Salem, MA
Salem, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 6/10 (10 is most accepting)
Last updated: 10.10.2024
Image source: Norwell Social
What You Need To Know
Salem, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. In Salem, one ADU per single-family home is allowed. Separately, owners who choose to rent their ADUs at or below 70% of the Fair Market Rent limit in Salem are eligible for a property tax exemption on their ADU.
Type of ADU Permit Required
ADUs in Salem do not require special permits, and can be built using a traditional building permit. For lots with two-five units, owners may apply for a special permit to build up to one ADU per unit. ADUs are not permitted on lots with over five units in Salem.
ADU Rules
An ADU can be maximum 900 square feet or half the Gross Floor Area of the main house; whichever is smaller.
The ADU and the main house must be owned by the same person(s).
Short-term rentals are prohibited.
No additional parking is required for an ADU.
ADUs may be attached or detached from the main house - if detached, they must be built at least 10 feet from the main house.
ADUs cannot be built in the front yard.
Detached ADUs can have a maximum height of 18 feet
Attached ADUs must maintain the architectural style of the main house to the extent possible.
ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall.
Exterior stairways need to be built on the side or rear of the ADU or main home.
Detached ADUs that are not owner occupied must have utilities on a separate service.
Resources:
https://library.municode.com/ma/salem/codes/zoning_ordinance?nodeId=S3.0USRE_3.2ACUS (See section 3.2.8)
Wayland, MA
Wayland, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 4/10
Last updated: 11.14.2024
Image source: Town of Wayland Facebook
What You Need To Know
Wayland, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. The rules for Wayland are outlined below.
Type of ADU Permit Required
ADUs in Wayland do not require special permits, and can be built using a traditional building permit.
ADU Rules
ADU Rules in Wayland:
Wayland allows one ADU per lot by right. To build more than one ADU, a special permit must be approved through the town.
An ADU can be maximum 900 square feet, or half the Gross Floor Area of the main house; whichever is smaller.
ADUs may be attached or detached from the main house.
Short-term rentals are not allowed. The minimum rental time for ADUs is 31 days.
ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall.
If the ADU is within 0.5 miles of a transit station, no additional parking is needed. If it is further than 0.5 miles from a transit station, one off-street parking spot must be added.
In addition to the by right ADU, Wayland, via special permit, allows for an Affordable Accessory Dwelling Unit. For more information on this path, please see the link below.
Resources:
Burlington, MA
Burlington, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 5/10
Last updated: 11/3/2025
Image source: HDPT Physical Therapy
What You Need To Know
Burlington, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. The rules for Burlington are outlined below.
Type of ADU Permit Required
ADUs in Burlington do not require special permits, and can be built using a traditional building permit. Residents are allowed to build one ADU per lot.
ADU Rules
An ADU can be maximum 900 square feet, or half the Gross Floor Area of the main house; whichever is smaller.
Short-term rentals are not allowed.
Detached ADUs cannot be built closer to the road than the main house.
Both the main house and the ADU must be connected to public water and sewer systems.
Properties within ½ mile of a transit station do not require additional parking. Properties outside of that area require additional off-street parking (driveway or garage) for all cars owned by the occupants of the ADU.
If an ADU has a separate exterior entrance or is detached, the ADU must be accessible from a path or walkway.
Attached ADUs must maintain the architectural style of the main house to the extent possible.
ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall.
Exterior entrances for attached ADUs must be located on the side or back of the dwelling, so that the main house retains the appearance of having only one front door.
The main house and ADU must be owned by the same person(s).
Exterior staircases above the first floor are only allowed in special circumstances.
Resources:
Resources:
https://www.burlington.org/ArchiveCenter/ViewFile/Item/608 (See pages 135-137)
Wellesley, MA
Wellesley, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 6/10
Last updated: 10.29.2024
Image source: Town of Wellesley Facebook
What You Need To Know
Currently not in compliance with the Massachusetts Affordable Homes Act.
