Can I build an ADU in Scituate, Massachusetts?
Yes. Scituate allows one accessory dwelling unit per lot through Planning Board Site Plan Review if it is no larger than half the main home's floor area or 900 sq ft, whichever is smaller. It can be inside the house, attached, or detached; it needs one off-street parking space (none within 0.5 miles of a commuter rail station, ferry terminal or bus station) and can't be rented for stays of 31 days or less.
| Approval for a standard ADU | Site Plan Review (Planning Board) [2] |
| Max size (standard ADU) | Half the main home's gross floor area or 900 sq ft, whichever is smaller [2] |
| Large ADU (over 900 sq ft, up to 40% of main home) | Special Permit [3] |
| Owner-occupancy | Not required for a standard ADU; required for a Large ADU [8] |
| Number allowed | 1 per lot (a second, standard ADU is allowed only if the first one was a Large ADU) [12] |
| Parking | 1 off-street space (none within 0.5 mi of a commuter rail station, ferry terminal or bus station) [7] |
| Short-term rental | Not allowed; minimum rental term 31 consecutive days [8] |
What's allowed
Scituate's zoning bylaw defines an ADU as a self-contained unit with its own sleeping, cooking and sanitary facilities and a separate entrance, on the same lot as the main home [1]. It can be within the house, attached in a connected structure, or detached (for example in a garage or carriage house), and it must meet setback, height and yard rules [6]. Generally only one ADU is allowed per lot [5]; an existing ADU rules out a second, except that if a Large ADU was approved first, a standard (Protected Use) ADU may be added by right with Site Plan Review [12]. A detached ADU must satisfy all setbacks and can't be placed in front of the main house [10].
Size and approval
- Standard ADU: up to half the main home's gross floor area or 900 sq ft, whichever is smaller. It's allowed by Site Plan Review before the Planning Board [2].
- Large ADU: over 900 sq ft but no more than 40% of the main home's floor area. It needs a Special Permit [3], and the owner must live in one of the units as a primary residence and certify that to the Planning Office every year [9].
Parking, septic and design
One off-street parking space is required for the ADU, unless it's within 0.5 miles of a commuter rail station, ferry terminal or bus station [7]. Sewage and drainage must meet Board of Health or DPW Sewer and Water requirements [11]; the bylaw asks for a letter confirming the existing system is adequate as part of Site Plan Review. The house should look as unchanged as feasible, and the ADU can't be sold separately from the main house.
Rental rules
A standard ("Protected Use") ADU has no owner-occupancy requirement, and every ADU must have a minimum lease or rental term of 31 consecutive days [8]. ADUs can't be used as short-term rentals, and a restrictive covenant saying so must be recorded before the occupancy permit is issued [4].
State law
Massachusetts protects one ADU per lot by right in single-family zones. Scituate's standard ADU follows the state size limit, and state law lets towns ban short-term rental of ADUs. The owner-occupancy rule applies only to Large ADUs, which are bigger than the state-protected size.
See how Scituate compares with 8+ other Massachusetts towns on accessory dwelling units (adus) →
Next steps
- Measure the main home's gross floor area to see whether your ADU is a standard ADU (up to 900 sq ft or half the house) or a Large ADU that needs a Special Permit.
- Get a letter from the Board of Health (781-545-8725) or the DPW Sewer Division confirming your septic system or sewer connection can handle the ADU.
- File a Site Plan Review application with the Planning Board through the Planning Office, with the items on the town's ADU application form and proof of the required parking space.
- Record the short-term rental restrictive covenant at the Registry of Deeds, then get building and occupancy permits from the Building Department (781-545-8716).
Common questions
- Can I build an ADU in Scituate, Massachusetts?
- Yes. Scituate allows one accessory dwelling unit per lot through Planning Board Site Plan Review. It can be inside the house, attached, or detached.
- How big can an ADU be in Scituate, Massachusetts?
- A standard ADU can be no larger than half the main home's floor area or 900 sq ft, whichever is smaller. A large ADU, over 900 sq ft and up to 40% of the main home, needs a special permit.
- Does an ADU need parking in Scituate, Massachusetts?
- It needs 1 off-street space, with none required within 0.5 miles of a commuter rail station, ferry terminal or bus station.
- Can I rent my ADU on Airbnb in Scituate, Massachusetts?
- No. An ADU can't be rented for stays of 31 days or less. The minimum rental term is 31 consecutive days.
Massachusetts' statewide ADU law
Since February 2, 2025, the Affordable Homes Act (St. 2024, c. 150, §8) has protected one accessory dwelling unit (ADU) per lot in any zoning district that allows single-family homes (M.G.L. c. 40A, §3). Your town cannot ban it, require a special permit or other discretionary approval, or "unreasonably restrict" building or renting it.
