Key Requirements
Permit Type
By Right
Permit Authority
Building Department
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
No
Historic District Review
—
Energy Code
Specialized Code
HERS Rating Required
Yes
Max HERS Index (ADU)
52
Quick Summary
- 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).
Requirements at a Glance
| Requirement | Rule |
|---|---|
| Permit type | By right; Site Plan Review for additions over 800 sq ft |
| Max size | 900 sq ft or 50% of principal dwelling, whichever is smaller |
| Footprint addition limit | 800 sq ft for attached ADU additions |
| Bedrooms | No local limit specified |
| Attached / Detached / Internal | All types allowed |
| Parking | 1 space required; waived within 0.5 miles of transit |
| Owner occupancy | Not required |
| Short-term rental | Prohibited (minimum 30 consecutive days) |
| Setbacks (detached) | 5 feet from side and rear lot lines |
| Permit authority | Building Department |
ADU Questions in Swampscott
Can I build an ADU in Swampscott, MA?
Yes. Accessory dwelling units are allowed by right in Swampscott, 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 Department. Swampscott calls these "ADU."
How big can an ADU be in Swampscott, MA?
Swampscott 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 Swampscott, MA?
Swampscott 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 Swampscott, MA require extra parking for an ADU?
Swampscott'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 Swampscott, MA?
No. Swampscott 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 Swampscott, MA?
Swampscott has adopted the Specialized Opt-In 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 Swampscott, MA as a short-term rental?
No. Swampscott 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 Swampscott’s bylaw as last verified 2026-02-26. Bylaws change at annual town meetings — confirm with the Building Department / Planning Board before you build.