ADU rules in Wellesley are pretty relaxed but still do not conform to the new Affordable Homes Act because of the permits needed and approval from the Planning Department.
Type of ADU Permit Required
ADUs require a building permit from the Inspector of Buildings and an annual certificate from the Planning Department.
ADU Rules
ADUs must match the principal dwelling’s style, including siding, roof pitch, trim, windows, and doors.
Exterior ADU doors cannot face public streets or private ways unless in pre-existing detached structures.
Exterior staircases must be hidden from public view and complement the main dwelling.
ADU construction must not exceed the principal dwelling’s height before ADU construction.
Detached ADUs are allowed only in the rear or side yard or in pre-existing buildings.
ADU size: minimum of 250 sq ft, maximum of 900 sq ft or 50% of the main dwelling’s gross area.
ADU must meet all applicable area and yard regulations.
Operational Requirements:
ADU owners must file a notice with the Registry of Deeds.
Owners must reside on the property for at least 184 days per year and cannot lease the owner unit when absent.
Minimum lease term for the non-owner-occupied unit is 30 days.
No product pickups or deliveries beyond typical residential activities.
ADUs cannot be used for a home business.
Resources:
https://wellesleyma.gov/DocumentCenter/View/30044/Section-513-Accessory-Dwelling-Units
Rehoboth, MA
Rehoboth, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 2/10 (10 is most accepting)
Last updated: 10.29.2024
Image source: Massachusetts Municipal Association
What You Need To Know
Currently not in compliance with the Massachusetts Affordable Homes Act.
In-law apartments are the only defined unit type in Rehoboth and can not must be used as an extension of the main dwelling.
Type of ADU Permit Required
Currently, a special permit is required, but that will have to change once Rehoboth rewrites their rules to be compliant with the state guidelines.
ADU Rules
Definition: An in-law apartment is an extension of a single-family dwelling providing facilities for sleeping, eating, bathing, and living.
Egress Requirements: The in-law unit must have a code-compliant means of egress through the main dwelling; garages or service areas cannot serve as the primary egress.
Size Limit: The total livable area of the in-law apartment cannot exceed 750 square feet.
Rental Restriction: The in-law apartment cannot be rented as a separate or independent unit from the main dwelling.
Unit Limitation: Only one in-law apartment is allowed per single-family dwelling.
Notarized Letter Requirement: Before a building permit is issued, the owner must submit a notarized letter stating:
The owner will occupy one of the dwelling units as their primary residence, except for temporary absences.
The in-law apartment is an extension of the single-family dwelling and is not an independent rental unit.
Recording Requirement: The notarized letter must be recorded in the County Registry of Deeds or Land Court within the property's chain of title.
Resources:
Stoneham, MA
Stoneham, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 4/10
Last updated: 10.29.2024
Image source: Town of Stoneham
What You Need To Know
Currently not in compliance with the Massachusetts Affordable Homes Act.
A single ADU is allowed with a permit on single-family home properties, must share a wall with the main structure and can not exceed 750 SF. Permits are not transferrable to new owners outside of the family.
Type of ADU Permit Required
ADUs require a special permit.
ADU Rules
Permit Filing: A Special Permit is required, filed with the Registry of Deeds, and can be amended or rescinded if ownership or conditions change.
Automatic Reversion: If ownership changes outside of the family, the property reverts to single-family use unless a new permit is applied for.
Size and Structure: The ADU cannot exceed 750 square feet and must share at least 75% of a wall with the main dwelling; utilities must be single-metered.
Parking: One additional parking space is required for the ADU, in addition to two spaces for the primary residence.
Occupancy Limit: ADU occupancy is limited to two people and cannot be used for commercial purposes.
Deed Restriction: A deed restriction confirming owner occupancy must be filed, and a Certificate of Occupancy requires proof of the permit’s recording.
Single Ownership: The main and accessory dwellings must be under the same ownership and cannot be separated. Only one ADU is permitted per lot.
