Key Requirements
Permit Type
By Right
Permit Authority
Building Commissioner
Local Terminology
AADU
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
Specialized Code
HERS Rating Required
Yes
Max HERS Index (ADU)
52
Affordability Cap
70% FMR
Quick Summary
- Salem allows Affordable Accessory Dwelling Units (AADUs) by right under its locally adopted ordinance (Section 3.2.8), which predates the state ADU law.
- ADUs must rent at no more than 70% of HUD Fair Market Rent for Salem -- a unique affordability requirement enforced through a recorded deed restriction.
- Maximum size is 900 sq ft or 50% of the principal dwelling, whichever is smaller; minimum 350 sq ft.
- Attached, detached, and internal ADUs are all permitted across most residential districts (R1-R4, R5 for detached new construction, plus B1, B3, BPD).
- Short-term rentals of ADUs are prohibited. Owner-occupancy requirement was removed in May 2025 per state law compliance.
Requirements at a Glance
| Requirement | Rule |
|---|---|
| Permit type | By right (building permit) |
| Max size | 900 sq ft or 50% of principal dwelling, whichever is smaller |
| Min size | 350 sq ft |
| Attached allowed | Yes |
| Detached allowed | Yes |
| Internal allowed | Yes |
| Parking | 1 space max; 0 spaces if within 0.5 miles of transit |
| Owner occupancy | Not required (removed May 2025) |
| Short-term rental | Prohibited |
| Affordability | Rent capped at 70% of HUD FMR for Salem |
| Deed restriction | Required (affordability covenant recorded before CO) |
| Design standards | Must maintain single-family appearance (attached); height cannot exceed principal dwelling or district max (detached) |
ADU Questions in Salem
Can I build an ADU in Salem, MA?
Yes. Accessory dwelling units are allowed by right in Salem, 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. Salem calls these "AADU."
How big can an ADU be in Salem, MA?
Salem 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 Salem, MA?
Salem 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 Salem, MA require extra parking for an ADU?
Salem'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 Salem, MA?
No. Salem 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 Salem, MA?
Salem 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 Salem, MA as a short-term rental?
No. Salem 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 Salem’s bylaw as last verified 2026-02-25. Bylaws change at annual town meetings — confirm with the City of Salem Building Department before you build.