Accessory Structures in Somerville, MA (2026)
4 verified accessory structures rules for Somerville, Massachusetts, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Somerville was an early Massachusetts adopter of ADU zoning and now complies with the 2024 Affordable Homes Act mandating ADUs by right in all single-family zones statewide.
Somerville ADU Rules
Few RestrictionsM.G.L. c. 40A, Section 3
No zoning ordinance or by-law shall prohibit, unreasonably restrict or require a special permit or other discretionary zoning approval for the use of land or structures for a single accessory dwelling unit, or the rental thereof, in a single-family residential zoning district; provided, that the use of land or structures for such accessory dwelling unit under this paragraph may be subject to re...
Shed & Carport Rules
Somerville caps backyard sheds at 12 feet in height and lets them sit as close as 3 feet from a side or rear lot line, but bars any encroachment into the required front setback. Sheds are permitted by-right, so no special permit is needed if the shed goes up after the main house.
Somerville Shed Rules
Some RestrictionsSomerville Zoning Ordinance §§ 10.2.1, 10.2.2(u)
10.2.1 General a. Unless otherwise specified, accessory structures are permitted by-right. ... e. Unless otherwise specified, accessory structures are permitted to encroach any side or rear setback, provided that at least three (3) feet is maintained from the vertical plane of any lot line. f. Accessory structures are not permitted to encroach into any maximum front setback. ... 10.2.2 Permitte...
Garage Conversions
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.
Somerville Garage Conversions
Some RestrictionsM.G.L. c. 40A, Section 3A
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...
Tiny Homes
Somerville's zoning ordinance permits one detached Backyard Cottage per lot in the Neighborhood Residence district, capping the accessory building at a 576-square-foot floor plate, 24 feet wide, 32 feet deep, and 1.5 stories under Zoning Ordinance Section 3.1.12. The cottage holds only one dwelling unit and must sit at least 3 feet from the side and rear lot lines.
Somerville Backyard Cottage Size Limits
Some RestrictionsSomerville Zoning Ordinance § 3.1.12
3.1.12 Backyard Cottage A small floor plate, detached, accessory building type typically providing space for one (1) small dwelling unit, a home occupation, a playhouse for children, or vehicular parking on the same lot as a principal building type. ... Side Setback (min) 3 ft ... Rear Setback (min) 3 ft ... Building Separation (min) 10 ft ... Width (max) 24 ft ... Depth (max) 32 ft ... Floor p...