Resources:
https://www.stoneham-ma.gov/DocumentCenter/View/1223/Ch15-Zoning-Part-1
Reading, MA
Reading, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 5/10
Last updated: 10.29.2024
Image source: Reading Recap
What You Need To Know
Currently not in compliance with the Massachusetts Affordable Homes Act.
A single ADU is allowed with a permit on single-family home properties. The ADU size cannot exceed one third of the residence and must maintain a single family appearance. Occupants limited to three.
Type of ADU Permit Required
ADUs require a special permit.
ADU Rules
An Accessory Apartment must not exceed the lesser of 1,000 square feet or one-third of the gross floor area of the primary residence, excluding garages, unfinished basements, sheds, or other accessory structures.
At least one owner must reside in either the Principal Dwelling or Accessory Apartment on the property.
The Accessory Apartment should maintain the single-family appearance of the property; new entries must be on the side or rear, and stairways to upper-level apartments should be enclosed within the building.
All motor vehicles associated with the Accessory Apartment must be parked off the street in a driveway or garage, without compromising the neighborhood’s single-family character.
Both the Principal Dwelling and Accessory Apartment must be connected to public water and sewer systems.
The apartment is limited to two bedrooms and a maximum of three occupants.
For detached structures built before 1910 or listed in the Historical Inventory, any exterior alterations should preserve the structure’s historical features, with limited footprint expansion (up to 10%).
A Detached Accessory Apartment cannot be located in the front yard or any area between the Principal Dwelling and a right-of-way, unless an existing structure in that area is converted.
Any Special Permit issued must ensure that the Accessory Apartment maintains the neighborhood's character and complements the Principal Dwelling.
Resources:
https://www.readingma.gov/DocumentCenter/View/2242/Zoning-Bylaw-PDF - page 38
Sudbury, MA
Sudbury, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 9/10 (10 is most accepting)
Last updated: 9.11.2024
Source: Sudbury Chamber of Commerce
What You Need To Know
Sudbury, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. The rules for Sudbury are outlined below.
Type of ADU Permit Required
ADUs in Sudbury can be built using a traditional building permit. They do not require a special permit.
ADU Rules
Sudbury allows one ADU per lot
An ADU can be maximum 900 square feet, or half the Gross Floor Area of the main house; whichever is smaller.
ADUs may be attached or detached from the main house.
ADUs cannot be used as short-term rentals.
ADUs must maintain a similar architectural style to the main house to the extent possible.
ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall.
If the ADU is within 0.5 miles of a transit station, no additional parking is needed. If it is further than 0.5 miles from a transit station, one off-street parking spot must be added.
The main house and ADU must be owned by the same person(s).
Exterior stairways need to be built on the side or rear of the ADU or main home.
Resources:
Waltham, MA
Waltham, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 2/10 (10 is most accepting)
Last updated: 9.10.2024
Source: City of Waltham MA
What You Need To Know
Currently not in compliance with the Massachusetts Affordable Homes Act.
Currently, ADUs are only allowed within an existing single family home. There is currently just an ADU definition on the books in Waltham, but there is nothing that specifies a size maximum or minimum, rental rules, or owner occupancy.
Type of ADU Permit Required
ADUs require a special permit through the Board of Appeals.
ADU Rules
Accessory dwelling units. The Board of Appeals shall only grant such special permit when it has determined that the following limitations have been complied with and the Board shall include the following in its decision:
The proposed dwelling unit is in harmony with and will promote the purposes of this chapter.
The dwelling unit is accessory to the principal residence and either the dwelling unit or the principal residence is occupied by the owner of the lot on which the dwelling unit is to be located, which owner shall have owned the lot for not less than five years.
The dwelling unit is designed for and may be occupied by not more than two persons.
Adequate provision has been made for access to such dwelling unit, separate from the access of the principal residence.
No alteration to the exterior of the dwelling shall be made.
