Swampscott

• Swampscott has an adopted ADU bylaw, amended at the May 2025 annual town meeting to comply with the state Affordable Homes Act.
• ADUs are permitted by right in all single-family residential zoning districts (A-1, A-2, A-3, B-1, B-2).
• Maximum size is 900 sq ft or 50% of existing dwelling, whichever is smaller; attached additions changing footprint are limited to 800 sq ft (larger additions require Site Plan Review).
• Short-term rentals prohibited -- minimum 30-day rental period.
• Owner-occupancy is not required (state law preempts previous local requirement).

1. Determine ADU type:

   • Internal ADU or attached ADU within existing structure: By right -- standard building permit only.
   • Attached ADU addition up to 800 sq ft: By right -- building permit required.
   • Attached ADU addition over 800 sq ft: Requires Site Plan Review by the Planning Board.
   • Detached ADU in existing accessory structure: By right -- building permit. If the structure is preexisting nonconforming, it can be converted without a variance or special permit, but the degree of nonconformity cannot be increased.
   • New detached ADU structure: Must comply with all dimensional requirements (setbacks, lot coverage, height).

2. Submit plans: Provide site plans, floor plans, and elevations to the Building Department.

3. Building permit: Apply for and obtain a building permit from the Building Department.

4. Comply with building code: Construction must meet the Massachusetts State Building Code (780 CMR).

5. Certificate of occupancy: Obtain before the ADU is occupied.

• Maximum size: 900 square feet or 50% of the floor area of the existing dwelling, whichever is smaller.
• Footprint addition limit: If changing the footprint of an existing structure, the addition is limited to 800 square feet. Additions over 800 sq ft require Site Plan Review by the Planning Board.
• Separate entrance: Required for the ADU.
• Appearance: ADU must maintain appearance compatible with the neighborhood. The 2025 zoning amendment removed design standards that cannot otherwise be applied to single/two-family construction.
• Detached ADU relationship: Must maintain a secondary relationship to the principal dwelling.
• Detached ADU setbacks: 5 feet from side and rear lot lines.
• Dimensional compliance: Must comply with district dimensional requirements for setbacks, lot coverage, and height.

• One additional parking space required for the ADU, in addition to minimum parking requirements for the principal dwelling.
• Transit exemption: Parking is waived if the ADU is within 0.5 miles of a commuter rail station, subway station, ferry terminal, or bus station.

• Preexisting nonconforming structures: Existing detached accessory structures that are preexisting nonconforming can be converted to ADUs without a variance or special permit, provided the degree of nonconformity is not increased. This is a practical advantage for homeowners with older structures.
• 800 sq ft footprint addition limit: This is a local provision that creates a tiered permitting approach -- additions up to 800 sq ft are by right, while larger additions require Site Plan Review. This is more restrictive than the state's 900 sq ft overall cap.
• Data quality note: This file is based on a third-party summary (BackyardADUs.com) and local news coverage, not the full official bylaw text. Some details may be incomplete or imprecise. Verify with the Town of Swampscott Building Department for authoritative guidance.
• 2025 amendments: Swampscott voted in May 2025 to amend its zoning bylaw to further comply with the state ADU law, removing design standards not applicable to single/two-family construction and adding/maintaining the 30-day minimum rental period.

Note: The full official bylaw text was not available in the source materials. The following is a summary compiled from third-party sources and local news coverage. For the authoritative text, consult the Town of Swampscott Zoning Bylaws available at swampscottma.gov.

Swampscott ADU Regulations (Compiled Summary)

Type of ADU Permit Required: ADUs are permitted by right in Swampscott.

