ADU rules in Somerville, MA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
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 adopted accessory dwelling unit provisions in its 2019 zoning overhaul, well before the 2024 Massachusetts Affordable Homes Act. The state law (MGL c.40A s.3A as amended by the Affordable Homes Act of 2024) requires every municipality to allow ADUs up to 900 square feet by right in any district that allows single-family housing, without owner occupancy requirements, additional parking mandates, or special permits. Somerville Zoning Ordinance implements this with clear dimensional standards. ADUs may be interior (basement or attic conversion), attached (addition), or detached (backyard cottage). Building permits and plumbing permits are required. Short-term rental (Airbnb) of ADUs is separately regulated and may not be allowed depending on owner occupancy of the primary dwelling.
Contact your local code enforcement office for specific penalty information.
Somerville, MA
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Somerville, MA
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Somerville, MA
Overnight street parking in Somerville requires a resident permit citywide. Snow emergencies trigger odd-even or posted-side bans.
Somerville, MA
Commercial vehicles over 2.5 tons cannot park overnight on Somerville residential streets. Loading zones are time-limited and signed by block.
Somerville, MA
Most Somerville streets are resident-permit zones. Non-residents are limited to 2 hours on posted blocks from 8 AM to 8 PM daily including weekends.
Somerville, MA
Somerville requires a building permit for most fence installations, with historic districts adding a Historic Preservation Commission review step for visible...
Side-by-side rule comparisons with other cities in Middlesex County.
See how other cities in Middlesex County handle adu rules.
See how Somerville's adu rules rules stack up against other locations.
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