel said a catio can be a safe way to keep a house cat entertained.

"I'm actually trying to talk my husband into building a catio," Merkel said.

Laura Moss is editor-in-chief and co-founder of AdventureCats.org, a website devoted to promoting safe outdoor experiences for cats. She endorses catios, along with walks on harnesses, expeditions in backpacks or trips in strollers for felines.

Kronfeld said her cats have been in their catio for about a month. Coco uses it the most, often coming out in the morning to lounge in the sun and then visiting again in the evening.

Kronfeld and Baum expect the patio to be a three-season attraction for the cats, but Kronfeld said she'll allow the cats to go out in the winter if they choose.

"If Coco wants to come out, I'll come out with her," Kronfeld said. "Right, Coco?"

Richard Chin • 612-673-1775