ADU Rules: Boston vs Chelsea
How do adu rules rules compare between Boston, MA and Chelsea, MA?
Boston and Chelsea have similar restriction levels.
Boston, MA
Suffolk County
ADUs are now allowed by right statewide in Massachusetts under the 2024 Affordable Homes Act, with a maximum of 900 square feet. Boston cannot require owner-occupancy or special permits for protected ADUs.
View full Boston rules →Chelsea, MA
Suffolk County
ADUs are now allowed by right in Chelsea under Massachusetts Affordable Homes Act (Ch. 150, Acts of 2024, §8, effective Feb 2, 2025). Max 900 sq ft or 50% of principal dwelling. Chelsea's Planning Board was developing a local ADU ordinance in early 2025 to implement the state mandate, with design review retained.
View full Chelsea rules →Key Facts Comparison
| Fact | Boston | Chelsea |
|---|---|---|
| Max Size | 900 sq ft or 50% of home | 900 sq ft or 50% of principal dwelling |
| Approval | By right statewide | - |
| Owner-Occupancy | Cannot be required | - |
| Transit Parking | None within 0.5 mi | - |
| State Law | - | Affordable Homes Act §8 (Feb 2025) |
| Allowed | - | By right in single-family zones |
| Local Ordinance | - | Draft under Planning Board review (2025) |
Highlighted rows indicate differences between cities.
Boston FAQ
Can I build an ADU on my property in Boston?
ADUs are now allowed by right statewide in Massachusetts under the 2024 Affordable Homes Act, with a maximum of 900 square feet. Boston cannot require owner-occupancy or special permits for protected ADUs.
What are the size limits for an accessory dwelling unit in Boston?
Max Size: 900 sq ft or 50% of home. Approval: By right statewide. Owner-Occupancy: Cannot be required. Transit Parking: None within 0.5 mi.
Chelsea FAQ
Can I build an ADU on my property in Chelsea?
ADUs are now allowed by right in Chelsea under Massachusetts Affordable Homes Act (Ch. 150, Acts of 2024, §8, effective Feb 2, 2025). Max 900 sq ft or 50% of principal dwelling. Chelsea's Planning Board was developing a local ADU ordinance in early 2025 to implement the state mandate, with...
What are the size limits for an accessory dwelling unit in Chelsea?
State Law: Affordable Homes Act §8 (Feb 2025). Max Size: 900 sq ft or 50% of principal dwelling. Allowed: By right in single-family zones. Local Ordinance: Draft under Planning Board review (2025).
Compare other topics
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