What counts as a protected ADU:
- A self-contained unit with its own sleeping, cooking and bathroom facilities, on the same lot as the main home.
- No larger than 900 sq ft or half the main home's floor area, whichever is smaller.
- It can be attached or detached, and it needs a separate entrance that meets the building code.
What towns cannot require:
- That the owner live in the main home or the ADU.
- More than 1 extra parking space, or any extra space if the lot is within 0.5 miles of a subway, commuter rail, ferry or bus station.
- A minimum lot size, caps on the number of ADUs, or limits on who may live there (age, income, relationship).
What towns can still do: use reasonable site plan review, setback, height and bulk rules, require Title 5 septic compliance, and restrict or ban short-term rentals of ADUs. A second ADU on the same lot needs a special permit. State regulations at 760 CMR 71.00 (in effect since January 31, 2025) explain which rules count as unreasonable.
What the bylaw says
- Sec. 200 (Definitions, Accessory Dwelling Unit), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 5
A self-contained housing unit, inclusive of sleeping, cooking and sanitary facilities on the same Lot as a Principal Dwelling, subject to otherwise applicable dimensional and parking requirements, that: (i) maintains a separate entrance, either directly from the outside or through an entry hall or corridor shared with the Principal Dwelling sufficient to meet the requirements of the state building code for safe egress; (ii) is not larger in Gross Floor area than ½ the Gross Floor Area of the Principal Dwelling or 900 square feet, whichever is smaller; and (iii) is subject to such additional restrictions as may be imposed by the municipality, including, but not limited to, additional size restrictions or prohibitions on Short-term Rental; provided, however, that no Municipality shall unreasonably restrict the creation or rental of an ADU that is not a Short-term rental.
- Sec. 530.1A(A), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 58
Accessory dwellings no larger than half (50%) of the gross floor area of the Principal dwelling or 900 sq. ft, whichever is smaller, are allowed by Site Plan Review in accordance with the requirements in Section 530.2 and Section 770 of the zoning bylaw.
- Sec. 530.1A(B), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 58
Accessory dwelling unit, LARGE are greater than 900 sq. ft. but no larger than 40% of the gross floor area of the principal dwelling are allowed by Special Permit in accordance with the requirements of Section 530.2.
- Sec. 530.1A(D), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 58
Accessory Dwelling Units shall not be used as short-term rental units as defined in MGL Ch 64G, § 1, meaning periods of occupancy of 31 days or less. A restrictive covenant shall be recorded against the property to that effect prior to an occupancy permit for the accessory dwelling unit.
- Sec. 530.2(C), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 59
Only one accessory dwelling unit shall be created within a principal dwelling or on a lot containing a principal dwelling subject to Section 530.1A F.
- Sec. 530.2(D), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 59
An accessory dwelling unit associated with a principal dwelling must be located within the interior of and under the same roof as the principal dwelling, in a structure attached thereto, or in a detached structure on the same lot that complies with all required setback, building height, and yard requirements to the greatest extent allowable by law.
- Sec. 530.2(G), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 59
No additional parking space shall be required for an accessory dwelling unit located not more than 0.5 miles from a commuter rail station, ferry terminal or bus station; otherwise, one private off-street parking space shall be required for occupants of each accessory dwelling unit.
- Sec. 530.2(J)-(K), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 60
Protected Use ADUs shall not require owner occupancy of the accessory dwelling unit or primary dwelling. K. Accessory Dwelling Units shall have a minimum lease or rental term of 31 consecutive days.
- Sec. 530.2(O), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 60
In an accessory dwelling unit in a residential district that requires a special permit as it is larger than 900 sq. ft., the owner must occupy one of the dwelling units under the special permit as their primary residence and provide an annual certification to the Planning Office of the owner occupancy requirement.
- Sec. 530.2(N), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 60
A detached accessory dwelling shall be designed, to the maximum extent practicable, so that the appearance on the property in which it is located remains that of a residential property and shall satisfy all setbacks and not be located in the front of any primary dwelling and any addition or new construction shall be consistent with the design of the principal dwelling considering the following: architectural details, roof design, building spacing, and orientation, door and window location and building materials.
- Sec. 530.2(I), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 59
Adequate provisions shall be made for the disposal of sewage, waste and drainage generated by the occupancy of accessory dwelling units in accordance with the requirements of the Board of Health and/or DPW Sewer and Water Divisions.
- Sec. 530.2(T), Zoning Bylaw (including changes approved by April 13, 2026 Annual Town Meeting; AG approved July 9, 2026), p. 61
The existence of an existing accessory dwelling unit prohibits a second one. If a large ADU is obtained first, a Protected Use ADU is allowed by right with Site Plan Review.