Garage apartment ADU in Kensington, MD by BeyondDC licensed under Creative Commons.

Montgomery County recently updated its zoning code to allow more homeowners to build additional housing on their property, such as english basements or “granny flats.” Groups like the Coalition for Smarter Growth, Habitat for Humanity Metro Maryland, and the Sierra Club’s Montgomery group supported the accessory apartment initiative, and it received a lot of attention, both inside and outside the Washington region.

Still, accessory apartments (also known as Accessory Dwelling Units, ADUs, and other names) seem like a small fix, especially given the magnitude of the housing shortage and the urgency of national politics. Why should anyone care? What role do accessory apartments play in creating a more equitable, livable world?

Accessory apartments help us to rethink housing

The US has a long history of exclusionary housing policies, through pointed methods like redlining and restrictive covenants, but also through the use of single-family zoning. Single-family zoning keeps out other housing types, such as duplexes, townhomes, or apartment buildings. These “missing middle” housing types are often more affordable to low- and moderate-income households – especially renters and owners.

Image by Tracy Hadden Loh.

The primary intention of zoning is to separate incompatible land uses, like residential and industrial, not to separate people. We once built neighborhoods that included a mix of housing types, and many of those remain among the most walkable, mixed-use, and attractive in our country.

Allowing more accessory apartments doesn’t overhaul zoning a la Minneapolis or Oregon, but provides a first step towards allowing a mix of compatible residential uses in single-family zones. It also starts a larger conversation about how we can provide more inclusive neighborhoods for those who are currently left out.

Montgomery County has some of the highest median home prices and rents in the Washington region, and it’s running out of land to build new housing. More than 47% of the county’s housing stock is single-family detached homes.

Without providing a greater diversity of housing options, including affordable housing, in high demand neighborhoods close to jobs and transit, housing prices will only continue to be out of reach for most people. More families will be forced to search for a home farther from job centers, thus increasing their commute times, congestion, and pollution.

With so much need, accessory apartments may seem like just a drop in the bucket. But when compared with one of the county’s most successful affordable housing programs, accessory apartments emerge as a useful tool.

Impact of accessory apartments in Montgomery County

Montgomery County led the country when it created the first inclusionary housing program in the 1970s, known as the Moderately Priced Dwelling Unit (MPDU) program. MPDU legislation requires that a minimum of 12.5% to 15% of homes in a new housing development of 20 or more units must be made affordable to households earning between 60 to 80% of area median income.

The program has been lauded nationally as one of the most successful programs of its type, producing an annual average of 126 rental MPDUs through 2016. The new accessory apartments regulations could increase accessory apartment production from between 40 to 60 accessory apartments per year to around 100 accessory apartments per year.

If accessory apartments – which are not income-restricted, but are typically moderately priced and much more feasible than buying a home in, say, Bethesda – can create over half as much new housing as one of the country’s most successful inclusionary housing programs, then accessory apartments are a significant housing solution.

No single housing solution is enough to solve the housing crisis alone. By combining these initiatives with tenant protections, affordable housing preservation, and production of more transit-oriented homes, in addition to other policies, we can make a substantial movement towards making neighborhoods more welcoming and affordable.

Accessory apartments are smart growth

Not only are accessory dwelling units a housing solution, but they’re an environmental solution too. My research showed that the overwhelming number of accessory apartments in Montgomery County built to date are in Silver Spring and Bethesda, two of the most transit-accessible places in the county.

The new zoning update makes accessory apartments even more feasible in those areas by allowing for detached accessory apartments in the smaller residential lots that are characteristic of down-county areas.

Every accessory apartment built on an existing lot in Silver Spring or Bethesda is a new home where infrastructure already exists, rather than in a greenfield farther out that would require new roads, schools, sewers, and water and the destruction of forests and farmland.

More homes closer to jobs and amenities inside the Beltway will require investment in existing infrastructure, like transit and schools, but are not as high of a fiscal or environmental cost. Accessory apartments do this while maintaining existing lot coverage limits and stormwater management requirements.

This isn’t the first time Montgomery County has grown, and in fact, it grew much more rapidly in the past. In the 1980s, the population increased at a rate of 31%, which compares to 8% in the 2010s. Montgomery County can be a part of the solution for our growing region by offering more diverse housing choices in transit-accessible, walkable locations. Accessory apartments are a great way to do this in an inclusive, environmentally-friendly way.

This isn’t the end

Building an accessory apartment is still an expensive, intimidating process from an individual homeowner’s perspective. The county can take low-cost steps to make that process easier, especially regarding financing. Options include creating a financing guide, partnering with local banks and organizations like Habitat for Humanity, and providing interest-free loans to low-income homeowners.

In DC, the Coalition for Smarter Growth has teamed with the United Planning Organization, local architects, builders, bankers, and city staff to identify and implement ways to make accessory apartments easier to design, finance, and build – with lessons that can be applied in Montgomery County and other area jurisdictions.

None of these initiatives would make a difference if a large swath of homes were barred from building an accessory apartment in the first place. That’s why updating zoning to allow for more accessory apartments was such an important move.

Accessory apartments are a first step towards thinking about land use and housing in a more inclusive way. The land use of our cities, towns, and counties represents the spatial economy. To build a more equitable economy and the world, we have to improve local land use, and the housing and transit policies related to it.