Demand for Multifamily Homes Keeps Soaring in the U.S accounted for a staggering 38.4 percent of total house sales.

Multi-generational homes are one more reason for the surge in multifamily housing units in the United States right now.

By Christina Scotti

The rush to rent is starting to show up in homebuilding statistics. Construction starts for multifamily homes have been soaring in recent years, hitting an all-time high in November when they accounted for a staggering 38.4 percent of total house sales. And this trend doesn't seem to be slowing down.

"The rally in multifamily house building is in response to an increase in demand for such homes," says Capital Economics economist Paul Diggle. "Renting has become more prevalent over the past nine years, and two-thirds of renters live in multifamily accommodations. The cyclical rebound in household formation over the next few years will be driven by renters, so it doesn't look like multifamily demand is going to weaken anytime soon." Whether or not this is a bad thing for housing is up for debate. Diggle explains that since home ownership became artificially and unsustainably high during the boom years, a return to a lower level could even be viewed as a good thing. Still, he points out, what is bad for housing demand is the number of people who are doubled up with friends and family or staying in mom "We're seeing a lot of the baby boomers looking for a simpler life." and pop's basement, crimping housing demand.

"The increase in the rental rate is a legacy of the crash -- the hit to earnings and wealth; the pool of people foreclosed upon and ejected from home ownership; the drought of mortgages; the hit to FICO scores, meaning fewer people could borrow; and finally a possible attitudinal change," he says. Another trend that is going on in some cases within the rise in multifamily houses is multi-generational homes."Many are realizing that, for economic reasons, it makes more sense," said Leslie Piper, consumer housing specialist for Realtor.com and an active Realtor in the San Francisco Bay Area. "I recently had a client sell their family home in order to buy a bigger place with her parents. Both families planned on cohabitating so they could get more house and more land." Piper says she is also seeing many basements converted into in-law units.

"We're seeing a lot of the baby boomers looking for a simpler life," she says. "So, unlike their parents, they sell their bigger house and are maybe living one place six months out of the year and another place, maybe with their adult children's family, the other six months."

In fact, according to research from a 2012 Pew Research Center study, the share of Americans living in multigenerational family households was at the highest it's been since the 1950s, with a record 51.4 million people sharing homes. (Adults age 25-34 are among the most likely to be living in these households, says Pew.)

The multigenerational home, which has become more popular in the U.S., does not represent a large percentage of total multifamily homes. But multi-generational homes are one more reason that the surge in multifamily housing units -- largely driven by the majority of young adults renting -- are such a big part of the housing recovery right now. While this shift is not a bad thing, and real estate investors are enjoying a strong rental market, the overall economy usually does better when more are buying single-family homes, explains Diggle.

"More multifamily homebuilding means housing makes a slightly smaller contribution to GDP per home built," he says, "since multifamily homes are produced using less material and labor per unit."

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