No increase in the floor area of the dwelling shall be made.
The construction, reconstruction and occupancy of the dwelling unit will not be detrimental or injurious to persons or property.
The lot on which the dwelling is located contains at least 20,000 square feet in Residence A-1 Districts and 15,000 square feet in Residence A-2 Districts.
The building in which the proposed dwelling unit is to be located existed on the date of the adoption of this subsection.
There shall be provided on the lot a parking area sufficient to hold at least four cars designed in accordance with Sections 5.3 through 5.35 and in such a manner that cars can exit onto the street in a forward direction.
Any special permit granted under this section shall require that the applicant request recertification of the permit at periods not exceeding three years, and failure to request such recertification shall cause the permit to lapse. The Board of Appeals may, in appropriate cases, impose further restrictions on the apartment or the lot as a condition of the special permit.
The special permit, if granted, shall clearly state that it is not transferable to a purchaser of the lot and shall require, as a condition of its validity, that a copy of the permit be filed in the Registry of Deeds by the applicant.
Resources:
Middleborough, MA
Middleborough, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 4/10
Last updated: 8.28.2024
Image source: Wikipedia
What You Need To Know
Middleborough, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. The rules for Middleborough are outlined below.
Type of ADU Permit Required
ADUs in Middleborough do not require special permits, and can be built using a traditional building permit.
ADU Rules in Middleborough:
Middleborough allows one ADU per building lot.
An ADU can be a maximum of 900 square feet.
ADUs can be attached or detached from the main house.
Short-term rentals are prohibited.
Detached ADUs cannot be taller than 2 stories, or 25 feet - whichever is shorter.
ADUs must maintain the architectural style of the main house to the extent possible.
ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall.
No multi-level exterior stairs are allowed as the main method of access to the ADU.
Detached ADUs cannot be built in the front yard.
Detached ADUs need to be built at least 10 feet from any other structure on the lot.
If the ADU is within 0.5 miles of a transit station, no additional parking is needed.
If it is further than 0.5 miles from a transit station, one off-street parking spot must be added.
If off-street parking is necessary, it must be in the side or back yard of the main house and use the existing driveway.
The water connection for the ADU must come from the main house.
ADUs must have a separate electric meter, located outside.
ADUs need a separate water shut off.
ADUs and the main house must remain in single ownership - a deed restriction recorded at the Registry of Deeds is required.
Propane is not allowed on a lot that has an existing gas connection (from MG&E) - we build all-electric homes, so this isn’t a problem!
Resources:
Pembroke, MA
Pembroke, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 2/10 (10 is most accepting)
Last updated: 8.15.2024
Source: Town of Pembroke
What You Need To Know
Currently not in compliance with the Massachusetts Affordable Homes Act.
Currently, there are some hoops to jump through with ADUs in Pembroke. In addition to requiring a special permit, owners must sign a 15 year use restriction and agree to a maximum rent to be charged. ADUs must be rented to a person having an annual income of no more than 80% of the area median income. The Pembroke Housing Authority will monitor compliance with the ADU rules.
Type of ADU Permit Required
ADUs are allowed by special permit through the Zoning Board of Appeals in Pembroke.
ADU Rules
ADUs may be allowed on lots with at least 20,000 square feet of contiguous upland except for ADUs already in existence prior to the current ordinance.
The owner of the property must occupy the primary dwelling and rent the ADU.
The ADU cannot be larger than 800 square feet.
ADUs are limited to one bedroom and two occupants.
Two parking spaces must be provided for the ADU
An ADU must be attached to the existing single family home.
Resources:
Northborough, MA
Northborough, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 7/10 (10 is most accepting)
Last updated: 8.14.2024
Source: Town of Northborough
What You Need To Know
Northborough, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. The rules for Northborough are outlined below.
Type of ADU Permit Required
ADUs are permitted by right in Northborough and require a building permit.
