Somerville's Accessory Structures: The Rules That Matter
Every city handles accessory structures a little differently. In Somerville, Massachusetts, there are 5 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.
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.
Key details: 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.
Contact your local code enforcement office for specific penalty information.
Tiny Homes
Tiny homes on foundations can qualify as ADUs in Somerville under the 2024 Affordable Homes Act. Tiny homes on wheels are treated as RVs and generally cannot be used as permanent dwellings.
Key details: Foundation tiny home: Allowed as ADU. State code: 780 CMR Appendix AQ. Max as ADU: 900 sq ft. Tiny homes on wheels: Not permanent dwelling. RV residency: Prohibited long-term.
Contact your local code enforcement office for specific penalty information.
Compared to other cities, Somerville takes a harder line on tiny homes. The enforcement and penalty structure reflects that.
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.
Key details: State mandate: Affordable Homes Act 2024. Max size: 900 sq ft by right. Owner occupancy: Not required. Parking mandate: Prohibited by state. Permit: Building permit required.
Contact your local code enforcement office for specific penalty information.
Somerville is more permissive than most cities when it comes to adu rules. That said, there are still limits.
Carport Rules
Carports are treated as accessory structures in Somerville and require building permits and zoning setback compliance. Many lots cannot accommodate a carport due to dimensional limits.
Key details: Permit: Building permit required. Setbacks: 3 ft side/rear typical. Front yard: Not allowed. Height: 15 feet typical. Fabric canopies: Not permanent structures.
Contact your local code enforcement office for specific penalty information.
Shed Rules
Sheds under 200 square feet typically do not need a building permit in Somerville but must meet zoning setbacks. Larger sheds require a building permit from Inspectional Services.
Key details: Permit-free size: Under 200 sq ft. Side/rear setback: 3 feet typical. Max height: 15 feet typical. Front yard sheds: Not allowed. Electric/plumbing: Separate permits.
Contact your local code enforcement office for specific penalty information.
The Bottom Line
Somerville's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Somerville is broadly strict or permissive.
This guide is based on Somerville's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.