Somerville, MA Accessory Structures: ADU Rules (2026)

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 reasonable regulations, including, but not limited to, 310 CMR 15.000 et seq., if applicable, site plan review, regulations concerning dimensional setbacks and the bulk and height of structures and may be subject to restrictions and prohibitions on short-term rental, as defined in section 1 of chapter 64G. The use of land or structures for an accessory dwelling unit under this paragraph shall not require owner occupancy of either the accessory dwelling unit or the principal dwelling; provided, that not more than 1 additional parking space shall be required for an accessory dwelling unit; and provided further, that no additional parking space shall be required for an accessory dwelling located not more than 0.5 miles from a commuter rail station, subway station, ferry terminal or bus station. For more than 1 accessory dwelling unit, or rental thereof, in a single-family residential zoning district there shall be a special permit for the use of land or structures for an accessory dwelling unit. The executive office of housing and livable communities may issue guidelines or promulgate regulations to administer this paragraph.