When you test-drive a house by living in it for two days, what can you learn?

Your must-have list will shrink as you realize that you can do just fine without the living room fireplace and the kitchen island, while other things you never considered — such as traipsing up and down four levels and downsizing to one car or even going carless in the suburbs — enter the realm of possibility.

At least that was my experience when I spent two days living in EYA’s furnished, 1,620-square-foot, $714,900 Aster model townhouse in Mosaic District in Fairfax.

If I were buying a new house, this one would be a serious contender. But at the outset, things did not look too promising.

In the nearly 20 years that I have been writing about new homes in the Washington area, I have toured countless furnished townhouses. The ones I could have imagined living in varied widely in design but shared one important characteristic: They didn’t seem like townhouses.

In some cases, the units were unusually wide so that the proportions of the main living areas more closely resembled single-family houses. In other cases, the garage was on the same level as the main living areas so that you didn’t have to lug a lot of groceries up the stairs, or the back overlooked a wooded preserve, which lent a decidedly rural cast despite the proximity of the neighbors.

This townhouse has none of these things. It is only 16 feet wide, and no one would mistake it for anything but a townhouse. The development is surrounded by high-rise apartments, nondescript low-rise office buildings, a cellphone tower, a major U.S. Postal Service sorting center and a tennis club. And, yes, you have to lug the groceries up a flight of stairs. But the main living area, a loft-style space that runs through the entire second floor, simply “felt right,” an opinion that was also expressed by each of five guests at various points during the evening I had a dinner party.

What made the space a winner?

Although many home buyers tend to think that bigger is intrinsically better, most people perceive smaller spaces as cozy and intimate, and hence more comfortable. I’d spend most of my time in the living area if I owned the place. What makes this area so appealing is that the space is both large and small.

Open from one end to the other, the second-floor living area, 15 feet wide by 34 feet long with a 9-foot ceiling, is large by any measure. But functional elements along one wall — a fireplace and chimney, a staircase, a powder room and pantry closet — project into the space and shrink it down to three smaller areas, each about 11 by 12 feet, a very comfortable size for a living room, dining room and a kitchen, and similar in size to the other rooms in the house.

But the main living space that “felt right” was not “perfect,” and after two days of careful study, this architectural designer was ready to make a few changes.

The first thing to go, to my surprise, was the fireplace. This resale must-have occupied too much space, a sentiment that I found was shared by most of the residents whom I interviewed. As many of them had done with the freed-up floor area, I would install base cabinets with shelving above and a dedicated niche for a large flat-panel television.

Stairs were an issue for this prospective move-down buyer, but not for the reason you might expect. Going up and down the stairs in these four-level townhouses multiple times a day, was, as Mosaic resident Craig Annear characterized it, “a good cardiovascular workout.” The issue was communicating between levels. You can yell up one story, but not three. Some residents said they used cellphones, others said they walked all the way up — or down, if they had to answer the front door. My solution: an intercom, which EYA offers but few buyers elect to get.

The lighting package provided by EYA and installed in the model would suit most people, but I would engage a lighting specialist to get it right for me. The issue wasn’t how to illuminate the living and dining areas at night; it was how to do this during the day. The morning sun pouring through unusually large windows was wonderful, but it also produced glare, and the central dining area was too far from the windows to get enough light.

For many buyers, the kitchen has a major deficit that was such a non-issue for me I didn’t even realize it until I reflected on my visit several days later. There is no island. Instead there is a peninsula with an overhang and room for two seats.

The other standout feature in the Aster is the fourth-level loft that affords a degree of flexibility that’s unheard of in a townhouse.

There are different spatial options. You can have a light-filled aerie with large windows at both ends, close off some space to add a bathroom and close off more space to create a very private third bedroom — a great option for households with a teenager or frequent houseguests. The loft lends itself to many different uses, judging by the comments from homeowners: “my man cave,” “a place to hang out with male friends,” “a teenage hangout,” “home office,” “entertain friends,” and “a place for grandchildren to play and sleep on pull-down Murphy beds.”

A terrace running across the front of the fourth level is big enough to function as an outdoor room (it’s 10 by 15 feet) and clearly a special place for most homeowners. EYA President Bob Youngentob suggested that its appeal relates to its privacy: “Everybody likes to walk outside to get a breath of fresh air without leaving the confines of their house.” In expressing his preference for the terrace over a back yard, Annear couched it in more poetic terms: “I’d rather be up four floors and get the sunset. It reminds me of being at the beach in summer.”

Nearly as compelling as the Aster itself is the urban lifestyle that is part of the Mosaic District package, despite its location in the heart of suburbia. Going carless is possible because public transportation and substantial retail are accessible on foot. The Dunn Loring-Merrifield Metro stop is a 15-minute walk, and the Mosaic District homeowners association offers a rush-hour shuttle. The Mosaic District town center, a brand-new shopping and commercial area, is a five-minute walk. Now 70 percent completed, it has 40 stores and restaurants, including a Target with a full-service grocery and pharmacy, a Hyatt hotel and an Angelika multiplex.

“Walkable” communities such as Mosaic District first began to appear in the Washington market about 10 years ago, said Dan Fulton, senior vice president at John Burns Real Estate Consulting, who has followed new home trends in the Washington market for more than two decades. They have appealed to both young professionals (loosely defined as buyers between ages 28 and 40) and empty-nesters because both groups want “a vibrant lifestyle” and both are willing to “trade off space for location and the ability to walk to shops and work,” he said.

Mosaic District is unusual in that it also has a third group: families with young kids. Praj Jhaveri and his wife, Marina, who are expecting their first child, chose Mosaic over a house in Ashburn that was twice the size because they could replicate the urban feel and convenience of their old Bethesda neighborhood.

Now in their early 30s, the couple ruled out a return to the District where they had once lived because at this point in their lives, Praj said, “We don’t need the excitement of bars and clubs. When we go out, we want to go to a restaurant and get home quickly.”

Travis and Lindsay Clarke moved with their young daughter to Mosaic from a house in Annandale. A Fairfax County native, Clarke had wanted to be near his family, but after 11 years in Manhattan, he said, “the driving hit us right away.” He still drives to work, but on the weekend, he said, “we never drive, we walk everywhere.”

EYA has sold out its first phase at Mosaic District, but the firm expects to open a second one in September. The prices of the houses are expected to be similar: $714,900 for the 1,620-square-foot Aster and $814,900 for the 2,100-square-foot Bryant.

Katherine Salant has an architecture degree from Harvard. A native Washingtonian, she grew up in Fairfax County and now lives in Ann Arbor, Mich. If you have questions or column ideas, she can be contacted at salanthousewatch@gmail.com or www.katherinesalant.com.