The state should encourage accessory apartments

Could be a partial answer to housing shortage

TEN YEARS AGO, I did a study of zoning regulations in the 187 communities within 50 miles of Boston. I wanted to find out if our region was allowing for diverse types of housing to be built. Single family homes are not for everyone.

It turned out that the greater Boston area is highly restrictive when it comes to housing development.  This restrictive approach drives up prices and causes sprawl.

With population growth and economic growth comes increased demand for housing. If zoning prevents housing supply from keeping up with demand, then buyers bid up the prices of the limited housing.  If housing density in developed areas cannot be increased, then housing will sprawl over open space. And if municipal laws favor development of single family houses over other types of housing, they put at a disadvantage people for whom single family housing is not a good fit.

Ten years ago, there was a rush of policy activity at the state level to take on the issue, while housing prices escalated.  There were endless meetings with the full who’s who of housing and environmental advocates on Beacon Hill. No game-changing agenda emerged, and then in 2008 the recession came and deflated energy to reform housing policy, which was going to be hard to reform anyway.

With housing development picking up again in recent years, the same issues with our housing regulation – price, sprawl, and injustice – have reemerged. Last year, the Metropolitan Area Planning Commission (MAPC) concluded that, based on demographic and economic trends, our region needs to build 435,000 new housing units—mostly multifamily—by 2040.  Buildout under current zoning laws will not get us there.


According to the 2014-15 Greater Boston Housing Report Card published by the Boston Foundation, the number of smaller households is growing at a much faster rate than the number of larger households (four or more people.)  The Report Card describes a growing “housing mismatch,” the increasing oversupply of single family houses relative to demand.  Rising condo prices and rents and the slower appreciation of single-family home prices are evidence of this mismatch. The report emphasizes: “In the absence of plans to build significantly more rental housing, moderate and low-income families will continue to bear the brunt of Greater Boston’s housing crisis.” The report also points out that many aging baby boomers on fixed incomes will not be able to keep up with maintenance, taxes, and utility bills for their houses in the coming years.

Of all of the state-level policy options I have heard considered, there is one simple change I wish the state would make right away.  Allow accessory apartments; do not leave the decision to municipalities.

Accessory apartments are secondary dwelling units located within, attached to, or on the same lot as an owner-occupied single-family house. The accessory dwelling has its own kitchen, bathroom, and bedroom or bedrooms.

The way to add lots of relatively affordable and unsubsidized rental housing in the suburbs without paving new roads, extending sewer lines, or even constructing buildings is to let the owners of single family homes add accessory apartments. As an added perk, accessory apartments provide a new source of income for homeowners, including retiring baby boomers.

In my study of zoning laws in 187 communities in Eastern Massachusetts, I found that 107 communities, or 57 percent, technically allow some form of accessory apartment. But a closer examination of the zoning laws revealed restrictions that make it difficult for accessory apartments to get built.

More than half of the communities only allow relatives of the homeowners (“in-law apartments”) or caretakers to live in the units. The kitchen must be removed when the grandmother or au pair moves out. Only 50 communities (27 percent) allowed any person to rent the unit, but most of them dramatically limited the number of eligible houses, with qualifications including a large house, large lot, and pages of other requirements. At the time of the study, planners in a few municipalities reported permitting up to a dozen units per year, while others mentioned permitting a single unit only every several years.

Right now, we ask neighbors to battle each other to get ordinances or bylaws passed in their city or town to allow accessory apartments. Communities have been debating accessory apartments for decades. The end result: few accessory units are actually allowed and created in our region.

State government should intervene. The state should pass an accessory apartment law that gives municipalities the authority to grant permits for accessory apartments without adopting a local ordinance or bylaw, which is so very hard to do.  The state law would specify requirements for accessory units to protect the single-family feel of neighborhoods. For example, owners could be required to live in the house with absences extending no more than two years. There could be restrictions on the size and location of accessory units, and the number of bedrooms contained in the units. There could also be an overall limit on accessory units permitted in a single community.

With such an approach, municipalities would not be able to prohibit accessory apartments that meet the state’s specifications, but they could pass ordinances or bylaws that are less restrictive, such as allowing more bedrooms in the accessory unit than permitted by the state law or permitting more total accessory units that the state law authorizes. Accessory apartments and the houses containing them would still need to meet all of the local non-zoning requirements, such as for septic systems where sewer connections are not available, the state building code, and all local zoning requirements dealing with setbacks and parking.

The city of Boston is not included in the state’s 40A Zoning Act, and Boston should be exempt from a state law on accessory apartments.  Boston is ahead of the region in permitting multi-family development. Mayor Marty Walsh’s administration has committed to creating 53,000 new housing units by 2030. Policymakers could consider exempting additional communities where a large portion of the housing is multi-family.

Opponents to accessory apartments argue that they exacerbate parking issues and traffic.  Indeed, population growth typically brings challenges associated with parking and traffic, no matter where the new residents find housing.  Accessory units, though, will be distributed across the region, not causing acute problems in any one area.  Another fear is that accessory apartments will bring college students, and their parties, into the neighborhoods.  Newton allows accessory apartments, but not around Boston College.  Indeed, co-existing with college students is not a trivial problem.  At least accessory apartments are owner occupied, and on-site landlords are generally better at limiting noise than off-site landlords.  Also, providing housing for students is an important policy goal for the region.

Another challenge is that municipalities have limited capacity to enforce the complicated rules.  This is a reason to keep the rules as simple as possible. In general, it should be easier to enforce these requirements for accessory apartments than it is to ensure compliance with “in-law apartment” rules mandating that residents must be related to the homeowner and that the kitchen must be removed when the relative moves out.

Homeowners generally pay a significant premium to buy in a single family neighborhood, not in a two-family neighborhood, so revising the zoning restrictions is high-stakes for them. If the new state law sets an 8 percent cap on accessory units in each community, fewer than one in ten houses would have the extra units. Single family streets with a couple of accessory units will not feel like tenement neighborhoods.

Meet the Author

Amy Dain

Public policy research consultant, Dain Research, Newton
An accessory apartment law would be a small but important step to make Greater Boston more affordable and environmentally friendly. Cities and towns would still be on the hook to revise zoning for more density in appropriate places, but they would not need to host any more heated debates about accessory dwelling units.

Amy Dain is a consultant to MassINC, the publisher of CommonWealth magazine.