Betsy McCann and her husband, Jim Forbes, often worried that his mother was becoming isolated in her Los Angeles-area home. At 90, Lois Brokus had stopped driving and sometimes was afraid to be alone in her house.
Jane and William Merrill also decided that they didn't want Mr. Merrill's mother living on her own any more.
Then 81, Jane Merrill, who has the same name as her daughter-in-law, was still active but in need of companionship.
Both families considered nursing homes, assisted living, and retirement communities. But they reached the same conclusion: Their homes were the best places for their mothers.
But they needed more home.
So Ms. McCann and Mr. Forbes added a 400-square-foot bedroom and bathroom to their Escondido, Calif., house; the Merrills converted a two-car garage at their eight-acre spread in Carmel, Ind., a suburb of Indianapolis.
Home builders across the country say they are getting an increasing number of requests for such additions, known as mother-in-law suites, granny flats, or accessory dwellings.
According to the National Association of Home Builders, 62 percent of builders surveyed were working on a home modification related to aging in 2010.
About one in five builders added an entry-level bedroom.
About 3.5 million American households last year included adult children and their parents -- a number expected to rise as the country ages and baby boomers move into retirement, Nancy Thompson, an AARP spokesman, said.
AARP teamed up with the home builders association to create a designation for Certified Aging in Place Specialists, who are trained in designing and modifying buildings for the elderly. About 3,000 builders, contractors, remodelers, and architects have been certified.
One is Todd Jackson, head of a San Diego firm that handled the addition at Ms. McCann's home.
Ms. Brokus, now 93, was involved in the planning of the addition, which was built in 2008 for $250,000.
"We didn't want her to feel like a guest intruding on our house," Ms. McCann said.
Ms. Brokus now calls the addition "her apartment." Every month, she writes a rent check covering the cost of utilities -- an act that adds to her sense of independence.
The arrangement has given the family more time together and greater peace of mind.
The addition includes a bedroom, wet bar, and wheelchair-accessible doorways and bathroom.
For the Merrills, the cost of converting the garage 11 years ago, was $25,000. The apartment has a separate entrance, full kitchen, and wheelchair-accessible features.
Nancy Thompson of AARP offered other tips for families considering building a suite for an aging parent:
● Decide what your expectations are well in advance and make sure everyone agrees. Involve the elderly parent in the process.
● Make sure construction adheres to universal-design guidelines. Are counters, bathrooms, and doorways wheelchair accessible? Is there a walk-in shower with grab bars? Opt for entry-level additions to eliminate stairs. Look for a contractor or builder with experience in universal design or aging in place.
● Check municipal building codes to make sure that accessory dwellings are allowed.