Lowell, MA Accessory Structures: ADU Rules (2026)
ADU rules in Lowell, MA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- State law
- M.G.L. c.40A S.1A & S.3; Ch. 150, Acts of 2024, S.8
- State regulation
- 760 CMR 71.00
- Permitting
- By-right in single-family districts
- Max ADU size
- 900 sq ft OR 50% of principal dwelling GFA, whichever is smaller
- Allowed types
- Internal, external (addition), or detached
- Separate entrance
- Required
- Owner occupancy
- Not required
- Short-term rental
- Prohibited citywide
- Parking
- None required within 0.5 mi of a transit station
- Contact
- Development Services 978-674-4144
Summary
Lowell allows one accessory dwelling unit by-right on any lot that permits single-family homes, capped at 900 square feet or 50% of the principal dwelling's gross floor area (whichever is smaller), with no owner-occupancy requirement, under Massachusetts's statewide ADU law.
An ADU is a small residential living space located on the same lot as another home. ADUs can be internal within the existing primary structure on a site, external as an addition to the existing structure, or detached within a new or existing accessory structure on a site (such as a detached garage or carriage house). The maximum size for an ADU is 900 square feet OR 50% of the Gross Floor Area of the Principal Dwelling, whichever is smaller. Each ADU must maintain a separate entrance, either directly from the exterior of the home, or through an entry hall. There is no owner-occupancy requirement for either the Principal Dwelling or ADU. ADUs may be rented; however, Short Term Rentals (STRs) are NOT allowed in the City of Lowell. No off-street parking may be required for an ADU if the property is located within 0.5 miles of a Transit Station.
Full Breakdown
1A. An ADU is a small, self-contained residential living space on the same lot as a principal dwelling, and may be internal (within the existing structure), external (an addition), or detached (in a new or existing accessory structure such as a detached garage or carriage house). The maximum size for an ADU is 900 square feet OR 50% of the gross floor area of the principal dwelling, whichever is smaller. Each ADU must maintain a separate entrance, either directly from the exterior of the home or through an entry hall.
There is no owner-occupancy requirement for either the principal dwelling or the ADU, and the ADU may be rented as a long-term unit. However, short-term rentals (STRs) are not allowed in the City of Lowell, so an ADU cannot be operated as a short-term rental. 00. Protective ADUs (those built by-right under state law) must comply with the State Building Code and local building, plumbing, and electrical permitting administered by the City Development Services Office.
Violations & Fines
Building or occupying an ADU without the required building, plumbing, and electrical permits can trigger code-enforcement action, stop-work orders, and after-the-fact permit fees, and the unit must be brought into compliance with the Massachusetts State Building Code before it can be legally occupied. Operating an ADU as a prohibited short-term rental can result in zoning enforcement under the City's short-term-rental prohibition.
Frequently Asked Questions
How big can an ADU be in Lowell?
Do I have to live in my Lowell home to build an ADU?
Can I rent my ADU on Airbnb in Lowell?
Do I need parking for an ADU in Lowell?
Sources & Official References
Other rules in Lowell
How Lowell compares: Easiest Cities to Build an ADU·Compare Lowell to another location·View the Massachusetts accessory structures overview
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ADU Rules in Nearby Cities
How other cities in this county handle adu rules.