Size Restrictions:

• Generally: 50% of floor area of existing dwelling or 900 sq ft, whichever is smaller
• Attached ADUs changing footprint: Addition limited to 800 sq ft
• Addition greater than 800 sq ft: Subject to Site Plan Review by Planning Board

Attached ADUs:

• Allowed within existing structure or as addition
• Must maintain single-family appearance
• Additions over 800 sq ft require Site Plan Review

Detached ADUs (two pathways):

1. Within existing detached accessory structures:

   • If preexisting nonconforming structure, can convert without need for variance/special permit
   • But cannot increase the degree of nonconformity

2. New detached structures:

   • Must comply with all dimensional requirements (setbacks, lot coverage, height)
   • Must maintain secondary relationship to principal dwelling

Setbacks:

• 5 feet from side and rear lot lines (noted as local requirement)
• Must comply with district dimensional requirements

Parking:

• One additional parking space required for the ADU
• In addition to minimum parking requirements for principal dwelling
• Waived if within 0.5 miles of transit

Design Standards:

• ADU must maintain appearance compatible with neighborhood
• Separate entrance required
• 2025 amendment removed design standards that cannot be applied to single/two-family construction

Short-Term Rental Restriction:

• ADUs may not be rented for less than 30 consecutive days
• This was added/maintained in the 2025 zoning amendment

Owner-Occupancy:

• Not required under state law (effective Feb 2, 2025)

2025 Zoning Bylaw Amendments

Per Itemlive (May 22, 2025), Swampscott voted to amend its zoning bylaw:

1. ADUs up to 900 sq ft allowed by right in any single-family zoning district
2. Removed design standards that cannot otherwise be applied to single/two-family construction
3. Added/maintained 30-day minimum rental period
4. Complies with state Affordable Homes Act requirements

Zoning Districts where ADUs are permitted: A-1, A-2, A-3 (Single-family residential), B-1, B-2 (General residential)

Swampscott has adopted the Specialized Opt-In Energy Code, the most stringent tier in Massachusetts. A certified HERS Rater is required for all new construction, including ADUs.

Your ADU must achieve a HERS index of 52 or lower (mixed-fuel) or 55 or lower (all-electric). Going all-electric earns a 3-point offset, making compliance easier. Budget $500–$1,500 for HERS testing.

Additional Specialized Code requirements include ERV/HRV mechanical ventilation (bath fans alone don't qualify), EV-ready wiring if on-site parking is provided, and stricter standards for larger projects. All-electric construction is strongly encouraged.

Swampscott's 2025 zoning bylaw amendments were specifically intended to bring the town into compliance with the state Affordable Homes Act. Key preemption considerations:

1. Owner-occupancy requirement removed -- The previous local bylaw required the owner to live in either the primary dwelling or the ADU. This was preempted by 760 CMR 71.03, which prohibits owner-occupancy requirements.
2. Design standards limited -- The 2025 amendment removed design standards that cannot otherwise be applied to single/two-family construction, consistent with state law's prohibition on unreasonable restrictions.
3. Parking aligned with state law -- One space maximum, waived near transit.
4. By-right permitting maintained -- Consistent with state law's requirement for by-right approval.

The 30-day minimum rental period (short-term rental restriction) is permitted under state law, which allows municipalities to restrict or prohibit short-term rentals of ADUs.

• BackyardADUs.com -- Swampscott ADU Rules: https://backyardadus.com/adu-regulations-ma/swampscot-ma-adu-rules
• Itemlive -- "Swampscott votes to amend zoning bylaw" (May 22, 2025): https://itemlive.com/2025/05/22/swampscott-votes-to-amend-zoning-bylaw/
• Town of Swampscott Zoning Bylaws: https://www.swampscottma.gov/sites/g/files/vyhlif1296/f/pages/swampscott_zoning_by-laws_version_5_15_23.pdf
• Town of Swampscott website: https://www.swampscottma.gov
• Massachusetts Affordable Homes Act (H.4977): https://www.mass.gov/info-details/accessory-dwelling-units
• 760 CMR 71.00 (Protected Use ADUs): https://www.mass.gov/regulations/760-CMR-7100-protected-use-accessory-dwelling-units