With high design defining every room of the house, it’s only logical that the garage, a prime piece of real estate, has become one of the latest expressions of luxury living.

Whether decked out as a storage space and showcase for collectible cars, remodeled as an elegant and efficient living/car space or turned into an auto-centric entertainment venue, the 21st century garage is revving up its curb appeal.

"The showroom garage is becoming one of those amenities that the high-end buyer is looking for," said Mitchell Cal, owner of the entertainment blog-style website PriceyPads.com. "For many buyers, the garage is just as important as the kitchen or living room. They want a space that is just as beautiful as the main living areas of the home."

Paul Maki, senior architect for Nor-Son Builders, which has offices in Minnesota and North Dakota, said the typical garage redo, which features radiant in-floor heating, a concrete or epoxy floor, sheetrock walls with wood or metal wainscoting, custom cabinetry, a high-end door and decorative lighting, "is just as nice as the family room, except there’s a car parked in it."

Having a great garage, said Linda Fiore Ceolin, creative director of Garage Living, a design-build company with four showrooms in Canada and 10 in the United States, adds order and aesthetics to the property.

"It’s about a better lifestyle—it’s like a feeling of luxury the moment you arrive because everything is organized and within reach so you don’t waste time looking for things," she said.

More: Get Yourself a High-Tech Garage

All in the Details

Glamorous garages, which are used for everything from large-scale entertaining to man caves and museum-like displays of coveted classic cars and collectibles, usually feature a workspace defined by custom cabinetry.

Their style often follows that of the other rooms in the house and exploits the architectural features of the estate.

Mr. Cal mentioned a 17,000-square-foot mansion in Kelowna, British Columbia, Canada, that was featured in HGTV’s "Million Dollar Rooms." Its two-story garage, which includes a large car lift, has glass doors on each level that open to admit the view of Okanagan Lake.

So important has the designer garage become, it’s not uncommon for people to spend tens or even hundreds of thousands of dollars outfitting them, added Chad Haas, founder and chief gearhead of VAULT, a garage design firm and maker of custom garage cabinetry based in Beaverton, Oregon.

More: In Luxury Homes, Walk-In Closets Dazzle

While his typical garage fan spends $40,000 to $65,000, Mr. Haas, who has done projects around the world, has a client in San Jose, California, who spent $600,000 to convert her 5,000-square-foot car condo to an entertainment, display and workspace for her cars.

Another client, in Houston, created a Hard Rock Cafe-style showplace for his collectible guitars and cars that features a porcelain tile floor, cabinetry with heavy-glass countertops, mood lighting and sophisticated sound speakers.

For a condo at Brainerd International Raceway in Minnesota, Nor-Son Custom Builders designed a garage that has display and entertainment spaces separated by a glass wall. Scott Amundson Photography

Added Value—Both in Terms of Resale and Dream Fulfillment

When it comes to price "the sky’s the limit," said Bryan Evans, residential sales manager for Dura Fitted Garages in Northamptonshire, England, which serves clients not only in the U.K. but also in Europe, Australia and South Africa.

He recently gave a £104,000 (US$134,569) price quote on a 12-bay standalone garage for a four-acre estate on Henley-on-Thames, England. "The owner has a driver and a nice selection of cars, including two Rolls-Royces, an Aston Martin and a Ferrari, that he uses all the time," he said.

Spending such large amounts, according to Mr. Evans, "adds value to the property; this has been proven through sales and property surveys."

That may be one justification for the wallet-busting over-the-top conversions, but far more often it’s simply the fulfillment of the owner’s dream.

More: As Homeowners Focus on Wine Storage, Rooms Replace Cellars

Mr. Cal mentioned garages with glass floors, restored gas pumps that actually can top off a tank and even built-in car washes.

He pointed to an estate in Corona Del Mar, California, as an example of such elaborately extravagant treatments. The owners turned the lower level of the home into a mini-mall that has a jewelry store, a bowling alley, a home theater, a diner and a place to display a car. (The rest of the cars are stored in a showroom 16-car garage that has a mechanical workshop.)

Mr. Haas was once commissioned to spruce up a garage at a custom residence in Littleton, Colorado. The 10,500-square-foot house, styled like a circa 1700s Tuscan villa, was named the 2010 best custom-built home in the U.S. by the National Association of Home Builders.

"The house was spectacularly beautiful, but the owner told me the garage was a sore spot," he said. "All I could think was, ‘How can I make the garage as perfect as the house, and how can I make it look like they go together?’"

To ground the garage in history, Mr. Haas chose mahogany sliding doors that have wrought-iron hardware, travertine porcelain floor tile and car-themed neon signs of his own design. "We also hand-textured the walls and added false beams to the ceiling that were made of foam and wood veneer reclaimed from old industrial projects," he said.

VAULT designed a garage for a Tuscan-style villa in Denver, Colorado, that matches the style of the house. It has a beamed ceiling, mahogany sliding doors with wrought-iron hardware, travertine porcelain floor tile and car-themed neon signs. John Vanderpool Photography

The delighted owner claimed the space as his own. "He uses it to hang out with his son," Mr. Haas said. "He watches football, drinks Scotch and smokes cigars."

More: High-Tech Humidors: The smartest ways to keep your cigars fresh

For some homeowners, necessity is the prime driver of the glorified garage.

Architect Scott Hommas of Gelotte Hommas Drivdahl Architecture in Seattle was commissioned to create what he calls the Garage Mahal on waterfront property on Mercer Island, Washington, for a client who had more cars and money than space.

"The garage is a luxury-car showroom on steroids with an auto shop and hoists so you can stack cars double tall," Mr. Hommas said. "There’s a helicopter hanging from the ceiling; it’s like walking into an air and space museum. But it only has room for 12 cars. The client needed room for 22 more, so he bought a second property up the street and built a house there that is mostly garage."

For a house on Seattle’s Mercer Island, Gelotte Hommas Drivdahl designed what has come to be called a Garage Mahal for the owner’s collection of cars. The room also contains a helicopter that hangs from the center of the ceiling. Ben Benschneider

In South Austin, Texas, the so-called Auto Haus also devotes more living space to cars than people.

"The garage, which takes up about 2,180 of the home’s 4,120 square feet of gross floor area, is like a museum—a clean, white box—because it’s more about the objects," said Architect Matt Fajkus, founding principal of Matt Fajkus Architecture in Austin. "There is a small residential component. The biggest challenge was making it adaptable to a total residence if the owners wanted to convert it later."

Ms. Fiore Ceolin said that some clients rethink their garages when they are remodeling or when their family situations change.

A husband and wife, for instance, created his-and-hers garages that had separate spaces. Another client had her add a car lift for his 911 Porsche," Ms. Fiore Ceolin said, "so his son could practice hockey in the garage without damaging it."

More: Over-Customizing a Home May Lead to Trouble Selling It

Garage ‘Infancy’

In terms of garage design, Mr. Haas believes details will become more important across the board.

"We’re in the infancy of garages," he said. "They will become more mainstream, and people will pay more attention."

Indeed, Architect David Birt of Austin’s Matt Fajkus Architecture is fielding requests for Auto Haus-style homes.

"People are asking for larger showcase pieces because they have a deep appreciation for well-made products whether these are cars or boats or other objects," he said. "They want to show them off or have them in a space where they can appreciate them. Some of them even want to bring the car into the living space."