Key Requirements
Permit Type
By Right
Permit Authority
Building Commissioner
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
Stretch Code
HERS Rating Required
Yes
Max HERS Index (ADU)
52
Quick Summary
- Newbury adopted comprehensive ADU amendments at Town Meeting on May 15, 2025 (Yes-129, No-17), after extensive Planning Board review and public hearings.
- ADUs are permitted by right via administrative review by the Building Commissioner. No special permit is required for conforming ADUs.
- Maximum size is 900 sq ft or 50% of the principal dwelling, whichever is smaller. Uniquely, the ZBA may grant a Special Permit allowing ADUs up to 15% above 900 sq ft (approximately 1,035 sq ft).
- Short-term rentals of ADUs are prohibited (no weekly or daily rental use).
- Plum Island Overlay District properties have additional bedroom count and dimensional restrictions.
Requirements at a Glance
| Requirement | Rule |
|---|---|
| Permit type | By right (administrative review by Building Commissioner) |
| Max ADUs per lot | 1 |
| Max size (by right) | 900 sq ft or 50% of principal dwelling, whichever is smaller |
| Max size (Special Permit) | Up to 15% above 900 sq ft (~1,035 sq ft) via ZBA |
| Attached allowed | Yes |
| Detached allowed | Yes |
| Internal allowed | Yes |
| Parking | 1 space (0 within 0.5 mi of commuter rail or bus station) |
| Short-term rental | Prohibited (no weekly or daily rentals) |
| Owner-occupancy | Not required |
| Septic | Total bedrooms (primary + ADU) must not exceed septic capacity |
| Plum Island | Additional bedroom and dimensional restrictions |
ADU Questions in Newbury
Can I build an ADU in Newbury, MA?
Yes. Accessory dwelling units are allowed by right in Newbury, 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 Commissioner. Newbury calls these "ADU."
How big can an ADU be in Newbury, MA?
Newbury 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 Newbury, MA?
Newbury 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 Newbury, MA require extra parking for an ADU?
Newbury'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 Newbury, MA?
No. Newbury 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 Newbury, MA?
Newbury 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 Newbury, MA as a short-term rental?
No. Newbury prohibits using an accessory dwelling unit as a short-term rental. 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 Newbury’s bylaw as last verified 2026-02-25. Bylaws change at annual town meetings — confirm with the Planning Board / Building Department before you build.