APEX, N.C. – Viewed from the street, the single-family home at the entrance to Lennar’s Traditions at Bella Casa community looks just like any of the homebuilder’s other models.

Until you spot the second door.

From the home’s porch, visitors have the choice of entering into the main home or a side door that leads to a 500-square-foot suite. The suite, which has all the amenities of a second private residence, is the latest – and most emphatic – attempt by a Triangle homebuilder to appeal to a growing demographic of buyers: those with multiple generations of family members living under one roof.

Lennar calls this its “Next Gen” house. The Miami-based builder is now offering the model at subdivisions in Apex and Clayton, N.C., after having success selling it in western states such as California, Arizona and Texas.

“We market it as two homes, one payment,” says Trish Hanchette, Lennar’s Raleigh division president.

The idea of designing a home to appeal to a larger, multigenerational family is not a new one. But in the past, the plans were designed more to appeal to buyers from cultures where having multiple generations living together was expected.

The market for such homes has expanded in recent years as economic factors and demographic shifts have reshaped the nuclear family and altered its housing needs.

The severity and length of the economic downturn has created a need for what the housing industry calls “bounce back” rooms, meaning space for adult children struggling to make it on their own.

“The number of 22- to 30-year-olds that are still living at home is at a record high right now,” said Hampton Pitts, an executive vice president with Ashton Woods Homes, an Atlanta-based builder that is active in eight North Carolina communities. “So you have that college graduate that’s back at home looking for a job and maybe got their first job but not ready to be in an ownership or rent situation.”

Meanwhile, the country’s baby boomer generation is entering old age – and living longer – just as the cost of health care is skyrocketing.

“Assisted living is very expensive, and it cuts into any savings that folks have,” Hanchette said.

That Lennar has decided to offer its Next Gen model in North Carolina is a sign that the homebuilder doesn’t believe the move toward multigenerational housing will slow once the economy picks up. The region is an attractive place for such a product in part because it is so appealing to retirees – in many cases, a young family will move to the state and be followed several years later by parents eager to be close to their grandchildren.

Terri Aves, a real estate agent with Allen Tate in Cary, N.C., recently represented a buyer who bought a new home in Bella Casa, though not a Next Gen model. The owners moved here from the Northeast and specifically wanted a plan that had a first-floor guest room that could be used when their aging parents came to visit.

“Over the years, I’ve had a few clients, but I’m seeing it increase,” Aves said of such requests.

Like most housing trends, the move to more multigenerational floor plans started at the very the upper end of the market.

“In the higher-end homes, probably starting four years or maybe five years ago, you really improved your ability to sell that home with a first-floor bedroom,” said Rich Van Tassel of the Raleigh-based Royal Oaks Building Group. “Now every home we build that’s over $500,000 is going to have a first-floor bedroom and full bath, in addition to a study.”

The Next Gen model in Bella Casa contains about 3,700 square feet and sells for $414,000. Other Lennar models offered within the subdivision range from $250,000 to $375,000.

Hanchette said Lennar doesn’t expect to build entire communities of Next Gen homes, but rather to have them mixed in with more traditional plans. As for how large the buyer pool is for such a house, Block said the jury is still out.

“It’s so early that I think it’s going to be really hard to tell at this point,” she said. “But honestly, I think it’s a product whose time is here.”