Marblehead

• Marblehead has an adopted ADU bylaw (Section 200-42), originally passed at May 2023 Town Meeting and updated at May 2025 Town Meeting to comply with the state Affordable Homes Act.
• Attached ADUs within existing structures that do not change footprint or height are allowed by right with only a building permit.
• Detached ADUs and additions that change the footprint or height require Site Plan Review by the Planning Board, which must approve or approve with conditions and cannot deny the application.
• Short-term rentals (less than 30 consecutive days) are prohibited for ADUs.
• Owner-occupancy is not required (removed in the 2025 amendments to comply with state law).

1. Determine ADU type:

   • Internal or attached ADU with no footprint or height change: Proceed directly to building permit (by right).
   • Detached ADU or attached ADU requiring footprint or height change: Site Plan Review by the Planning Board is required first.

2. For by-right ADUs (internal/attached, no structural changes):

   • Submit site plans, floor plans, and elevations to the Building Inspector.
   • Obtain a building permit.
   • Complete construction per Massachusetts State Building Code.
   • Obtain certificate of occupancy.

3. For Site Plan Review ADUs (detached or structural changes):

   • Submit application to the Planning Board with site plans, floor plans, and elevations.
   • The Planning Board must approve or approve with conditions -- it cannot deny the application.
   • Upon Planning Board approval, obtain a building permit from the Building Inspector.
   • Complete construction and obtain certificate of occupancy.

4. Ensure compliance with all dimensional requirements of the applicable zoning district (lot coverage, setbacks, open space).

• Maximum size: 900 square feet of gross floor area or 50% of the gross floor area of the principal dwelling, whichever is less.
• Separate entrance: Required for the ADU occupant(s), either directly from the exterior or through a shared entry hall sufficient to meet state building code requirements.
• Common interior door: An attached ADU may have a common interior door with the principal dwelling.
• Detached ADU height: Cannot exceed the height of the principal dwelling or the maximum height allowed in the zoning district, whichever is less.
• Detached ADU setbacks: Must comply with all setback requirements of the zoning district.
• Detached ADU location: Must be located behind the front building wall of the principal dwelling and maintain a secondary relationship to the principal structure.
• Dimensional compliance: The ADU must comply with all dimensional requirements of the applicable zoning district, including lot coverage, setbacks, and open space requirements.

• One parking space required for the ADU, in addition to parking required for the principal dwelling.
• Transit exemption: If the ADU is located within half a mile of a commuter rail station, subway station, ferry terminal, or bus station, no parking spaces are required.

• Site Plan Review for detached ADUs: While this is an additional step compared to a simple building permit, the Planning Board is required to approve (or approve with conditions) and cannot deny the application. This provides certainty to applicants while allowing the town to impose reasonable conditions.
• Historic district: Marblehead has significant historic areas. The bylaw does not explicitly address historic district review, but properties in historic districts may be subject to additional review under other local regulations. Check with the Planning Department.
• Limited uptake under old bylaw: Only 3 ADU permits were pulled under Marblehead's original 2023 bylaw, which required Planning Board approval (effectively a special permit). The 2025 amendments significantly simplified the process.
• No condo conversion: The ADU and principal dwelling cannot be sold or transferred separately.

The following is the full text of Marblehead Zoning Bylaw Section 200-42: Accessory Dwelling Units, as amended at the May 2025 Town Meeting (Article 24).

SECTION 200-42 ACCESSORY DWELLING UNITS

[Added 5-1-2023 ATM by Art. 39; Amended 2025 ATM by Art. 24]

A. Purpose. This section authorizing the provision of accessory dwelling units is intended to:

(1) Increase the number of small dwelling rental units available in the Town;

(2) Increase the number of affordable rental units available in Town;

(3) Increase the range of choice of housing accommodations to meet the needs of households;

(4) To increase the supply of housing and the diversity of housing options, in response to demographic changes such as smaller households and older households;

(5) To encourage the efficient use of the Town's housing supply while preserving the character of the town's neighborhoods;

(6) To maximize privacy, dignity, and independent living among family members preserving domestic family bonds as well as to protect the stability, property values, and the residential character of the neighborhood.

B. General requirements.

(1) No more than one accessory dwelling unit shall be permitted for each single-family lot.

(2) Accessory dwellings units are only allowed in or as an accessory to single-family dwellings.