ADU Rules
ADU Rules in Northborough:
Northborough allows one ADU per building lot.
An ADU can be maximum 900 square feet, or half the Gross Floor Area of the main house; whichever is smaller.
Short-term rentals are prohibited.
ADUs can be attached or detached from the main house.
Attached and detached ADUs must maintain the architectural style of the main house to the extent possible.
ADUs should be no taller than the main house.
ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall.
When possible, a detached ADU must be built to the rear or side of the main house and 10 feet from other buildings on the lot.
Multi-level exterior staircases are not allowed on attached or detached ADUs.
One dedicated off-street parking spot must be added for the ADU.
Detached ADUs must have a separate water meter and dedicated water service from the main to the ADU.
When possible, the sewer service for a detached ADU should connect from the main house.
Any direct connections from the ADU to the public sewer must be reviewed and approved from the Department of Public Works.
The main house and ADU must be owned by the same person(s).
Resources:
https://www.town.northborough.ma.us/sites/g/files/vyhlif12221/f/uploads/warrant_articles_approved_at_2025_annual_town_meeting.pdf (See pages 1-2)
Beverly, MA
Beverly, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 9/10 (10 is most accepting)
Last updated: 7.9.2024
Source: Town of Beverly, MA
What You Need To Know
ADUs are permitted in Beverly within dwellings, attached, and detached. The intention for ADUs in Beverly is to create spaces for older individuals who want to remain in their homes or on their property as well as provide rental units.
Type of ADU Permit Required
ADUs are by right in Beverly and require a building permit.
ADU Rules
ADUs must be occupied by at least one of the owners of the property.
There is only one ADU allowed on a property.
ADUs must meet minimum requirements for sanitary and building codes as well as municipal codes.
All units on the property must have utility services, including electricity, water, oil, and gas, active if present.
The design of the ADU must be complementary to the primary dwelling.
ADUs are limited to 1,000 square feet or 50% of the primary dwelling’s gross floor area, whichever is less.
Side and rear setbacks must be met for the specific zoning district.
Short term rentals are not allowed.
Any exterior lighting must be designed and installed so that it does not cast light on adjacent properties.
One off-street parking spot must be provided and reserved for the ADU. The spot must be distinct from other off-street parking spaces.
The ADU must remain in common ownership.
Attached ADU provisions
One entrance is permitted on the front of the home, and the new entrance should be on the rear or side of the home if feasible. Any front entrance to an ADU must appear secondary.
Any stairways must be within the exterior.
Detached ADU provisions
Detached ADU cannot be taller than the existing dwelling and cannot be greater than 35 feet.
ADUs must appear clearly secondary to the primary dwelling and must be located behind the front building edge of the primary dwelling.
The design of the ADU must be complementary to the primary dwelling.
Resources:
Swampscott, MA
Swampscott, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10 (10 is most accepting)
Last updated: 7.2.2024
Image Source: North of Boston
What You Need To Know
Last winter, at Swampscott’s annual town meeting, a law was passed to make ADUs by right. There are a number of restrictions and design requirements based upon what type of ADU you want to build.
Type of ADU Permit Required
ADUs are permitted by right in Swampscott.
ADU Rules
Size Restrictions
Generally, ADUs are permitted to be as large as 50% of the floor area of the existing dwelling or 900 feet, whichever is smaller
Attached ADUs
If changing the footprint of an existing structure the floor area addition is limited to 800 square feet.
An addition of greater than 800 square feet is subject to site plan review by the Swampscott planning board
Detached ADUs can be built in two ways
ADUs can be built in existing detached accessory structures.
If in a preexisting, nonconforming location, it can be demolished and rebuilt within the same footprint. These cases are subject to a finding from the Zoning Board of Appeals.
If building a new construction detached ADU, the ADU must meet the dimensional requirements for a detached structure.
5 feet from side and rear setbacks and no less than 10 feet from the primary structure.
Additional Rules
Only one ADU is permitted per lot.
