Key Requirements
Permit Type
By Right
Permit Authority
Building Inspector
Local Terminology
ADU
Max Size (sq ft)
900
Max Size (% of principal)
50%
Size Rule
Whichever is smaller
Attached Allowed
Yes
Detached Allowed
Yes
Internal Allowed
Yes
Parking Spaces Required
1
Transit Exemption
Yes
Short-Term Rental
Prohibited
Owner Occupancy Required
No
Design Review Required
Yes
Historic District Review
—
Energy Code
Stretch Code
HERS Rating Required
Yes
Max HERS Index (ADU)
52
Quick Summary
- 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).
Requirements at a Glance
| Requirement | Rule |
|---|---|
| Permit type | By right (building permit only) for internal/attached with no footprint change; Site Plan Review for detached or footprint/height changes |
| Max size | 900 sq ft or 50% of principal dwelling, whichever is less |
| Bedrooms | No local limit specified |
| Attached / Detached / Internal | All types allowed |
| Parking | 1 space required; 0 if within 0.5 miles of transit |
| Owner occupancy | Not required |
| Short-term rental | Prohibited (minimum 30 consecutive days) |
| Separate sale | Prohibited |
| Permit authority | Building Inspector (Site Plan Review by Planning Board for detached/additions) |
ADU Questions in Marblehead
Can I build an ADU in Marblehead, MA?
Yes. Accessory dwelling units are allowed by right in Marblehead, MA, meaning you do not need a special permit or a zoning variance as long as the unit meets the town's dimensional rules. You still need a building permit from the Building Inspector. Marblehead calls these "ADU."
How big can an ADU be in Marblehead, MA?
Marblehead limits an accessory dwelling unit to 900 square feet or 50% of the principal dwelling, whichever is smaller. State law protects ADUs up to 900 square feet on single-family lots, so a town cannot enforce a smaller cap on a protected-use ADU.
What types of ADU are allowed in Marblehead, MA?
Marblehead permits 3 forms of accessory dwelling unit: detached (a separate structure in the yard); attached (an addition to the house); internal (a conversion of existing space). Which one makes sense usually comes down to your lot, your septic or sewer situation, and whether you want the unit connected to the main house.
Does Marblehead, MA require extra parking for an ADU?
Marblehead's bylaw calls for 1 additional off-street parking space(s) for an ADU. Under state law, towns cannot require more than one space for a protected-use ADU, and no parking at all can be required within a half mile of transit.
Do I have to live on the property to rent out an ADU in Marblehead, MA?
No. Marblehead does not impose an owner-occupancy requirement, and state law bars towns from requiring it for protected-use ADUs. You can rent the unit without living on site.
What energy code applies to an ADU in Marblehead, MA?
Marblehead has adopted the Stretch Energy Code. That means a new ADU must hit a HERS rating of 52 or lower, which drives real decisions about insulation, air sealing, windows, and heating — typically an all-electric heat pump system. Budget for a HERS rater on the project from day one.
Can I use an ADU in Marblehead, MA as a short-term rental?
No. Marblehead prohibits using an accessory dwelling unit as a short-term rental; the minimum lease term is 30 days. The unit is intended for long-term housing. State law expressly allows towns to restrict short-term rental of ADUs, so this restriction does hold up.
Based on Marblehead’s bylaw as last verified 2026-02-25. Bylaws change at annual town meetings — confirm with the Planning Department before you build.