A retirement community with lots of activities would have been ideal for Parsons’ widowed mother. “But when Covid-19 hit it was like, what are we thinking?” Parsons said.

So she went with a $230,000 “accessory dwelling unit” or ADU—more commonly known as a granny or in-law flat, alley flat, or coach house. In a few months when the construction is complete, she won’t have to worry about her mother getting home safely after dinner with the family. Her mother, who is in her 70s, will just walk about 15 feet across the backyard to the stylish, 495-square-foot space.

Unlike basic sheds or semi-finished pool houses, these units often have a bedroom area, full kitchen and bathroom. They can be standalone structures or over garages. Some owners rent them out for extra income.

Over the past few years, an increasing number of households have included several generations, according to a Pew Research Center analysis of census data.