Realtors are waiting on millennials to revive home sales. But when it comes to custom home building and remodeling, aging is where the action is.

Whether they are looking to stay in place in their current homes — homes that were not designed to accommodate the changes that come with aging — or build the home of their dreams, baby boomers are investing in upgrades and modifications that will make their homes more accessible and supportive in the years ahead.

And making kitchens and bathrooms age-friendly is at the top of their list.

According to the new 2015 State of the Nation's Housing report from the Joint Center for Housing Studies at Harvard University, homeownership rates have dropped nationwide, but homeownership rates among the population 50 and older have held steady. At some point in the future, however, these individuals may no longer be able to remain in their homes.

"By 2025, the large and growing population of seniors is likely to drive up demand for alternative housing arrangements that offer a combination of affordability, accessibility and supportive services," states the report. For now, they intend to remain in place, and they want their homes to be safe and comfortable.

The most recent Home Design Trends Survey from the American Institute of Architects, for the first quarter of 2015, shows a significant jump in aging-in-place-friendly accessible additions.

"An increase in home square footage with the rising popularity of accessible design concepts points to a population that is preparing to age-in-place, or, perhaps, is anticipating responsibility for caretaking of older relatives in the future," notes AIA chief economist Kermit Baker.

Compared to the first quarter of last year, this year's survey finds a 5 percent increase in activity for in-home accessibility design, and an 11 percent rise in requests for open space layouts, as well as a 4 percent increase in more accessible in/out entryways.

This year's Houzz and Home Report, released last month, reveals similar trends. More than half the homeowners age 60 and older who participated in Houzz's online survey said they plan to stay in their current home indefinitely, and more than half of those plan to renovate in the near future.

Last year, 1 in 5 remodeled a kitchen, and 60 percent of those made upgrades with aging in mind. Another 1 in 4 remodeled a bathroom, and 69 percent of those made upgrades with aging in mind. Improving accessibility, ease of operation, safety and storage were the most frequently requested upgrades.

There's more good news for kitchen and bath designers and remodelers. Boomers spent more than any other age group on remodels, additions and upgrades twice the amount spent by millennials. They also are more likely to seek the advice and services of building professionals, including contractors, kitchen and bath remodelers, and kitchen and bath designers. And they are most likely to pay in cash.

One word of caution. The Houzz study also found that half of homeowners upgrading their kitchens took six months or more from the initial stage of gathering ideas to the start of construction, and nearly half took six months or more when upgrading a bathroom. Moreover, they found, "As homeowners get older, the length of the planning cycle increases for all types of interior upgrades."

Patience and persistence are required when working with this clientele, but they will pay off in the end.