If an ADU is constructed where the entrance is located on the front of the home, only one entrance may appear to be the primary entrance.
Any exterior stairways to the ADU must be located on the side or rear of the dwelling.
All utilities must be shared between the ADU and the primary dwelling.
The owner of the lot must either live in either the primary dwelling or the ADU, except for a bona fide temporary absence.
In addition to minimum parking requirements, one additional parking space is required for the ADU.
Resources:
Town of Swampscott Zoning By-law- Article 5.11.0.0/Page 119
Arlington, MA
Arlington, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 8/10
Last updated: 6.2.2024
Image source: Visit Lexington
What You Need To Know
Arlington, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. The rules for Arlington are outlined below.
Type of ADU Permit Required
ADUs in Arlington do not require special permits, and can be built using a traditional building permit. If you have a particularly tight lot, it may be possible to get a special permit to reduce your setbacks.
ADU Rules in Arlington
ADUs are allowed in residential and business districts.
An ADU can be maximum 900 square feet, or half the Gross Floor Area of the main house; whichever is smaller.
ADUs may be attached, detached, or built within the existing house.
Short-term rentals are not allowed.
ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall.
No additional off-street parking spaces are required.
Owners don’t need to live on the property to build an ADU.
The main house and ADU must be owned by the same person(s).
Resources:
https://www.arlingtonma.gov/home/showpublisheddocument/43413/638962138242730000 (Pages 101-103)
https://www.arlingtonma.gov/departments/inspectional-services/accessory-dwelling-units-adus
https://arlington.novusagenda.com/Agendapublic/CoverSheet.aspx?ItemID=20003&MeetingID=2254
Medway, MA
Medway, Massachusetts’ Accessory Dwelling Unit (ADU) Rules
Last updated: 2019
What you need to know:
Medway, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. The rules for Arlington are outlined below.
Type of ADU permit required:
ADUs in Medway do not require special permits, and can be built using a traditional building permit. If you have a particularly tight lot, it may be possible to get a special permit to reduce your setbacks.
ADU Rules in Medway:
Medway allows ADUs by right in single-family zoning districts.
An ADU can be maximum 900 square feet, or half the Gross Floor Area of the main house; whichever is smaller.
ADUs may be attached, detached, or built within the existing house.
Short-term rentals of ADUs are not allowed.
ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall.
Properties within ½ mile of a transit station do not require additional parking. Properties outside of that area require one additional off-street parking spot for the ADU.
The main house and ADU must be owned by the same person(s).
Resources:
https://storage.googleapis.com/juniper-media-library/117/2025/10/Zoning%20Bylaw%20Final%20-%20AG%20Approved.pdf (See PDF pages 130-131)
Medfield, MA
Medfield, MA Accessory Dwelling Unit (ADU) Rules
Last updated: 2004
Photo courtesy of Town of Medfield
The town of Medfield, MA had the following provisions for Accessory Dwelling Units:
A dwelling unit within a single structure for use by a family member
The house was in existence prior to 1938
The house has a minimum of 2000 sq. ft. of existing floor area
The house meets the lot area requirement for a one-family dwelling in its district
An addition to the house of up to 10% of the existing floor area must be allowed in the rear or side yard, provided the addition is architecturally consistent with the existing house
The exterior of the house must not be altered except for restoration consistent with the existing architecture and exits required by law, which exits must be in the rear or at the side of the house.
The accessory unit must have a minimum floor area of 500 sq. ft., plus 100 sq. ft. for each bedroom over one
The accessory unit must have a bathroom and a kitchen or kitchenette
One off street parking space must be provided for each bedroom in the accessory unit, in addition to spaces required for the existing dwelling
The owner of the house must occupy the house or the accessory unit, except for bona fide temporary absences of up to one year
The Special Permit must be a personal permit restricted to the individual owner-applicant and shall terminate when said owner-applicant ceases to own the dwelling
In the event of a change of ownership of a house for which a Special Permit has been issued for an accessory unit, the new owner or holder of a purchase and sale agreement with the owner may apply for a renewal of the Special Permit.
