Somerville, MA Accessory Structures: Garage Conversions (2026)
Garage conversion rules in Somerville, MA, sometimes called garage-to-ADU or accessory living unit conversions, govern permits, ceiling height, egress, and parking replacement.
Key Facts
- Building permit
- Required
- Code compliance
- 780 CMR full residential
- As ADU
- Up to 900 sq ft by right
- Parking loss
- Generally not a barrier
- Reviewer
- Inspectional Services
Summary
Converting a garage to living space in Somerville requires a building permit and may qualify as an ADU under the 2024 Affordable Homes Act with relaxed zoning review.
Section 3A. (a)(1) An MBTA community shall have a zoning ordinance or by-law that provides for at least 1 district of reasonable size in which multi-family housing is permitted as of right; provided, however, that such multi-family housing shall be without age restrictions and shall be suitable for families with children. For the purposes of this section, a district of reasonable size shall: (i) have a minimum gross density of 15 units per acre, subject to any further limitations imposed by section 40 of chapter 131 and title 5 of the state environmental code established pursuant to section 13 of chapter 21A; and (ii) be located not more than 0.5 miles from a commuter rail station, subway station, ferry terminal or bus station, if applicable.
(b) An MBTA community that fails to comply with this section shall not be eligible for funds from: (i) the Housing Choice Initiative as described by the governor in a message to the general court dated December 11, 2017; (ii) the Local Capital Projects Fund established in section 2EEEE of chapter 29; (iii) the MassWorks infrastructure program established in section 63 of chapter 23A, or (iv) the HousingWorks infrastructure program established in section 271/2 of chapter 23B.
Full Breakdown
A garage conversion changes the use of an existing accessory structure into conditioned habitable space, which under the Massachusetts State Building Code requires full compliance with energy code, egress, ceiling height, fire separation, and ventilation standards. In Somerville, a building permit is required, along with plumbing, electrical, and mechanical permits as applicable. If the conversion creates a separate dwelling unit, it qualifies as an ADU and can proceed by right under MGL c.40A s.3A up to 900 square feet, without a special permit. If the garage conversion is simply expanded primary dwelling space, it is treated as an addition. Parking minimums in Somerville have been largely eliminated, so losing a garage stall typically does not trigger variance review.
Frequently Asked Questions
Can I turn my garage into an apartment?
Do I lose the parking stall?
Sources & Official References
Other rules in Somerville
Compare Somerville to another location·View the Massachusetts accessory structures overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.
Garage Conversions in Nearby Cities
How other cities in this county handle garage conversions.