Accessory Structures in Chelsea, MA (2026)
3 verified accessory structures rules for Chelsea, Massachusetts, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
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.
Chelsea ADU (Accessory Dwelling Unit) Rules
Some RestrictionsM.G.L. c. 40A, § 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 Rules
Accessory structures including sheds in Chelsea are governed by the Zoning Ordinance (Ch. 34) and 780 CMR (state building code). Permits required for structures over 120–200 sq ft or any structure with electrical/plumbing. Setback requirements vary by zoning district.
Chelsea Shed & Outbuilding Rules
Some RestrictionsGarage Conversions
Garage conversions to living space in Chelsea require a building permit and zoning compliance. Under the MA Affordable Homes Act (2025), garage conversions are one of the protected ADU types that must be allowed by right in single-family zones. Design review applies.
Chelsea Garage Conversion Rules
Some RestrictionsMGL c. 40A, §§ 1A & 3 (Affordable Homes Act)
The Affordable Homes Act, Section 7 and 8, amended M.G.L. Chapter 40A Section 1A and M.G.L. Chapter 40A Section 3 to allows accessory dwelling units — or ADUs — under 900 square feet to be built by-right in single-family zoning districts. An ADU must: Maintain a separate entrance, either directly from the outside or through an entry hall or corridor shared with the principal dwelling sufficient...
Looking for Suffolk County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Chelsea city rules.
Accessory Structures in Suffolk County →