Arlington County is considering whether to relax regulations that allow homeowners to legally rent to long-term tenants on a portion of their property, after only 20 homeowners out of 28,000 eligible successfully obtained licenses over the past eight years.

At a time when people increasingly are sharing cars, bicycles and workspaces, and are renting out rooms by the night on Airbnb, the idea of providing a legal way for residents to safely lease their garage or basement room to a young adult — or anyone else — seemed like a no-brainer.

But the detailed regulations, written in part to mollify wary neighbors, apparently stopped the practice from taking off, county officials said.

“We’re trying to remove some of the unnecessary, administratively burdensome barriers,” said Arlington County Board chairman Jay Fisette (D).

The reconsideration is part of a nationwide effort to promote the age-old practice of turning spare rooms into profit-making spaces, which experts say can help older Americans stay in their homes as they age, and improve the supply of low- and moderate-income housing stock during an ongoing affordability crisis.

While official numbers of licensed accessory dwelling units — less formally known as granny flats or in-law suites — are well below one percent across the nation, the number of units seems to increase when the licensing process becomes easier.

After Portland, Ore. eased it regulations in 2009, ADU registrations jumped from 27 per year to 220 per year, according to research done by Arlington’s housing and planning department. Similar jumps occurred in Seattle and Santa Cruz, Calif.

California's legislature passed bills in 2016 that made it easier for local communities to create ADUs, prompting cities throughout the state to adopt ordinances that are designed to be more user-friendly.

Closer to home, 179 ADUs are licensed out of 195,000 single-family homes in Fairfax County, Virginia’s largest jurisdiction. In Montgomery County, where there are 182,000 single-family homes, 80 permits have been issued.

But housing officials — who acknowledge that people share or rent space without going through formal zoning and regulatory checks — believe high housing prices and demand to live near transit and other amenities have created the potential for many more.

The requirements that Arlington has proposed easing include limiting the size of the apartments to 750 square feet, banning free-standing units such as converted garages, and requiring that entrances not be visible from the street.

Other provisions also may be eliminated, including ones that bar ADUs from lots that are less than 50 feet in width or do not conform to the local land-use plan.

A county report estimates that those changes would make another 20 percent of Arlington’s single-family properties eligible to house rental units.

Information technology consultant Ethan Smith, 35, and his wife began a major renovation a year ago to transform their two-bedroom, one-bath Penrose-neighborhood house into a much larger residence where they hope to raise a family.

They dug out a brand-new basement and built a prospective rental unit with a full kitchen, bathroom and living area.

Months into the process, they discovered that their 5,550-square-foot lot was slightly too small to meet the county’s ADU requirements.

“We should be clear that we didn’t do the project just for the rental,” Smith said the other day as he walked through the nearly completed space. “We really like our neighborhood and knew we couldn’t afford to buy a house that had everything we wanted. This [rental] was going to help us pay for the project.”

The bureaucratic hassles that the Smiths encountered are all too familiar to another resident.

“So few [ADUs] have been done that the county staff has not been consistent or coordinated” in their inspections and requirements, said Betts Abel, a retired county employee who has one of the licenses for her Ballston-area home. “It’s really left to the individual decisions of the zoning inspectors.”

Providing housing flexibility is the whole point of ADUs, said Harriet Tregoning, former principal deputy assistant secretary of the Office of Community Planning and Development at the U.S. Department of Housing and Urban Development during the Obama administration, and past director of the D.C. Office of Planning. She was a keynote speaker last week at a D.C.-centric session on the topic.

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Under Tregoning's leadership in Washington, the city rewrote its decades-old zoning code and, in 2016, made it easier to rent out accessory dwelling units. But "this is not restricted to urban places," Tregoning said. "Dozens and dozens of cities and states, from Pittsburgh to Portland, have tackled this issue."

Zoning codes put in place after World War II, when suburbs took off, did not foresee the modern necessity for denser use of existing housing, said Tregoning and Eli Spevak, a Portland-based developer who has been a longtime proponent of ADUs.

Many of those codes specifically outlawed having more than one household on a property zoned as single-family, in part to prevent the creation of boardinghouses in neighborhoods where they are not wanted.

“This is a balancing act cities are doing, but it’s less about safety and it’s more about what single-family-home residents will allow into their neighborhoods,” Spevak said. “Every city has its own little hot-button issue. . . . There’s parking, roof lines, designs — but if you toss in all those things, you won’t see any ADUs getting built. These are not done by big developers. These are done by individual homeowners who are intimidated by all these requirements.”

Arlington County Board member Libby Garvey (D) first started talking about ADUs in 2012, when one of her daughters came with two children and a dog to live with Garvey and her cat. For two years, the three-generation family shared Garvey’s Fairlington-neighborhood home, and she became aware of other families living in the same circumstances.

“I loved living with my daughter, but if we do this again, I want my own kitchen,” Garvey said. That would require converting the house into an ADU, which requires a separate kitchen, bathroom and an air-exchange and heating system.

Even as savvy a county resident as Abel, who worked for Arlington’s affordable housing office for 13 years, ran into trouble when she and her husband sought an ADU permit for their newly built-out basement.

One rule is that ADUs must be recorded on the property’s deed covenant. But when Abel went to do that, courthouse workers had no idea what she was talking about. It took several tries before everyone figured out what was needed.

Abel and her husband have rented the unit to two separate tenants so far. But that doesn’t mean they aren’t thinking about the next trend.

“We hope to continue. But we are now considering making it into an Airbnb,” she said.

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