Rockville City Hall. Credit: City of Rockville.

The kinds of zoning changes that were adopted to allow accessory dwelling units (ADUs) in Gaithersburg and Montgomery County as a whole are up for consideration in Rockville, more than three years after the process began there. The long-researched proposal is moving to the Planning Commission with the expectation of a vote in coming months by the mayor and City Council.

Amid an affordable housing crisis, backers of the Rockville proposal say it would allow homeowners to construct an additional dwelling that could be used by older residents or grown children who need somewhere affordable to live.

Opponents say that ADUs – sometimes called granny flats or in-law suites — could be out of character in certain neighborhoods and could reduce tree canopy and green space. They also say that residents could use ADUs as high-profit, short-term rentals to see a return on their investment, meaning they wouldn’t be truly affordable housing.

The proposal presented last week to Mayor Bridget Donnell Newton and City Council members would allow ADUs on single-family lots in city limits, given the following provisions:

  • The gross floor area must not be more than 50% of the primary dwelling unit or 750 square feet, whichever is less. But applicants with smaller homes could have an ADU that is 400 square feet.
  • There must be two off-street parking spaces. Exceptions can be made if the ADU is within 0.7 miles of a Metro station; if so, one space is required.
  • No ADUs are allowed on lots with accessory apartments. Rockville considers accessory apartments as attached to the main structure or as part of a garage, according to Ricky Barker, the city’s director of planning and development services.
  • The property owner must reside in one of the units, except for temporary absences.

Barker said in an interview that the discussion on ADUs—which began around mid-2019, according to city staff packets—came from citizen input and the fact that Gaithersburg and Montgomery County were making updates to their ADU policies.

Montgomery County has an ADU policy that allows detached structures that are 50% of the size of the principal structure, 10% of the lot area, or 1,200 square feet, whatever is smallest. Gaithersburg’s ADU policy allows for up to 1,200 square feet, and the maximum height is 30 feet, or two and a half stories.


Opponents include members of the West End Citizens Association, per city staff documents. They have raised the concerns about neighborhood character, the environment and short-term rentals.

Barker said the proposals require that ADUs use similar materials and look consistent to the primary structure on the lot. Short-term rentals, separate from ADUs, also are restricted to 120-day periods, and Barker believes residents wouldn’t apply for an ADU to only serve people for that limited amount of time, given the investment needed to build one.

He admitted that the ADU policy is a small piece of the affordable housing puzzle. But a piece nonetheless.


“The affordable housing issue is a tough nut to crack, and this is more of an alternative way for people to address their needs from their individual circumstances,” Barker said of the ADU policy.

Barker emphasized that several civic organizations support the ADU policy. Vincent Russo, president of the Twinbrook Community Association, is one resident who supports it.

Russo said the issue reflects that there are more multigenerational families living under the same roof than before, along with the need to create housing that suits residents with developmental disabilities. The ADU proposal allows for residents to decide whether such a structure is right for them, he said.


But he agreed with Barker that they’re only one small part of addressing affordable housing issues.

“This is really making changes around the edges, I don’t see this as a housing panacea or an answer to the housing shortage that we have,” Russo said. “It’s just an option, under certain circumstances, and [I’m] happy to see in these cases, where the stars align. … It just gives the homeowner that option.”

But Brian Shipley, president of the West End Citizens Association, said his neighborhood has consistently been opposed to the ADU policy as proposed, noting it does not align with the city’s master plan, Rockville 2040—especially concerning how it should be applied to the West End.


“The proposed text amendment does not include a process for implementing this policy, nor was it discussed on the [Mayor and Council] meeting of January 23rd.  We hope and look forward to the Mayor and Council telling the community how they will  consult with the community and preserve the unique character and development patterns in our neighborhood in their implementation of the text amendment,” Shipley wrote in an email to Bethesda Beat.

Barker said one of the reasons the ADU policy has undergone a review process over multiple years is that city officials were busy finalizing Rockville 2040,—among other planning issues.

Newton and City Council members should have a final ADU policy to vote on in about four to six months, after getting recommendations from the city’s Planning Commission, Barker said.