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The following is a letter we sent to the Somerville City Council, Planning Board, and Land Use Committee on .

To: Somerville City Council, Planning Board and Land Use Committee From: Somerville YIMBY Re: Advancing SomerVision 2040 goals with Accessory Dwelling Units

SomerVision goals include creating new mid-price housing and reducing car dependency in the city. Creating new accessory dwelling units (ADUs), and especially converting existing garages to ADUs, advances these goals. Restricting on-street parking for these new homes would both address abutter concerns and further decrease car dependency.


Somerville, like many cities, must confront three deeply intertwined issues: transportation, pollution, and scarce housing. Cars and car infrastructure produce enormous amounts of pollution, and housing sprawl contributes significantly to increased reliance on automobiles. Restrictions on building densely enshrine both auto-centric infrastructure and housing sprawl. Moreover, these restrictions make housing scarce and exorbitantly expensive.

The EPA has stated that building more homes in dense, transit-oriented communities like Somerville will mitigate all three of these issues. This statement aligns squarely with Somerville’s long-term climate and housing goals. However, Somerville’s zoning laws stand in the way. As a result, the city struggles to build enough homes to lower housing costs and reduce carbon emissions.

Although the city has strong programs for building subsidized affordable housing, it lacks market rate housing in the “missing middle” price range. Fortunately, it does have ample room for small Backyard Cottages, especially if those buildings replace detached garages (above right) or small accessory buildings (below right).

Though small in size, these structures are plentiful in Somerville, and their sheer number provides an immediate and meaningful opportunity for adaptation into “missing middle” housing without displacing any current residents.

Best Practices

Cities with successful ADU policies have low regulatory barriers to ADU creation. The Massachusetts Smart Growth Alliance, the Pioneer Institute, and the Massachusetts Executive Office of Energy and Environmental Affairs recommend that:

  • ADU creation should be aligned with the city’s comprehensive planning goals.
  • Regulations should be clear enough for non-expert homeowners to understand.
  • ADUs should be allowed by right, without special permits.
  • Cities should not restrict who is allowed to live in them or their price.
  • Expensive features such as off-street parking and large setbacks should not be required.

In Somerville, ADUs align with our comprehensive planning goals and our zoning is reasonably clear about the definitions and requirements for the “Backyard Cottage” building type. However, the city has imposed onerous regulatory burdens that make ADUs financially infeasible.


The city should take a two-phase approach. First: adjust regulations to allow ADU creation by right. Second: encourage such conversions. Separately, mitigate parking and traffic impacts by stipulating that residents of these new units cannot have on-street parking permits.

Phase One: Legalize ADUs

The first task for the city involves revising zoning regulations to maximize ADU creation. SomerVision 2040 explicitly notes the need for such zoning revisions.

Build By Right: Allow creation of the Backyard Cottage building type without special permits.

Adjust Dimensional Requirements: Reduce the 60-foot front setback and increase the maximum height of 12 feet/1.5 stories for Backyard Cottage buildings. Allow garages with nonconforming setbacks to maintain existing footprints if converted to or replaced with housing.

Accelerate Permitting: Reduce permitting burden. For example, garage conversion should be exempt from the site plan approval process if the building footprint remains unchanged.

Remove Price Restrictions: In Neighborhood Residence zones, allow 2-family homes to create a third unit without triggering inclusionary zoning requirements.

Avoid Creating New Obstacles: The city should not create rules that make ADU construction infeasible or impossible (e.g. forbidding the sale of ADUs as a separate property or limiting square footage to a percentage of the primary dwelling size). The sole restriction should be the parking restriction mentioned above.

Phase Two: Encourage ADUs

Even with a simplified process, construction represents a substantial undertaking for most property owners. To accelerate the production of homes, the city should:

Inform Homeowners: Actively reach out to homeowners and inform them about these policy changes. Create clear and accessible guidance documents to help homeowners determine if their property is eligible.

Create Pre-approved Plans: Hire an architect to develop a small number of pre-approved and easily-adapted designs to reduce the cost of design and shorten project timelines.

Reduce Fees: Consider waiving or discounting permitting fees to accelerate the permitting process. Tax revenue from the newly built units would help offset the cost of these promotional activities.

Anticipating and Addressing Objections

All changes in a city will naturally draw some opposition. The most likely objections include:

Neighborhood Character: Larger projects might change a neighborhood’s character, but this proposal permits small changes from individual homeowners, which reduces impact.

Parking: The parking permit restriction should allay concerns about parking scarcity.

Affordability: This policy is a complement to programs focused on housing low- and very low-income residents; it is designed to create homes affordable to families at or near the median income.


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City of Somerville. 2019. The Path Since 2010: A SomerVision Progress Report. Retrieved September 21, 2021 from

City of Somerville. (2019, December 12). Somerville Zoning Ordinance. Retrieved September 21, 2021, from

City of Somerville. 2021. SomerVision 2040: Comprehensive Plan Update, 2010-2040. Retrieved September 21, 2021 from

Dain, A. (2018, July). The State of Zoning for Accessory Dwelling Units. Pioneer Institute. Retrieved September 21, 2021 from

Dineen, J. K. (2021, October 12). San Francisco mayor breed wants to make it easier to turn gas stations into housing. San Francisco Chronicle. Retrieved October 22, 2021, from

Environmental Protection Agency. (n.d.). Fast Facts on Transportation Greenhouse Gas Emissions. EPA. Retrieved September 21, 2021, from

Equitable Arlington. (2021, May 8). Article 43 (ADUs): Frequently Asked Questions. Retrieved September 24, 2021 from

Freemark, Yonah and Velasco, Gabriella. (2021, May). Keys to a Successful ADU Rollout in Lousiville: Accessory Dwelling Unit Strategies to Build Better Communities for All. Urban Institute. Retrieved October 28, 2021 from

Gabbe, C. J., & Pierce, G. (2018). The Hidden Cost of Bundled Parking. Access Magazine.

Massachusetts Executive Office of Energy and Environmental Affairs. (n.d.). Case studies - accessory dwelling units (ADU). Retrieved September 21, 2021, from

Massachusetts Executive Office of Energy and Environmental Affairs. (n.d.). Smart Growth / Smart Energy Toolkit Modules - Accessory Dwelling Units (ADU). Retrieved September 21, 2021, from