Living with mom and dad it is trending. That is, whether due to financial, health or other circumstances, young adults are moving back home after college and older adults are moving in with their children later in life, bringing multigenerational households to the forefront once again.

This style of living, wherein two or more adult generations or the combination of grandparents, parents and grandchildren live together under one roof, has a long history. Whereas 19% of the U.S. population, or 60.6 million people, had such an arrangement in 2014, a 21% share of the population did so in 1950, according to data from the Pew Research Center. The more recent figure is up from the category low of 12% in 1980.

Elderly parents moving in with their adult children once drove the trend. Today, however, young adults moving back in with their parents, or to not yet have left home, are the leading factor. In 2014, 31% of young adults ages 25 to 29 lived in multigenerational households. Meanwhile, 23% of adults ages 55 to 64 and 21% of those 65 years of age and older lived with other generations, according to Pew.

The trend is only expected to grow. Chris Porter, vice president and chief demographer for John Burns Real Estate Consulting, said that in a recent survey issued by the company, 44% of baby boomers reported that they were looking to accommodate their parents in their next home and 42% expected to lodge their adult children.

Recent college grads, baby boomers refilling their nest, and senior citizens looking to retain their independence all have different needs when it comes to housing. And so when they live together, worlds collide and those needs aren’t often all met, especially with today’s existing housing stock. Builders are using a range of strategies to address those varied criteria as well as the upsides of overlap, including offering new-home floorplans with a mix of shared and private spaces, as well as taking the time to understand the economic and cultural factors driving the trend to meet the needs of future multigenerational households.

Who is closing the generation gap?

There are many reasons for multiple generations to live together. They range from elderly parents moving in with their children rather than to a nursing home; baby boomers and their adult children deciding to share a household to help care for grandchildren; financial challenges like medical bills, student debt or large mortgages; health issues; as well as young adults not being ready or able to head out on their own.

“There have also been changes in the family structure and it’s more acceptable today to still live at home with parents,” Porter says. “That used to be a stigma.”

Kira Sterling, chief marketing officer for Toll Brothers, says that while the company doesn’t track who lives in their homes, baby boomers in their 50s and 60s doubling up with their adult children is a key driver of multigenerational households today.  “They can help out with the grandkids and then maybe also have a second place somewhere else,” she said.

Multigenerational differentiators

Today’s existing housing stock doesn’t meet the needs of multigenerational households, Porter says. “The minimum needed is a bedroom and bathroom on the first floor,” he added. “But now people want more, like a walk-off area, independent living space and a kitchenette.”

Sterling says that the need for an extra bedroom or bathroom for multigenerational households has grown over the last seven years to include separate entrances, expanded living spaces and entire bedroom suites. The need for dedicated space is particularly important for the older generation, which could include elderly parents or relatives, who have given up their former home by way of downsizing but would like to retain some independence.

Elderly parents might not need a full kitchen, Porter says, but they may want a private bathroom accessible only from their quarters as well as a non-bedroom area included within their dedicated space so it feels less like living in a single room but without the need to keep up an entire house. Separate entries and outdoor patios are also wish-list items. Porter recommends builders consider incorporating temperature controls in those parts of the home to further separate such suites.

Having an entertainment area or space that the older generation can spend time in is important. And even with downsizing, most older parents have accumulated objects over their lifetime they’d like to keep. “It would be nice if there was a place where they could display their possessions,” Porter says.

Looking to the future

It’s likely that most of today’s multigenerational households are living in existing homes, Porter says. Remodels or new builds to accommodate such a living arrangement tend to expand the space or create a separate unit, either inside or outside of the main structure. More builders are incorporating this option into their home plan offerings — or are at least thinking about it, he says.

Each municipality treats multigenerational housing and how it’s defined to meet zoning regulations differently. Kyle Dalton, principal city planner with the city of Denver, notes that accessory dwelling units (ADUs) — including what’s typically referred to as “granny flats” — are allowed in about 22% of the city’s land area. ADUs are self-contained units with their own kitchen, bedroom and bathroom and can be located within an existing or new house or can be freestanding on the lot.  

Not all lots and locations can accommodate multigenerational housing, but Sterling says Toll Brothers, like other large builders, offers the choice almost everywhere the company builds single-family detached housing. Lot size matters in what options builders have when creating a new home or remodeling one to meet the needs of multigenerational households. “Since typically we can’t change the footprint, we have to decide what space the owners are willing to give up to provide these options, so it’s easier to accommodate where we build bigger homes,” she said.

ADUs come with building restrictions. In Denver, that includes maximum and minimum floor area requirements and where they can be located on the lot. The units also can’t be sold separately and the owner must occupy either the primary dwelling or the ADU, Dalton says.

But with demand for multigenerational housing trending upward, such housing options can be a solution for residents and a growing business opportunity for builders.