Special Permit will terminate upon the happening of any of the following events: (a) Sale of the property (b) Death of those persons occupying the Family Apartment, (c) Permanent change of domicile of all of the persons occupying the Family Apartment from said Family Apartment to some other location either within or without the Town of Medfield
Read more:
Lexington, MA
Lexington, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 7/10
Last updated: 11/4/2025
Image source: Yankee Magazine
What You Need To Know
Lexington, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. There are two pathways to building an ADU in Lexington. A Protected Use Accessory Dwelling Unit (PADU) and an Accessory Apartment are the two pathways to building. Each has specific regulations associated with it and are detailed below.
Type of ADU Permit Required
A PADU does not require a special permit and can be built using a traditional building permit, while an accessory apartment requires a special permit.
ADU Rules
Protected Use ADU Regulations:
An ADU can be maximum 900 square feet, or half the Gross Floor Area of the main house; whichever is smaller.
There are no minimum lot size requirements for building an ADU.
ADUs can be rented, but may not be able to be rented short-term.
The property owners are not required to live on site.
The property owners are allowed to build one ADU on their property.
The ADU may be attached or detached to the primary dwelling.
One additional parking space (on-street or off-street) is required if the property is further than 0.5 miles from a transit station.
General requirements for Accessory Apartments in Lexington:
There is only one ADU permitted per lot.
The owner of the main house must live in either the primary dwelling or the ADU.
If the owner is away from the property for less than two years, both the main house and ADU may be rented as long as:
Notice is given to the Building Commissioner
The owner must reside on the property at least two years before and after such leave
The ADU must be have a similar architectural style to the single family dwelling and meet the following criteria:
No exterior stairways.
Only one door can have the appearance of a principal entrance.
Lexington distinguishes between three different ADUs
Basic ADU
Maximum of 1,000 square feet for gross floor area
There cannot be greater than two bedrooms
The ADU must be located in the main house
Expanded ADU
The gross floor area cannot be greater than 40% of the gross floor area of the main house
The ADU is designed so that it is consistent with the appearance of a single family home
The ADU must be located in the main house
Accessory Structure ADU
This is an ADU in an accessory structure, i.e. a garage
Maximum of 1,000 square feet for gross floor area
The ADU is designed to have a similar architectural style of the single family home on that lot and surrounding lots
Resources:
https://www.lexingtonma.gov/2226/Accessory-Dwelling-Units-ADUs
https://www.lexingtonma.gov/DocumentCenter/View/14679/760-CMR-7100-Protected-Use-ADUs---Final
Cambridge, MA
Cambridge, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last updated: 6.21.2024
Image source: USNews
What You Need To Know
ADUs are allowed in Cambridge in all zoning districts in structures in existence as of February 1st 2019. A single-family, two-family, or accessory structure may be altered to provide an ADU.
Type of ADU Permit Required
ADUs in Cambridge require a special permit.
ADU Rules in Cambridge
ADUs are only permitted in structures that have been in existence since on or before February, 1, 2019.
The principal residence must have at least 1,800 square feet of gross floor area.
The ADU is limited to 900 square feet or 35% of the gross floor area of the primary residence, whichever is less.
Only one ADU is permitted on any given lot.
A two-family home may be converted to a single family home with an ADU by right - no need for a special permit.
An ADU within or attached to an accessory structure cannot be greater than 900 square feet
The authority granting the special permit must determine that the appearance is compatible with the primary residence as well as the homes in the surrounding area.
For both ADUs within or attached to a principal residence and accessory structure
Special Permit Information
ADUs are not included in lot area per dwelling calculations.
The Board of Zoning Appeal may relax space requirements for ADUs built within structures; however, any gross floor area added must comply with ADU requirements.
To ensure a safe environment, setbacks and height restrictions may be altered.
