And they can provide some space for the next generation as well. From MNN February 2016.

Of the 78 million baby boomers in the United States, most appear to want to retire in a nice big, single floor house on a cul-de-sac. Having seen too many of my parent’s generation do that and be totally miserable, I’ve tried to make the case that boomers should be doing the opposite, and should be looking to live in walkable communities where they won’t be trapped when they’re forced to hang up the car keys.
Alex Bozikovic, who covers architecture for the Globe and Mail, looks at three projects that show how boomers are staying in their houses in those walkable neighborhoods, noting:
Young adults are getting squeezed out of the housing market. Their parents, meanwhile, want to downsize without leaving familiar neighbourhoods. The solution couldn’t be simpler to a growing group of designers: Rethink (and rebuild) the family home to suit several generations for the long haul.
Alex Bozikovic

My wife Kelly and I are one of the families studied, and the article opens embarrassingly:
When a strange young man entered her bedroom, Kelly Rossiter wasn’t entirely surprised. “He had had a bit too much to drink,” says Rossiter, who lives in Toronto, “and had gotten lost on the way to the front door.” On the way, that is, from a party at her daughter’s place; Rossiter and her husband Lloyd Alter live below their daughter Emma, now 28, in a 1913 house that’s been split into two apartments. The door that links the suites in their home is usually left unsecured. “But after that night, I began locking the door whenever she had a party,” Rossiter says.
That’s one of the very few untoward events we have experienced since we had what I called on TreeHugger a radical decluttering and downsizing; you can take the tour there.

Grange Triple Double has stairs. (Photo: Williamson Chong Architects)
A much more interesting project is the Grange Triple Double house by Williamson Chong Architects. It’s a new house built for a much younger couple in their 30s with a young son who are seriously planning ahead. It’s designed with a main three-bedroom unit and two other units that can be rented or used for family as things change, “a bespoke house that would accommodate them all together with rental income – and then change, multiple times, as the family’s needs evolve through the decades.” Bozikovic writes:
The tenant space can be configured as one or two apartments; half or all of it can also be joined to the main house with the removal of cabinets or wall sections. In addition, one of the house’s bedrooms can be closed off as a semi-private area for the older residents. In time, the architects imagine that the house could take many different configurations; for instance, one or both of the grandparents might move into the main floor rental space.
Alex Bosikovic

Then there’s the house that Janna Levitt and Dean Goodman of LGA Architectural Partners designed for themselves over a decade ago, when their kids were teenagers. Planning ahead, they built it with a high basement apartment and even buried a stair for an exit which they can dig out. (“We thought, if we give the kids their own door when they are 14 or 15 years old, we’ll never see them,” Goodman explains.)
There is a lesson in this: Design matters. Levitt and Goodman are excellent architects, and their house is efficiently planned to be comfortable and adaptable despite its relatively modest size. “It’s important to think about what you’re building for,” Goodman says, “not just right now, but in the longer term. And how much longer?”
Like my wife and I, Dean and Janna are not worrying too much about stairs. Alex wondered about this, given that the conventional wisdom about aging in place is that people should live on one level with everything wheelchair accessible. Alex writes:
Alter argues passionately that being located in a walkable neighbourhood, served by transit and connected to neighbours, is what matters as one ages. “Older people, when they move into single-family houses in subdivisions, they’re setting themselves up for failure,” he says. “It’s a hell of a lot likelier that they’ll lose their keys before they lose their ability to walk up the stairs. This is one solution: this re-intensification of our neighbourhoods.”
This is not a solution for everyone. Building or renovating a house to make it multi-family is not inexpensive, especially if you want good sound isolation. However the rental income can more than cover the costs. And as Starre Vartan noted on Facebook, “Brilliant idea for those families who like each other! Unfortunately, most people I know don’t even want to be in the same state as their parents.” In our case, we are lucky that way. We’ll see how it goes down the road; if nothing else, we will never be lonely.
Housing itself has to change, the psychology(Mathew White, environmental/psychologist, University of Vienna) of the townhouse is depressing and only incites aggressive displays of manliness in vehicles, what they buy, and how they use them. Natural greenspace has to be included in housing design at grade, the contoured greenspace(garden) moved to the roof. It can be done, especially in a finanicial environment where the house is overpriced and doesn’t reflect the cost of construction. It means a complete reconsideration of the established contours of the house, and urban planning. The design starts with the beehive and the tree, and ends with a forest. It has beem a lot to get this far, now a team is needed to take the patience that has established the concept in this mind, and make it real.
Sincerely; John Ivanyi, P.Eng. (Structural, Civil Engineer), @ 1116 Kipling Ave., Etobicoke(Echo Valley Park)
P.S. It’s disturbing to realize Bamboo is the number one building material,and only recently 2019 that “Bamboo design and construction”, from the Universidad de los Andes, Columbia, the first relative design specification came out, and furthermore the recent development of Laminated Bamboo by the firm Lanboo. Bamboo taking from 3 to 11 years to grow, and having a strength up to 12 times more than timber. As a column bamboo, in its’ natural form, easily outperforms conventional lumber.