(3) Accessory dwelling units are allowed within or attached to an existing single-family structure or detached from the principal dwelling on the lot.

(4) An accessory dwelling unit shall not contain in excess of 900 square feet of gross floor area or exceed 50% of the gross floor area of the principal dwelling, whichever is less.

(5) An accessory dwelling unit shall have a separate entrance for use by its occupant(s), either directly from the exterior or through a shared entry hall sufficient to meet the requirements of the state building code.

(6) An attached accessory dwelling unit may have a common interior door with the principal dwelling.

C. Permitting.

(1) An accessory dwelling unit within or attached to an existing single-family structure that does not change the footprint or height of the structure shall be allowed by right with only a building permit required.

(2) A detached accessory dwelling unit, or an attached accessory dwelling unit that requires changes to the footprint or height of the existing structure, shall require Site Plan Review by the Planning Board. The Planning Board shall approve or approve with conditions but shall not deny the application.

[NOTE: This replaced the former special permit requirement per 2025 Town Meeting amendments]

D. Parking.

(1) One parking space shall be required for the accessory dwelling unit.

(2) If the accessory dwelling unit is located within half a mile from a commuter rail station, subway station, ferry terminal or bus station, no parking spaces shall be required.

E. Occupancy.

(1) The accessory dwelling unit need not be owner-occupied.

[NOTE: Owner-occupancy requirement removed per 2025 amendments to comply with state law]

(2) The accessory dwelling unit shall not be used as a short-term rental (less than 30 consecutive days).

F. Design standards for detached ADUs.

(1) A detached accessory dwelling unit shall not exceed the height of the principal dwelling or the maximum height allowed in the zoning district, whichever is less.

(2) A detached accessory dwelling unit shall comply with all setback requirements of the zoning district.

(3) A detached accessory dwelling unit shall maintain a secondary relationship to the principal structure and shall be located behind the front building wall of the principal dwelling.

G. Dimensional requirements.

(1) The creation of an accessory dwelling unit shall comply with all dimensional requirements of the applicable zoning district, including but not limited to lot coverage, setbacks, and open space requirements.

2025 Town Meeting Amendments (Article 24)

Key changes adopted at Marblehead Town Meeting 2025:

1. Removed owner-occupancy requirement (state law compliance)
2. Detached ADUs now require Site Plan Review (not special permit) -- Planning Board must approve or approve with conditions, cannot deny
3. Size limit confirmed: 900 sq ft or 50% of principal dwelling, whichever is less
4. Parking: 1 space required, 0 if within 0.5 miles of transit
5. Short-term rental prohibition maintained (minimum 30 days)

History:

• May 2023: Original ADU bylaw adopted (Art. 39) -- required Planning Board approval
• September 2024: State Affordable Homes Act signed
• February 2, 2025: State law takes effect, preempting more restrictive local provisions
• May 2025: Marblehead updates bylaw to comply with state law (Art. 24)
• Under old bylaw: Only 3 ADU permits pulled (significant barrier to uptake)

Marblehead has adopted the Stretch Energy Code. 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.

ERV/HRV mechanical ventilation is now required (bath fans alone don't qualify). If on-site parking is provided, EV-ready wiring is also required.

Marblehead proactively updated its bylaw at the May 2025 Town Meeting to comply with the state Affordable Homes Act. The following changes reflect state preemption:

1. Owner-occupancy requirement removed -- State law (760 CMR 71.03) prohibits owner-occupancy requirements for Protected Use ADUs.
2. Special permit replaced with Site Plan Review -- State law requires by-right approval for the first ADU in single-family residential districts. Marblehead's Site Plan Review process for detached ADUs complies because the Planning Board cannot deny the application.
3. Parking aligned with state law -- Maximum 1 space, with transit proximity exemption.

The updated Marblehead bylaw is generally well-aligned with state law. The Site Plan Review process for detached ADUs is a reasonable local regulation that does not constitute a barrier to ADU creation, as the Planning Board is required to approve all compliant applications.

• Marblehead Zoning Bylaw Section 200-42 (ecode360): https://ecode360.com/44936513
• Marblehead Current -- "Housing Crisis: State Law to Override Marblehead's New ADU Rules": https://marbleheadcurrent.org/2024/09/04/housing-crisis-state-law-to-override-marbleheads-new-adu-rules/
• Town of Marblehead website: https://www.marblehead.org
• 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