EX: safe egress
Resources:
Cambridge Massachusetts Land Use Regulations- Article 4.20
Lincoln, MA
Lincoln, MA Accessory Dwelling Unit (ADU) Rules
City Acceptance Rating: 10/10
Last updated: 6.21.2024
Image source: deCordova Sculpture Park and Museum
What You Need To Know
In Lincoln, ADUs are allowed both within a single family home as well as in a detached structure. Additionally, through the Affordable Accessory Apartment Program in Lincoln, ADUs are allowed under other guidelines, detailed below, with the intention of creating affordable housing to families and individuals whose income is between 60%-80% area median income. They emphasize a desire to serve populations such as families, single parents, veterans, seniors, town employees, and employees of small local businesses.
Type of ADU Permit Required
ADUs within an existing dwelling require a building permit whereas an ADU in an accessory structure, outside the main structure, or through the Affordable Accessory Apartment Program require a special permit.
ADU Rules
For ADUs not part of the Affordable Accessory Apartment Program:
ADUs (not part of the Affordable Accessory Apartment Program) are limited to 5% of the residential units in Lincoln.
The ADU is limited to 1,200 square feet
An ADU within a single family home cannot be greater than 35% of the floor area of the single family home and the ADU combined.
EX. 2,500 square foot single family home +1,200 square foot ADU = 3,700 square feet total x .35 = 1,295 square feet.
In this example, the ADU would have to be smaller.
An ADU is only permitted on lots that contain at least 40,000 square feet.
The owner of the property must own both the ADU and the single family home and live in either the ADU or the single family home.
For both building and special permits, dimensional floor plans and a site plan must be submitted showing the following:
Location, setbacks, height, and location of a parking space for the ADU
ADUs must meet setback and height requirements laid out in the zoning bylaw for primary structures or accessory structures depending on the location.
Provision for sewage must be made per the requirements of the Board of Health.
Proper ingress and egress as well as one parking space must be provided.
The primary residence must retain the appearance of a single family home.
If the ADU is rented, it must be rented for a minimum of seven days
ADUs through Lincoln’s Affordable Accessory Apartment Program are intended to:
Provide families and individuals whose income is between 60%-80% area median income (AMI) housing
Provide young families, single parents, veterans, seniors, town employees, and employees of small local businesses housing
Allow residents of Lincoln with modest income to get income that will allow them to stay in their homes
Add units to the Subsidized Housing Inventory at little cost to Lincoln
Spread affordable housing throughout Lincoln
Contribute to efficient use of land and structures in Lincoln
Add units without changing the footprint of the existing structure
Requirements
Special permit through the Zoning Board of Appeals
A deed restriction
This is a 15 year deed restriction recorded at the South Middlesex Registry of Deeds
The deed restriction ends if the property is sold
The deed restriction can be voluntarily terminated with 60 days notice at the end of a tenant’s lease
An affirmative fair marketing plan
This refers to the process of selecting tenants in a way that advances fair housing and equity.
Homeowners are required to select tenants from a waiting list generated by the Affordable Accessory Apartment Program
Family members or employees of the homeowner may not be a tenant through the Affordable Accessory Apartment Program
The home must retain the appearance of a single family home
The ADU will have a separate entrance
Off-street parking is available
The changes that are made must not be a detriment to the neighborhood
The ADU may not exceed 1,200 square feet or more than 35% of the home’s square footage
The septic system is adequate
The plans provided are certified by an architect
Homeowner Benefits
Homeowners qualify for a real estate tax exemption on the portion of property dedicated to an Affordable Accessory Apartment. Essentially, homeowners are not charged for the portion of property used for affordable housing purposes.
Zero interest loans totalling $25,000 over a ten year period will be granted to homeowners.
After ten years the loan is forgiven
Resources:
https://www.lincolntown.org/DocumentCenter/View/27060/Affordable-Accessory-Apartment-Program